Apparatus and process for monovalent ion extraction

Abstract

There is described an apparatus for reducing the ratio of divalent ions, such as divalent cations, to a target monovalent ion, such as a target monovalent cation, in an aqueous solution from a source aqueous solution that contains a higher ratio of divalent ions to the target monovalent ion. The apparatus comprises optionally a pretreatment portion operable to receive the source aqueous solution and produce a pretreated source aqueous solution. A first separation portion operable to receive an optionally pretreated aqueous solution and form an intermediate aqueous solution having a lower ratio of divalent ions to the monovalent ion than the optionally pretreated aqueous solution. An adsorbent separation portion operable to receive the intermediate aqueous solution and form a product aqueous solution having a lower ratio of the divalent ions to the monovalent ion than the intermediate solution.

Description

[0001] APPARATUS AND PROCESS FOR MONOVALENT ION EXTRACTION FIELD

[0001] The present invention relates to extraction of a target monovalent ion from a sourceaqueous solution. More specifically, the present invention relates to an apparatus and process for reducing the ratio of divalent ions to a target monovalent ion in an aqueous solution from a source aqueous solution. The present invention also relates to an apparatus and process for increasing the ratio of a target monovalent ion to other ions in an aqueous solution from a source aqueous solution. BACKGROUND

[0002] Some monovalent ions, such as lithium, are used for various applications includingceramics and glass, lubricants and greases, catalysts, and more recently in batteries. The global consumption of monovalent ions such as lithium has more than doubled over the past 10 years, from 24.5 kt in 2010 to 56.0 kt in 2020. There are currently four primary resources for lithium: seawater, mineral deposits, brines, geothermal fluids. Extraction of lithium from seawater is currently economically infeasible because of low feed concentration (0.2ppm). Compared to lithium extraction from ores, lithium extraction from brines is less time-consuming, and less energy and cost intensive. However, the traditional way of extraction lithium from brines is still far from efficient and environmentally friendly, involving natural evaporation and a series of precipitations with additions of huge amount of chemicals.

[0003] Current direct lithium extraction (DLE) technologies involve drawbacks such as tedioussteps and low efficiency. The operating costs can be significantly reduced by decreasing the number of stages. When a relatively pure (>99.5%) but dilute (usually less than the lithium concentration in the brines) LiCl or LiOH solutions are obtained through DLE, the final stage is usually concentration of lithium to a certain level (>5000ppm) where Li2CO3 can be precipitated as final product. Such a final product may be termed a “dry product” being substantially free of a carrier liquid.

[0004] Current DLE methods typically employ ion exchange resins as the key stage to separatedivalent ions from monovalent ions; however the majority of the water feed, such as ArgentinaSalars, geothermal brines, have high concentration of divalent and monovalent ions, the ionexchange resins are not capable of separating divalent ions from monovalent ions (or vice versa) at high purity and are associated with high frequency of regeneration, shortened life span of ionresins, and longer down time. The use of ion exchange resins can also require chemicals, suchas acids, to regenerate the resin.

[0005] It is therefore an object of aspects of the present invention to address one or more of theabove mentioned or other problems. SUMMARY

[0006] According to a first aspect of the present invention, there is provided an apparatus forreducing the ratio of divalent ions, such as divalent cations, to a target monovalent ion, such as atarget monovalent cation, in an aqueous solution from a source aqueous solution that contains ahigher ratio of divalent ions to the target monovalent ion, the apparatus comprising optionally, a pretreatment portion operable to receive the source aqueous solution and produce a pretreated source aqueous solution;a first separation portion operable to receive an optionally pretreated aqueous solution andform an intermediate aqueous solution having a lower ratio of divalent ions to the monovalent ion than the optionally pretreated aqueous solution; andan adsorbent separation portion operable to receive the intermediate aqueous solution andform a product aqueous solution having a lower ratio of the divalent ions to the monovalent ion than the intermediate solution.

[0007] According to a second aspect of the present invention, there is provided a process forreducing the ratio of divalent ions to a monovalent ion in an aqueous solution, comprising:a. optionally, contacting a source aqueous solution comprising the divalent ions and themonovalent ion with a pretreatment portion operable to produce a pretreated aqueoussolution; b. contacting the optionally pretreated aqueous solution with a first separation portion toform an intermediate aqueous solution having a lower ratio of the divalent ions to the monovalent ion than the optionally pretreated aqueous solution;c. contacting the intermediate solution with an adsorbent separation portion to form aproduct aqueous solution having a lower ratio of the divalent ions to the monovalent ion than in the intermediate solution.

[0008] According to a third aspect of the present invention, there is provided a product aqueoussolution obtained by the process of the second aspect of the present invention. The productaqueous solution may be a concentrated product aqueous solution.

[0009] According to a fourth aspect of the present invention, there is provided a dry productobtained by the process of the second aspect of the present invention.DETAILED DESCRIPTION

[0010] The apparatus and / or process of the present invention may be for use in (critical) metalextraction, such as for lithium, tungsten, tin, gold and / or silver extraction.

[0011] The apparatus and / or process of the present invention may be for use in lithium extraction,such as for direct lithium extraction (DLE).

[0012] The aqueous solution obtainable by the apparatus and / or obtained by the process of thepresent invention may be operable to produce an aqueous solution comprising the targetmonovalent ion, such as lithium, in improved purity. ‘The target monovalent ion’ may be one ormore monovalent ion(s) that are to be increased in purity compared to other ions and contaminants.

[0013] Advantageously, the apparatus and process of the present invention provides improvedproduct solutions and efficiency of extraction. In particular, the present invention may provideimproved purity of the resulting solution, improved target monovalent ion recovery and / orsuppressed recovery for monovalent ions other than the target monovalent ion. The presentinvention may provide lower concentrations of divalent ions. The apparatus and process of thepresent invention may provide improved efficiency and reduced cost downstream.

[0014] The apparatus and / or process of the present invention may comprise a pretreatmentportion that is operable to receive the source aqueous solution, wherein the prefiltration portion isoperable to form a pretreated aqueous solution that may comprise reduced amounts of totalsuspended solids, such as silica, bacteria, and / or oil, compared to the source aqueous solution, and / or a reduced number of divalent ions.

[0015] The pretreatment portion may comprise a prefiltration portion, a chemical precipitationportion, a settling tank portion, and / or a centrifuge portion.

[0016] For an aqueous source solution comprising ≥10,000 ppm divalent ions, such as ≥15,000ppm, the pretreatment portion may be operable to reduce the number of divalent ions in theresulting pretreated solution. Such a pretreatment portion may comprise a chemical precipitation portion, such as comprising sodium carbonate.

[0017] The prefiltration portion may comprise a separation portion comprising a membrane, suchas a microfiltration and / or ultrafiltration membrane; a strainer and / or a filter.

[0018] The separation portion of the prefiltration portion may comprise a mean average pore sizein the range of up to 100 µm, such as up to 75 µm, or up to 50µm, such as up to 10 µm, such as up to 5 µm or up to 2 µm. The separation portion of the prefiltration portion may comprise a mean average pore size of at least from 200 nm, such as at least from 500 nm or at least from 1 µm, such as at least from 5 µm.

[0019] The separation portion of the prefiltration portion may comprise a polymer membrane, suchas comprising polysulfone, polyethersulfone, polyvinylidene fluoride, polyester, polypropylene, polytetrafluoroethylene and / or polyamide (e.g. nylon); a ceramic membrane, such as comprising aluminium oxide, titanium oxide, and / or zirconium dioxide; a metal membrane, such as comprisingcarbon steel, galvanised steel, stainless steel, aluminium, and / or copper; or a combinationthereof, such as a composite membrane comprising a polymeric composite, a ceramic composite, and / or a metallic composite.

[0020] The prefiltration portion may comprise a first and a second separation portion, such as afirst and a second membrane, wherein the first portion has a mean average pore size that is largerthan the mean average pore size of the second portion. Wherein the flow path of the aqueoussolution contacts the first portion before it contacts the second portion.

[0021] The second portion may be selected from, but not limited to, a membrane, ion exchange,solvent extraction, adsorbent, thermal evaporation or other processes that separate Li+ from othermonovalent or impurities.

[0022] The ratio of the mean average pore size of the first separation to the second separationmay be at least >1:1, such as at least 3:1 or at least 4:1. The first separation portion may have a mean average pore size of at least 20 µm, such as at least 30 µm, or at least 40 µm. The second separation portion may have a mean average pore size of at least 1 µm, such as at least 5 µm, or at least 7 µm.

[0023] The source aqueous solution may be contacted with the separation portion of theprefiltration separation portion at a temperature of ≥5 °C, such as ≥25°C. The source aqueous solution may be contacted with the separation portion of the prefiltration separation portion at atemperature of ≤250°C, such as ≤200°C, or such as ≤150°C, such as ≤100°C, such as ≤90°C or≤70°C. The temperature may be measured according to ASTM E2877-12(2019): Standard Guide for Digital Contact Thermometers.

[0024] The source aqueous solution may be contacted with the separation portion of theprefiltration portion at a transmembrane pressure of ≥0.1 bar, such as ≥0.5 bar. The source aqueous solution may be contacted with the separation portion of the prefiltration portion at atransmembrane pressure of ≤5 bar, such as ≤3 bar, such as ≤2bar, such as ≤1.5bar. The pressuremay be measured by a differential pressure transducer according to ASTM F2070-00(2017): Standard Specification for Transducers, Pressure and Differential, Pressure, Electrical and Fiber- Optic.

[0025] The source aqueous solution may be contacted with the separation portion of theprefiltration portion at a pH of ≥0, such as ≥3, such as ≥5, such as ≥6. The source aqueous solution may be contacted with the separation portion of the prefiltration portion at a pH of ≤14,such as ≤10, such as ≤8. The pH may be measured according to ASTM ASTM E70-19: StandardTest Method for pH of Aqueous Solutions With the Glass Electrode.

[0026] The separation portion of the prefiltration portion may have a total suspended solidsrejection of ≥90 %, such as ≥95% or ≥99%.

[0027] As used herein, “total suspended solids (TSS)” means the dry-weight of suspendedparticles, that are not dissolved. The TSS may be measured according to ASTM D5907: Standard Test Methods for Filterable Matter (Total Dissolved Solids) and Nonfilterable Matter (Total Suspended Solids) in Water. For example, the TSS may be measured as follows:TSS (mg / L) = (Wfss – Wf) / VsWhere: Wfss: weight of filter with suspended solids Wf: weight of the filter Vs: volume of sample 1. Sample is filtered through a 1.5 μm, washed and dried, glass fibre filter. 2. Filtrate is transferred into an evaporating dish and liquid is allowed to evaporate to dryness.3. Dish and residue are heated to 180°C for one hour.4. Dish and residue are cooled to room temperature and weighed on balance. 5. Repeat cycle of 180°C heating, cooling, and weighing until two consecutive ± 0.0005 g results.

[0028] The separation portion of the prefiltration portion may have a rejection rate for the targetmonovalent ion of ≤5%, such as ≤2% or ≤1%.

[0029] The first separation portion may comprise a membrane, such as a nanofiltration membrane,electrodialysis membrane and / or a metal-organic framework (MOF) membrane. The firstseparation portion may comprise a nanofiltration membrane in a nanofiltration separation portion.

[0030] Membrane separation uses a porous material to separate a mixture of components,generally by the application of a driving force applied across the surface of the membrane, suchas pressure, or without an applied driving force, such as by gravity.

[0031] Membrane separation may be favoured over other separation technologies due to, inprinciple, lower cost, less space required for installation, no significant thermal input, lower energy consumption, reduced chemical treatments, higher removal efficiency and / or a lower requirement for the regeneration of spent media.

[0032] The nanofiltration membrane may comprise a mean average pore size in the range of ≤10nm, such as ≤5 nm or ≤2 nm. The nanofiltration membrane may comprise a mean average pore size of ≥0.1 nm, such as ≥0.2 nm or ≥0.5 nm. Pore size of the membrane can be measured by using a model of solute transport and an appropriate correlation between the hydrodynamic radius and molecular weight of the specific type of solute (e.g., polyethylene glycols). Background and examples can be found in: Hassan, A. R., and A. F. Ismail. "Characterization of nanofiltration membranes by the solute transport method: Some practical aspects in determining of mean pore size and pore size distributions" Regional Symposium on Membrane Science and Technology. 2004.

[0033] The nanofiltration membrane may comprise a molecular weight cut-off (MWCO) of ≤800Da, such as ≤600 Da or ≤500 Da. The nanofiltration membrane may comprise a MWCO of ≥100 Da, such as ≥200 Da or ≥300 Da. The MWCO as used herein refers to the lowest molecular weight of a solute in Daltons in which 90% of that solute is retained by the membrane.

[0034] The nanofiltration membrane may comprise an organic and / or inorganic nanofiltrationmembrane, such as polymer and / or ceramic membrane.

[0035] The nanofiltration membrane may comprise a spiral wound membrane, tubular membrane,hollow fibre membrane and / or flat sheet membrane. The nanofiltration membrane may comprise a spiral wound membrane.

[0036] The nanofiltration membrane may comprise a polymer membrane, such as comprisingpolysulfone, polyethersulfone, and / or polyvinylidene fluoride; a ceramic membrane, such as comprising aluminium oxide, titanium dioxide, and / or zirconium dioxide; a metal membrane, such as comprising carbon steel, galvanised steel, stainless steel, aluminium, and / or copper; or a combination thereof, such as a composite membrane comprising a polymeric composite, a ceramic composite, and / or a metallic composite.

[0037] The nanofiltration membrane may comprise a polymer membrane, such as comprisingpolyacrylonitrile (PAN); polyester such as polyethylene terephthalate (PET); polycarbonate (PC); polyamide (PA); poly(ether) sulfone (PES); polybutylene terephthalate (PBT); polysulfone (PSf); polypropylene (PP); cellulose acetate (CA); poly(piperazine-amide); polyvinylidene difluoride (PVDF); polytetrafluoroethylene (PTFE); chlorinated polyvinyl chloride (CPVC); poly(phthalazinone ether sulfone ketone) (PPESK); polyamide-urea; polyether ether ketone (PEEK); and / or poly(phthalazinone ether ketone; and / or a thin film composite porous film (TFC). The TFC may comprise an ultra-thin ‘barrier’ layer polymerised in situ over a porous polymeric support membrane, such as a commercially available polyamide derived TFC of an interfacially synthesized polyamide formed over a polysulfone (PSf) membrane. The TFC may comprise a poly(piperazine-amide) / poly(vinyl-alcohol) (PVA); poly(piperazine-amide) / poly(phthalazinone biphenyl ether sulfone (PPBES); and / or hydrolyzed cellulose tri-acetate (CTA) / cellulose acetate (CA). Preferably, the nanofiltration membrane comprises a polyethylene terephthalate-based (PET) membrane, such as poly(ether) sulfone (PES) and / or polyethylene terephthalate / polypropylene.

[0038] The nanofiltration membrane may comprise polyamide, such as a top layer comprisingpolyamide. The polyamide of the nanofiltration membrane may comprise the reaction product ofa reaction mixture comprising acid chloride (such as trimesoyl chroride) and an amine (such aspiperazine). The polyamide layer of the nanofiltration membrane may comprise the reaction product of a reaction mixture comprising a carboxylic acid (such as terephthalic acid) and an amine (such as poly(ethylene glycol) diamine) in the presence of a coupling reagent (such as 1- Ethyl-3-(3-dimethylaminopropyl)carbodiimide).

[0039] The nanofiltration membrane may comprise a multi-layered membrane comprising asupport layer, an intermediate layer and a top layer. The support layer may comprise polyester, such as non-woven polyester, for example formed by electrospinning. The intermediate layer may comprise polysulfone and / or polyethersulfone, for example formed by phase inversion. The top layer may comprise polyamide, such as formed by interfacial polymerisation.

[0040] The optionally pretreated source aqueous solution may be contacted with the nanofiltrationmembrane at a temperature of ≥5 °C, such as ≥20°C or ≥30°C. The optionally pretreated sourceaqueous solution may be contacted with the nanofiltration membrane at a temperature of ≤130°C,such as ≤100°C, or ≤90°C or ≤75°C. When the nanofiltration membrane comprises a polymermembrane the optionally pretreated source aqueous solution may be contacted with thenanofiltration membrane at a temperature of ≤70°C.

[0041] The optionally pretreated source aqueous solution may be contacted with the nanofiltrationmembrane at a transmembrane pressure of ≥5 bar, such as ≥10 bar, such as ≥15 bar. Theoptionally pretreated source aqueous solution may be contacted with the nanofiltration membraneat a transmembrane pressure of ≤60 bar, such as ≤40 bar, such as ≤35 bar.

[0042] The optionally pretreated source aqueous solution may be contacted with the nanofiltrationmembrane at a pH of ≥3, such as ≥5. The optionally pretreated source aqueous solution may becontacted with the nanofiltration membrane at a pH of ≤11, such as ≤10 or ≤9.

[0043] The optionally pretreated source aqueous solution may be contracted with the nanofiltrationmembrane at a crossflow velocity of ≥0.05 m / s, such as ≥0.1 m / s or ≥0.3 m / s. The optionallypretreated source aqueous solution may be contracted with the nanofiltration membrane at acrossflow velocity of ≤5 m / s, such as ≤3.5 m / s, or ≤3 m / s or ≤1.5 m / s, such as ≤1 m / s or ≤0.8 m / s.

[0044] The nanofiltration separation portion may comprise a series of nanofiltration membranes,such as a series of fluidly connected sequential membranes. The nanofiltration separation portionmay comprise a series of nanofiltration membranes wherein the permeate of a first nanofiltrationmembrane is operable to feed into at least one further nanofiltration membrane, such as at least two further nanofiltration membranes, suitably sequentially.

[0045] The nanofiltration separation portion may comprise at least two sets of nanofiltrationmembrane, each set comprising a series of nanofiltration membranes. In such an arrangement,the optionally pretreated aqueous source solution may be formed into two or more branched flowsoperable to contact different sets of nanofiltration membranes in parallel. The discrete flows may be combined from the permeate outlet flows of the nanofiltration membrane sets.

[0046] The apparatus / process may comprise a batch apparatus / process for the nanofiltrationseparation portion. The apparatus / process may comprise means operable to recirculate the retentate stream of the nanofiltration membrane, such as via a feed tank wherein the retentate isoptionally contacted with new optionally pretreated aqueous source solution. The retentate steammay be recirculated for at least 5 hours per batch operation, such as at least 10 hours per batchoperation. The retentate steam may be recirculated for up to 24 hours per batch operation, suchas up to 20 hours per batch operation.

[0047] The apparatus / process may comprise a continuous apparatus / process for the nanofiltrationseparation portion. During processing, the feed tank may receive a continuous stream of brine,wherein the total flow rate of the permeate is around (+ / - 10%) of 95% of the incoming brine flow(such as selecting a suitable number of membranes). Such a process may provide around (+ / -10%) 95% hydraulic recovery. When the permeate flow rate is lower than the incoming brine flowrate a portion of the retentate stream may be removed from the system. Advantageously, thismay allow for the total of the permeate flow rate and the flow rate of the diverted stream to matchthe incoming brine flow rate, thereby maintaining a balance in the flow.

[0048] The apparatus / process may comprise a sequential batch-type apparatus / process for thenanofiltration separation portion wherein multiple tanks (such as at least 2) are alternatelyprocessed by the membrane system. The number of membranes used may be so that the timeit takes to fill an empty tank is around (+ / - 10%) the time taken to process the active (fuller) tank.

[0049] The nanofiltration membrane may have a divalent ion rejection of ≥60%, or ≥70%, such as≥80% or ≥90%. The nanofiltration membrane may have a divalent ion rejection of ≤99%, such as ≤98% or ≤95%.

[0050] The nanofiltration membrane may have a rejection rate for the target monovalent ion of≤50%, such as ≤20% or ≤5%.

[0051] The first separation portion or the nanofiltration separation portion of any aspects maycomprise means operable to provide cleaning in process (CIP) to the separation portion, such as to the nanofiltration membrane. The CIP means may be operable to flush the separation portion,such as the membrane, with an aqueous solution and / or clean the separation portion by passinga cleaning solution through the separation portion. The cleaning solution may comprise an acidcleaning solution and / or an alkaline cleaning solution. The sequence of acid cleaning and alkalinecleaning may be switched according to the type of fouling / scaling. The aqueous solution mayhave a pH of ≥6, such as ≥6.5 and / or ≤8, such as ≤7.5. The acid cleaning solution may have a pH of ≥1, such as ≥1.5 and / or ≤3, such as ≤2. The alkaline cleaning solution may have a pH of ≥8, such as ≥8.5 and / or ≤13, such as ≤12. The CIP means may be operable to flush the separationportion with an aqueous solution between acid cleaning and alkaline cleaning, and / or after thealkaline cleaning.

[0052] The aqueous solution and / or the cleaning solution of the CIP means may be contacted withthe first separation portion, such as the nanofiltration membrane, at a temperature of ≥20 °C, suchas ≥25°C or ≥30°C. The aqueous solution and / or the cleaning solution of the CIP means may becontacted with the first separation portion, such as the nanofiltration membrane, at a temperatureof ≤50°C, such as ≤45°C or ≤40°C.

[0053] The aqueous solution and / or the cleaning solution of the CIP means may be contacted withthe first separation portion, such as the nanofiltration membrane, at a transmembrane pressureof ≥0.5 bar, such as ≥1 bar, such as ≥2 bar. The aqueous solution and / or the cleaning solutionof the CIP means may be contacted with the first separation portion, such as the nanofiltration membrane at a transmembrane pressure of ≤15 bar, such as ≤10 bar, such as ≤5 bar.

[0054] The aqueous solution and / or the cleaning solution of the CIP means may be contacted withthe first separation portion, such as the nanofiltration membrane, at a crossflow velocity of ≥0.05m / s, such as ≥0.1 m / s or ≥0.3 m / s. The aqueous solution and / or the cleaning solution of the CIP means may be contacted with the first separation portion, such as the nanofiltration membrane,at a crossflow velocity of ≤5 m / s, such as ≤3.5 m / s, or ≤3 m / s or ≤1.5 m / s, such as ≤1 m / s or ≤0.8m / s.

[0055] The adsorbent separation portion (adsorbent isolation portion) may have a higher affinityfor certain ions due to it’s crystalline structure and / or affinity, such as an affinity for monovalentions, such as monovalent cations, for example lithium, over divalent ions, such as divalent cations. The adsorbent separation portion may be substantially selective for monovalent ions over divalent ions. For example, the adsorbent separation may be selective to lithium, sodium, potassium, copper, strontium, cesium, silver, and / or gold cations. The adsorbent separation portion may be lithium selective.

