Process and system

Abstract

A process and / or a system for extracting lithium from an aqueous solution containing lithium. The process comprising (i) contacting an aqueous solution containing lithium with a lithium sorbent to produce a mixture of a lithium loaded sorbent and lithium depleted solution, (ii) separating the lithium loaded sorbent and the lithium depleted solution, (iii) treating the lithium loaded sorbent to produce a lithium eluate solution and a regenerated sorbent, (iv) separating the lithium eluate solution and the regenerated sorbent. Step (i) and / or step (iii) may be performed in a plug flow reactor.

Description

PROCESS AND SYSTEMTECHNICAL FIELD

[0001] This disclosure relates to a process and / or a system for extracting lithium from an aqueous solution containing lithium to produce a lithium eluate and / or a lithium salt. More particularly, this disclosure relates to the use of a manganese sorbent to extract lithium from an aqueous solution containing lithium. This disclosure also relates to the direct lithium extraction circuit and recycling circuits in the process to reduce waste streams.BACKGROUND ART

[0002] Lithium has many uses, but one of the most dominant is the manufacture of batteries, which has high demand due to the growing use of electronics, electric vehicles and storage of renewable energy such as solar power.

[0003] Lithium is present naturally in many rocks (such as pegmatites), ocean water, brines, mineral springs and ground waters. Lithium solutions can also be a side product from lithium processing facilities, battery recycling plants, oil well brines, formation waters or other waste streams. However, these sources may only contain low concentrations of lithium, for example sea water contains less than 1 mg / l of lithium. Therefore, to be extracted for use, the lithium must be concentrated and / or converted into a useful chemical form.

[0004] Direct lithium extraction (DLE) is a technology used to efficiently and selectively extract lithium from solutions with low concentrations of lithium such as geothermal, oilfield and continental fluids. Unlike traditional methods like evaporation ponds or conventional mining, DLE utilizes advanced techniques like adsorption, ion exchange, and membrane processes to selectively extract lithium. Scaling up the DLE process requires advanced engineering and design to handle larger volumes of brine efficiently whilst maintaining efficient recovery rates in large-scale process and this remains a challenge.

[0005] US 10,332,950 B2 describes a lithium adsorbent, a method for producing the same, and a method for recovering lithium from a dilute solution using the same.

[0006] Transitional metal oxides (such as lithium manganese oxides and lithium titanium oxides) are examples of materials that can be applied in the DLE process due to their efficient lithium extraction / insertion reactions. These materials have been studied for development of selective adsorbents and cathode materials for rechargeable batteries.

[0007] In this specification, where reference has been made to external sources of information, including patent specifications and other documents, this is generally for the purpose of providing a context for discussing the features of the present invention. Unless stated otherwise, reference to such sources of information is not to be construed, in any jurisdiction, as an admission that such sources of information are prior art or form part of the common general knowledge in the art.SUMMARY OF THE INVENTION

[0008] It is an object of this disclosure to provide a process for extracting lithium from an aqueous solution containing lithium and / or a system for extracting lithium from an aqueous solution containing lithium which goes at least some way towards overcoming one or more of the above mentioned problems or difficulties, or to at least provide the public with a useful choice.

[0009] In a first aspect, the invention provides a process for extracting lithium from an aqueous solution containing lithium, the process comprising:(i) contacting an aqueous solution containing lithium with a lithium sorbent to produce a mixture of a lithium loaded sorbent and a lithium depleted solution,(ii) separating the lithium loaded sorbent and the lithium depleted solution,(iii) treating the lithium loaded sorbent to produce a lithium eluate and a regenerated sorbent,(iv) separating the lithium eluate and the regenerated sorbent, wherein step (i) and / or (iii) are performed in a plug flow reactor.

[0010] In a second aspect, the invention provides a process for extracting lithium from an aqueous solution containing lithium, the process comprising:(i) contacting an aqueous solution containing lithium with a lithium sorbent to produce a mixture of a lithium loaded sorbent and a lithium depleted solution,(ii) separating the lithium loaded sorbent and the lithium depleted solution,(iii) treating the lithium loaded sorbent to produce a lithium eluate and a regenerated sorbent,(iv) separating the lithium eluate and the regenerated sorbent, wherein step (i) and / or (iii) are performed in a plug flow reactor and at least part of the lithium eluate from step (iv) is recycled to step (iii).

[0011] In a third aspect, the invention provides a process for extracting lithium from an aqueous solution containing lithium, the process comprising: i) contacting an aqueous solution containing lithium with a lithium sorbent to produce a mixture of a lithium loaded sorbent and a lithium depleted solution, ii) separating the lithium loaded sorbent and the lithium depleted solution, iii) treating the lithium loaded sorbent to produce a lithium eluate and a regenerated sorbent, iv) separating the lithium eluate and the regenerated sorbent, v) repeating steps (iii) and (iv) with at least part of the lithium eluate to produce a lithium rich solution, wherein step (i) and / or step (iii) are performed in a plug flow reactor.

[0012] In a fourth aspect, the invention provides a process for extracting lithium from an aqueous solution containing lithium, the process comprising: i) contacting an aqueous solution containing lithium with a lithium sorbent to produce a mixture of a lithium loaded sorbent and a lithium depleted solution, ii) separating the lithium loaded sorbent and the lithium depleted solution, iii) treating the lithium loaded sorbent with an acid to produce a lithium eluate and a regenerated sorbent, iv) separating the lithium eluate and the regenerated sorbent, v) concentrating and / or purifying the lithium eluate to produce a lithium rich solution wherein step (i) and / or step (iii) are performed in a plug flow reactor.

[0013] In a fifth aspect, the invention provides a process for extracting lithium from an aqueous solution containing lithium, the process comprising: i) contacting an aqueous solution containing lithium with a lithium sorbent to produce a mixture of a lithium loaded sorbent and a lithium depleted solution, ii) separating the lithium loaded sorbent and the lithium depleted solution, iii) treating the lithium loaded sorbent with an acid to produce a lithium eluate and a regenerated sorbent, iv) separating the lithium eluate and the regenerated sorbent, v) concentrating and / or purifying the lithium eluate to produce a lithium rich solution,vi) treating the lithium rich solution to produce a solid lithium salt and a spent mother liquor, vii) separating the solid lithium salt from the spent mother liquor wherein at least part of the spent mother liquor from step (vii) is recycled in steps (i and / or v).

[0014] In a sixth aspect, the invention provides a process for extracting lithium from an aqueous solution containing lithium, the process comprising: i) contacting an aqueous solution containing lithium with a lithium sorbent to produce a mixture of a lithium loaded sorbent and a lithium depleted solution, ii) separating the lithium loaded sorbent and the lithium depleted solution, iii) treating the lithium loaded sorbent with an acid to produce a lithium eluate and a regenerated sorbent, iv) separating the lithium eluate and the regenerated sorbent, v) concentrating and / or purifying the lithium eluate to produce a lithium rich solution, wherein purifying the lithium eluate comprises treating the lithium eluate with a base to precipitate one or more impurities as one or more by-products and separating the byproducts from the lithium eluate, wherein at least part of the by-products is recycled in step (i),

[0015] In a seventh aspect, the invention provides a system for extracting lithium from an aqueous solution containing lithium, the system comprising, i) a first reactor for contacting an aqueous solution containing lithium with a lithium sorbent to absorb the lithium to produce a lithium loaded sorbent and lithium depleted solution, ii) a first separating device for separating the lithium loaded sorbent and the lithium depleted solution, iii) a second reactor for contacting the lithium loaded sorbent with a means for treating the lithium loaded sorbent to produce a lithium eluate and a regenerated sorbent, iv) a second separating device for separating the lithium eluate and the regenerated sorbent, wherein the first reactor and / or the second reactor is a plug flow reactor.

[0016] In an eighth aspect, the invention provides a system for extracting lithium from an aqueous solution containing lithium, the system comprising, i) a first reactor for contacting an aqueous solution containing lithium with a lithium sorbent to absorb the lithium to produce a lithium loaded sorbent and a lithium depleted solution, ii) a first separating device for separating the lithium loaded sorbent and the lithium depleted solution, iii) a second reactor for contacting the lithium loaded sorbent with a means for treating the lithium loaded sorbent to produce a lithium eluate and a regenerated sorbent, iv) a second separating device for separating the lithium eluate and the regenerated sorbent, and v) a third reactor for contacting the lithium eluate with a further lithium loaded sorbent wherein one or more of the first reactor, the second reactor and the third reactor is a plug flow reactor.

[0017] In a ninth aspect, the invention provides a system for extracting lithium from an aqueous solution containing lithium, the system comprising, i) a first reactor for contacting an aqueous solution containing lithium with a lithium sorbent to absorb the lithium to produce a lithium loaded sorbent and a lithium depleted solution, ii) a first separating device for separating the lithium loaded sorbent and the lithium depleted solution, iii) a second reactor for contacting the lithium loaded sorbent with a means for treating the lithium loaded sorbent to produce a lithium eluate and regenerated sorbent iv) a second separating device to separate the lithium eluate solution and the regenerated sorbent, and v) means for conveying the lithium eluate from the second separating device to the second reactor, wherein the first reactor and / or the second reactor is a plug flow reactor.