[0056] Adsorbents (or sorbents) involve the adsorption of ions on the adsorbent material. As usedherein, ‘adsorbent separation portion’ may be distinguished from an ion-exchange separationportion by the ability to use a neutral water wash (or lithium solution) to elute the adsorbate ion.Ion exchange (or IX) resins involve the exchange of ions and a pH neutral water wash solution(or lithium solution) does not effectively elute the exchanged ion. Typically, an acid solution isused to strip the exchanged ion from the ion-exchange resin. Additionally, after stripping with acid, the ion exchange resins may need to be further conditioned by alkaline solutions before they are ready for reuse. The regeneration process for ion exchange resins also typically requires intermittent rinses with deionized water to clean out the residual chemicals applied for elution of the absorbate ion and regeneration. Adsorbents (or sorbents) on the other hand involve theadsorption of ions on the adsorbent material and subsequently the adsorbate ion can be elutedfrom the adsorbent material using a pH neutral aqueous strip (wash) solution.

[0057] The adsorbent may be utilised in a single column or a multi-column system. The single bedsystem may be a fixed bed column system. The multi-column system may be a fixed bed, a moving bed, a simulated moving bed or a carousel system.

[0058] The adsorbent may be utilised in various configurations such as single-column systems,multi-column systems, and advanced configurations such as lead-lag-lag, carousel, simulated moving bed (SMB), and true moving bed (TMB) arrangements, preferably, simulated moving bed.

[0059] The adsorbent may be utilised in a single-column system, where the adsorbent is housedin a single column. The column alternates between adsorption and desorption (regeneration) phases, allowing for periodic recovery of the adsorbed components. This configuration is suitablefor batch processes or applications with low throughput requirements.

[0060] The adsorbent may be utilised in a multi-column system, where multiple columns operatein parallel or series. In the lead-lag-lag configuration, one column (lead) performs primary adsorption, while subsequent columns (lag) act as secondary or polishing stages, enhancing overall separation efficiency. A carousel configuration, involves a circular arrangement of columns that cycle sequentially through adsorption and desorption (regeneration) phases. This setup ensures continuous operation by maintaining a dynamic distribution of phases among the columns.

[0061] The adsorbent may be utilised in a more sophisticated configuration, such as the SMB andTMB. In the SMB system, the stationary adsorbent bed is periodically shifted to simulate the movement of the adsorbent relative to the fluid, creating a countercurrent-like interaction. This enhances selectivity and reduces solvent (water) usage. TMB systems, on the other hand, involve the physical movement of the adsorbent bed in a true countercurrent manner relative to the fluid stream. These configurations are particularly effective in applications requiring high-purity separations.

[0062] The SMB configuration may contain a fractal vein process or fractal valving system whichutilises an electrical signal to deposit flow in a microchannel, creating a fractal structure that changes the interaction between the fluid and the surface.

[0063] In some embodiments, the adsorbent separation portion may be configured as a single-column system or a multi-column system. The single-column system may be a fixed bed system. The multi-column system may be a fixed bed, a moving bed, simulated moving bed or carousel system.

[0064] The multi-column system may be a fixed bed system in a lead-lag configuration, a lead-lag-lag configuration, or configured as a lead column followed by two lag columns.

[0065] The multi-column system may be a moving bed system, for example, a true moving bed.

[0066] The absorbent separation portion is preferably configured in a multi-column system, morepreferably, as a simulated moving bed.

[0067] The aqueous strip solution may comprise at least partially demineralised water. Theaqueous strip solution may comprise dissolved ions. The aqueous strip solution may comprisedissolved target monovalent ions. The aqueous strip solution may comprise dissolved target monovalent ions in an amount of from 1 to 2000 ppm, such as from 10 to 1500 ppm, such as from 20 to 1250 ppm, such as from 30 to 1000 ppm, such as from 40 to 750 ppm, such as from 50 to 500 ppm.

[0068] The aqueous strip solution may be neutral in pH or may be only weakly acidic or weaklyalkaline. The aqueous strip solution may have a pH of from 6.0 to 8.0, such as from 6.5 to 7.5, such as from 6.9 to 7.1.

[0069] The adsorbent separation portion may comprise an inorganic adsorbent. The inorganicadsorbent may comprise an inorganic material, such as an inorganic crystalline solid, inorganic polycrystalline solid, inorganic polymorphic solid, and / or inorganic polymorphous solid.

[0070] The inorganic crystalline solid may comprise aluminium oxide, activated alumina,aluminium hydroxide.

[0071] The inorganic material may comprise target monovalent ion aluminate. The targetmonovalent ion aluminate may comprise the target monovalent ion, aluminum atoms, oxygen atoms, and at least one anionic species X selected from halide (fluoride, chloride, bromide, or iodide), nitrate, sulfate, carbonate, and / or bicarbonate.

[0072] The target monovalent ion aluminate may comprise oxygen atoms in the form of oxide ions(O2-) and / or in the form of hydroxide ions (-OH).

[0073] The target monovalent ion aluminate may be according to the formula MX / Al(OH)3 whereM is the target monovalent ion and X is at least one an anionic species selected from halide (fluoride, chloride, bromide, or iodide), nitrate, sulfate, carbonate, and / or bicarbonate.

[0074] The inorganic adsorbent may comprise a metal hydroxide, such as an aluminum hydroxide(AlOH) or derivative thereof. The inorganic adsorbent may comprise an aluminum trihydroxide,such as gibbsite, bayerite, and / or nordstrandite. The inorganic adsorbent may comprise aluminum hydroxide containing materials, such as aluminum hydroxide containing zeolites.

[0075] The inorganic adsorbent may comprise a layered inorganic material. The inorganicadsorbent may comprise a target monovalent ion aluminate intercalate, such as a lithiumaluminate intercalate. A target monovalent ion-aluminate intercalate may comprise targetmonovalent cations incorporated into voids that are of a size operable to receive the targetmonovalent cations but are not of a size operable to receive (are too small) water molecules, atleast one of the divalent ions of the solution and / or or at least one of the other monovalent ions ofthe solution.

[0076] The inorganic adsorbent may comprise a two-dimensional (2D) layered inorganic material.

[0077] A ‘two-dimensional (2D) inorganic layered material’ as used herein may be a materialcomprising multiple layers each having a X, Y, Z plane wherein the Z plane thickness is less than 100 nanometres (nm).

[0078] The inorganic adsorbent may comprise a layered metal hydroxide. The inorganicadsorbent may comprise a layered metal double hydroxide. The layered metal double hydroxide may comprise an intercalated layered structure comprising metal cations, hydroxide anions, and intercalated anions, and may be comprise water or hydrates.

[0079] The layered metal double hydroxide may comprise first and second layers comprising metalcations and hydroxide ions with an intercalating layer arranged between the first and a second layers. The intercalating layer may comprise an anion or neutral molecule, such as water molecules. The layered metal double hydroxide inorganic adsorbent may comprise a plurality of repeating first and second intercalated layers.

[0080] The metal cations of the layered metal double hydroxide may comprise monovalent and / ordivalent metal cations such as lithium and / or aluminium. The metal cations of the layered metaldouble hydroxide may comprise the target monovalent ions. The layered metal double hydroxide may comprise lithium and aluminum metal cations.

[0081] The layered metal double hydroxide may comprise an intercalated anion such as fluoride,chloride, bromide, iodide, nitrate, sulfate, chromate, borate, and / or permanganate. The layered double hydroxide may comprise an intercalated anions such as fluoride, chloride, bromide, and / or iodide. The layered double hydroxide may comprise chloride intercalated anions.

[0082] The inorganic adsorbent may comprise a layered metal double hydroxide comprisingaluminum. In other words, the inorganic adsorbent may comprise a layered aluminum double hydroxide material. The layered aluminum double hydroxide may comprise a first layer comprising aluminum hydroxide and metal cations and a second layer comprising water molecules and intercalated anions.

[0083] The inorganic adsorbent may comprise a lithium-incorporated aluminum hydroxide (LIAH).For example, the inorganic adsorbent may comprise a lithium-incorporated layered hydroxide, such as a lithium-incorporated layered double hydroxide.

[0084] The lithium-incorporated aluminum hydroxide may be according to formula (I):LiX. ^Al(OH)^. ^H^O(I) wherein: X is a monovalent anion, such as fluoride, chloride, bromide, and / or iodide, preferably chloride; and mis from 1.2 to 3.0; andn is from 0.2 to 5.0.

[0085] The use of a layered aluminum double hydroxide material may advantageously providebeneficial effects, in particular for large-scale industrial plants such as low cost, environmental friendliness, and / or ease of regeneration.

[0086] The lithium-incorporate aluminum hydroxide may have a two-dimensional layered structurethat facilitates intercalation of anions between the layers. A two-dimensional layered lithium- incorporate aluminum hydroxide may comprise hexagonal cavities operable to receive the positively charged lithium cation.

[0087] The adsorbent separation portion may comprise a carrier, such as a solid carrier. Thecarrier may act as a dispersant phase or continuous phase for an inorganic adsorbent. In other words, the carrier may comprise an inorganic adsorbent.

[0088] The carrier may be organic or inorganic. The carrier may comprise a polyvinyl alcohol,methacrylate, phenol, synthetic polymer, polysaccharide, biopolymer, polysilicate, metal organicframework (MOF), alginate, biochar, carbonaceous ore, clay, graphene and / or nanotube.

[0089] The carrier may comprise an organic polymer. The carrier may comprise an organicpolymer matrix.

[0090] The adsorbent separation portion may comprise a composite material comprising a matrixof an organic polymer comprising an inorganic adsorbent.

[0091] The carrier may be porous to allow for the flow of feed solutions through the carrier to theinorganic adsorbent.

[0092] Advantageously, when the inorganic adsorbent comprises an inorganic material, such asa layered lithium-aluminum double hydroxide material, and an organic matrix, such as a polymer matrix, the inorganic adsorbent may have improved desirable characteristics, such as desirable physical and chemical properties, improved strength indicators, and / or high durability.

[0093] The intermediate aqueous solution may be contacted with the adsorbent followed by theapplication of an aqueous strip (wash) solution to the adsorbent to elute the target monovalent ion and produce a product aqueous solution.

[0094] The intermediate aqueous solution may be contacted with the adsorbent at a temperatureof ≥5°C, such as ≥20°C, or ≥30°C, or ≥40°C. The intermediate aqueous solution may becontacted with the adsorbent at a temperature of ≤80°C, such as ≤70°C or ≤60°C. Theintermediate aqueous solution may be contacted with the adsorbent at a temperature of ≤60°C,such as ≤50°C.

[0095] The intermediate aqueous solution may be contacted with the adsorbent at a pressure of≤2.5 bar, ≤1.5 bar, such as ≤1 bar.

[0096] The intermediate aqueous solution may be contacted with adsorbent at a pressure drop of≥0.1 bar, such as ≥0.2 bar. The intermediate aqueous solution may be contacted with the adsorbent at a pressure drop of ≤2 bar, such as ≤1 bar or ≤0.5 bar.

[0097] The intermediate aqueous solution may be contacted with the adsorbent at a pH of ≥4.5,or ≥6. The intermediate aqueous solution may be contacted with the adsorbent at a pH of ≤8,such as ≤7.5.

[0098] The intermediate aqueous solution may be contacted with the adsorbent at a volumetricflowrate of ≥0.2 BV / h, such as ≥1 BV / h, such as ≥5 BV / h. The intermediate aqueous solution maybe contacted with the adsorbent at a volumetric flowrate of ≤25 BV / h, such as ≤20 BV / h. As usedherein, ‘BV’ refers to ‘Bed Volume’, which is the volume of the resin that is used in the adsorbent column.

[0099] The source aqueous solution may be obtained from a brine source or from hard rockleaching solution that contains the target monovalent ion. The source aqueous solution may beseawater brine, saline lake brine, shallow groundwater brine, geothermal brine, deep brine insedimentary basin and / or industrial brine. The source aqueous solution may be a geothermal brine, such as a geothermal brine obtained from a deep or a shallow geothermal source. The source aqueous solution may be leachate produced after processing, for example roasting, a mineral rock source, such as Spodumene mineral.

[0100] The source aqueous solution may be a produced water solution, such as a produced watersolution obtained as a by-product during the extraction of oil and natural gas. The source aqueous solution may be leachate produced after processing of recycled batteries, for example leachate from recycled lithium-ion batteries.

[0101] The source aqueous solution may be an ocean seawater brine; a shallow brine beneath adry lake, such as from Clayton Valley, Nevada, from a Chilian salar and / or Salar de Olaroz mine, Argentina; a geothermal brine, such as from Cornwall, United Kingdom and / or Salton Sea, California; and / or a deep brine, such as from Paradox Basin, Utah.

[0102] The source aqueous solution may be a deep or shallow geothermal brine, such as fromCornwall, United Kingdom and / or Salton Sea, California. The source aqueous solution may be a deep geothermal brine, such as from Cornwall, United Kingdom. A deep geothermal brine may be defined as brine extracted from a depth of >150 m. The source aqueous solution may be a shallow geothermal brine, such as from Cornwall, United Kingdom. A shallow geothermal brine may be defined as brine extracted from a depth of ≤150 m.

[0103] The divalent ions of any of the aspects may be divalent cations. The source solution maycomprise divalent cations, and optionally trivalent cations, such as Ca, Mg, B, Ba, Fe, Mn, Zn, Mo, Sr, Zr, V, Cr, Te, Ti, Ga, Hg, Be, In, Ta, Ce, Hf, Sm, La, Nb, Th, Al, Tl, As, Ni, Cu, Sc, Sn, Sb,Co, Pb, U, Cd, Y and / or Bi. Preferably, Ca, Mg, Sr and / or B.

[0104] The target monovalent ion may be a target monovalent cation, such as a metal monovalentcation.

[0105] The target monovalent cation of the source solution may comprise Na, K, Li, Cs, Rb, W,Au and / or Ag. Preferably, the target monovalent cation of the source solution comprises Li, W, Au, Ag, Na and / or K. More preferably, Li, W, Au and / or Ag. Most preferably, Li.

[0106] The different type of monovalent ion to the target monovalent ion may be a different typeof monovalent cation, such as a different type of metal monovalent cation.

[0107] The source solution may comprise an anion, such as Cl, F, Br, SO4, HCO3, and / or CO3.The source solution may comprise Cl and / or SO4.

[0108] The source aqueous solution may comprise total suspended solids in an amount of ≥1 ppm,such as ≥5 ppm or ≥20 ppm.

[0109] The source aqueous solution may comprise total suspended solids in an amount of ≤2,000ppm, such as ≤1,500 ppm or ≤1,000 ppm, or ≤500ppm.

[0110] The source solution may comprise the divalent ions in an amount of ≤60,000 ppm, such as≤55,000 ppm or ≤50,000 ppm.

[0111] The source solution may comprise the divalent ions in an amount of ≥100 ppm, such as≥200 ppm or ≥500 ppm.

[0112] The source solution may comprise the target monovalent ion in an amount of ≤120,000ppm, such as ≤50,000 ppm or ≤10,000 ppm.

[0113] The source solution may comprise the target monovalent ion in an amount of ≥20 ppm,such as ≥500 ppm or ≥1,000 ppm. It will be appreciated that the aqueous solutions may comprisedifferent types of monovalent ions in addition to the target monovalent ion.

[0114] The source solution may comprise the target monovalent ion, such as lithium, in an amountof ≤5,000 ppm, such as ≤3,000 ppm or ≤1,000 ppm.

[0115] The source solution may comprise the target monovalent ion, such as lithium, in an amountof ≥10 ppm, such as ≥20 ppm or ≥50 ppm.

[0116] The source solution may comprise monovalent ions other than the target monovalent ionin an amount of ≤170,000 ppm, such as ≤150,000 ppm, or ≤100,000 ppm.

[0117] The source solution may comprise monovalent ions other than the target monovalent ionin an amount of ≥10 ppm, such as ≥20 ppm, or ≥50 ppm.

[0118]

[0119] The source solution may comprise a ratio of the divalent ions to the target monovalent ionof <6000:1, such as <5000:1, such as <4000:1, such as <3000:1, such as <2500:1, such as<2000:1. The pretreated source aqueous solution may comprise substantially the same amountsof divalent and monovalent ions as the source aqueous solution, such as within 5% difference in ppm, or within 2% difference in ppm, or within 1% difference in ppm.

[0120] The pretreated source aqueous solution may comprise divalent cations, and optionallytrivalent cations, such as Ca, Mg, B, Ba, Fe, Mn, Zn, Mo, Sr, Zr, V, Cr, Te, Ti, Ga, Hg, Be, In, Ta, Ce, Hf, Sm, La, Nb, Th, Al, Tl, As, Ni, Cu, Sc, Sn, Sb, Co, Pb, U, Cd, Y, and / or Bi. Preferably, Ca, Mg and / or B.

[0121] The target monovalent cation of the pretreated source aqueous solution may comprise Na,K, Li, Cs, Rb, W, Au, and / or Ag. Preferably, the target monovalent cation of the pretreated sourcesolution comprises Li, W, Au, Ag, Na and / or K. More preferably, Li, W, Au and / or Ag. Most preferably, Li.

[0122] The pretreated source aqueous solution may comprise anions, such as Cl, F, Br, SO4,HCO3, and / or CO3. The pretreated source aqueous solution may preferably comprise Cl and / orSO4.

[0123] The pretreated source aqueous solution may comprise a lower amount of total suspendedsolids, such as silica, bacteria, and / or oil / grease, than the source aqueous solution. Thepretreated source aqueous solution may comprise total suspended solids in an amount of ≤100ppm, such as ≤50 ppm or ≤10 ppm.

[0124] The pretreated source aqueous solution may comprise the divalent ions in an amount of≤60,000 ppm, such as ≤55,000 ppm or ≤50,000 ppm.

[0125] The pretreated source aqueous solution may comprise the divalent ions in an amount of≥100 ppm, such as ≥200 ppm or ≥500 ppm.

[0126] The pretreated source aqueous solution may comprise the divalent ions in an amount of>3,000 ppm, such as >3,500 ppm or >4,000 ppm.

[0127] The pretreated source aqueous solution may comprise the target monovalent ion in anamount of ≤120,000 ppm, such as ≤50,000 ppm or ≤10,000 ppm.

[0128] The pretreated source aqueous solution may comprise the target monovalent ion in anamount of ≥20 ppm, such as ≥500 ppm or ≥1,000 ppm. It will be appreciated that the pretreated source aqueous solutions may comprise other monovalent ions in addition to the target monovalent ion.

[0129] The pretreated source aqueous solution may comprise the target monovalent ion in anamount of ≤5,000 ppm, such as ≤3,000 ppm or ≤1,000 ppm.

[0130] The pretreated source aqueous solution may comprise the target monovalent ion in anamount of ≥10 ppm, such as ≥20 ppm or ≥50 ppm.

[0131] The pretreated source aqueous solution may comprise monovalent ions other than thetarget monovalent ion in an amount of ≤170,000 ppm, such as ≤150,000 ppm or ≤100,000 ppm.

[0132] The pretreated source aqueous solution may comprise monovalent ions other than thetarget monovalent ion in an amount of ≥10 ppm, such as ≥20 ppm or ≥50 ppm.

[0133] The preteated source solution may comprise a ratio of the divalent ions to the targetmonovalent ion of <6000:1, such as <5000:1, such as <4000:1, such as <3000:1, such as <2500:1, such as <2000:1.

[0134] The intermediate solution may comprise divalent cations, and optionally trivalent cations,such as Ca, Mg, B, Ba, Fe, Mn, Zn, Mo, Sr, Zr, V, Cr, Te, Ti, Ga, Hg, Be, In, Ta, Ce, Hf, Sm, La, Nb, Th, Al, Tl, As, Ni, Cu, Sc, Sn, Sb, Co, Pb, U, Cd, Y, and / or Bi. Preferably, Ca, Mg and / or B.

[0135] The target monovalent cation of the intermediate source solution may comprise Na, K, Li,Cs, Rb, W, Au, and / or Ag. Preferably, the target monovalent cation of the intermediate solution comprises Li, W, Au, Ag, Na and / or K. More preferably, Li, W, Au and / or Ag. Most preferably, Li.

[0136] The intermediate source solution may comprise anions, such as Cl, F, Br, SO4, HCO3,and / or CO3. The source solution may preferably comprise Cl and / or SO4.

[0137] The intermediate solution may comprise the divalent ions in an amount of ≤4,000 ppm,such as ≤3,500 ppm or ≤3,000 ppm.

[0138] The intermediate solution may comprise the divalent ions in an amount of ≥10 ppm, suchas ≥30 ppm or ≥150 ppm.

[0139] The intermediate solution may comprise the target monovalent ion in an amount of≤120,000 ppm, such as ≤50,000 ppm or ≤10,000 ppm.

[0140] The intermediate solution may comprise the target monovalent ion in an amount of ≥20ppm, such as ≥500 ppm or ≥1,000 ppm. It will be appreciated that the intermediate solution may comprise other monovalent ions in addition to the target monovalent ion.

[0141] The intermediate solution may comprise the target monovalent ion in an amount of ≤5,000ppm, such as ≤3,000 ppm or ≤1,000 ppm.

[0142] The intermediate solution may comprise the target monovalent ion in an amount of ≥10ppm, such as ≥20 ppm or ≥50 ppm.

[0143] The intermediate solution may comprise monovalent ions other than the target monovalention in an amount of ≤170,000 ppm, such as ≤150,000 ppm or ≤100,000 ppm.

[0144] The intermediate solution may comprise monovalent ions other than the target monovalention in an amount of ≥10 ppm, such as ≥20 ppm or ≥50 ppm.

[0145] The intermediate solution may comprise a ratio of the divalent ions to the target monovalention of <2000:1, such as <1800:1, such as <1600:1, such as <1400:1, such as <1000:1, such as <800:1, such as <750:1.

[0146] The product solution may comprise divalent cations, and optionally trivalent cations, suchas Ca, Mg, B, Ba, Fe, Mn, Zn, Mo, Sr, Zr, V, Cr, Te, Ti, Ga, Hg, Be, In, Ta, Ce, Hf, Sm, La, Nb, Th, Al, Tl, As, Ni, Cu, Sc, Sn, Sb, Co, Pb, U, Cd, Y, and / or Bi. Preferably, Ca, Mg and / or B.

[0147] The target monovalent cation of the product solution may comprise Na, K, Li, Cs, Rb, W,Au and / or Ag. Preferably, the target monovalent cation of the product solution comprises Li, W, Au, Ag, Na and / or K. More preferably, Li, W, Au and / or Ag. Most preferably, Li.

[0148] The product solution may comprise anions, such as Cl, F, Br, SO4, HCO3, and / or CO3. Theproduct solution may preferably comprise Cl and / or SO4.

[0149] The product solution may comprise the divalent ions in an amount of ≤3,000 ppm, such as≤2,700 ppm or ≤2,000 ppm.