[0018] In a tenth aspect, the invention provides a system for extracting lithium from an aqueous solution containing lithium, the system comprising,i) a first reactor for contacting an aqueous solution containing lithium with a lithium sorbent to absorb the lithium to produce a lithium loaded sorbent and a lithium depleted solution; ii) a first separating device for separating the lithium loaded sorbent and the lithium depleted solution; iii) a second reactor for contacting the lithium loaded sorbent with a means for treating the lithium loaded sorbent to produce a lithium eluate and a regenerated sorbent, iv) a second separating device for separating the lithium eluate and the regenerated sorbent; v) one or more means for concentrating and / or purifying the lithium eluate to produce a lithium rich solution, e.g.: a. means for conveying the lithium elute to the third second reactor, b. a third reactor for precipitating one or more impurities from the lithium eluate as one or more by products and, optionally, means for conveying the byproducts to the first reactor, and / or c. a lithium concentration system; vi) means for treating the lithium rich solution to produce a solid lithium salt and a spent mother liquor; vii) a third separating device for separating the solid lithium salt and the spent mother liquor; viii) means for conveying at least part of the spent mother liquor from the third separating device to the first reactor and / or the third reactor.

[0019] The following embodiments and preferences may relate alone or in any combination of any two or more to any of the above aspects.

[0020] In some embodiments, the lithium sorbent is a metal oxide-based ion exchange sorbent. In some embodiments, the metal oxide-based ion exchange sorbent is a hydrogen manganese oxide sorbent or hydrogen titanium oxide sorbent. In some embodiments, the metal oxide-based ion exchange sorbent is a hydrogen manganese oxide sorbent.

[0021] In some embodiments, the process is performed as a continuous process.

[0022] In some embodiments, step (i) is performed as a continuous process, and the aqueous solution and sorbent are dosed at a constant rate. In some embodiments, step (i) is performedas a continuous process, and the aqueous solution and the sorbent is dosed at a rate to maintain an excess of the lithium sorbent to the amount of lithium in the aqueous solution.

[0023] In some embodiments, step (iii) is performed as a continuous process. In some embodiments, the lithium loaded sorbent is dosed at a constant rate into the plug flow reactor. In some embodiments, step (iii) is performed as a continuous process and the lithium loaded sorbent is dosed at a constant rate into the plug flow reactor. In some embodiments, acid is continuously dosed into step (iii).

[0024] In some embodiments, the plug flow reactor comprises a feed port. In some embodiments, the plug flow reactor comprises two or more feed ports. In some embodiments, the feed ports are for introducing the lithium sorbent and / or the aqueous solution in the plug flow reactor. In some embodiments, the plug flow reactor comprises one or more feed ports positioned along the plug flow reactor to allow introduction of an acid or a base to maintain the pH of the aqueous solution within a desired pH range along the length of the plug flow reactor. In some embodiments, the lithium sorbent is dosed in the plug flow reactor to contact the aqueous solution. In some embodiments, the aqueous solution is dosed in the plug flow reactor to contact the lithium sorbent. In some embodiments, both the lithium sorbent and the aqueous solution are dosed in the plug flow reactor simultaneously through different feed ports.

[0025] In some embodiments, the plug flow in the plug flow reactor comprises an axial flow. In some embodiments, the plug flow reactor is operated to achieve substantially axial flow. In some embodiments, the plug flow reactor is operated with an axial velocity with turbulent flow sufficient to suspend the sorbent particles. In some embodiments, the aqueous solution and the sorbent are transferred into the plug flow reactor with a minimum velocity to suspend the sorbent particles. In some embodiments, a high axial velocity with turbulent flow is applied to suspend the sorbent particles. In some embodiments, the flow velocity of the aqueous solution in the plug flow reactor is 0.5-10 m / s. In some embodiments, the flow velocity of the aqueous solution in the plug flow reactor is 0.75-3 m / s.

[0026] In some embodiments, the length of the plug flow reactor is about 50 to 1500 m. In some embodiments, the length of the plug flow reactor is about 50 to 1000 m, about 50 to 800 m. about 50 to 600 m, about 100 to 400 m, about 100 to 300 m or about 100 to 200 m. In some embodiments, the length of the plug flow reactor is about 100 to 200 m. In some embodiments, the plug flow reactor has a diameter of about 5 to 2,000 mm. In someembodiments, the plug flow reactor has a diameter of about 5 to 155 mm. In some embodiments, the plug flow reactor has a diameter of about 10 to 140 mm, about 10 to 120 mm, about 15 to 100 mm, about 15 to 80 mm, about 15 to 60 mm, about 20 to 40 mm or about 20 to 30 mm. In some embodiments, the plug flow reactor has a diameter of about 20 to about 30 mm.

[0027] In some embodiments, the aqueous solution and the lithium sorbent are flowed through the plug flow reactor with a residence time ranging from about 1 to 120 minutes. In some embodiments, the residence time ranges from about 1 to 60 minutes, about 1 to 40 minutes, about 1 to 20 minutes or about 1 to 10 minutes. In some embodiments, the residence time is about 1 to 10 minutes. In some embodiments, the residence time in the plug flow reactor is about 5 minutes.

[0028] In some embodiments, the sorbent dose flow in the plug flow reactor is calculated based on the lithium concentration in the aqueous solution and the aqueous solution flow rate. In some embodiments, the sorbent is dosed in the plug flow reactor at about 0.01 to 100 g / s flow rate. In some embodiments, the sorbent is dosed as a slurry with solids concentration ranging from 0.1 to 99 wt%. In some embodiments, the sorbent is suspended in water at 30wt% slurry concentration with the flow rate dose ranging from 0.1 to 353 g / s.

[0029] In some embodiments, the aqueous solution and lithium sorbent are pumped through the plug flow reactor. In some embodiments, the system comprises a pump connected to the plug flow reactor to pump the aqueous solution and lithium sorbent through the plug flow reactor. In some embodiments, the flow of the aqueous solution and lithium sorbent through the reactor is assisted by gravity. In some embodiments, the plug flow reactor input flow occurs at a higher elevation to the output flow to facilitate the flow of the aqueous solution and lithium sorbent along the plug flow reactor. In some embodiments, the aqueous solution and the lithium sorbent are pumped into the plug flow reactor with separate pumps.

[0030] In some embodiments, the aqueous solution containing lithium is not mixed forward and backward in the plug flow reactor when contacted with the lithium sorbent. In some embodiments, the acid is not mixed forward and backward in the plug flow reactor to suspend the sorbent particles when contacted with the lithium loaded sorbent. In some embodiments, the plug flow reactor does not comprise mixing elements (e.g. baffles or static mixers). In some embodiments, the aqueous solution containing lithium and the lithium sorbent moves indistinct, non-mixing plugs, with each plug having a specific residence time and composition as it flows forward through the reactor.

[0031] In some embodiments, the aqueous solution containing lithium is at a temperature of about 0 to 100°C when contacted with the lithium sorbent. In some embodiments, the aqueous solution containing lithium is at a temperature of about 0 to less than 100 °C when contacted with the lithium sorbent. In some embodiments, the aqueous solution containing lithium is at a temperature of about 10 to 90°C when contacted with the lithium sorbent. In some embodiments, the aqueous solution containing lithium is at a temperature of about 20 to 90°C when contacted with the lithium sorbent. In some embodiments, the aqueous solution containing lithium is at a temperature of about 30 to 90°C when contacted with the lithium sorbent. In some embodiments, the aqueous solution containing lithium is at a temperature of about 40 to 90°C when contacted with the lithium sorbent.

[0032] In some embodiments, the aqueous solution is contacted with the sorbent for about 1 to 120 minutes. In some embodiments, the aqueous solution is contacted with the sorbent for about 1 to 60 minutes, about 2 to 40 minutes, about 2 to 20 minutes or about 3 to 10 minutes. In some embodiments, the aqueous solution is contacted with the sorbent for about 5 minutes.

[0033] In some embodiments, the aqueous solution is contacted with the hydrogen manganese oxide sorbent for about 1 to 120 minutes. In some embodiments, the aqueous solution is contacted with the hydrogen manganese oxide sorbent for about 1 to 60 minutes, about 2 to 40 minutes, about 2 to 20 minutes or about 3 to 10 minutes. In some embodiments, the aqueous solution is contacted with the hydrogen manganese oxide sorbent for about 5 minutes.

[0034] In some embodiments, the sorbent is brought into contact with the aqueous solution containing lithium at about 1 to 700 g / L, 1 to 500 g / L, 1 to 200 g / L, 1 to 100 g / L or 1 to 50 g / L. In some embodiments, the sorbent is added continuously to match the continuous incoming flow of aqueous solution containing lithium.

[0035] In some embodiments, the sorbent is added along the plug flow reactor. In some embodiments, freshly activated sorbent is added at one or multiple points along the plug flow reactor. In some embodiments, freshly activated sorbent is added at one or multiple points along the plug flow reactor via feed ports.

[0036] In some embodiments, a base is added to the aqueous solution containing lithium to maintain the pH when the lithium is being absorbed.

[0037] In some embodiments, the aqueous solution containing lithium comprises a buffer to maintain the pH when the lithium is being absorbed.