[0150] The product solution may comprise the target monovalent ion in an amount of ≤120,000ppm, such as ≤50,000 ppm or ≤10,000 ppm.

[0151] The product solution may comprise the target monovalent ion in an amount of ≤5,000 ppm,such as ≤3,000 ppm or ≤1,000 ppm.

[0152] The product solution may comprise the target monovalent ion in an amount of ≥10 ppm,such as ≥20 ppm or ≥50 ppm. It will be appreciated that the aqueous solutions may comprise other monovalent ions in addition to the target monovalent ion.

[0153]

[0154] The product solution may comprise monovalent ions other than the target monovalent ionin an amount of ≤150,000 ppm, such as ≤135,000 ppm or ≤90,000 ppm.

[0155] The product solution may comprise monovalent ions other than the target monovalent ionin an amount of ≥10 ppm, such as ≥20 ppm or ≥50 ppm.

[0156] The product solution may comprise a ratio of the divalent ions to the target monovalent ionof <750:1, such as <700:1, such as <650:1, such as <600:1, such as <580:1, such as <550:1, such as <500:1..

[0157] The apparatus and / or process of the present invention may be operable to reduce the ratioof a different type of monovalent ion to a target monovalent ion in an aqueous solution, such asa product aqueous solution, that contains a higher ratio of the different type of monovalent ion tothe target monovalent ion than an upstream solution, such as the source or intermediate solution.The apparatus and / or process of the present invention may be operable to reduce the ratio of allother types of monovalent ion / cation to a target monovalent ion / cation in an aqueous solution,such as a product aqueous solution, that contains a higher ratio of the different types ofmonovalent ions to the target monovalent ion than an upstream solution, such as the source orintermediate solution.

[0158] The adsorbent separation portion may be operable to reduce the ratio of a different type ofmonovalent ion to a target monovalent ion and also reduce the ratio of divalent ions to the targetmonovalent ion. The adsorbent separation portion may be operable to reduce the ratio of a different type of monovalent ion to a target monovalent ion and also reduce the ratio of divalentions to the target monovalent ion during the same pass of the feed solution through the adsorbent.

[0159] Advantageously, the adsorbent separation stage of the present invention may allow forimproved ease of processing and reduced cost by reducing the ratios of both the divalent ions and other monovalent ions to the target monovalent ion in a single stage rather than requiring multiple stages.

[0160] The apparatus / process of the present invention may comprise a further separation portionoperable to receive the product aqueous solution and form a refined product aqueous solutionhaving a lower ratio of the divalent ions to the monovalent ion than the product aqueous solution.

[0161] The apparatus and / or process of any aspect of the present invention may comprise aconcentration portion operable to receive the (refined) product aqueous solution and reduce the water content of the solution such as to produce a concentrated product aqueous solution. The concentration portion may comprise a reverse osmosis membrane, forward osmosis,electrodialysis, and / or a membrane comprising a porous ceramic member as defined herein.

[0162] Advantageously, the use of a reverse osmosis membrane may provide an efficient meansof concentrating high purity monovalent ions solutions, such as lithium, for example before lithium carbonate is produced by evaporation / precipitation / crystallisation.

[0163] In the method of the second or fourth aspect of the present invention, the method mayfurther comprise: contacting the (refined) product solution with a concentration portion operable to receive the (refined) product aqueous solution and reduce the water content of the solution such as to produce a concentrated product aqueous solution.

[0164] The concentration portion may be contacted with the (refined) product solution as step (d).

[0165] The concentration portion may comprise a series of concentration membranes, such as aseries of fluidly connected sequential membranes. The concentration portion may comprise a series of membranes wherein the retentate of a first membrane is operable to feed into at least one further membrane, such as at least two further membranes, or at least 4 or at least 6 membranes, suitably sequentially.

[0166] The concentration portion may comprise at least two sets of concentration membranes,each set comprising a series of membranes. In such an arrangement, the (refined) productaqueous source solution may be formed into two or more branched flows operable to contactdifferent sets of membranes in parallel. The discrete flows may be combined from the permeate outlet flows of the reverse osmosis membrane sets.

[0167] The concentration portion may be operable to purify water obtained from the effluent of theadsorbent separation portion. The purified water may be operable to be returned for use in theprocess. Advantageously, such a configuration may reduce the running costs of the process.

[0168] The concentrated product solution, such as from a reverse osmosis concentrationconcentrate, may comprise divalent cations, and optionally trivalent cations, such as Ca, Mg, B, Ba, Fe, Mn, Zn, Mo, Sr, Zr, V, Cr, Te, Ti, Ga, Hg, Be, In, Ta, Ce, Hf, Sm, La, Nb, Th, Al, Tl, As, Ni, Cu, Sc, Sn, Sb, Co, Pb, U, Cd, Y, and / or Bi. Preferably, Ca, Mg and / or B.

[0169] The target monovalent cation of the concentrated product solution may comprise Na, K, Li,Cs, Rb, W, Au and / or Ag. Preferably, the target monovalent cation of the product solution comprises Li, W, Au, Ag, Na and / or K. More preferably, Li, W, Au and / or Ag. Most preferably, Li.

[0170] The concentrated product solution may comprise anions, such as Cl, F, Br, SO4, HCO3,and / or CO3. The concentrated product solution may preferably comprise Cl and / or SO4.

[0171] The concentrated product solution may comprise the divalent ions in an amount of ≤2,500ppm, such as ≤2,000 ppm, or ≤1,500 ppm.

[0172] The concentrated product solution may comprise the target monovalent ion in an amountof ≤15,000 ppm, such as ≤10,000 ppm or ≤5,000 ppm.

[0173] The concentrated product solution may comprise the target monovalent ion in an amountof ≥10 ppm, such as ≥50 ppm or ≥100 ppm. It will be appreciated that the concentrated product solution may comprise other monovalent ions in addition to the target monovalent ion. The majority of the monovalent ions may be the target monovalent ion.

[0174] The concentrated product solution may comprise monovalent ions other than the targetmonovalent ion in an amount of ≤140,000 ppm, such as ≤125,000 ppm or ≤80,000 ppm.

[0175] The concentrated product solution may comprise monovalent ions other than the targetmonovalent ion in an amount of ≥10 ppm, such as ≥20 ppm or ≥50 ppm.

[0176] The concentrated product solution may comprise a ratio of the divalent ions to the targetmonovalent ion of <750:1, such as <700:1, such as <650:1, such as <600:1, such as <580:1, such as <550:1, such as <500:1.

[0177] The concentrated product solution may comprise a concentration of the target monovalention of ≥0.5%, such as ≥2%, or such as ≥5%.

[0178] The apparatus and / or process of the present invention may be operable to produce aproduct aqueous solution (product-, refined product- and / or concentrated-product solution) havingthe target monovalent ion, such as lithium, retention compared to the amount of the targetmonovalent ion, such as lithium, in the source aqueous solution of ≥10%, such as ≥20% or ≥30%.

[0179] The apparatus and / or process of the present invention may be operable to form aconcentrated product solution comprising ≥0.5% solid content, such as ≥2% solid content, or ≥5% solid content.

[0180] The apparatus and / or process of the present invention may be operable to form aconcentrated product solution comprising ≥10% of the target monovalent ion / compound thereof, such as lithium / lithium compound, by solid content, such as ≥20%, or comprising ≥50% by solids.

[0181] The apparatus and / or process of the present invention may be operable to form aconcentrated product solution comprising ≥90% of the target monovalent ion / compound thereof, such as lithium / lithium compound, by solid content, such as ≥95%, or comprising ≥99% by solids.

[0182] The membrane / resin of the pretreated portion, first separation portion, nanofiltrationseparation portion, second separation portion, adsorbent separation portion, further separationportion, and / or concentration portion may comprise a coating. The membrane of the nanofiltrationseparation portion and / or concentration portion may comprise a coating.

[0183] The coating may be operable to provide a separation effect. As such, the coating may beoperable to selectively promote passage of some of the material to be separated through the member.

[0184] The nanofiltration portion may comprise a coating on the nanofiltration membrane. Thecoated portion of the membrane may have a mean average pore size of ≤2 nm, such as ≤1.5 nm or ≤1 nm. The coated portion of the membrane may be a non-porous membrane.

[0185] The coating may comprise a hydrophilic agent.

[0186] The coating of any aspect of the present invention may comprise a hydrophilic agent anda superhydrophilic agent. The coating may comprise a first coating layer comprising a hydrophilicagent and a second coating layer comprising a superhydrophilic agent. The second coating layermay be arranged over at least a part of the first coating layer.

[0187] The coating layer comprising a superhydrophilic agent may be arranged on the upper faceof the membrane such that it is operable to contact the separation mixture in use.

[0188] The coating may be at least partially crosslinked and comprise a superhydrophilic agent.

[0189] The coating comprising a hydrophilic agent, optionally a superhydrophilic agent, and / orbeing at least partially crosslinked and comprising a superhydrophilic agent, may be formed from a coating composition comprising the hydrophilic agent or precursor thereof, when present, and / or the superhydrophilic agent or precursor thereof.

[0190] The surface of the membrane substrate operable to receive a coating may be hydrophilic.The contact angle of water on the substrate surface may be ≤65o, such as ≤60⁰ and preferably ≤55o.

[0191] The membrane substrate may be a pre-treated substrate. The substrate may be treatedprior to the addition of the coating formulations. For example, a surface of the membrane substrate may have been subjected to hydrophilisation to form a hydrophilic surface. Said substrate treatment may comprise the addition, suitably the grafting, of functional groups and / or the addition of hydrophilic additives. The added functional groups may be selected from one ormore of hydroxyl, ketone, aldehyde, carboxylic acid and amine groups. Preferably hydroxyl orcarboxylic acid groups.

[0192] The grafting of functional groups may be achieved by plasma treatment, corona discharge,redox reaction, radiation, UV-ozone treatment, and / or chemical treatment. One example of plasma treatment is using an oxygen plasma on the substrate for thirty seconds.

[0193] An example of a treated substrate is grafted hydroxyl groups on a polyethersulfonesubstrate introduced by plasma treatment. The functionalised groups of the substrate may beoperable to interact with a functional group of the adjacent coating layer, such as with physicaland / or chemical bonding. For example, the said grafted hydroxyl groups may be operable to react with carboxylated hydrophilic cellulosic materials in a coating layer via esterification or react with a siloxane component in an intermediate layer.

[0194] Additionally, or alternatively, surface treatment may be achieved by incorporatinghydrophilic materials into the membrane substrate materials. As such, the membrane substrate may comprise hydrophilic material.

[0195] The hydrophilic material that may be incorporated into the substrate may comprisecellulose acetate, quaternized polyethersulfone, polylactic acid, polyethylenimine, polyetherimide, polyvinylpyrrolidone and / or poly(vinyl alcohol).

[0196] The hydrophilic material may be pre-blended into membrane substrate material. Thehydrophilic material may be incorporated using methods such as phase inversion, extrusion and / or interfacial polymerisation.

[0197] The membrane substrate may comprise ≥1 % hydrophilic material by weight of thesubstrate, such as ≥5 wt%, or ≥7 wt%. The substrate may comprise ≤50 % hydrophilic material by weight of the substrate, such as ≤35 wt%, or ≥ 25 wt%. The substrate may comprise from 1 to 50 % hydrophilic material by weight of the substrate, such as from 5 to 35 wt%, or from 7 to 25 wt%.

[0198] Advantageously, surface treatment of polymeric substrates may provide improvedadhesion and uniformity of the subsequent coating layers applied on the substrate. The presence of said hydrophilicity and / or functionality on the polymeric substrate may provide a coating having a more robust mechanical integrity, a more uniform structure and improved continuity. The said hydrophilicity and / or functionality may also provide improved life span and / or stability. Surface treatment can also improve properties such as enhanced permeability.

[0199] The hydrophilic agent may be a material having a surface energy that is lower than thesurface energy of the substrate.

[0200] The hydrophilic agent, and / or coating layer comprising the hydrophilic agent, may have acontact angle of ≤65°, such as ≤60°, or ≤55°, such as ≤50°.

[0201] The hydrophilic agent, and / or coating layer comprising the hydrophilic agent, suitably hasa higher contact angle than the superhydrophilic agent, or the coating layer comprising the superhydrophilic agent.

[0202] The hydrophilic agent or precursor thereof may comprise a (co)polymer or oligomer, suchas a polyelectrolyte, polydopamine, and / or polyethylenimine, or precursor thereof.

[0203] The hydrophilic agent (co)polymer or oligomer may be formed from a reaction mixturecomprising a phenol (such as dopamine, tannic acid, vanillyl alcohol, eugenol, morin, and quercetin, for example dopamine) and a polyamine (such as polyethylenimine or polyallylamine, for example polyethylenimine), and / or a derivative thereof. The reaction mixture may comprise aphenol and a polyamine, and / or a derivative thereof, in a ratio of 5:1 to 1:5, such as 3:1 to 1:3, or2:1 to 1:2 by weight.

[0204] The phenol may be co-deposited with the polyamine, and / or derivative thereof, such that acoating composition comprising both a phenol and polyamine, and / or a derivative thereof is applied to the membrane. Additionally or alternatively, the phenol and the polyamine, and / or a derivative thereof, may be applied sequentially from separate coating compositions, such as to form the reaction mixture on the surface of the membrane.

[0205] The polyamine or derivative thereof, may have a Mw of at least 200 Da, such as at least300 Da or at least 400 Da or at least 500 Da. The polyamine or derivative thereof, may have a Mw of up to 750,000 Da, such as up to 25,000 Da or up to 10,000 Da.

[0206] The reaction mixture / coating composition may comprise an oxidant, such as sodiumperiodate, potassium persulfate, sodium persulfate, ammonium persulfate, ferric chloride, hydrogen peroxide and / or copper sulphate.

[0207] The hydrophilic agent (co)polymer may be branched.

[0208] The hydrophilic agent (co)polymer may have a weight average molecular weight (Mw) ofat least 5,000 Da, such as at least 10,000 Da or at least 15,000 Da. The hydrophilic agent(co)polymer may have a weight average molecular weight (Mw) of up to 50,000 Da, such as upto 40,000 Da or up to 30,000 Da. The hydrophilic agent (co)polymer may have a weight average molecular weight (Mw) of from 5,000 to 50,000 Da, such as from 10,000 to 40,000 Da or from 15,000 to 30,000 Da.

[0209] The hydrophilic agent (co)polymer may be formed from vinylpyrrolidone, vinyl alcohol,allylamine, ethylenimine, allylammonium chloride, vinylamine, lysine, chitosan, silane-based and / or its derivatives; acrylics, such as water soluble acrylics; acrylamide (e.g., copolymerscontaining 2-acrylamido-2-methylpropane sulfonic acid - AMPS); and / orhydroxyalkylmethacrylate, such as hydroxyethylmethacrylate (e.g. poly HEMA), and copolymers thereof, such as with acrylic acid, methacrylic acid, and / or 2-acrylamido-2-methylpropane sulfonic acid.

[0210] The hydrophilic agent may be a copolymer formed from acrylamide and acrylic acidmonomers with polyallylammonium chloride.

[0211] The hydrophilic agent may comprise a two-dimensional material and / or a nanoparticlematerial.

[0212] The hydrophilic agent may comprise a graphene-based material, metal organic frameworkmaterial, silicene, germanene, stanene, boron-nitride, suitably h-boron nitride, carbon nitride, metal-organic nanosheets, molybdenum disulfide, tungsten disulfide, polymer / graphene aerogel, and / or positively charged polymers.

[0213] The hydrophilic agent may have an average platelet size of from 1 nm to 100,000 nm, suchas from 10 nm to 50,000 nm, or from 100 nm to 15,000 nm, preferably from 500 nm to 14,000 nm.

[0214] The hydrophilic agent may have a platelet size distribution D50 of from 1 nm to 15,000 nm,preferably from 100 nm to 14,000 nm. The graphene-based material may have a platelet size distribution D90 of from 5 nm to 15,000 nm, preferably from 100 nm to 14,000 nm.

[0215] The hydrophilic agent may have an oxygen atomic content of from 1% to 70%, such asfrom 5% to 60%, or from 10% to 50%, preferably from 15% to 55%.

[0216] Suitably, the hydrophilic agent, preferably graphene-based material such as grapheneoxide, comprises hydroxyl, carboxylic and / or epoxide groups. The oxygen content of the hydrophilic agent, preferably with functional groups of hydroxyl and / or carboxylic groups, may be up to 60% oxygen atomic percentage, such as up to 50% or up to 45% oxygen atomic percentage. Suitably, the oxygen content is from 20 to 25% or from 25 to 45%. Advantageously, when the oxygen content is from 25 to 45% a surfactant may not be required to maintain stability of thecoating composition. Preferably, the oxygen content is from 25 to 40% oxygen atomic percentage.Such a range can provide improved stability of the coating composition despite the absence of other stabilising components such as surfactants, and provide enhanced interaction with a primer layer. Oxygen content may be characterised by X-ray photoelectron spectroscopy (XPS), K- Alpha grade, from ThermoFisher Scientific.

[0217] The oxygen content of the hydrophilic agent may be up to 50% oxygen atomic percentage.

[0218] The oxygen content of the hydrophilic agent may be from 25 to 45%.

[0219] The size distribution of the hydrophilic agent may be such that at least 30 wt% of thematerial have a diameter of between 1 nm to 5,000 nm, such as between 1 to 750 nm, 100 to 500 nm, 100 to 400 nm, 500 to 1000 nm, 1000 to 3000 nm, 1000 to 5000 nm, 1500 to 2500 nm, or 500 to 1500 nm, preferably 100 to 3000 nm, more preferably at least 40 wt%, 50 wt%, 60 wt%, 70 wt% and most preferably at least 80 wt% or at least 90 wt% or 95 wt% or 98 wt% or 99 wt%. The size of the hydrophilic agent and size distribution may be measured using transmission electron microscopy (TEM, JEM-2100F, JEOL Ltd. Japan).

[0220] Suitably, the d-spacing between adjacent lattice planes in the hydrophilic agent or mixturethereof is from 0.34 nm to 5000 nm, such as from 0.34 nm to 1000 nm, or from 0.4 to 500 nm, or from 0.4 to 250 nm, such as from 0.4 to 200 nm, or from 0.4 to 150 nm, or from 0.4 to 100 nm, orfrom 0.4 to 50 nm, or from 0.4 to 25 nm, or from 0.4 to 10 nm, or from 0.4 to 8 nm, such as from 0.4 to 7 nm, from 0.45 to 6 nm, 0.50 to 5 nm, or 0.55 to 4 nm, or 0.6 to 3 nm, for example 0.6 to 2.5 nm, 0.6 to 1 nm, 0.6 to 2 nm, or 0.6 to 1.5 nm.

[0221] The water contact angle of the superhydrophilic agent, the coating layer, or coatingcomposition, suitably the water contact angle of the second coating layer comprising the superhydrophilic agent, may be ≤25°, such as ≤20°, such as ≤15°, preferably ≤10°. When usedherein, the water contact angle was measured according to ASTM D7334 – 08.

[0222] The water contact angle of the superhydrophilic agent, or the coating layer, suitably thewater contact angle of the second coating layer comprising the superhydrophilic agent, may be ≤20°.

[0223] The superhydrophilic agent may comprise a (co)polymer or oligomer, such as a polymerelectrolyte, or precursor thereof.

[0224] The superhydrophilic (co)polymer and / or hydrophilic (co)polymer may comprise a hydrogel,or be operable to form a hydrogel upon contact with water.

[0225] The superhydrophilic agent (co)polymer may be formed from monomers including a vinylmonomer, such as styrene sulfonate salt, vinyl ether (such as methyl vinyl ether), N-vinyl-2-pyrrolidone (NVP), vinyl acetate (VAc); a silane-based monomer and / or its derivatives; an acrylicmonomer, such as a (hetero)aliphatic (alk)acrylate, acrylic acids and salts thereof, bisphenolacrylics, fluorinated acrylate, methacrylate, polyfunctional acrylate, hydroxyethoxyethylmethacrylate (HEEMA), hydroxydiethoxyethylmethacrylate (HDEEMA), methoxyethyl methacrylate (MEMA), methoxyethoxyethyl methacrylate (MEEMA), methoxydiethoxyethyl methacrylate (MDEEMA), ethylene glycol dimethacrylate (EGDMA), acrylic acid (AA), PEG acrylate (PEGA), PEG methacrylate (PEGMA), PEG diacrylate (PEGDA), PEG dimethacrylate (PEGDMA), bis(trimethylsilyloxy)methylsilylpropyl glycerol methacrylate (SiMA), methacryloyloxyethyl phosphorylcholine (MPC), 6-acetylthiohexyl methacrylate, acrylic anhydride, [2-(acryloyloxy)ethyl]trimethylammonium chloride, 2-(4-benzoyl-3- hydroxyphenoxy)ethyl acrylate, benzyl acrylate, or their trimethacrylate, dimethacrylate tri-block derivatives; thiol functionalised acrylate monomers, such as thiol functionalised (meth)acrylate;acryloyl chloride; acrylonitrile; maleimide; an acrylamide based monomer, such as acrylamide,methacrylamide; N,N-dimethylacrylamide (DMA), 2-acrylamido-2-methylpropane sulfonic acid, N- isopropyl AAm (NIPAAm), N-(2-hydroxypropyl) methacrylamide (HPMA), 4-acryloylmorpholine; carbohydrate monomer; a polyacid and / or polyol, such as maleic acid (such as maleic acid with a vinyl ether (e.g., Gantrez, partially neutralised with sodium)), ethylene glycol (EG); gelatinmethacryloyl; and / or methacrylated hyaluronic acid, optionally with crosslinkers such asepichlorohydrin (ECH), N,N’-methylene-bis-acrylamide (BIS) and / or divinyl sulfone (DVS).

[0226] A superhydrophilic agent (co)polymer may have a molecular weight (Mw) of ≥2,000 g / mol,such as ≥4,000 g / mol, or ≥6,000 g / mol. For example, up to ≤30,000 g / mol, such as up to ≤20,000 g / mol, or up to ≤15,000 g / mol. For example, from 2,000 to 30,000 g / mol, such as from 4,000 to 20,000 g / mol, or from 6,000 to 15,000 g / mol.

[0227] The superhydrophilic agent (co)polymer may have a molecular weight (Mw) of ≥6,000g / mol.

[0228] The superhydrophilic agent (co)polymer may have a molecular weight (Mw) of from 2,000to 30,000 g / mol.

[0229] The coating or coating composition may comprise a film former, such as a linear and / orhydrophilic polymer (e.g. PVP etc). A film former may be selected from a polysaccharide orderivative thereof, such as cellulose or a derivative thereof, for example methylcellulose,hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose, cellulose acetate phthalate, hydroxypropyl methylcellulose phthalate, carboxymethyl ethylcellulose, hydroxypropylmethylcellulose acetate succinate, ethylcellulose, sodium alginate; acrylic (co)polymers; vinyl(co)polymer, such as polyvinyl pyrrolidone; polyvinyl alcohol, polyvinyl acetate phthalate;polyethylene glycol, polyethyleneimine (PEI); and / or poly(ethylene) oxide. Preferably, the filmformer comprises a water-soluble film former, such as hydroxypropyl methylcellulose acetate succinate.

[0230] The amount of film former in the coating composition may be ≤10 wt % by dry weight of thecoating composition, such as ≤5 wt %, such as ≤4 wt %, ≤3.5 wt %, ≤3 wt %, ≤2.5 wt %, preferably ≤2 wt %

[0231] The hydrophilic agent, superhydrophilic agent, or precursors thereof, coating layer and / orfilm former, when present, may be at least partially crosslinked, or be operable to be at least partially crosslinked. The hydrophilic agent, superhydrophilic agent, or precursors thereof, film former and / or coating layer may be at least partially crosslinked by using an additive crosslinker. As such, the coating composition comprising the hydrophilic agent, superhydrophilic agent and / or film former may further comprise an additive crosslinker. The hydrophilic agent, superhydrophilic agent, or precursors thereof, coating layer and / or film former, may be at least partially self- crosslinked, or be operable to be self-crosslinked prior to application. As used herein “self- crosslinked” means crosslinking between two or more polymer chains wherein the crosslinking moiety was a functional group present on the polymer backbone prior to crosslinking.

[0232] The hydrophilic, superhydrophilic (co)polymer, or precursors thereof, and / or film former(co)polymer, when present, may be formed from a crosslinker or residue thereof, suitably in an amount of ≥0.5 % by weight of the total monomers of the (co)polymer, or ≥0.8 wt% or ≥1 wt%. For example, up to ≤15 % by weight of the total monomers of the (co)polymer, up to ≤10 wt% or up to ≤5 wt%. For example, from 0.5 to 15 % by weight of the total monomers of the (co)polymer, or from 0.8 to 10 wt% or from 1 to 5 wt%.

[0233] The coating composition may comprise a crosslinker in an amount of ≥0.5 % by dry weightthe composition, such as ≥0.8 wt% or ≥1 wt%. For example, up to ≤15 % by dry weight the composition, such as up to ≤10 wt% or up to ≤5 wt%. For example, from 0.5 to 15 % by by dry weight the composition, such as from 0.8 to 10 wt% or from 1 to 5 wt%.

[0234] The superhydrophilic (co)polymer may be formed from a crosslinker in an amount of ≥0.5% by weight of the total monomers of the (co)polymer.

[0235] The hydrophilic, superhydrophilic (co)polymer, or precursors thereof, and / or film former(co)polymer, when present, may be formed from a crosslinker or residue thereof, suitably in an amount of from 0.5 to 15 % by weight of the total monomers of the (co)polymer.

[0236] The crosslinker may be a multi-functional acrylic or vinyl monomer, a divalent metal ion,multi-functional carbodiimide, multi-functional aziridine, silane; multi-functional epoxide and / ormulti-functional isocyanate, or residue thereof.

[0237] The crosslinker may comprise tetramethylethylenediamine, methylene bis-acrylamide,ethylene glycol dimethacrylate, polyethylene glycol dimenthacrylate, triethylene glycoldimethacrylate N-isopropylacrylamide; N,N-diethylacylamide, epichlorohydrin (ECH), N,N’- methylene-bis-acrylamide (BIS), divinyl sulfone (DVS), citric acid, dicysteine peptides, dithiothreitol (DTT), glutaraldehyde; enzymatic crosslinking, such as transglutaminase, and acombination of horseradish peroxidase (HRP) and hydrogen peroxide, or a residue thereof.

[0238] The hydrophilic agent, superhydrophilic agent, or precursors thereof, and / or film formerwhen present, may comprise a functional group that is operable to be crosslinked, or residue thereof. For example, the hydrophilic agent, superhydrophilic agent, or precursors thereof, and / or film former when present, may comprise acid functionality, such as carboxylic acid functionality, or residues thereof. In the coating, the crosslinking density may be at least 2 molar % of the crosslinkable functional groups, such as at least 5 molar % or at least 10 molar %.

[0239] The crosslinking density may be at least 2 molar % of the crosslinkable functional groups.

[0240] As used herein, the crosslinking density was measured by the following method. Thepolymer was swelled in a solvent until equilibrium. The swollen gel was then isolated and weighed. The weights of swelling solvent and polymer were determined after removing the solvent by vacuum-drying. The following equation was then applied: Crosslink density, network chain per gram = [ln(1-Vp) + (Vp) + X(Vp)^2] / {Dp(Vo)[(Vr)^(1 / 3) - (Vp) / 2]} where Vp=Volume fraction of polymer in the swollen polymer X= Huggins polymer-solvent interaction constant Dp=Density of polymer (g / cm^3) Vo=Molar volume of solvent (cm^3 / mol) Do=Density of solvent (g / cm^3) Here, Vp=1 / (1+Q), Where Q is the ratio of the weight of solvent in swollen polymer (XDp) and the weight of polymer (XDo).

[0241] The superhydrophilic agent may be a polyelectrolyte (co)polymer selected from a(meth)acrylic acid (co)polymer; and / or a styrene sulfonate acid (co)polymer, wherein at least part of the acid is in the form of a suitable salt.

[0242] The superhydrophilic agent may be a polyelectrolyte copolymer selected from poly(styrene-alt-maleic acid) sodium, chitosan-g-poly(acrylic acid) copolymer sodium; 2-propenoic acid, 2- methyl, polymer with sodium; and / or 2-methyl-2((1-oxo-2-propen-1-yl)amino)-1- propanesulfonate.

[0243] The superhydrophilic agent may comprise a (co)polymer hydrogel selected from:carboxymethyl cellulose (CMC), and / or polyvinylpyrrolidone (PVP) hydrogel, crosslinked for example by tetra(ethylene glycol) dimethacrylate, such as via free radical polymerisation, suitably wherein at least part of the acid is in the form of a suitable salt, such as a carboxymethyl cellulose (CMC) sodium; N-isopropylacrylamide (NIPAAm) with poly(ethylene glycol)-co-poly(ε- caprolactone) (PEG-co-PCL), crosslinked for example by N,N′-methylene bisacrylamide and / or sodium alginate, for example by using template copolymerisation, or UV light or crosslinked by N,N,N′,N′-tetramethylethylenediamine (TEMED) and / or ammonium persulphate (APS) with UV light, such as alginate and alginate derivatives; 3- (methacryloyloxy)propyltris(trimethylsiloxy)silane, N,N-dimethylacrylamide, 3- (methacryloyloxy)propyltris(trimethylsiloxy)silane 1-vinyl-2-pyrrolidinone, and / or 2- hydroxyethylmethacrylate (TRIS-DMA-NVP-HEMA copolymer hydrogel).

[0244] Hydrogel when used herein in relation to the hydrophilic agent and the superhydrophilicagent may mean an insoluble polymeric network characterized by the presence of physical and / orchemical crosslinking among the polymer chains and the presence of water, suitably in a non-insignificant amount, such as in an amount of at least 10% of the total weight of the polymer composition. The hydrophilic agent and / or the superhydrophilic agent may be in the form of a dehydrated hydrogel that is operable to form a hydrated hydrogel upon contact with water.

[0245] The superhydrophilic agent may comprise a poly(styrene sulphonate salt) and / or apolyacrylic acid salt.

[0246] The term “precursor” when used herein in relation to the hydrophilic and superhydrophilicagents refers to a compound that is operable to form the hydrophilic or superhydrophilic agent using methods known to the skilled person. For example, the precursor may be an oligomer, or pre-crosslinked polymer which form the hydrophilic or superhydrophilic agent after chemical or physical crosslinking, such as with UV-light with photo-initialiser, heat treatment, etc. For example, a precursor may comprise a mixture of acrylamide and acrylic acid monomers with poly(allylamonium chloride), and with 2,2′-Azobis(2-methylpropionamidine) dihydrochloride (AIBA) as initiator, and N,N’-methylene bisacrylamide (MBAM) as crosslinker. This mixture may be considered to be a hydrophilic agent precursor as it is operable to form a hydrophilic agent in the coating via template polymerisation. Another example of a suitable precursor includespolyethylene glycol (PEG) mixed with triethylene glycol dimethacrylate (TEGDMA), which isoperable to form the hydrophilic agent in the coating layer via UV light with a photo-initiator.

[0247] The coating composition / reaction mixture may comprise a buffer agent, operable tomaintain the composition / mixture at a suitable pH range, such astris(hydroxymethyl)aminomethane (Tris). The pH of the coating composition may be from 8 to 9, such as from 8 to 8.5.

[0248] The thickness of the coating, suitably of the first coating layer / layer comprising a hydrophilicagent, may be from 1 nm to 2000 nm, such as from 1 to 1000 nm, or from 5 to 500 nm, such as 5 to 200 nm.

[0249] The thickness of the coating layer comprising the superhydrophilic agent may be up to 100µm.

[0250] The membrane may comprise an intermediate layer between the membrane substrate anda first coating layer, and / or between a first coating layer and a second coating layer.

[0251] The intermediate layer may comprise an adhesion promoter selected from silane or aderivative thereof, tannic acid, dopamine or a derivative thereof, and / or dopamine peptide; amine; diamine; methacrylate; epoxy; methyl, isobutyl, phenyl, octyl, or vinyl, chloroalkyl; vinylbenzylamino based adhesion promoter; organometallic such as organotitanate, organozirconate, organoaluminate; chlorinated or chlorine-free polyolefin; polyol based adhesion promoter; and / or polyester based adhesion promoter.

[0252] The adhesion promoter may comprise a silane based adhesion promoter such as anacrylate and / or methacrylate functional silane, aldehyde functional silane, amino functional silane; such as amino alkoxysilane, anhydride functional silane, azide functional silane, carboxylate phosphonate and / or sulfonate functional silane, epoxy functional silane, ester functional silane, halogen functional silane, hydroxyl functional silane, isocyanate and / or masked isocyanate functional silane, phosphine and / or phosphate functional silane, sulfur functional silane, vinyl and / or olefin functional silane, multi-functional and / or polymeric silane, UV active and / or fluorescent silane, and / or chiral silane, trihydrosilane.

[0253] The adhesion promoter may comprise 3-aminopropyl trimethoxy silane

[0254] The coated membrane may be formed by:a. optionally, preparing a substrate by treating the substrate with physicalrinsing, chemical treatment, radiation treatment, plasma treatment, and / or thermal treatment; b. optionally, contacting the substrate with an intermediate layer coatingcomposition to form an intermediate layer; c. contacting the membrane substrate with a coating composition comprisinga hydrophilic agent or precursor thereof, and optionally further comprising a superhydrophilic agent or precursor thereof, to form a coating layer; d. optionally, contacting the coating layer with an intermediate layer coatingcomposition to form an intermediate layer; e. optionally contacting the coated substrate with a coating compositioncomprising a superhydrophilic agent or precursor thereof to form a further coating layer, for example if a superhydrophilic agent was not contacted with the substate in step (c).

[0255] The coated membrane may be formed by:a. optionally, preparing a substrate by treating the substrate with physicalrinsing, chemical treatment, radiation treatment, plasma treatment, and / or thermal treatment; b. optionally, contacting the membrane substrate with an intermediate layercoating composition to form an intermediate layer; c. optionally, contacting the membrane substrate with a coating compositioncomprising a hydrophilic agent or precursor thereof to form a coating layer; d. optionally, contacting the coating layer with an intermediate layer coatingcomposition to form an intermediate layer; e. contacting the optionally coated substrate with a coating compositioncomprising a superhydrophilic agent or precursor thereof to form a coating layer; wherein the coating layer comprising the superhydrophilic agent is at least partially crosslinked.

[0256] The coating may comprise a lamellar structure comprising at least two layers of two-dimensional material, and wherein the two-dimensional material comprises graphene or a derivative thereof. The coating may be formed from a coating composition comprising graphene or a derivative thereof.

[0257] The graphene or derivative thereof may be selected from one or more of graphene oxide,reduced graphene oxide, hydrated graphene and amino-based graphene, alkylamine functionalised graphene oxide, ammonia functionalised graphene oxide, amine functionalised reduced graphene oxide, octadecylamine functionalised reduced graphene oxide, and / or polymer graphene aerogel. Preferably, the graphene or derivative thereof is graphene oxide. Graphene and its derivatives may be obtained commercially from Sigma-Aldrich.

[0258] The graphene or derivative thereof, suitably graphene oxide, may be optionally substitutedwith further functional groups. The optional functional groups may be grafted functional groups, and preferably grafted via reaction with the existing hydroxyl, carboxylic and epoxide groups of the graphene or derivative thereof. Functionalisation includes covalent modification and non- covalent modification. Covalent modification method can be subcategorised to nucleophilic substitution reaction, electrophilic substitution reaction, condensation reaction, and addition reaction. Examples of optional functional groups are amine groups; aliphatic amine groups, such as long-chain (e.g. C18 to C50) aliphatic amine groups; porphyrin-functionalised secondary amine groups, and / or 3-amino-propyltriethoxysilane groups. The graphene or derivative thereof may comprise amino groups, suitably grafted amino groups, and preferably to graphene oxide. Such functionalisation can provide for the improved selective sieving of ferric acid.

[0259] The materials of the coating may be produced using any of the suitable methods known tothe skilled person. Two-dimensional silicene, germanene and stanene may be produced by surface assisted epitaxial growth under ultrahigh vacuum. Hexagonal two-dimensional h-boron nitride may be produced by several methods, such as mechanical cleavage, unzipping of boron nitride nanotubes, chemical functionalisation and sonication, solid-state reaction and solvent exfoliation and sonication. Among these methods, chemical method has been found to provide the highest yield. For example, h-boron nitride may be synthesised on single-crystal transition metal substrates using borazine as boron and nitride sources. Two-dimensional carbon nitride can be prepared via direct microwave heating of melamine and carbon fibre. Metal-organic frameworks (MOFs) can be produced by in-situ solvothermal synthesis method by mixing ingredients at high temperatures such as 100-140oC, followed by filtration. Two-dimensional molybdenum disulfide can be obtained by a few methods, such as mechanical exfoliation, liquid exfoliation and chemical exfoliation. Among these methods, chemical exfoliation has been foundto provide a high yield. One example is chemical exfoliation using lithium to chemically exfoliatemolybdenum disulfide using centrifuge and filtration. Two-dimensional tungsten disulfide can beprepared by a deposition-thermal annealing method: vacuum deposition of tungsten and followed by thermal annealing by addition of sulphur. Polymer / graphene aerogel can be produced via coupling and subsequent freeze-drying using polyethylene glycol grafted graphene oxide.

[0260] The method of applying the coating composition to the membrane substrate may comprisethe step of applying a coating composition comprising the graphene or derivative thereof onto the substrate. The method may comprise contacting the coating composition onto the substrate using gravity deposition, vacuum deposition, pressure deposition; printing such as inkjet printing, aerosol printing, 3D printing, offset lithography printing, gravure printing, flexographic printing techniques, pad printing; curtain coating, dip coating, spin coating, and other printing or coating techniques known to those skilled in the art.

[0261] Further details of the application methods are disclosed in the published PCT patentapplication WO2019106344, specifically, paragraphs

[0047] to

[0049] and

[0061] to

[0069] inclusive. Theentire contents of paragraphs

[0047] to

[0049] and

[0061] to

[0069] inclusive thereof are fully incorporatedherein by reference.

[0262] The coating composition may be a liquid composition comprising a liquid medium and thegraphene or derivative thereof. The coating compositions of the present invention may comprise solvent, non-solvent or solvent-less, and may be UV curable compositions, e-beam curablecompositions etc. When formulated as a liquid composition for use in the invention, e.g. as asolution, dispersion or suspension, a suitable carrier liquid or solvent may be aqueous or organic,and other components will be chosen accordingly. For example, the liquid carrier may comprise water or an organic solvent such as ethanol, terpineol, dimethylformamide N-Methyl-2- pyrrolidone, isopropyl alcohol, mineral oil, ethylene glycol, or their mixtures, optionally with other materials to enhance performance and / or rheology of the composition including any one or more of binders, drying additives, antioxidants, reducing agents, lubricating agents, plasticisers, waxes, chelating agents, surfactants, pigments, defoamers and sensitisers.

[0263] Further details of the coating composition are disclosed in published PCT patent applicationWO2019106344, specifically, paragraphs

[0051] to

[0060] inclusive. The entire contents paragraphs

[0051] to

[0060] inclusive thereof are fully incorporated herein by reference.

[0264] The coating may comprise a lamellar structure comprising at least two layers of two-dimensional material, and wherein the two-dimensional material comprises a transition metal dichalcogenide. The coating may be formed from a coating composition comprising a transition metal dichalcogenide.

[0265] The transition metal dichalcogenide may be according to formula (I)MaXb, (I) wherein with M is a transition metal atom, such as Mo, W, Nb and Ni; X is a chalcogen atom, preferably S, Se, or Te; wherein 0<a≤1 and 0<b≤2.

[0266] The transition metal dichalcogenide may be selected from one or more of MoS2, MoSe2,WS2, WSe2, MoaW1-aS2, MoaW1-aSe2, MoSbSe2-b, WSbSe2-b, or MoaW1-aSbSe2-b, where 0<a≤1 and 0<b≤2, or combination thereof. Preferably, the transition metal dichalcogenide is selected from MoS2, WS2, MoSe2, WSe2. Most preferably from MoS2 and WS2. Such transition metal dichalcogenide is available commercially from ACS Material.

[0267] The transition metal dichalcogenide may be in the form of flakes having an average size offrom 1 nm to 5000 nm, such as between 50 to 750 nm, 75 nm to 500 nm, 100 nm to 400 nm, for example 130 nm to 300 nm, 150 nm to 290 nm, or 160 nm to 280 nm, suitably 170 nm to 270 nm, 180 nm to 260 nm or preferably 190 nm to 250 nm. Suitably, the size distribution of the transition metal dichalcogenide flakes is such that at least 30wt% of the transition metal dichalcogenide flakes have a diameter of between 1 nm to 5000 nm, such as between 50 to 750 nm, 75 nm to 500 nm, 100 nm to 400 nm, for example 130 nm to 300 nm, 150 nm to 290 nm, or 160 nm to 280 nm, suitably 170 nm to 270 nm, 180 nm to 260 nm or preferably 190 nm to 250 nm more preferably at least 40wt%, 50wt%, 60wt%, 70wt% and most preferably at least 80wt% or at least 90wt% or 95wt% or 98wt% or 99wt%. The size of the transition metal dichalcogenide thereof and size distribution may be measured using transmission electron microscopy (TEM, JEM-2100F, JEOL Ltd. Japan).

[0268] For example, lateral sizes of the two-dimensional layers across a sample may be measuredusing transmission electron microscopy (TEM, JEM-2100F, JEOL Ltd. Japan), and the number (Ni) of the same sized nanosheets (Mi) measured. The average size may then be calculated by Equation 1: Average size where Mi is the diameter of the nanosheets, and Ni is the number of the size with diameter Mi.

[0269] The transition metal dichalcogenide may be in the form of a monolayer or multi-layeredparticle or flake, preferably a monolayer. The transition metal dichalcogenide flakes may be formed of single, two or few layers of transition metal dichalcogenide, wherein few may be defined as between 3 and 100 layers. Suitably, the transition metal dichalcogenide flakes comprise between 1 to 100 layers, such as between 2 to 75 layers or 5 to 50 layers or 10 to 25 layers. Suitably, at least 30wt% of the transition metal dichalcogenide comprise between 1 to 30 layers, such as between 5 to 30 layers or 5 to 10 layers, more preferably at least 40wt%, 50wt%, 60wt%, 70wt% and most preferably at least 80wt% or at least 90wt% or 95wt% or 98wt% or 99wt%. The number of layers in the transition metal dichalcogenide flakes thereof may be measured usingatomic force microscopy (AFM or transmission electron microscopy (TEM)) (TT-AFM, AFMworkshop Co., CA, USA).

[0270] Suitably, the d-spacing between adjacent lattice planes in the transition metaldichalcogenide or mixture thereof is from 0.34 nm to 5000 nm, such as from 0.34 nm to 1000 nm,or from 0.4 to 500 nm, or from 0.4 to 250 nm, such as from 0.4 to 200 nm, or from 0.4 to 150 nm,or from 0.4 to 100 nm, or from 0.4 to 50 nm, or from 0.4 to 25 nm, or from 0.4 to 10 nm, or from 0.4 to 8 nm, such as from 0.4 to 7 nm, from 0.45 to 6 nm, 0.50 to 5 nm, or 0.55 to 4 nm, or 0.6 to 3 nm, for example 0.6 to 2.5 nm, 0.6 to 1 nm, 0.6 to 2 nm, or 0.6 to 1.5 nm.

[0271] The coating may comprise materials, suitably two-dimensional materials, other than thetransition metal dichalcogenide thereof. For example, other materials of the coating may be selected from one or more of silicene, germanene, stanene, boron-nitride, suitably h-boron nitride, carbon nitride, metal-organic nanosheets, graphene, graphene oxide, reduced graphene oxide functionalised graphene oxide and polymer / graphene aerogel.

[0272] Further details of the application methods are disclosed in published PCT patent applicationWO2019 / 122828, specifically, paragraphs

[0073] to

[0077] inclusive. The entire contents paragraphs

[0073] to

[0077] inclusive thereof are fully incorporated herein by reference.

[0273] Further details of the coating composition are disclosed in published PCT patent applicationWO2019 / 122828, specifically, paragraphs

[0046] to

[0061] inclusive. The entire contents paragraphs

[0046] to

[0061] inclusive thereof are fully incorporated herein by reference.

[0274] The coating may comprise a metal-organic framework (MOF). The coating may be formedfrom a coating composition comprising a MOF.

[0275] The metal-organic framework materials of any aspect of the present invention may be one-dimensional, two-dimensional or three-dimensional. Preferably, the MOF is porous. The MOF may comprise a network of secondary building units (SBUs), or metal ion core / metal subunit cluster core nodes, and organic linkers (or ligands) connecting the SBUS or nodes.

[0276] The MOF may be in continuous phase in the coating or may be in the form of flakes and / orparticles. A MOF synthesised in the presence of first support portion may be in the form of continuous phase. A MOF formed prior to contact with the first support portion may be in the form of flakes and / or particles.