[0038] In some embodiments, the pH of the aqueous solution containing lithium is maintained at an average pH of about 3 to 10 when the lithium is being absorbed. In some embodiments, the pH of the aqueous solution containing lithium is maintained at an average pH of about 5 to 7 when the lithium is being absorbed. In some embodiments, the pH of the aqueous solution containing lithium is maintained at an average pH of about 5 to 6 when the lithium is being absorbed.

[0039] In some embodiments, a base is continuously added to maintain the aqueous solution pH at an average pH of about 5 to 6 when the lithium is being absorbed. In some embodiments, a base is added at multiple points along the plug flow reactor. In some embodiments, a base is added at one single point along the plug flow reactor. In some embodiments, a base is added to the aqueous solution to buffer the pH prior to the upload process.

[0040] In some embodiments, the sorbent is dialysed to remove entrained lithium depleted solution. In some embodiments, the water is added to the separated lithium loaded sorbent to dilute the mixture to about 1 to 1000 g / L, about 200 to 900 g / L, about 400 to 900 g / L, about 600 to 900 g / L or about 700 g / L of the sorbent.

[0041] In some embodiments, the separating step (ii) and / or the separating step (iv) comprises filtering the mixture using a physical separation method. In some embodiments, the physical separation method is a filter press or an ultrafiltration membrane. In some embodiments, the ultrafiltration membrane is a hollow fiber or spiral wound membrane. In some embodiments, the filtration is cross flow filtration. In some embodiments, the mixture of the lithium loaded sorbent and lithium depleted solution from step (i) is transferred to a tank for storage and / or separation. In some embodiments, the separating step (ii) and / or the separating step (iv) are carried out in a separation tank, e.g., a stirred tank and / or a recirculation tank.

[0042] In some embodiments, steps (i to iv) are performed at a temperature ranging from 0 to 100°C, about 0 to 80°C, about 0 to 60°C or about 0 to 40°C. In some embodiments, steps (i to vi) are performed at a temperature ranging from 0 to 100°C, about 0 to 80°C, about 0 to 60°C or about 0 to 40°C.

[0043] In some embodiments, the amount of lithium sorbent contacted with the aqueous solution containing lithium is in excess dose to the amount of lithium in the aqueous solution;preferably, wherein the amount of the lithium sorbent is about over 1 to 3 times the dose to the amount of lithium in the aqueous solution.

[0044] In some embodiments, the treatment in step (iii) comprises contacting the lithium loaded sorbent with an acid to produce a mixture of a lithium eluate and a regenerated sorbent. In some embodiments, the means for treating the lithium loaded sorbent in (iii) is a source of acid. In some embodiments, the acid in step (iii) or the source of acid is selected from one or more mineral acids and / or organic acids. In some embodiments, the acid in step (iii) the source of acid is selected from one or more of HCI, H2SO4, HBr, HI and phosphoric acid or a combination of any two or more thereof. In some embodiments, the source of acid is a lithium eluate solution with excess acid. In some embodiments, the source of acid is a recycled lithium eluate solution with excess acid. In some embodiments, the source of acid is a recycled acid solution form the concentration step (v).

[0045] In some embodiments, the process further comprises: (v) concentrating and / or purifying the lithium eluate to produce a lithium rich solution.

[0046] In some embodiments, step (v) comprises concentrating the lithium eluate to produce a lithium rich solution with a lithium concentration of at least about 1000 mg / l. In some embodiments, step (v) comprises concentrating the lithium eluate to produce a lithium rich solution with a lithium concentration of at least about 1,200 mg / l. In some embodiments, step (v) comprises concentrating the lithium eluate to produce a lithium rich solution with a lithium concentration of at least about 1,400 mg / l. In some embodiments, step (v) comprises concentrating the lithium eluate to produce a lithium rich solution with a lithium concentration of at least about 1,600 mg / l. In some embodiments, step (v) comprises concentrating the lithium eluate to produce a lithium rich solution with a lithium concentration of at least about 1,800 mg / l. In some embodiments, step (v) comprises concentrating the lithium eluate to produce a lithium rich solution with a lithium concentration of at least about 10,000 mg / l.In some embodiments, step (v) comprises contacting the further lithium loaded sorbent with the lithium eluate solution at about 1 to 700 g / L; or, about 1 to 500 g / L; or, about 1 to 200 g / L; or, about 1 to 100 g / L; or, about 1 to 50 g / L.

[0047] In some embodiments, at least about 10% v / v of the lithium eluate from step (iv) is recycled to step (iii). In some embodiments, at least about 30% v / v, 50% v / v, 70% v / v or 90% v / v of the lithium eluate from step (iv) is recycled to step (iii). In some embodiments, about

[0048] In some embodiments, the lithium eluate from step (iv) is recycled to step (iii) until the lithium eluate has a lithium concentration of at least about 1,000 mg / l. In some embodiments, the lithium eluate from step (iv) is recycled to step (iii) until the lithium eluate has a lithium concentration of at least about 1,200 mg / l. In some embodiments, the lithium eluate from step(iv) is recycled to step (iii) until the lithium eluate has a lithium concentration of at least about 1,400 mg / l. In some embodiments, the lithium eluate from step (iv) is recycled to step (iii) until the lithium eluate has a lithium concentration of at least about 1,600 mg / l. In some embodiments, the lithium eluate from step (iv) is recycled to step (iii) until the lithium eluate has a lithium concentration of at least about 1,800 mg / l. In some embodiments, the lithium eluate from step (iv) is recycled to step (iii) until the lithium eluate solution has a lithium concentration of at least about 10,000 mg / l.

[0049] In some embodiments, step (v) comprises contacting at least about 10% v / v of the lithium eluate with a further lithium loaded sorbent. In some embodiments, step (v) comprises contacting at least about 30% v / v, 50% v / v, 70% v / v or 90% v / v of the lithium eluate with a further lithium loaded sorbent. In some embodiments, step (v) comprises contacting about 100% v / v of the lithium eluate with a further lithium loaded sorbent.

[0050] In some embodiments, steps (iii) and (iv) are repeated. In some embodiments, steps (iii) and (iv) are repeated 2, 3, 4, 5, 10, 50 or 100 times.

[0051] In some embodiments, steps (iii) and (iv) are repeated until the lithium rich solution has a lithium concentration of at least about 1000 mg / l. In some embodiments, steps (iii) and(v) are repeated until the lithium rich solution has a lithium concentration of at least about 1,200 mg / l. In some embodiments, steps (iii) and (iv) are repeated until the lithium rich solution has a lithium concentration of at least about 1,400 mg / l. In some embodiments, steps (v) and(vi) are repeated until the lithium rich solution has a lithium concentration of at least about 1,600 mg / l. In some embodiments, steps (iii) and (iii) are repeated until the lithium rich solution has a lithium concentration of at least about 1,800 mg / l. In some embodiments, steps (v) and (vi) are repeated until the lithium rich solution has a lithium concentration of at least about 10,000 mg / l.

[0052] In some embodiments, step (v) comprises concentrating the lithium eluate with an osmosis process. In some embodiments, the osmosis process is low-pressure reverse osmosis, high-pressure reverse osmosis, forward osmosis, reverse osmosis or a combination of any two or more thereof. In some embodiments, step (v) comprises concentrating the lithium eluatewith an osmosis process to produce a lithium rich solution and a permeate, wherein the permeate is recycled in step (iii). In some embodiments, step (v) comprises concentrating the lithium eluate with a reverse osmosis process to produce a lithium rich solution and a permeate, wherein the permeate is recycled in step (iii).

[0053] In some embodiments, the system further comprises a lithium concentration system. In some embodiments, the lithium concentration system is configured to receive the lithium eluate. In some embodiments, the lithium concentration system comprises a low-pressure reverse osmosis membrane. In some embodiments, the lithium concentration system comprises a high-pressure reverse osmosis membrane. In some embodiments, the lithium concentration system comprises a forward osmosis membrane. In some embodiments, the lithium concentration system comprises a combination of two or more membrane systems. In some embodiments the lithium concentration system comprises of an evaporation process.

[0054] In some embodiments, a draw solution is used in combination with a forward osmosis membrane in the lithium concentration process to create an osmotic pressure difference, drawing water from a feed solution across a semi-permeable membrane. In some embodiments, the draw solution has higher osmotic pressure than the feed solution. In some embodiments, the draw solution is a high TDS solution (e.g. a high molecular weight salt such as ammonium bicarbonate or trimethyl ammonium bicarbonate, a polymer based draw solution such as PAA, PEG or co-block polymers, a brine, spent brine, lithium depleted brine, lithium depleted brine after DLE process, sea water, saline water or combination of any two or more thereof).

[0055] In some embodiments, the acid used in step (iii) may be recovered using a lithium concentration system. In some embodiments, the lithium concentration in the lithium eluate is increased with the use of a lithium concentration system. In some embodiments, both increased lithium concentration and acid recovery are achieved in the concentration step (v).

[0056] In some embodiments, the acid recovery rate using a lithium concentration system is10%. In some embodiments, the acid recovery rate using a lithium concentration system is50%. In some embodiments, the acid recovery rate using a lithium concentration system is80%. In some embodiments, the acid recovery rate using a lithium concentration system is89%.

[0057] In some embodiments, the concentration of the lithium eluate is increased with the use of a lithium concentration system by a factor of 2. In some embodiments, the concentrationof the lithium eluate is increased with a lithium concentration system by a factor of 10. In some embodiments, the concentration of the lithium eluate is increased with a lithium concentration system by a factor of 50.