[0277] The SBUs or nodes, being sub units of the MOF, may comprise metal selected from oneor more transition metal cations, such as one or more of Cr(III), Fe(II), Fe(III), Al(III), Co(II), Ru(III), Os(III), Hf(IV), Ni, Mn, V, Sc, Y(III), Cu(II), Cu(I), Zn(II), Zr(IV), Cd, Pb, Ba, Ag (I), Au, AuPd, Ni / Co, lanthanides, actinides, such as Lu, Tb(III), Dy(III), Ho(III), Er(III), Yb(III). Preferably Cr(III), Fe(II), Fe(III), Al(III), Co(II), Ru(III), Os(III), Hf(IV), Ni, Mn, V, Sc, Y(III), Cu(II), Cu(I), Zn(II), Zr(IV), Cd, Pb, Ba, Ag (I), Ni / Co, lanthanides, actinides, such as Lu, Tb(III), Dy(III), Ho(III), Er(III), Yb(III). More preferably Cr(III), Fe(II), Fe(III), Al(III), Co(II), Hf(IV), Ni, Mn, V, Sc, Y(III), Cu(II), Cu(I), Zn(II), Zr(IV), Cd, Pb, Ag (I), Ni / Co, lanthanides, actinides, such as Lu, Tb(III), Dy(III), Ho(III), Er(III), Yb(III), more preferably Cr(III), Fe(II), Fe(III), Al(III), Co(II), Hf(IV), Ni, Mn, V, Y(III), Cu(II), Cu(I), Zn(II), Zr(IV), Cd, Ag (I), Ni / Co, lanthanides, actinides, such as Lu, Tb(III), Dy(III), Ho(III), Er(III), Yb(III). The secondary building unit (SBU) may comprise: three, four, five, six, eight, nine, ten, eleven, twelve, fifteen or sixteen points of extension.

[0278] The SBU or node may be a transition-metal carboxylate cluster. The SBUs or nodes maybe one or more selected from the group consisting of Zn4O(COO)6, Cu2(COO)4, Cr3O(H2O)3(COO)6, and Zr6O4(OH)10(H2O)6(COO)6), Mg2(OH2)2(COO), RE4(µ3- O)2(COO)8, RE4(µ3-O)2, wherein RE is Y(III), Tb(III), Dy(III), Ho(III), Er(III), and / or Yb(III)). The structures of SBUs can be identified by X-Ray diffraction using methods well known to the skilled person.

[0279] Organic linkers suitable for use in the present invention include those operable to be usedto form MOFs for water treatment, molecule separation, and biofiltration related applications. Such linkers may form strong bonds to metal cores, provide large pore sizes, provide high porosity, provide selective absorption and / or capacity.

[0280] The organic linkers of the MOF may be formed from a wide range of organic molecules,such as one or more carboxylate linkers; N-heterocyclic linkers; phosphonate linkers; sulphonatelinkers, metallo linkers, such a carboxylate-metallo linkers; and mixtures and derivatives thereof.

[0281] The organic linkers may comprise one or more of ditopic, tritopic, tetratopic, hexatopic,octatopic linkers. The organic linkers may comprise desymmetrised linkers.

[0282] MOFs suitable for use in the present invention include those operable to be used in watertreatment, molecule separation, biofiltration and related applications. Suitable MOFs preferably have water and chemical stability. The MOFs may have water insoluble linkers, and / or solvent- stable linkers, and / or strong covalent bonds between SBU and linkers, and / or multi-covalent bonds between SBU and linkers. Water and chemical stability may mean that the MOFs do not fully disassemble to linkers and SBUs in the presence of water and / or chemicals. Suitable MOFs may have covalent bond links between the linkers and the SBUs or nodes, and / or coordinate bonding between the linkers and the SBUs or nodes.

[0283] Suitable MOFs may have a high surface area and / or large pore sizes. The MOF may havea surface area of at least 10 m2 / g, such as 100 to 9,000 m2 / g, preferably 100 to 8,000 m2 / g or 500 to 8,000 m2 / g. The surface area can be measured using the known Brunauer, Emmett and Teller (BET) technique. The MOFs according to any aspect of the present invention, suitably in the form of porous flakes or particles, may have an average pore size of from 0.1 nm to 1000 nm, 0.1 to 950 nm, 0.2 to 900 nm, 0.2 to 850 nm, preferably 0.2 to 800 nm, 0.3 to 700 nm, preferably 0.4 to 650, 0.4 to 550 nm, 0.5 to 500 nm, 0.5 to 450 nm, 0.2 nm to 100 nm, such as between 0.2 nm to 90 nm, 0.3 nm to 75 nm, 0.4 nm to 50 nm, for example 0.4 nm to 40 nm, 0.4 nm to 30 nm, or 0.4nm to 20 nm, suitably 0.4 nm to 15 nm, 0.4 nm to 10 nm.

[0284] The MOF may comprise a pillared-layer MOF. Suitably, in a pillared-layer MOF 2D sheetsfunction as scaffolds for organic linkers, such as dipyridyl linkers. Advantageously, this can allow for diverse functionalities to be incorporated into the MOF, such as –SO32-_groups. The use of – SO32-_groups can induce a polarized environment and strong acid–base interaction with acidicguests like CO2. Furthermore, different pillar linker groups, such as –N=N– compared to –CH=CH–, provide different selectivity to H2O and methanol.

[0285] The MOF may comprise a functional group. The MOF may in particular be adapted forwater treatment, molecule separation, and biofiltration related applications by the MOF comprising a functional group, suitably on one or more of the organic linkers. Said functional groups may provide selectivity and / or increase pore sizes for high adsorption capacity or high flux rate. The functional group may be selected from one or more of the group consisting of -NH2, - Br, -Cl, -I, -(CH2)n-CH3 wherein n is 1 to 10, such as CH3CH2CH2O-, CH3CH2CH2CH2O-, ben- C4H4, methyl, -COOH, -OH. For example, the MOF may be an IRMOF, such as IRMOF-1, IRMOF-2, IRMOF-3, IRMOF-4, IRMOF-5, IRMOF-6, IRMOF-7, IRMOF-8, IRMOF-9, IRMOF-10, IRMOF-16, IRMOF-11, IRMOF-12, IRMOF-13, IRMOF-14, IRMOF-15; and / or a CAU, such as CAU-10-OH, CAU-10-NH2, CAU-10-H, CAU-10-CH3; and / or MIL-125-NH2; and / or UiO-66(Zr)- (CH3)2.

[0286] The coating may be operable to provide size exclusion filtration, fouling resistance, and / oradsorption, such as size exclusion and fouling resistance.

[0287] The pore size of the MOF may be tailored by using different species of MOFs or differentorganic linkers with different lengths. For example, the pore size of the MOF may be at least 0.6nm (e.g. ZIF-78), such as at least 0.8nm (e.g. ZIF-81), or at least 0.9nm (e.g. ZIF-79) or at least 1.2nm (e.g. ZIF-69), or at least 1.3nm (e.g. ZIF-68) or at least 1.6nm (e.g. ZIF-82), such as at least 1.8nm (e.g. ZIF-70), or at least 1.8nm (e.g. IRMOF-10), or at least 2.8nm (e.g. MOF-177).

[0288] The MOF may comprise MOF-74 adapted by replacing one or more of the original linkerscontaining one phenyl ring with a linker containing two, three, four, five, six, seven, nine, ten or eleven phenyl rings. Such an adaption can alter the pore size from ~1.4nm to ~2.0nm, to ~2.6nm, to ~3.3nm, to ~4.2nm, to ~4.8nm, to ~5.7nm, to ~7.2nm, to ~9.5 nm, respectively.

[0289] The MOF may be hydrophobic. The hydrophobic MOF may be selected from one or moreof MIL-101(Cr), NiDOBDC, HKUST-1, Al(OH)(2,6-ndc) (ndc is naphthalendicarboxylate), MIL- 100-Fe, UiO-66, ZIF family, such as ZIF 71, ZIF 74, ZIF-1, ZIF-4, ZIF-6, ZIF-11, ZIF-9, and ZIF 8. Advantageously, the use of such MOFs can improve the fouling resistance of the membrane.

[0290] The MOF may comprise an adsorption promoting MOF, for example UiO-66 or UiO-66-NH2, preferably UiO-66-NH2, which has been found to adsorb cationic dyes from aqueous solution more effectively than anionic dyes due to favourable electrostatic interactions between the adsorbents and cationic dyes. In particular, UiO-66-NH2 has been found to provide much higher adsorption capacity for cationic dyes and lower adsorption capacity for anionic dyes than UiO-66.

[0291] The MOFs may comprise nanochannels, suitably the MOFs are in the form of flakes orparticles comprising nanochannels. The average nanochannel diameter may be from 0.2 nm to 100 nm, such as between 0.2 to 90 nm, 0.3 nm to 75 nm, 0.4 nm to 50 nm, for example 0.5 nm to 40 nm, 0.5 nm to 30 nm, or 0.5 nm to 20 nm, suitably 0.5 nm to 15 nm, 0.5 nm to 10 nm or preferably 0.5 nm to 8 nm.

[0292] The MOF may comprise functional groups selected from one or more of amine, aldehyde,alkynes, and / or azide. MOFs pores may be modified for selective sieving and to provide higher efficiency by modification methods, suitably post-synthetic, on the linkers and / or the secondary building units / nodes, such as covalent post-synthetic modification method of amine, or aldehyde, or alkynes, or azides functional groups. Specific functional groups may be induced to MOF(s) for specific application. For example, adding -NH2 to UiO-66 to make UiO-66-NH2 has been found to improve ferric acid adsorption, and adding sulfone bearing groups to iso IRMOF-16 by, for example, oxidation using dimethyldioxirane, in order to create compatible interaction between the coating and first support portion.

[0293] The MOFs of the present invention may be synthesised according to the required propertyor purchased from commercial supplier. Suitable commercially available metal-organic framework materials can be purchased from BASF, Sigma-Aldrich, or Strem Chemicals.

[0294] The methods used to synthesise MOFs for the current invention are those conventional inthe art and may be solvothermal synthesis, microwave-assisted synthesis, electrochemical synthesis etc.

[0295] A modulator may be used during synthesis of the MOF to control the MOF particle size, themodulator may be benzoic acid.

[0296] The MOF may be in the form of a crystallised continuous phase or particles or flakescompacted and interacting or fused to each other forming the coating. Preferably the MOF is in the form of particles or flakes.

[0297] The size distribution of the MOF flakes or particles may be such that at least 30wt% of theMOF flakes or particles have a size of between 1 nm to 10000 nm, such as between 2 to 7500 nm, 5 nm to 5000 nm, 10 nm to 4000 nm, for example 15 nm to 3500 nm, 20 nm to 3000 nm, or 25 nm to 3000 nm, suitably 30 nm to 2500 nm, 40 nm to 2500 nm or preferably 50 nm to 2500 nm more preferably at least 40wt%, 50wt%, 60wt%, 70wt% and most preferably at least 80wt% or at least 90wt% or 95wt% or 98wt% or 99wt%. The size of the MOF and size distribution may be measured using transmission electron microscopy (TEM, JEM-2100F, JEOL Ltd. Japan).

[0298] For example, lateral sizes of two-dimensional layers across a sample of a MOF may bemeasured using transmission electron microscopy (TEM, JEM-2100F, JEOL Ltd. Japan), and the number (Ni) of the same sized nanosheets (Mi) measured. The average size may then be calculated by Equation 1: Average where Mi is diameter of the nanosheets, and Ni is the number of the size with diameter Mi.

[0299] The coating may comprise additives to tailor the properties of the coating, such as othermetals; and / or fibres, such as metal oxide nanostrands; and / or dopants such as Au, Fe, Cu, Cu(OH)2, Cd(OH)2 and / or Zr(OH)2. Such additives may be added to the membrane to control the pore sizes and channel architecture of MOF and / or create nanochannels for high water flux rate.Any type of suitable fibres, such as continuous or stapled fibres, having diameter of 0.1 – 1000nm may be incorporated within the membrane. Such as 0.1 to 850nm, 0.5 to 500nm, or 0.5 to 100nm, 0.75 to 75nm, preferably, 0.75 to 50nm. Suitably, the fibres are removed before use, such as by mechanical removal or by dissolution, etc.

[0300] Further details of the application methods are disclosed in the published PCT patentapplication WO2019 / 186134, specifically, paragraphs

[0117] ,

[0118] and

[0126] to

[0130] inclusive.The entire contents of paragraphs

[0117] ,

[0118] and

[0126] to

[0130] inclusive thereof are fullyincorporated herein by reference.

[0301] Further details of the coating composition are disclosed in the published PCT patentapplication WO2019 / 186134, specifically, paragraphs

[0097] to

[0116] inclusive. The entire contentsof paragraphs

[0097] to

[0116] inclusive thereof are fully incorporated herein by reference.

[0302] The coating may comprise multiple coating layers, wherein at least one of the layers wastreated before deposition of a subsequent layer. Preferably, each layer was treated before deposition of the subsequent layer. The layers of coating comprising multiple coating layers may have been subjected to different treatments, in terms of the type of treatment and / or the extent of the treatment. As such, at least one of the layers may comprise two-dimensional material having different functionality to another layer. For example, the layers may comprise a gradient of decreasing reduction level in the two-dimensional material from the top of the coating layer towards the bottom of the coating layer adjacent to the substrate. The gradient may be created in the reverse direction.

[0303] The presence of the gradient may increase the adhesion between the coating andsubstrate, and may also increase the fouling resistance of the overall membrane.

[0304] Treatment of the two-dimensional material on the substrate may cause a change in thefunctional groups of the two-dimensional material, for example changed the number, species and / or distribution of the functional groups. For example, treatment may reduce the two- dimensional material and / or may functionalise the two-dimensional material by adding functionality to the two-dimensional material.

[0305] Treatment of the two-dimensional material thereof to functionalise the two-dimensionalmaterial may add or change the functional groups of the two-dimensional material, for example by reaction with existing hydroxyl, carboxylic and / or epoxide groups of the two-dimensional material. Functionalisation includes covalent modification and non-covalent modification. Covalent modification method can be subcategorised to nucleophilic substitution reaction, electrophilic substitution reaction, condensation reaction, and addition reaction.

[0306] The two-dimensional material may be treated, suitably reduced, by exposing the two-dimensional material to radiation, such as laser radiation, microwave radiation, UV radiation, E – beam radiation, plasma treatment, electron radiation, soft X-ray radiation, gamma radiation, alpha radiation; chemical treatment and / or thermal treatment. Preferably, laser radiation and plasma treatment.

[0307] Chemical, thermal or radiation treatment of the two-dimensional material on the substratecan be used to form chemically reduced GO (CRGO), thermally reduced graphene oxide (TRGO) or radiation reduced graphene oxide (RRGO).

[0308] The hydrophilicity of the treated membrane may be controlled by the functional groups orpolar atom percentage, such as oxygen or nitrogen left at the surface after treatment.

[0309] The pretreatment portion and / or nanofiltration separation portion of the present invention,and / or the concentration portion, may comprise a membrane comprising a porous ceramic member, wherein the porous ceramic member comprises a first support portion operable tosupport a coating and further comprises a second support portion, wherein the second supportportion has a higher D75 average pore size than the D75 average pore size of the first support portion, wherein the second support portion comprises a lattice structure that has a porosity percentage of ≥40%, and wherein the porous ceramic member has a tensile strength operable to withstand feed application pressure of ≥100kPa (1 bar). The membrane comprising a porous ceramic member may further comprise a coating supported on the porous ceramic member, specifically, wherein the coating extends across at least a portion of the first support portion.

[0310] In the present invention, a membrane comprising the porous ceramic member may havethinner walls due to an additively manufactured porous ceramic lattice structure which allows increased packing density of membrane structures, creating more active surface area within the membrane. Thinner membrane walls also lead to less dead-end pores and a less tortuous pathway, increasing flux across the membrane.

[0311] The first support portion may have an average thickness of ≥10 µm, such as ≥20 µm, ≥30µm, ≥40 µm, such as ≥50 µm. The first support portion may have an average thickness of ≤1000 µm, such as ≤800 µm, ≤600 µm, ≤400 µm, such as ≤200 µm. The first support portion may have an average thickness of from between 10 µm to 1000 µm, such as from 20 to 800 µm or from 30 to 600µm, such as 40 to 400 µm or 50 to 200 µm, such as 50 to 150 µm or 50 to 100 µm. The first support portion as referred to herein, may refer to a ceramic surface between the feed inlet side and the permeate outlet side.

[0312] The second support portion may be operable to produce substantially laminar flow towardsa permeate collection point.

[0313] The second support portion may comprise turbulent flow paths. Advantageously, thisallows better homogenisation of fluid content.

[0314] The membrane of the present invention may comprise a feed flow channel, suitably aplurality of feed flow channels, such as a plurality of substantially linear, and optionally substantially parallel feed flow channels. The feed flow channel may be substantially cylindrical.

[0315] The average width / diameter of the feed flow channel may be ≥0.1 mm, such as ≥0.3 mmor ≥0.5 mm. The “width” in the present context is intended to mean the largest lateral dimension of the channel. The average width / diameter of the feed flow channel may be ≤10 mm, such as ≤7 mm or ≤5 mm. The average width / diameter of the feed flow channel may be from 0.1 to 10 mm, such as from 0.3 to 7 mm or from 0.5 to 5 mm.

[0316] The membrane may comprise at least two feed flow channels that are spaced along atleast a portion of their lengths by the first and second support portions, for example spaced by two first support portions with a second support portion arranged between the two first support portions.

[0317] The membrane may comprise a channel pitch, such an average pitch, of ≤14mm, such as≤10mm or ≤7mm. The membrane may comprise a channel pitch, such an average pitch, of ≥0.13mm, such as ≥0.36mm or ≥0.59mm. The membrane may comprise a channel pitch, such an average pitch, of from 0.13mm to 14mm, such as from 0.36mm to 10mm or from 0.59 to 7mm. As used herein, “channel pitch” refers to the distance between two adjacent feed channels as measured from the centre points of the feed channels.

[0318] The membrane may have a membrane packing density, such as a coating packing density,of ≥200 m2 / m3, such as ≥350 m2 / m3, such as ≥500 m2 / m3.

[0319] Packing density may be calculated by any suitable method known to the skilled person. Ingeneral terms: ^^^^^^^ ^^^^^^^ = ^^^^^^^^ ^^^^^^^ ^^^^^^^^^^ ^^^^^^

[0320] For example, when the membrane comprises cylindrical feed flow channels that packingdensity may be calculated as follows; Dimensional measurements are made of: rc = Single channel radius L = Channel length rf = Ceramic filter radius Lf = Ceramic filter length ^= 2 × ^ × ^^^ = ^^×^ × ^^^ C = Channel Circumference Lc = Channel length N = number of channels V = ceramic filter volume

[0321] The feed flow channel may extend into the porous ceramic member, suitably extendthrough the porous ceramic member, such as from one side of the porous ceramic member / membrane to a substantially opposed side of the member / device. The channel may be a cylindrical channel.

[0322] The flow channel may be integrally formed with the first and second support portions. Theflow channel may comprise a channel wall formed at least partially of the first support portion, which may optionally comprise a coating arranged at least partially thereon the internal surface of the channel. The feed flow channel wall may be substantially formed by the first support member, optionally with a coating arranged at least partially thereover. Feed flowing through the channel may be operable to pass through the optional coating and the first support portion to thereby be filtered and form permeate flow through the second support portion and then flow out of the porous ceramic member to a permeate collection point. The second support portion may be shelled to provide a secondary permeate flow path through the porous ceramic member to the permeate collection point.

[0323] A “lattice structure” as referred to herein, means a three-dimensional structure composingone or more repeating unit cells, wherein the cells are interconnected such as to allow for fluid flow to adjacent cells. Triply period surfaces are included as part of the term “lattice”.

[0324] The lattice structure may comprise a unit cell that has a unit cell size of ≥0.01 mm, such as≥0.1 mm, or ≥0.25 mm. The lattice structure may comprise a unit cell that has a unit cell size of ≤10mm, such as ≤7mm, or ≤5 mm.

[0325] The lattice structure may comprise a unit cell having a diamond structure, a cubic structure,a fluorite structure, an octet structure, a Kelvin cell structure, an iso-truss structure, a hex prism diamond structure, a truncated tube structure, a truncated octahedron structure, a Weaire-Phelan structure, a body centred cubic structure, and / or a face centred cubic structure. Optionally, the lattice structure may comprise a unit cell having a TPMS structure selected from a gyroid structure, a schwarz P structure, a schwarz D structure, a schwarz CLP structure, a schwarz H structure, a splitP structure, a neovius structure, or a double gyroid structure.

[0326] The second support portion may comprise a non-uniform lattice structure. Non-uniformlattice refers to a lattice structure where one or more type of unit cell is different from another type of unit cell in the overall lattice structure. Lattice non-uniformity may arise due to one or more different structural features. For example, a difference in the thickness of the lattice struts; a difference in the void space of the lattice unit cells; and / or a difference in the shape of the lattice unit cells.

[0327] The non-uniform lattice may comprise a gyroid structure with a gradient, suitably a lineargradient, changing bias length; a gyroid structure with (linear) gradient changing wall thickness;and / or a diamond lattice structure with (linear) gradient changing strut thickness.

[0328] The porous ceramic member may have a tensile strength operable to withstand feedapplication pressure of ≥0.5 MPa, such as ≥1MPa or ≥2 MPa, optionally, in the range of 2 MPa to 200 GPa. As used herein, “operable to withstand feed application pressure” means that the porous ceramic member is operable to substantially function as required in the membrane at the given pressure substantially without damage to the structure of the porous ceramic member. As used herein, tensile strength was measured using a 3-point bend test.

[0329] A non-uniform lattice may comprise different lattice cell shapes.

[0330] When the second support portion comprises a non-uniform lattice structure, the averagethickness of the second support portion may be from between 10 to 2000 μm.

[0331] Advantageously, a non-uniform lattice can be thicker in only the areas which requirestrength, thus reducing the amount of material used. The thickness also has a direct impact onthe porosity, with thicker areas having a lower porosity and thinner areas having a higher porosity.A higher porosity means more area for liquid to move through, increasing the flux, so having only thickening areas where required, means higher porosity in the overall porous ceramic member.

[0332] The lattice unit cell may be shelled to form an internal hollow structure. At least a portionof the internal structure may form a series of interconnected voids with other shelled unit cells. This internal series of interconnected voids may be operable to provide a further conduit for the permeate to pass through. Advantageously, the interconnecting voids increase the overall porosity of the support portion while maintaining the required strength. The interconnecting voidsmay increase the porosity of the second support portion by about 5 to 15%, such as an increasein porosity of 10%. Suitably, the second support portion may have a porosity percentage of ≥45%, such as ≥50%, or ≥55%. The internal interconnected voids further add to the reduction of material used in the manufacturing of the membrane, reducing the weight and cost.

[0333] The porous ceramic member, the first support portion and / or the second support portionmay be formed from a composition comprising a ceramic material that may comprise alumina, titania, zirconia, silicon carbide, hydroxyapatite, silicates, zeolite, metal oxides, or combinations thereof. The ceramic material may comprise alumina, titania, zirconia, silicon carbide, hydroxyapatite, silicates, zeolite, metal oxides, or combinations thereof. The first and second support portions comprise the same or different ceramic material.