[0058] In some embodiments, the lithium concentration achieved in the lithium rich solution in step (v) is 0.5%. In some embodiments, the lithium concentration achieved in the lithium rich solution in step (v) is 1%. In some embodiments, the lithium concentration achieved in the lithium rich solution in step (v) is 1.5%. In some embodiments, the lithium concentration achieved in the lithium rich solution in step (v) is 2%. In some embodiments, the lithium concentration achieved in the lithium rich solution in step (v) is 5%.

[0059] In some embodiments, step (v) comprises filtering the lithium eluate with a nanofiltration membrane. In some embodiments, step (v) comprises filtering the lithium eluate with a nanofiltration membrane to selectively remove multivalent ions in the lithium eluate. In some embodiments, step (v) comprises filtering the lithium eluate with a nanofiltration membrane after a concentration process. In some embodiments, step (v) comprises filtering the lithium eluate with a nanofiltration membrane before a concentration process. In some embodiments, step (v) comprises filtering the lithium eluate with a nanofiltration membrane between concentration processes.

[0060] In some embodiments, the lithium eluate from step (iv) comprises excess acid. In some embodiments, the lithium eluate from step (iv) comprises excess acid and is contacted with the further lithium loaded sorbent in an amount to provide at least 1.2 times the stoichiometric equivalent mol ratio of hydrogen ions to lithium. In some embodiments, an acid is added to the lithium eluate before step (v). In some embodiments, an acid is added to the lithium eluate during step (v). In some embodiments, the lithium loaded sorbent is added to the lithium eluate during step (v).

[0061] In some embodiments, the lithium eluate from step (v) comprises LiCI. In some embodiments, the lithium eluate from step (v) comprises U2SO4. In some embodiments, the lithium eluate from step (v) comprises recycled LiCI with excess acid.

[0062] In some embodiments, the acid in step (iii) or the source of acid substantially does not dissolve the sorbent.

[0063] In some embodiments, the acid in step (iii) or the source of acid is a concentrated or dilute acid.

[0064] In some embodiments, in step (iii) an acid is added in a first feed port along the plug flow reactor. In some embodiments, in step (iii) an acid is added at multiple feed ports along the plug flow reactor. In some embodiments, in step (iii) an acid is added continuously to the plug flow reactor. In some embodiments, in step (iii) an acid is added to feed ports set along the length of the plug flow reactor. In some embodiments, acid dose rate is dependent on the position of the dosing point within the plug flow reactor. In some embodiments, acid dosing is decreased in each dosing point, along the length of the plug flow reactor.

[0065] In some embodiments, loaded sorbent is added at one single point at the start of the plug flow reactor. In some embodiments, loaded sorbent is added at multiple points along the plug flow reactor. In some embodiments, the process further comprising washing the lithium loaded sorbent; optionally, washing the lithium loaded sorbent with water.

[0066] In some embodiments, step (iii) is performed at a temperature of about 0 to 100°C, optionally about 10 to 100°C, about 20 to 100°C, about 30 to 100°C or about 40 to 100°C.

[0067] In some embodiments, the regenerated sorbent is reused in the process or the system.

[0068] In some embodiments, the hydrogen manganese oxide sorbent is produced by leaching the lithium from a lithium manganese oxide with an acid.

[0069] In some embodiments, the aqueous solution containing lithium is selected from a geothermal brine, salar brine, formation waters, sea water, concentrates from processing seawater, a waste stream from a lithium processing facility, a waste stream from a battery recycling plants, oil well brines, other ground water.

[0070] In some embodiments, the regenerated sorbent is recycled in the process for 10 cycles, 50, 100, 200 or 300 cycles. In some embodiments, the regenerated sorbent is recycled in the process for at least 10 cycles. In some embodiments, the regenerated sorbent is recycled in the process for at least 100 cycles. In some embodiments, the regenerated sorbent is recycled in the process for at least 200 cycles. In some embodiments, the regenerated sorbent is recycled in the process for 10, 50, 100, 200 or 300 upload and elution cycles. In some embodiments, the lithium sorbent shows an initial particle size of 100 pm or less.

[0071] In some embodiments, the first separating device comprises a physical separation device, e.g. a filter press or an ultrafiltration membrane. In some embodiments, the second separating device comprises a physical separation device, e.g. a filter press or an ultrafiltration membrane. In some embodiments, the filtration system comprises a tank, e.g. a stirred tank and / or a recirculation tank, for storing and / or separating the lithium loaded sorbent and thelithium depleted solution. In some embodiments, the system comprises a plug flow reactor. In some embodiments, the tank is in fluid connection with the first reactor. In some embodiments, the third and / or fourth separating device comprises a physical separation device, e.g. a filter press or an ultrafiltration membrane.