[0334] The composition may comprise further additives. For example, the composition maycomprise a pore forming agent (PFA), such as wheat particles, starch, PMMA, poppy seed and saw dust, a functionalising agent, a nano-material, a metal-organic framework and / or a twodimensional material such as a transition metal dichalcogenide and / or graphene oxide.

[0335] The second support portion may have any suitable D75 average pore size. Preferably, thesecond support portion may be macroporous. The D75 average pore size of the second support portion may be ≥0.1mm, such as ≥0.2 mm, such as ≥0.3 mm, such as ≥0.4 mm. The D75 average pore size of the second support portion may be ≤5 mm, such as ≤4 mm, such as ≤3 mm, such as ≤2 mm, such as ≤1 mm. The D75 average pore size of the second support portion may be from about 0.1 to 5 mm, such as from about 0.2 to 4 mm, such as about 0.3 to 3 mm, such as about 0.4 to 1 mm.

[0336] The first support portion may have any suitable D75 average pore size. The D75 averagepore size of the first support portion may be dictated by the components of the ceramic composition used, and the process of sintering the ceramic composition. The D75 average poresize of the first support portion may be from 0.05 to 20 µm, depending on the application. Forexample, the first support portion D75 average pore size may change depending on whether the application relates to particle-filtration, micro-filtration, nano-filtration, and reverse osmosis- filtration. The first support portion may typically be microporous. Typically, the D75 average poresize of the first support portion may be ≥1 µm, such as ≥2 µm, such as ≥3 µm, such as ≥5 µm.The D75 average pore size of the first support portion may be ≤20 µm, such as ≤15 µm, such as≤10 µm. The D75 average pore size of the first support portion may be from about 1 to 20 µm,such as about 2 to 15 µm, or about 3 to 10 µm.

[0337] The D75 average pore size may be measured according to methods well known to theskilled person, such as by mercury intrusion porosimetry.

[0338] The first support portion may have a porosity percentage of ≥5%, such as ≥10%, such as≥15% porosity. The first support portion may have a porosity percentage of ≤50%, such as ≤40%, typically, ≤35% porosity. The first support portion may have a porosity percentage of between about 5 to 50%, such as 10 to 40%, such as 15 to 35% porosity.

[0339] The second support portion may have a porosity percentage of ≥45%, such as ≥50%, suchas ≥55%, such as ≥60%. The second support portion may have a porosity percentage of ≤80%, such as ≤75%, such as ≤70%. The second support portion may have a porosity percentage of between about 40 to 80%, preferably, about 60 to 80%, such as 70% porosity

[0340] The porosity is a measurement of the void space of a structure wherein the solid volume ofthe structure is divided by the total volume occupied dimensionally by the structure, expressed as a percentage. where Vs is the soild and VT is the total volume.

[0341] The first and second support portions may be integrally formed so as to form a continuousstructure. Suitably, the first and second support portions are integrally formed by additive manufacturing.

[0342] The membrane of the present invention may be produced by:a. additively manufacturing the porous ceramic member to produce the latticestructure of the second support portion and to form the first support portion;b. optionally, removing binder from the first support portion to form pores inthe first support portion; c. optionally, applying a coating to at least a portion of the first supportportion, suitably by coating a coating composition onto the first support portion.

[0343] In step (a) the macrostructure of the first support portion may be formed but the porestructure of the first support portion may be formed in step (b). In such a process, step (a) may be considered to be the formation of the green part. Step (b) may be considered to be a de- binding and / or sintering step.

[0344] Advantageously, the first and / or second support portion may be produced, suitably printed,using an additive manufacturing process, preferably, the first and second support portions are additively manufactured so as to form an integral support structure. The additive manufacturing technique may be any suitable ceramic 3D printing technology. For example, the first and / or second support portion may be printed using binder jet printing, stereolithography, digital light processing, two-photon polymerisation, inkjet printing, direct ink writing, three-dimensional printing, selective laser sintering, selective laser melting, laminated object manufacturing, or fused deposition modelling.

[0345] The additive manufacture of the porous ceramic member provides a membrane with themechanical strength required to support a coating during manufacture and filtration, whilst also balancing the high porosity and increased packing density to provide improved fluid flow during the final filter application.

[0346] In the membrane of the present invention, pressure is used to push the water through thecoating where contaminates are separated out and left in the water feed and uncontaminated water passes through onto the permeate side, where it is pushed through the porous ceramic member towards an exit of the membrane.

[0347] The term “shelled” referred to herein, means hollowed solid parts of a structure with a givenwall thickness.

[0348] The pretreatment portion, a separation portion, such as the first separation portion, thenanofiltration separation portion and / or the concentration portion, may comprise a spiral wound membrane, such as a spiral wound membrane having a component comprising an integrally formed non-uniform lattice structure, wherein the lattice structure comprises a first and second repeating unit cell, wherein the first and second unit cells are different.

[0349] The spiral membrane component may be a feed flow carrier, permeate carrier, a backinglayer or a combined permeate-backing layer.

[0350] The second repeating unit cell may have a different size compared to the first repeatingunit cell.

[0351] The second repeating unit cell may have a different pore size compared to the firstrepeating unit cell.

[0352] The spiral wound membrane may comprise a backing layer component comprising anintegrally formed lattice structure, wherein the lattice structure comprises a repeating unit cell.

[0353] The pore size of the first and / or second unit cell, when present, of the lattice structure maybe ≥10 μm, such as ≥20 μm, such as ≥30 μm. The pore size of the first and / or second unit cell, when present, of the lattice structure may be ≤5 mm, such as ≤4 mm, such as ≤3 mm.

[0354] The pore size of the first and / or second unit cell, when present, of the lattice structure maybe ≥40 μm, such as ≥ 50 μm. The pore size of the first and / or second unit cell, when present, of the lattice structure may be ≤1 mm, such as ≤0.5 mm.

[0355] The second repeating unit cell may have a different strut thickness compared to the firstrepeating unit cell. The average strut thickness of the first and / or second unit cell, when present, of the lattice structure may be ≥10 μm, such as ≥20 μm, such as ≥30 μm. The average strut thickness of the first and / or second unit cell, when present, of the lattice structure may be ≤5 mm, such as ≤4 mm, such as ≤3 mm.

[0356] The average strut thickness of the first and / or second unit cell, when present, of the latticestructure may be ≥40 μm, such as ≥50 μm. The average strut thickness of the first and / or second unit cell, when present, of the lattice structure may be ≤1 mm, such as ≤0.5 mm.

[0357] The average thickness of the component may be ≤850 μm, such as ≤700μm, such as ≤650μm. The average thickness of the component may be ≤600 μm, such as ≤550 μm, such as ≤500μm, such as ≤350 μm, such as ≤250 μm.

[0358] The lattice structure may comprise a higher archival lattice structure.

[0359] The component may be a permeate-backing layer component wherein the averagethickness of the component is ≤120 μm, such as ≤100 μm, such as ≤80 μm, such as ≤50 μm,such as ≤30 μm.

[0360] The component may be operable to provide a Reynolds number (Re) of at least 2300 at aflow rate of between 0 and 1 m / s.

[0361] The component may be operable to function at a transmembrane pressure of 30 bar to 50bar, such as 32 bar to 48 bar, such as 34 bar to 46 bar, 36 bar to 44 bar, 38 bar to 42 bar, suchas when filtering sea water.

[0362] The component may be operable to function at a transmembrane pressure of 3 bar to 15bar, such as 5 bar to 12 bar, such as 6 bar to 9 bar.

[0363] The component may have a packing density of ≥650 m2 / m3, such as ≥750 m2 / m3, such as≥900 m2 / m3.

[0364] The first unit cell and / or second unit cell, when present, may be independently in the formof a diamond, cubic, fluorite, octet, kelvin cell, iso truss, hex prism diamond, truncated cube, truncated octahedron, weaire-phelan, body centered cubic, face centered cubic, or triply periodicminimal surface (TPMS).

[0365] The first unit cell and / or second unit cell, when present, may be independently in the formof a TPMS structure such as Gyroid, Schwarz Primitive, Schwarz Diamond, Schwarz Cross Layers of Parallels, Schwarz Hexagonal, Split P, Neovius, or Double Gyroid.

[0366] A unit cell may comprise the scalar fields of two or more unit cells mixed to produce a newmixed unit cell.

[0367] A unit cell may be shelled to form an internally hollow structure.

[0368] The term “lamellar structure” herein means a structure having at least two overlappinglayers. The term “membrane” herein means a porous barrier operable to assist with theseparation of desired dissolved materials (solutes), colloids or particulates from the feed solutions.It may represent an interface between the feed flow and the permeate flow. The term “two- dimensional material” herein means a material with at least one dimension of less than 100nm.

[0369] The term “higher archival lattice structure” herein means a lattice structure containingstructural elements which are built out of another lattice structure which can continue to be built out of subsequent lattice structure to an nthdegree.

[0370] Turbulence is measured by the Reynolds number (Re):

[0371] Wherein ^ is the density of the fluid, u is the flow speed, L is the characteristic lineardimension, and ^ is the dynamic viscosity of the fluid.

[0372] The apparatus / process may comprise carbonation, polishing and / or bipolar electrodialysis(BPED), such as of the (refined / concentrated) product solution.

[0373] The target monovalent ion product of the apparatus / process of the present invention maybe uses in the production of battery grade lithium.

[0374] The apparatus / process may also allow for significant reduction of CO2 emission, landusage, water usage and / or production cycle compared to current methods of separation and purification.

[0375] The term ‘brine’ as used herein may mean an aqueous solution of a salt.

[0376] The term ‘nanofiltration’ as used herein may refer to a separation technique that utilises amembrane to separate different components within a fluid mixture. The pore size of the nanofiltration membrane may be from 1 to 100 nm.

[0377] For the purpose of the present invention, an aliphatic group is a hydrocarbon moiety thatmay be straight chain (i.e. unbranched), branched, or cyclic and may be completely saturated, or contain one or more units of unsaturation, but which is not aromatic. The term “unsaturated” means a moiety that has one or more double and / or triple bonds. The term “aliphatic” is therefore intended to encompass alkyl, cycloalkyl, alkenyl cycloalkenyl, alkynyl or cycloalkenyl groups, and combinations thereof. The term “(hetero)aliphatic” encompasses both an aliphatic group and / or a heteroaliphatic group.

[0378] An aliphatic group is optionally a C1-30 aliphatic group, that is, an aliphatic group with 1, 2,3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 carbon atoms. Optionally, an aliphatic group is a C1-15 aliphatic, optionally a C1-12 aliphatic, optionally a C1-10 aliphatic, optionally a C1-8 aliphatic, such as a C1-6aliphatic group. Suitable aliphatic groups include linear or branched, alkyl, alkenyl and alkynyl groups, and mixtures thereof such as (cycloalkyl)alkyl groups, (cycloalkenyl)alkyl groups and (cycloalkyl)alkenyl groups.

[0379] The term "alkyl," as used herein, refers to saturated, straight- or branched-chainhydrocarbon radicals derived by removal of a single hydrogen atom from an aliphatic moiety. An alkyl group is optionally a “C1-20 alkyl group”, that is an alkyl group that is a straight or branched chain with 1 to 20 carbons. The alkyl group therefore has 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 carbon atoms. Optionally, an alkyl group is a C1-15 alkyl, optionally a C1-12 alkyl, optionally a C1-10 alkyl, optionally a C1-8 alkyl, optionally a C1-6 alkyl group. Specifically, examples of “C1-20 alkyl group“ include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, sec-pentyl, iso-pentyl, n- pentyl group, neopentyl, n-hexyl group, sec-hexyl, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n- pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-eicosyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group, 1-ethylpropyl group, n-hexyl group, 1-ethyl-2-methylpropyl group, 1,1,2-trimethylpropyl group, 1-ethylbutyl group, 1-methylbutyl group, 2-methylbutyl group, 1,1-dimethylbutyl group, 1,2- dimethylbutyl group, 2,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,3-dimethylbutyl group, 2-ethylbutyl group, 2-methylpentyl group, 3-methylpentyl group and the like.

[0380] The term "alkenyl," as used herein, denotes a group derived from the removal of a singlehydrogen atom from a straight- or branched-chain aliphatic moiety having at least one carbon-carbon double bond. The term "alkynyl," as used herein, refers to a group derived from theremoval of a single hydrogen atom from a straight- or branched-chain aliphatic moiety having at least one carbon-carbon triple bond. Alkenyl and alkynyl groups are optionally “C2-20alkenyl” and “C2-20alkynyl”, optionally “C2-15 alkenyl” and “C2-15 alkynyl”, optionally “C2-12 alkenyl” and “C2-12 alkynyl”, optionally “C2-10 alkenyl” and “C2-10 alkynyl”, optionally “C2-8 alkenyl” and “C2-8 alkynyl”, optionally “C2-6 alkenyl” and “C2-6 alkynyl” groups, respectively. Examples of alkenyl groups include ethenyl, propenyl, allyl, 1,3-butadienyl, butenyl, 1-methyl-2-buten-1-yl, allyl, 1,3-butadienyl and allenyl. Examples of alkynyl groups include ethynyl, 2-propynyl (propargyl) and 1-propynyl.

[0381] The terms "cycloaliphatic", "carbocycle", or "carbocyclic" as used herein refer to a saturatedor partially unsaturated cyclic aliphatic monocyclic or polycyclic (including fused, bridging and spiro-fused) ring system which has from 3 to 20 carbon atoms, that is an alicyclic group with 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 carbon atoms. Optionally, an alicyclic group has from 3 to 15, optionally from 3 to 12, optionally from 3 to 10, optionally from 3 to 8 carbon atoms, optionally from 3 to 6 carbons atoms. The terms "cycloaliphatic", "carbocycle" or "carbocyclic" also include aliphatic rings that are fused to one or more aromatic or nonaromatic rings, such as tetrahydronaphthyl rings, where the point of attachment is on the aliphatic ring. A carbocyclic group may be polycyclic, e.g. bicyclic or tricyclic. It will be appreciated that the alicyclic group may comprise an alicyclic ring bearing one or more linking or non-linking alkyl substituents, such as –CH2-cyclohexyl. Specifically, examples of carbocycles include cyclopropane, cyclobutane, cyclopentane, cyclohexane, bicyclo[2,2,1]heptane, norborene, phenyl, cyclohexene, naphthalene, spiro[4.5]decane, cycloheptane, adamantane and cyclooctane.

[0382] A heteroaliphatic group (including heteroalkyl, heteroalkenyl and heteroalkynyl) is analiphatic group as described above, which additionally contains one or more heteroatoms. Heteroaliphatic groups therefore optionally contain from 2 to 21 atoms, optionally from 2 to 16 atoms, optionally from 2 to 13 atoms, optionally from 2 to 11 atoms, optionally from 2 to 9 atoms, optionally from 2 to 7 atoms, wherein at least one atom is a carbon atom. Optional heteroatoms are selected from O, S, N, P and Si. When heteroaliphatic groups have two or more heteroatoms, the heteroatoms may be the same or different. Heteroaliphatic groups may be substituted or unsubstituted, branched or unbranched, cyclic or acyclic, and include saturated, unsaturated or partially unsaturated groups.

[0383] An alicyclic group is a saturated or partially unsaturated cyclic aliphatic monocyclic orpolycyclic (including fused, bridging and spiro-fused) ring system which has from 3 to 20 carbon atoms, that is an alicyclic group with 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 carbon atoms. Optionally, an alicyclic group has from 3 to 15, optionally from 3 to 12, optionally from 3 to 10, optionally from 3 to 8 carbon atoms, optionally from 3 to 6 carbons atoms. The term “alicyclic” encompasses cycloalkyl, cycloalkenyl and cycloalkynyl groups. It will be appreciated that the alicyclic group may comprise an alicyclic ring bearing one or more linking or non-linking alkyl substituents, such as –CH2-cyclohexyl. Specifically, examples of the C3-20 cycloalkyl group include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, adamantyl and cyclooctyl.

[0384] An aryl group or aryl ring is a monocyclic or polycyclic ring system having from 5 to 20carbon atoms, wherein at least one ring in the system is aromatic and wherein each ring in the system contains three to twelve ring members. An aryl group is optionally a “C6-12 aryl group” and is an aryl group constituted by 6, 7, 8, 9, 10, 11 or 12 carbon atoms and includes condensed ring groups such as monocyclic ring group, or bicyclic ring group and the like. Specifically, examplesof “C6-10 aryl group” include phenyl group, biphenyl group, indenyl group, anthracyl group,naphthyl group or azulenyl group and the like. It should be noted that condensed rings such as indan, benzofuran, phthalimide, phenanthridine and tetrahydro naphthalene are also included in the aryl group.

[0385] As used herein, unless otherwise expressly specified, all numbers such as thoseexpressing values, ranges, amounts or percentages may be read as if prefaced by the word"about", even if the term does not expressly appear. The term “about” when used herein means+ / - 10% of the stated value.

[0386] Singular encompasses plural and vice versa. For example, although reference is madeherein to "a" pretreated portion, “a” nanofiltration membrane, and the like, one or more of each ofthese and any other components can be used.

[0387] As used herein, the terms "on", "applied on / over", “extend over”, "formed on / over" and"provided on / over" mean formed or provided on but not necessarily in contact with the surface. For example, a coating "formed over" a substrate does not preclude the presence of another coating of the same or different composition located between the formed coating and the substrate.”

[0388] The terms "comprising" and "comprises" as used herein are synonymous with "including"or "containing" and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. Additionally, although the present invention has been described in terms of “comprising”, the apparatus detailed herein may also be described as “consisting essentially of” or “consisting of”.

[0389] Also, any numerical range recited herein is intended to include all sub-ranges subsumedtherein. Singular encompasses plural and vice versa.

[0390] As used herein, the term "polymer" refers to oligomers and both homopolymers andcopolymers, and the prefix "poly" refers to two or more. Including, for example and like terms means including for example but not limited to.

[0391] Additionally, although the present invention has been described in terms of “comprising”,the processes, materials, and compositions detailed herein may also be described as “consisting essentially of” or “consisting of”.

[0392] When used herein, “average” refers to mean average, unless otherwise provide for.

[0393] Where ranges are provided in relation to a genus, each range may also apply additionallyand independently to any one or more of the listed species of that genus.

[0394] All of the features contained herein may be combined with any of the above aspects in anycombination.

[0395] For a better understanding of the invention, and to show how aspects of the same may becarried into effect, reference will now be made, by way of example, to the following experimental data and figures. EXAMPLES

[0396] Figure 1 shows the lithium extraction process of the present invention in a wider context,contained within the initial stages of brine water extraction, heat exchange and possible energy generation that can be fed into the extraction process, and followed by downstream processingthat may include carbonation and polishing or bipolar electrodialysis (BPED), and the possibleuse in the production of battery grade lithium. Stage 3 may be the concentration stage and involveuse of forward osmosis (FO), electrodialysis, and / or reverse osmosis (RO)and / or a membranecomprising a porous ceramic member as defined herein. Optionally a further separation portionmay be used to further reduce the concentration of divalent ions after the adsorption stage.Nanofiltration membraneCoating formulations

[0397] A three-part, aqueous coating formulation was prepared by dissolving A) 10g of dopaminehydrochloride in 4L of deionized water, B) 10g of polyethyleneimine (600Da Mw) in 3L of deionized water and C) 10g of sodium periodate in 3L of deionized water. Production of coated spiral-wound nanofiltration membrane

[0398] A spiral-wound polyamide thin-film composite nano-filtration membrane was used as thesubstrate. The membrane was installed into a suitable housing and attached to a Alfa Laval M20cross-flow filtration system.

[0399] Prior to coating, the three components of the coating formulation A, B and C were combinedin a container to begin an oxidative polymerization / cross-linking reaction. The resulting solutionwas added to the feed tank of the Alfa Laval M20 cross-flow filtration system and was circulatedthrough the membrane for a period of 1 hour at a flow rate of 5 L / min. No additional pressure was applied to the system during this time.

[0400] After the coating period had finished, the membrane was flushed with a sufficient volumeof deionized water until the effluent was deemed to be colourless. The coated membrane was uninstalled from the housing and allowed to drain of excess water for a period of 1 hour. Examples 1-3 Processing of source solution feed through nanofiltration membrane separation portion

[0401] A feed tank of Alfa Laval M20 cross-flow filtration system was filled with 40L of therespective source aqueous solution brine feed A-C.

[0402] The coated spiral-wound nanofiltration membrane was installed in the appropriate housingon the Alfa Laval M20 cross-flow filtration system.

[0403] The source solutions were passed through the membrane at a flow rate of 20 L / min and apressure of 20 Bar. The filtration was run in a concentrate mode. Permeate streams were collected in a separate permeate tank and the membrane retentate was recirculated back to the feed tank until such a time that the feed volume was not sufficient to run the system.

[0404] During the cross-flow filtration testing, permeate flux was monitored by collecting thepermeate in a beaker on a weight balance connected with a data logger. Rejection was calculated based on concentration of different ions in permeate and feed tank monitored by inductively coupled plasma optical emission spectrometry (ICP-OES) and ion chromatography (IC). Processing of intermediate aqueous solution through adsorbent separation portion

[0405] The permeate collected from the nanofiltration membrane stage was used as theintermediate aqueous solution feed for the adsorbent stage.

[0406] LI-10A (available from Sunresin) was used as the adsorbent separation portion (adsorbentisolation portion).

[0407] 7 bed volumes (or BV, where bed volume is the volume of space in the column occupiedby the sorbent) of the intermediate aqueous solutions were transferred into columns containing the sorbent and the flowrates were controlled by a valve to obtain a flow rate of 3 BV / hr through the cross-section of the columns.

[0408] Effluent was collected at an interval of 0.5 and the compositions were monitored by ICP-OES.

[0409] 6.5 BV of deionized water was passed through the columns at a flow rate of 5 BV / hr inorder to strip the resins of the absorbed lithium. Effluent was again collected at an interval of 0.5 BV and the compositions were monitored by ICP-OES. Example 4 Processing of source solution feed through nanofiltration membrane separation portion

[0410] A feed tank of S67 cross-flow filtration system was filled with 3.843m3 of the sourceaqueous solution brine feed D.

[0411] The coated spiral-wound nanofiltration membranes were installed in the appropriatehousing on the S67 cross-flow filtration system.

[0412] The source solution was passed through the membranes at a flow rate of 18m3 / hr and apressure of 30 Bar. The filtration was run in a concentrate mode. Permeate streams werecollected in a separate permeate tank and the membrane retentate streams were recirculatedback to the feed tank until such a time that the feed volume was not sufficient to run the system.

[0413] During the cross-flow filtration testing, permeate flux was monitored using flowmeters.Rejection was calculated based on concentration of different ions in permeate and feed tank monitored by inductively coupled plasma optical emission spectrometry (ICP-OES) and ion chromatography (IC). Processing of intermediate aqueous solution through adsorbent separation portion

[0414] The permeate collected from the nanofiltration membrane stage was used as theintermediate aqueous solution feed for the adsorbent stage.

[0415] LI-10A (available from Sunresin) was used as the adsorbent separation portion (adsorbentisolation portion).

[0416] 4.6 bed volumes (or BV, where bed volume is the volume of space in the column occupiedby the sorbent) of the intermediate aqueous solutions were transferred into columns containingthe sorbent and the flowrates were controlled by a valve to obtain a flow rate of 4 BV / hr throughthe cross-section of the columns. Effluent was collected at an interval of 0.8 BV and the compositions were monitored by ICP-OES.

[0417] Out of the 4.6 BV operation, the last 0.6 BV of intermediate aqueous solutions was pushedby 0.6 BV deionized water through the columns at a flow rate of 4 BV / hr .

[0418] 6.6 BV of deionized water was passed through the columns at a flow rate of 4 BV / hr inorder to strip the resins of the absorbed lithium. Effluent was again collected at an interval of 0.8 BV and the compositions were monitored by ICP-OES.

[0419] Out of the 4.6 BV operation, the last 0.6 BV of deionized water was pushed by 0.6 BVintermediate aqueous solution feed through the columns at a flow rate of 4 BV / hr . Comparative Examples 1-4 Processing of source solution feed through adsorbent separation portion

[0420] For Comparative Examples 1-4 the respective source solution A-D was feed directlythrough the adsorbent stage (i.e without a nanofiltration stage) in the manner as described above for Examples 1-4 for the intermediate solution.

[0421] Test results are shown in Table 1 below and in Figures 2 to 5. Table 1: Results Reduction in Reduction in Li in Other Purity divalent ions monova Feed Type influent monovalents Divalent lent Influent to s TDS of in influen Overall Li of Li in due to ions due to adsorbent (ppm) in influent t influent recovery* effluent membrane membrane (ppm) (ppm) (ppm) ** treatment treatment (concentration) (concentration)Comp. Ex.1 Raw Feed A Feed 120 15,323 8,889 63,690Product 56 963 658 4,292 39% 3% NA NAExample 1 Membrane-Feed 98 10,074 1,248 29,357treated Feed AProduct 61 404 81 1,606 51% 11% 88% 58%Comp. Ex.2 Raw Feed B Feed 1,245 61,213 6,998 182,327Product 183 3,783 489 12,115 12% 4% NA NAExample 2 Membrane-Feed 1,156 52,714 2,342 143,025treated Feed BProduct 155 828 68 3,173 11% 14% 86% 78%Comp. Ex.3 Raw Feed C Feed 247 6,908 2,759 26,468Product 78 516 170 2,127 26% 10% NA NAExample 3 Membrane-Feed 177 4,621 235 13,310treated Feed CProduct 72 358 14 1,291 33% 16% 92% 31%Comp. Ex 4 Raw Feed D Feed 315 49,307 38,309 229,904Product 264 3,477 3,281 19,346 98% 4% NA NAExample 4 Membrane-Feed 439 64,026 29,723 243,564treated Feed DProduct 305 3,868 2,119 17,332 97% 5% 35% -11%*mass of Li desorbed / mass of Li in the influent. **concentration of Li in product / (sum of concentrations of all cations in product)

[0002]

[0422] All of the features disclosed in this specification (including any accompanying claims,abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive.

[0423] Each feature disclosed in this specification (including any accompanying claims, abstractand drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0424] The invention is not restricted to the details of the foregoing embodiment(s). The inventionextends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0425] The following clauses further reflect or emphasise aspects of the present disclosure thatmay be supplementary to or independent of the invention, but which fall within the totality of the disclosed inventive contribution. CLAUSES:1. An apparatus for reducing the ratio of divalent ions, such as divalent cations, to a targetmonovalent ion, such as a target monovalent cation, in an aqueous solution from a source aqueous solution that contains a higher ratio of divalent ions to the target monovalent ion,the apparatus comprising optionally, a pretreatment portion operable to receive the source aqueous solution and produce a pretreated source aqueous solution; a first separation portion operable to receive an optionally pretreated aqueous solution and form an intermediate aqueous solution having a lower ratio of divalent ions to the monovalent ion than the optionally pretreated aqueous solution; and an adsorbent separation portion operable to receive the intermediate aqueous solution and form a product aqueous solution having a lower ratio of the divalent ions to the monovalent ion than the intermediate solution.2. An apparatus according to clause 1, wherein the apparatus comprises a pretreatment portionthat comprises a prefiltration portion, a chemical precipitation portion, a settling tank portion, and / or a centrifuge portion, optionally wherein the prefiltration portion comprises microfiltration or ultrafiltration membrane; a strainer and / or a filter.3. An apparatus according to clause 2, wherein the apparatus comprises a prefiltration portionhaving a mean average pore size of up to 100 µm, such as up to 75 µm or up to 50 µm, and / or a prefiltration portion comprising a membrane having a mean average pore size of at least 200 nm, such as at least 500 nm, or at least 5 µm.An apparatus according to any of clauses 2 to 3, wherein the apparatus comprises aprefiltration portion comprising a first and a second separation portion, wherein the firstportion has a mean average pore size that is larger than the mean average pore size of the second portion.An apparatus according to any of clauses 2 to 4, wherein the apparatus comprises aprefiltration portion comprising a membrane with a total suspended solids rejection of ≥90 %,such as ≥95% or ≥99%, and / or a prefiltration portion comprising a membrane with a rejectionrate for the target monovalent ion of ≤5%, such as ≤2% or ≤1%.An apparatus according to any preceding clause, wherein the first separation portioncomprises a nanofiltration separation portion, such as comprising a nanofiltration membrane;electrodialysis cell comprising a membrane; and / or a metal-organic framework (MOF)membrane.An apparatus according to any preceding clause, wherein the first separation portioncomprises a nanofiltration separation portion.An apparatus according to clause 7, wherein the nanofiltration separation portion comprisesa nanofiltration membrane.An apparatus according to any preceding clause, wherein the first separation portioncomprises a membrane, such as a nanofiltration membrane, having mean average pore sizeof ≤10 nm, such as ≤5 nm or ≤2 nm, and / or the first separation portion comprises amembrane, such as a nanofiltration membrane, having a mean average pore size of ≥0.1nm, such as ≥0.2 nm or ≥0.5 nm.An apparatus according to any preceding clause, wherein the first separation portioncomprises a membrane, such as a nanofiltration membrane, with a divalent ion rejection of≥60%, such as ≥ 70% or ≥90%, and / or the first separation portion comprises a membrane,such as a nanofiltration membrane, with a divalent ion rejection of ≤99%, such as ≤98% or ≤95%.An apparatus according to any preceding clause, wherein the first separation portioncomprises a membrane, such as a nanofiltration membrane, with a rejection rate for thetarget monovalent ion of ≤50%, such as ≤20% or ≤5%.An apparatus according to any preceding clause, wherein the prefiltration portion and / or thefirst separation portion comprises a membrane, such as a nanofiltration membrane, thatcomprises a polymer membrane, such as comprising polysulfone, polyethersulfone, and / or polyvinylidene fluoride; a ceramic membrane, such as comprising aluminium oxide, titanium dioxide, and / or zirconium dioxide; a metal membrane, such as comprising carbon steel, galvanised steel, stainless steel, aluminium, and / or copper; or a combination thereof, such as a composite membrane comprising a polymeric composite, a ceramic composite, and / or a metallic composite.An apparatus according to any preceding clause, wherein the prefiltration portion and / or firstseparation portion comprises a membrane, such as a nanofiltration membrane, comprising polyamide; polyester, such as polyethylene terephthalate (PET); and / or, poly(ether) sulfone (PES).An apparatus according to any preceding clause, wherein the prefiltration portion and / or firstseparation portion comprises a membrane, such as a nanofiltration membrane, that comprises a polyethylene terephthalate-based (PET) membrane, such as poly(ether) sulfone (PES) and / or polyethylene terephthalate / polypropylene.An apparatus according to any preceding clause, wherein the first separation portioncomprises a membrane, such as a nanofiltration membrane, that comprises a spiral woundmembrane, a tubular membrane, a hollow fibre membrane and / or a flat sheet membrane.An apparatus according to any preceding clause, wherein the first separation portioncomprises a membrane, such as a nanofiltration membrane, that comprises a spiral woundmembrane.An apparatus according to any preceding clause, wherein the apparatus comprises meansoperable to recirculate the retentate stream of the membrane of the first separation portion,such as a nanofiltration separation portion, back to the inlet of the membrane of the firstseparation portion.An apparatus according to any preceding clause, wherein the adsorbent separation portionhas a higher affinity for the target monovalent ion than the divalent cations and / or a higheraffinity for the target monovalent ion than other monovalent ions.An apparatus according to any preceding clause, wherein the adsorbent separation portionis substantively selective for lithium ions.An apparatus according to any preceding clause, wherein the adsorbent separation portioncomprise an inorganic adsorbent, such as comprises an inorganic crystalline solid, inorganicpolycrystalline solid, inorganic polymorphic solid, and / or inorganic polymorphous solid.An apparatus according to any preceding clause, wherein the adsorbent separation portioncomprises an inorganic crystalline solid comprising aluminium oxide, activated alumina,and / or aluminium hydroxide.An apparatus according to any preceding clause, wherein the adsorbent separation portioncomprises an inorganic adsorbent material comprising target monovalent ion aluminate,such as comprising the target monovalent ion, aluminum atoms, oxygen atoms, and at least one anionic species X selected from halide (fluoride, chloride, bromide, or iodide), nitrate, sulfate, carbonate, and / or bicarbonate.An apparatus according to any preceding clause, wherein the adsorbent separation portioncomprises an inorganic adsorbent comprising a metal hydroxide, such as an aluminumhydroxide (AlOH) or derivative thereof, such as an aluminum trihydroxide, such as gibbsite, bayerite, and / or nordstrandite.An apparatus according to any preceding clause, wherein the adsorbent separation portioncomprises an inorganic adsorbent comprising an aluminum hydroxide-containing material,such as an aluminum hydroxide-containing zeolite.An apparatus according to any preceding clause, wherein the adsorbent separation portioncomprises an inorganic adsorbent comprising a layered inorganic material.An apparatus according to any preceding clause, wherein the adsorbent separation portioncomprises a target monovalent ion aluminate intercalate, such as a lithium aluminateintercalate.An apparatus according to any preceding clause, wherein the adsorbent separation portioncomprises an inorganic adsorbent comprising a two-dimensional (2D) layered inorganicmaterial.An apparatus according to any preceding clause, wherein the adsorbent separation portioncomprises an inorganic adsorbent comprising a layered metal hydroxide, such as a layeredmetal double hydroxide, such as comprising an intercalated layered structure comprisingmetal cations, hydroxide anions, and intercalated anions, and may be comprise water and / or hydrates.An apparatus according to any preceding clause, wherein the adsorbent separation portioncomprises a layered metal double hydroxide comprising first and second layers comprising metal cations and hydroxide ions with an intercalating layer arranged between the first anda second layers, optionally wherein the intercalating layer comprises an anion or neutralmolecule, such as a water molecule, wherein the layered metal double hydroxide inorganic adsorbent may comprise a plurality of repeating first and second intercalated layers.An apparatus according to any preceding clause, wherein the adsorbent separation portioncomprises a layered metal double hydroxide comprising metal cations wherein the metalcations comprise monovalent and / or divalent metal cations such as lithium and / or aluminium, optionally the metal cations of the layered metal double hydroxide may comprise the target monovalent ions.An apparatus according to any preceding clause, wherein the adsorbent separation portioncomprises a lithium-incorporated aluminum hydroxide (LIAH).An apparatus according to any preceding clause, wherein the adsorbent separation portioncomprises a lithium-incorporated layered hydroxide, such as a lithium-incorporated layereddouble hydroxide.An apparatus according to any preceding clause, wherein the adsorbent separation portioncomprises a lithium-incorporated aluminum hydroxide according to formula (I):LiX. ^Al(OH)^. ^H^O(I) wherein: X is a monovalent anion, such as fluoride, chloride, bromide, and / or iodide, preferably chloride; and mis from 1.2 to 3.0; andn is from 0.2 to 5.0.An apparatus according to any preceding clause, wherein the adsorbent separation portioncomprises a layered lithium aluminum double hydroxide.An apparatus according to any preceding clause, wherein the adsorbent separation portioncomprises a carrier, such as a solid carrier, such as a solid carrier in which an inorganicadsorbent is dispersed.An apparatus according to any preceding clause, wherein the adsorbent separation portioncomprises a carrier comprising a polyvinyl alcohol, methacrylate, phenol, synthetic polymer,polysaccharide, biopolymer, polysilicate, metal organic framework (MOF), alginate, biochar, carbonaceous ore, clay, graphene and / or nanotube.An apparatus according to any preceding clause, wherein the adsorbent separation portioncomprises a carrier comprising an organic polymer, such as an organic polymer matrix.An apparatus according to any preceding clause, wherein the prefiltration separation portionand / or first separation portions, such as a nanofiltration separation portion, comprises amembrane, such as a nanofiltration membrane, that comprises a membrane substrate anda coating extending over at least a part of the membrane substrate.An apparatus according to clause 38, wherein the coating comprises a hydrophilic agent.An apparatus according to clause 38 or 39, wherein the coating comprises a hydrophilicagent and a superhydrophilic agent.An apparatus according to any of clauses 38 to 40, wherein the coating comprises a firstcoating layer comprising a hydrophilic agent and a second coating layer comprising a superhydrophilic agent.An apparatus according to any of clauses 38 to 41, wherein the coating is at least partiallycrosslinked and comprises a superhydrophilic agent.An apparatus according to any of clauses 38 to 42, wherein the coating is formed from acoating composition comprising the hydrophilic agent or precursor thereof.An apparatus according to any of clauses 38 to 43, wherein the membrane substrate is apre-treated substrate, such as a membrane substrate that has been subjected to hydrophilisation to form a hydrophilic surface.An apparatus according to any of clauses 38 to 44, wherein membrane substrate comprisesa hydrophilic material.An apparatus according to any of clauses 38 to 45, wherein the hydrophilic agent comprisesa (co)polymer or oligomer formed from a reaction mixture comprising a phenol and a polyamine, and / or a derivative thereof.An apparatus according to clause 46 wherein the phenol or derivative thereof comprisesdopamine, tannic acid, vanillyl alcohol, eugenol, morin, and / or quercetin.An apparatus according to clause 46 or 47, wherein the phenol or derivative thereofcomprises dopamine.An apparatus according to any of clauses 46 to 48, wherein the polyamine or derivativethereof comprises polyethylenimine or polyallylamine.An apparatus according to any of clauses 46 to 49, wherein the polyamine or derivativethereof comprises polyethylenimine.An apparatus according to any of clauses 46 to 50, wherein the reaction mixture comprisesa phenol and a polyamine, and / or a derivative thereof, in a ratio of from 5:1 to 1:5.An apparatus according to any of clauses 46 to 51, wherein the reaction mixture comprisesa phenol and a polyamine, and / or a derivative thereof, in a ratio of from 3:1 to 1:3.An apparatus according to any of clauses 46 to 52, wherein the polyamine or derivativethereof has a molecular weight of at least 200 Da, such as at least 300 Da, such as at least 400 Da or at least 500 Da.An apparatus or separation portion according to any of clauses 46 to 53, wherein thepolyamine or derivative thereof has a molecular weight of up to 25,000 Da or up to 10,000 Da.An apparatus according to any of clauses 46 to 54, wherein the reaction mixture comprisesan oxidant, such as sodium periodate, potassium persulfate, sodium persulfate, ammonium persulfate, ferric chloride, hydrogen peroxide and / or copper sulphate.An apparatus according to any of clauses 46 to 55, wherein the coating comprising ahydrophilic agent has an average thickness of 1 to 1000 nm, or from 5 to 500 nm, such as from 5 to 200 nm.An apparatus according to any preceding clause, wherein the prefiltration portion and / or aseparation portion, such as the first separation portion or a nanofiltration separation portion,comprises a membrane comprising a porous ceramic member, wherein the porous ceramic member comprises a first support portion operable to support a coating and further comprises a second support portion, wherein the second support portion has a higher D75average pore size than the D75 average pore size of the first support portion, wherein thesecond support portion comprises a lattice structure that has a porosity percentage of ≥40%, and wherein the porous ceramic member has a tensile strength operable to withstand feed application pressure of ≥100kPa (1 bar).An apparatus according to any preceding clause, wherein the prefiltration portion and / or aseparation portion, such as the first separation portion or a nanofiltration separation portion,comprises a spiral wound membrane having a component comprising an integrally formed non-uniform lattice structure, wherein the lattice structure comprises a first and second repeating unit cell, wherein the first and second unit cells are different.An apparatus according to any preceding clause, wherein the apparatus, such as theadsorbent separation portion, is further operable to reduce the ratio of a different type ofmonovalent ion to a target monovalent ion.An apparatus according to any preceding clause, wherein the apparatus comprises meansto extract the target monovalent ion as eluent from the adsorbent separation portion.An apparatus according to clause 60, wherein the means to extract the target monovalention as eluent from the adsorbent separation portion comprises means to contact the adsorbent separation portion with an aqueous strip solution having a pH of from 6.0 to 8.0, such as from 6.5 to 7.5, such as from 6.9 to 7.1.The apparatus of the any preceding clause, wherein the apparatus may comprise a furtherseparation portion operable to receive the product aqueous solution and form a furtherrefined product aqueous solution having a lower ratio of the divalent ions to the targetmonovalent ion.An apparatus according to any previous clause, wherein the apparatus comprises aconcentration portion operable to receive the (refined) product aqueous solution and reduce the water content of the solution so as to produce a concentrated product aqueous solution.An apparatus according to clause 63, wherein the concentration portion is operable toreceive the refined product aqueous solution.An apparatus according to clause 63 or 64, wherein the concentration portion comprises areverse osmosis membrane, forward osmosis, electrodialysis, and / or a membrane comprising a porous ceramic member as defined herein.A process for reducing the ratio of divalent ions, such as divalent cations, to a targetmonovalent ion in an aqueous solution, comprising:a. optionally, contacting a source aqueous solution comprising the divalent ions andthe target monovalent ion with a pretreatment portion according to any of clauses1 to 65; b. contacting the optionally pretreated aqueous solution with a first separationportion according to any of clauses 1 to 65 to form an intermediate aqueoussolution having a lower ratio of the divalent ions to the target monovalent ion than the optionally pretreated aqueous solution;c. contacting the intermediate solution with an adsorbent separation portionaccording to any of clauses 1 to 65 to form a product aqueous solution having a lower ratio of the divalent ions to the target monovalent ion than in the intermediate solution.A process according to clause 66, wherein the first separation portion comprises ananofiltration separation portion comprising a nanofiltration membrane.A process or apparatus according to any preceding clause, wherein the source aqueoussolution comprises a geothermal brine, such as a geothermal brine obtained from a deep geothermal source.A process or apparatus according to any preceding clause, wherein the source aqueoussolution comprises a shallow geothermal brine.A process or apparatus according to any preceding clause, wherein the source aqueoussolution comprises a seawater brine, saline lake brine, produced water, and / or leachate from recycled batteries.A process or apparatus according to any preceding clause, wherein the divalent ion of thesource solution, prefiltered source solution, intermediate source solution and / or productsource solution is a divalent cation, and wherein one or more of the solutions optionallycomprises trivalent cations, and wherein the divalent cation and optional trivalent cation are optionally selected from Ca, Mg, B, Ba, Fe, Mn, Zn, Mo, Sr, Zr, V, Cr, Te, Ti, Ga, Hg, Be, In, Ta, Ce, Hf, Sm, La, Nb, Th, Al, Tl, As, Ni, Cu, Sc, Sn, Sb, Co, Pb, U, Cd, Y and / or Bi, such as Ca, Mg, Sr and / or B.A process or apparatus according to any preceding clause, wherein the target monovalention is a cation, such as Na, K, Li, Cs, Rb, W, Au and / or Ag.A process or apparatus according to any preceding clause, wherein the target monovalention is a metal cation.A process or apparatus according to any preceding clause, wherein the target monovalentcation comprises Li, W, Au, Ag, Na and / or K.A process or apparatus according any preceding clause, wherein the target monovalentcation comprises Li, W, Au and / or Ag.A process or apparatus according to any preceding clause, wherein the target monovalentcation comprises Li.A process or apparatus according to any preceding clause, wherein the target monovalention is an anion, wherein the target monovalent anion optionally comprises Cl, F, Br, SO4,HCO3, and / or CO3, or Cl and / or SO4.A process or apparatus according to any preceding clause, wherein the divalent cationcomprises Ca and / or Mg.A process or apparatus according to any preceding clause, wherein the source aqueoussolution comprises total suspended solids in an amount of ≥1 ppm, such as ≥5 ppm or ≥20ppm and / or the source aqueous solution comprises total suspended solids in an amount of≤2,000 ppm, such as ≤1,500 ppm or ≤1,000 ppm, or ≤500ppm.A process or apparatus according to any preceding clause, wherein the source solutioncomprises the divalent ions in an amount of ≤60,000 ppm, such as ≤55,000 ppm or ≤50,000ppm and / or the source solution comprises the divalent ions in an amount of ≥100 ppm, suchas ≥200 ppm or ≥500 ppm.A process or apparatus according to any preceding clause, wherein the source solutioncomprises the target monovalent ion in an amount of ≥10 ppm, such as ≥20 ppm or ≥50 ppm.A process or apparatus according to any preceding clause, wherein the source solutioncomprises the target monovalent ion in an amount of ≥100 ppm, such as ≥200 ppm or ≥500ppm.A process or apparatus according to any preceding clause, wherein the source solutioncomprises a ratio of the divalent ions to the target monovalent ion of <6000:1, such as<5000:1, such as <4000:1, such as <3000:1, such as <2500:1, or such as <2000:1.A process according to any of clauses 66 to 83, wherein the source aqueous solution iscontacted with the pretreatment portion at a temperature of ≥5 °C, such as ≥25°C and / orthe source aqueous solution is contacted with the pretreatment separation portion at atemperature of ≤250°C, such as ≤150°C or ≤70°C.A process according to any of clauses 63 to 84, wherein the source aqueous solution iscontacted with the membrane of the pretreatment portion at a transmembrane pressure of ≥0.1 bar, such as ≥0.5 bar and / or the source aqueous solution is contacted with the membraneof the pretreatment portion at a transmembrane pressure of ≤5 bar, such as ≤3 bar, such as≤2bar, such as ≤1.5bar.A process or apparatus according to any preceding clause, wherein the pretreated solutioncomprises the divalent ions in an amount of ≥100 ppm, such as ≥200 ppm or ≥500 ppm.A process or apparatus according to any preceding clause, wherein the pretreated solutioncomprises the target monovalent ion in an amount of ≥10 ppm, such as ≥20 ppm or ≥50 ppm.A process or apparatus according to any preceding clause, wherein the pretreated solutioncomprises the target monovalent ion in an amount of ≥20 ppm, such as ≥500 ppm or ≥1,000ppm.A process or apparatus according to any preceding clause, wherein the pretreated solutioncomprises a ratio of the divalent ions to the target monovalent ion of <6000:1, such as<5000:1, such as <4000:1, such as <3000:1, such as <2500:1, such as <2000:1.A process or apparatus according to any preceding clause, wherein the pretreated aqueoussolution comprises total suspended solids in an amount of ≤100 ppm, such as ≤50 ppm or ≤ 10 ppm.A process according to any of clauses 63 to 90, wherein the optionally pretreated aqueoussolution is contacted with the first separation portion, such as a nanofiltration membrane ofa nanofiltration portion, at a temperature of ≥5 °C, such as ≥20°C or ≥30°C and / or theoptionally pretreated aqueous solution is contacted with the first separation portion, such asthe nanofiltration membrane, at a temperature of ≤130°C.A process according to any of clauses 63 to 91, wherein the optionally pretreated aqueoussolution is contacted with the first separation portion, such as a nanofiltration membrane ofa nanofiltration portion, at a transmembrane pressure of ≥5 bar, such as ≥10 bar, such as ≥15 bar and / or the optionally pretreated aqueous solution is contacted with the nanofiltrationmembrane at a transmembrane pressure of ≤60 bar, such as ≤40 bar, such as ≤30 bar.A process or apparatus according to any preceding clause, wherein the intermediate solutioncomprises the divalent ions in an amount of ≤4,000 ppm, such as ≤3,500 ppm or ≤3,000 ppm.A process or apparatus according to any preceding clause, wherein the intermediate solutioncomprises the divalent ions in an amount of ≥10 ppm, such as ≥30 ppm or such as ≥150ppm.A process or apparatus according to any preceding clause, wherein the intermediate solutioncomprises the target monovalent ion in an amount of ≥10 ppm, such as ≥20 ppm or ≥50 ppm.A process or apparatus according to any preceding clause, wherein the intermediate solutioncomprises the target monovalent ion in an amount of ≥20 ppm, such as ≥500 ppm or ≥1,000ppm.A process or apparatus according to any preceding clause, wherein the intermediate solutioncomprises a ratio of the divalent ions to the target monovalent ion of <2000:1, such as<1800:1, such as <1600:1, such as <1400:1, such as <1000:1, such as <800:1.A process according to any of clauses 63 to 97, wherein the intermediate aqueous solutionis be contacted with the adsorbent separation portion at a temperature of ≥5 °C, such as ≥20°C, or ≥30°C and / or the intermediate aqueous solution is contacted with the adsorbentseparation portion at a temperature of ≤80°C.A process according to any of clauses 63 to 98, wherein the intermediate aqueous solutionis contacted with the adsorbent separation portion at a temperature of ≤60°C, such as ≤50°C.A process according to any of clauses 63 to 99, wherein the intermediate aqueous solutionis contacted with the adsorbent separation portion at a pressure of ≤2.5 bar, such as ≤0.2bar.A process according to any of clauses 63 to 100, wherein the intermediate aqueous solutionis contacted with the adsorbent separation portion with a pressure drop of ≥0.1 bar, such as≥0.2 bar, and / or the intermediate aqueous solution is contacted with the adsorbentseparation portion with a pressure drop of ≤2 bar, such as ≤1 bar, or such as ≤0.5 bar.A process according to any of clauses 63 to 101, wherein the intermediate aqueous solutionis contacted with the adsorbent separation portion at a pH of ≥4.5, such as ≥6, and / or theintermediate aqueous solution is contacted with the adsorbent separation portion at a pH of≤8, such as ≤7.5.A process according to any of clauses 63 to 102, wherein the intermediate aqueous solutionis contacted with the adsorbent separation portion at a volumetric flowrate of ≥0.2 BV / h, suchas ≥1 BV / h, such as ≥5 BV / h and / or the intermediate aqueous solution is contacted with theadsorbent separation portion at a volumetric flowrate of ≤25 BV / h, such as ≤20 BV / h.A process according to any of clauses 63 to 103, wherein the adsorbent separation portionis contacted with an aqueous strip solution after contact with the intermediate aqueous solution to elute the target monovalent ion and produce a product aqueous solution.A process according to clause 104, wherein the aqueous strip solution comprises at leastpartially demineralised water.A process according to clause 104 or 105, wherein the aqueous strip solution comprisestarget monovalent ions, such as target monovalent ions in an amount of from 1 to 2000 ppm, such as from 10 to 1500 ppm, such as from 20 to 1250 ppm, such as from 30 to 1000 ppm, such as from 40 to 750 ppm, such as from 50 to 500 ppm.A process according to any of clauses 104 to 106, wherein the aqueous strip solution has apH of from 6.0 to 8.0, such as from 6.5 to 7.5, such as from 6.9 to 7.1.A process or apparatus according to any preceding clause, wherein the product solutioncomprises a ratio of the divalent ions to the target monovalent ion to of <750:1, such as<700:1, such as <650:1, such as <600:1, such as <580:1, such as <550:1, such as <500:1.A process or apparatus according to any preceding clause, wherein the product solutioncomprises the divalent ions in an amount of ≤3,000 ppm, such as ≤2,700 ppm or ≤2,000 ppm.A process or apparatus according to any preceding clause, wherein the product solutioncomprises the target monovalent ion in an amount of ≥10 ppm, such as ≥20 ppm or ≥50 ppm.A process or apparatus according to any preceding clause, wherein the apparatus and / orprocess is operable to produce a product aqueous solution having the target monovalent ion, such as lithium, retention compared to the amount of the target monovalent ion, such as lithium, in the source aqueous solution of ≥10%, such as ≥20% or ≥30%.A process according to any of clauses 63 to 111, wherein the process further comprises:d. contacting the product solution with a further separation portion operable toreceive the product aqueous solution and form a further refined product aqueous solution having a lower ratio of the divalent ions to the target monovalent ion.A process or apparatus according to any of clauses 59 to 112, wherein the different type ofmonovalent ion to the target monovalent ion comprises a different type of monovalent cation,such as a different type of metal monovalent cation, such as Na, K, Rb and / or Cs.A process according to any of clauses 65 to 113, wherein the process further comprises:e. contacting the (refined) product solution with a concentration portion operable toreceive the (refined) product aqueous solution and reduce the water content of the solution such as to produce a concentrated product aqueous solution.A process according to clause 114, wherein the concentration portion is contacted with therefined product solution.An apparatus or process according to any of clauses 65 to 115, wherein the concentratedproduct solution comprises divalent ions in an amount of ≤2,500 ppm, such as ≤1,500 ppm.An apparatus or process according to any of clauses 65 to 116, wherein concentratedproduct solution comprises the monovalent ion in an amount of ≥10 ppm, such as ≥50 ppmor ≥100 ppm.An apparatus or process according to any of clauses 65 to 117, wherein concentratedproduct solution comprises a ratio of a different type of monovalent ion to the targetmonovalent ion of <750:1, such as <700:1, such as <650:1, such as <600:1, such as <580:1, such as <550:1, such as <500:1.An apparatus or process according to any of clauses 65 to 118, wherein the concentratedproduct solution comprises ≥0.5% solid content, such as ≥2% solid content, or ≥5% solidcontent.An apparatus or process according to any of clauses 65 to 119, wherein the concentratedproduct solution comprises ≥10% of the target monovalent ion, such as lithium, by weight ofsolid content, such as ≥20%, or ≥50%.An apparatus or process according to any of clauses 76 to 151, wherein the concentratedproduct solution comprises ≥90% of the target monovalent ion, such as lithium, by weight ofsolid content, such as ≥95%, or ≥99%.A process or apparatus according to any preceding clause, wherein the apparatus and / orprocess is operable to produce a refined product and / or concentrated product aqueous solution having the target monovalent ion, such as lithium, retention compared to the amount of the target monovalent ion, such as lithium, in the source aqueous solution of ≥10%, such as ≥20% or ≥30%.A process or apparatus according to any preceding clause, for use in lithium extraction.A product aqueous solution obtained by a process according to any of clauses 65 to 123.A dry product composition obtained by a process according to any of clauses 65 to 123.

Claims

CLAIMS1. An apparatus for reducing the ratio of divalent ions, such as divalent cations, to a targetmonovalent ion, such as a target monovalent cation, in an aqueous solution from a source aqueous solution that contains a higher ratio of divalent ions to the target monovalent ion,the apparatus comprising optionally, a pretreatment portion operable to receive the source aqueous solution and produce a pretreated source aqueous solution; a first separation portion operable to receive an optionally pretreated aqueous solution and form an intermediate aqueous solution having a lower ratio of divalent ions to the monovalent ion than the optionally pretreated aqueous solution; and an adsorbent separation portion operable to receive the intermediate aqueous solution and form a product aqueous solution having a lower ratio of the divalent ions to the monovalent ion than the intermediate solution.

2. An apparatus according to claim 1, wherein the apparatus comprises a pretreatment portionthat comprises a prefiltration portion, a chemical precipitation portion, a settling tank portion, and / or a centrifuge portion, optionally wherein the prefiltration portion comprises microfiltration or ultrafiltration membrane; a strainer and / or a filter.

3. An apparatus according to claim 2, wherein the apparatus comprises a prefiltration portionhaving a mean average pore size of up to 100 µm, such as up to 75 µm or up to 50 µm, and / or a prefiltration portion comprising a membrane having a mean average pore size of at least 200 nm, such as at least 500 nm, or at least 5 µm.

4. An apparatus according to any of claims 2 to 3, wherein the apparatus comprises aprefiltration portion comprising a first and a second separation portion, wherein the firstportion has a mean average pore size that is larger than the mean average pore size of the second portion.

5. An apparatus according to any of claims 2 to 4, wherein the apparatus comprises aprefiltration portion comprising a membrane with a total suspended solids rejection of ≥90 %,such as ≥95% or ≥99%, and / or a prefiltration portion comprising a membrane with a rejectionrate for the target monovalent ion of ≤5%, such as ≤2% or ≤1%.

6. An apparatus according to any preceding claim, wherein the first separation portioncomprises a nanofiltration separation portion, such as comprising a nanofiltration membrane;electrodialysis cell comprising a membrane; and / or a metal-organic framework (MOF)membrane.

7. An apparatus according to any preceding claim, wherein the first separation portioncomprises a nanofiltration separation portion.

8. An apparatus according to claim 7, wherein the nanofiltration separation portion comprisesa nanofiltration membrane.

9. An apparatus according to any preceding claim, wherein the first separation portioncomprises a membrane, such as a nanofiltration membrane, having mean average pore sizeof ≤10 nm, such as ≤5 nm or ≤2 nm, and / or the first separation portion comprises amembrane, such as a nanofiltration membrane, having a mean average pore size of ≥0.1nm, such as ≥0.2 nm or ≥0.5 nm.

10. An apparatus according to any preceding claim, wherein the first separation portioncomprises a membrane, such as a nanofiltration membrane, with a divalent ion rejection of≥60%, such as ≥ 70% or ≥90%, and / or the first separation portion comprises a membrane,such as a nanofiltration membrane, with a divalent ion rejection of ≤99%, such as ≤98% or ≤95%.

11. An apparatus according to any preceding claim, wherein the first separation portioncomprises a membrane, such as a nanofiltration membrane, with a rejection rate for thetarget monovalent ion of ≤50%, such as ≤20% or ≤5%.

12. An apparatus according to any preceding claim, wherein the prefiltration portion and / or thefirst separation portion comprises a membrane, such as a nanofiltration membrane, thatcomprises a polymer membrane, such as comprising polysulfone, polyethersulfone, and / or polyvinylidene fluoride; a ceramic membrane, such as comprising aluminium oxide, titanium dioxide, and / or zirconium dioxide; a metal membrane, such as comprising carbon steel, galvanised steel, stainless steel, aluminium, and / or copper; or a combination thereof, such as a composite membrane comprising a polymeric composite, a ceramic composite, and / or a metallic composite.

13. An apparatus according to any preceding claim, wherein the prefiltration portion and / or firstseparation portion comprises a membrane, such as a nanofiltration membrane, comprising polyamide; polyester, such as polyethylene terephthalate (PET); and / or, poly(ether) sulfone (PES).

14. An apparatus according to any preceding claim, wherein the first separation portioncomprises a membrane, such as a nanofiltration membrane, that comprises a spiral woundmembrane, a tubular membrane, a hollow fibre membrane and / or a flat sheet membrane.

15. An apparatus according to any preceding claim, wherein the apparatus comprises meansoperable to recirculate the retentate stream of the membrane of the first separation portion,such as a nanofiltration separation portion, back to the inlet of the membrane of the firstseparation portion.

16. An apparatus according to any preceding claim, wherein the adsorbent separation portionhas a higher affinity for the target monovalent ion than the divalent cations and / or a higheraffinity for the target monovalent ion than other monovalent ions.

17. An apparatus according to any preceding claim, wherein the adsorbent separation portion issubstantively selective for lithium ions.

18. An apparatus according to any preceding claim, wherein the adsorbent separation portioncomprises an inorganic adsorbent material comprising target monovalent ion aluminate,such as comprising the target monovalent ion, aluminum atoms, oxygen atoms, and at least one anionic species X selected from halide (fluoride, chloride, bromide, or iodide), nitrate, sulfate, carbonate, and / or bicarbonate.

19. An apparatus according to any preceding claim, wherein the adsorbent separation portioncomprises an inorganic adsorbent comprising a metal hydroxide, such as an aluminumhydroxide (AlOH) or derivative thereof, such as an aluminum trihydroxide, such as gibbsite, bayerite, and / or nordstrandite.

20. An apparatus according to any preceding claim, wherein the adsorbent separation portioncomprises an inorganic adsorbent comprising an aluminum hydroxide-containing material,such as an aluminum hydroxide-containing zeolite.

21. An apparatus according to any preceding claim, wherein the adsorbent separation portioncomprises an inorganic adsorbent comprising a layered inorganic material.

22. An apparatus according to any preceding claim, wherein the adsorbent separation portioncomprises an inorganic adsorbent comprising a two-dimensional (2D) layered inorganicmaterial.

23. An apparatus according to any preceding claim, wherein the adsorbent separation portioncomprises an inorganic adsorbent comprising a layered metal hydroxide, such as a layeredmetal double hydroxide, such as comprising an intercalated layered structure comprisingmetal cations, hydroxide anions, and intercalated anions, and may be comprise water and / or hydrates.

24. An apparatus according to any preceding claim, wherein the adsorbent separation portioncomprises a layered metal double hydroxide comprising first and second layers comprisingmetal cations and hydroxide ions with an intercalating layer arranged between the first and asecond layers, optionally wherein the intercalating layer comprises an anion or neutralmolecule, such as a water molecule, wherein the layered metal double hydroxide inorganic adsorbent may comprise a plurality of repeating first and second intercalated layers.

25. An apparatus according to any preceding claim, wherein the adsorbent separation portioncomprises a layered metal double hydroxide comprising metal cations wherein the metalcations comprise monovalent and / or divalent metal cations such as lithium and / or aluminium, optionally the metal cations of the layered metal double hydroxide may comprise the target monovalent ions.

26. An apparatus according to any preceding claim, wherein the adsorbent separation portioncomprises a lithium-incorporated aluminum hydroxide (LIAH).

27. An apparatus according to any preceding claim, wherein the adsorbent separation portioncomprises a lithium-incorporated layered hydroxide, such as a lithium-incorporated layereddouble hydroxide.

28. An apparatus according to any preceding claim, wherein the adsorbent separation portioncomprises a lithium-incorporated aluminum hydroxide according to formula (I):LiX. ^Al(OH)^. ^H^O(I) wherein: X is a monovalent anion, such as fluoride, chloride, bromide, and / or iodide, preferably chloride; and mis from 1.2 to 3.0; andn is from 0.2 to 5.0.

29. An apparatus according to any preceding claim, wherein the adsorbent separation portioncomprises a layered lithium aluminum double hydroxide.

30. An apparatus according to any preceding claim, wherein the adsorbent separation portioncomprises a carrier, such as a solid carrier, such as a solid carrier in which an inorganicadsorbent is dispersed.

31. An apparatus according to any preceding claim, wherein the adsorbent separation portioncomprises a carrier comprising a polyvinyl alcohol, methacrylate, phenol, synthetic polymer,polysaccharide, biopolymer, polysilicate, metal organic framework (MOF), alginate, biochar, carbonaceous ore, clay, graphene and / or nanotube.

32. An apparatus according to any preceding claim, wherein the adsorbent separation portioncomprises a carrier comprising an organic polymer, such as an organic polymer matrix.

33. An apparatus according to any preceding claim, wherein the prefiltration separation portionand / or first separation portions, such as a nanofiltration separation portion, comprises amembrane, such as a nanofiltration membrane, that comprises a membrane substrate anda coating extending over at least a part of the membrane substrate.

34. An apparatus according to any preceding claim, wherein the prefiltration portion and / or aseparation portion, such as the first separation portion or a nanofiltration separation portion,comprises a membrane comprising a porous ceramic member, wherein the porous ceramic member comprises a first support portion operable to support a coating and further comprises a second support portion, wherein the second support portion has a higher D75 average pore size than the D75 average pore size of the first support portion, wherein the second support portion comprises a lattice structure that has a porosity percentage of ≥40%, and wherein the porous ceramic member has a tensile strength operable to withstand feed application pressure of ≥100kPa (1 bar).

35. An apparatus according to any preceding claim, wherein the prefiltration portion and / or aseparation portion, such as the first separation portion or a nanofiltration separation portion,comprises a spiral wound membrane having a component comprising an integrally formed non-uniform lattice structure, wherein the lattice structure comprises a first and second repeating unit cell, wherein the first and second unit cells are different.

36. An apparatus according to any preceding claim, wherein the apparatus, such as theadsorbent separation portion, is further operable to reduce the ratio of a different type ofmonovalent ion to a target monovalent ion.

37. An apparatus according to any preceding claim, wherein the apparatus comprises means toextract the target monovalent ion as eluent from the adsorbent separation portion.

38. An apparatus according to claim 37, wherein the means to extract the target monovalent ionas eluent from the adsorbent separation portion comprises means to contact the adsorbent separation portion with an aqueous strip solution having a pH of from 6.0 to 8.0, such as from 6.5 to 7.5, such as from 6.9 to 7.1.

39. The apparatus according to any previous claim, wherein the apparatus comprises a furtherseparation portion operable to receive the product aqueous solution and form a further refined product aqueous solution having a lower ratio of the divalent ions to the targetmonovalent ion.

40. An apparatus according to any previous claim, wherein the apparatus comprises aconcentration portion operable to receive the (refined) product aqueous solution and reduce the water content of the solution so as to produce a concentrated product aqueous solution.

41. An apparatus according to claim 40, wherein the concentration portion is operable to receivethe refined product aqueous solution.

42. An apparatus according to claim 40 or 41, wherein the concentration portion comprises areverse osmosis membrane, forward osmosis, electrodialysis, and / or a membrane comprising a porous ceramic member as defined herein.

43. A process for reducing the ratio of divalent ions, such as divalent cations, to a targetmonovalent ion in an aqueous solution, comprising:a. optionally, contacting a source aqueous solution comprising the divalent ions andthe target monovalent ion with a pretreatment portion according to any of claims1 to 65; b. contacting the optionally pretreated aqueous solution with a first separationportion according to any of claims 1 to 42 to form an intermediate aqueoussolution having a lower ratio of the divalent ions to the target monovalent ion than the optionally pretreated aqueous solution;c. contacting the intermediate solution with an adsorbent separation portionaccording to any of claims 1 to 42 to form a product aqueous solution having alower ratio of the divalent ions to the target monovalent ion than in the intermediate solution.

44. A process according to claim 43, wherein the first separation portion comprises ananofiltration separation portion comprising a nanofiltration membrane.

45. A process or apparatus according to any preceding claim, wherein the source aqueoussolution comprises a geothermal brine, such as a geothermal brine obtained from a deep geothermal source.

46. A process or apparatus according to any preceding claim, wherein the source aqueoussolution comprises a shallow geothermal brine.

47. A process or apparatus according to any preceding claim, wherein the source aqueoussolution comprises a seawater brine, saline lake brine, produced water, and / or leachate from recycled batteries.

48. A process or apparatus according to any preceding claim, wherein the divalent ion of thesource solution, prefiltered source solution, intermediate source solution and / or product source solution is a divalent cation, and wherein one or more of the solutions optionallycomprises trivalent cations, and wherein the divalent cation and optional trivalent cation are optionally selected from Ca, Mg, B, Ba, Fe, Mn, Zn, Mo, Sr, Zr, V, Cr, Te, Ti, Ga, Hg, Be, In, Ta, Ce, Hf, Sm, La, Nb, Th, Al, Tl, As, Ni, Cu, Sc, Sn, Sb, Co, Pb, U, Cd, Y and / or Bi, such as Ca, Mg, Sr and / or B.

49. A process or apparatus according to any preceding claim, wherein the target monovalent ionis a cation, such as Na, K, Li, Cs, Rb, W, Au and / or Ag.

50. A process or apparatus according to any preceding claim, wherein the target monovalent ionis a metal cation.

51. A process or apparatus according to any preceding claim, wherein the target monovalentcation comprises Li, W, Au, Ag, Na and / or K.

52. A process or apparatus according any preceding claim, wherein the target monovalent cationcomprises Li, W, Au and / or Ag.

53. A process or apparatus according to any preceding claim, wherein the target monovalentcation comprises Li.

54. A process according to any of claims 43 to 53, wherein the process further comprises:d. contacting the product solution with a further separation portion operable toreceive the product aqueous solution and form a further refined product aqueous solution having a lower ratio of the divalent ions to the target monovalent ion.

55. A process or apparatus according to any of claims 43 to 54, wherein the different type ofmonovalent ion to the target monovalent ion comprises a different type of monovalent cation,such as a different type of metal monovalent cation, such as Na, K, Rb and / or Cs.

56. A process according to any of claims 43 to 55, wherein the process further comprises:e. contacting the (refined) product solution with a concentration portion operable toreceive the (refined) product aqueous solution and reduce the water content of the solution such as to produce a concentrated product aqueous solution.

57. A process according to claim 56, wherein the concentration portion is contacted with therefined product solution.

58. A process or apparatus according to any preceding claim, for use in lithium extraction.

59. A product aqueous solution obtained by a process according to any of claims 43 to 58.

60. A dry product composition obtained by a process according to any of claims 43 to 58.

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