[0072] In some embodiments, the first reactor is a plug flow reactor. In some embodiments, the second reactor is a plug flow reactor. In some embodiments, the first reactor and the second reactor are plug flow reactors. In some embodiments, the third reactor is a plug flow reactor. In some embodiments, the first reactor and the third reactor are plug flow reactors. In some embodiments, the second reactor and the third reactor are plug flow reactors. In some embodiments, the first reactor, the second reactor and the third reactor are plug flow reactors.

[0073] In some embodiments, step (v) comprises purifying the lithium eluate to remove one or more impurities from the lithium eluate. In some embodiments, purifying the lithium eluate to remove one or more impurities from the lithium eluate comprises precipitating the impurities as one or more by-products and separating the one or more by-products from the lithium eluate. In some embodiments, the one or more by-products are precipitated by modulation of the pH of the lithium eluate or evaporation of the lithium eluate. In some embodiments, the one or more by-products are selectively precipitated by increasing the pH of the lithium eluate. In some embodiments, the pH of the lithium eluate is increased by adding a base to the solution to precipitate the one or more by-products. In some embodiments, the base added to the lithium eluate to precipitate the one or more by-products is added in a stoichiometric dose relative to the by-products to be removed. In some embodiments, the base added to the lithium eluate to precipitate the one or more by-products is added in an excess dose (e.g. about 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0 times the stoichiometric dose) relative to the by-products to be removed. In some embodiments, the pH of the lithium eluate is increased by adding a dilute base to the solution to precipitate the one or more byproducts. In some embodiments, one or more by-products are selectively precipitated by contacting the lithium eluate with a carbonate and / or a hydroxide. In some embodiments, the carbonate is NazCOs, NaHCOs, a waste stream containing carbonate ions (e.g. spent mother liquor) or a combination of any two or more thereof. In some embodiments, the hydroxide is NaOH, Ca(OH)2, KOH, NH4OH, a waste stream containing hydroxyl ions (e.g. spent mother liquor) or a combination of any two or more thereof. In some embodiments, one or more by-products are precipitated in the form of carbonate. In some embodiments, one or more byproducts are precipitated in the form of hydroxide.

[0074] In some embodiments, precipitation of one or more by-products in step (v) is carried out in one single step by increasing the pH of the lithium eluate solution at a constant temperature. In some embodiments, precipitation of one or more by-products in step (v) is carried out in a sequence of separate precipitators at a constant pH. In some embodiments, a first precipitator is at pH 4. In some embodiments a second precipitator at pH 7. In some embodiments a third precipitator at pH 8. In some embodiments, a fourth precipitator at pH 9. In some embodiments, the solid by-products are separated by filtration. In some embodiments, the solid by-products are separated into one single filtration step. In some embodiments, the solid by-products are selectively separated into multiple filtration steps. In some embodiments, the solid by-products are separated in combination with one or more precipitators. In some embodiments, at least some of the by-products are disposed of as solid waste.

[0075] In some embodiments, the one or more by-products precipitated from the lithium eluate are recycled in step (i) to adjust the pH of the aqueous solution.

[0076] In some embodiments, precipitation of one or more by-products in step (v) is performed at a temperature of about 0 to 100°C, preferably, at a temperature of about 50 to 100°C, about 60 to 100°C, about 70 to 100°C or about 80 to 100°C.

[0077] In some embodiments, the precipitated by-products are separated from the concentrated lithium eluate solution by a filtration process. In some embodiments, the filtration process is selected from filter press, centrifuge, microfiltration, ultrafiltration and a combination of any two or more thereof.

[0078] In some embodiments, the one or more by-products are selected from MnCOs, CaCOs, MgCOs and SrCOs, Mn(OH)2, Ca(OH)2, Mg(OH)2, Sr(OH)2 and a combination of any two or more thereof. In some embodiments, the by-products are solid.

[0079] In some embodiments, step (v) comprises contacting the lithium eluate from step (iv) with an ion exchange resin for a sufficient period of time to adsorb one or more impurities, then separating the ion exchange resin from the lithium eluate. In some embodiments, the ion exchange resin is a cationic ion exchange resin.

[0080] In some embodiments, step (v) comprises filtering the lithium eluate through a nanofiltration membrane to remove one or more impurities, e.g. one or more divalent ions.

[0081] In some embodiments, step (v) comprises removing one or more impurities comprising Ba, Ca, Mg, Mn, Sr or a combination of any two or more thereof. In some embodiments, step(v) comprises removing one or more impurities comprising Ba, Ca, Mg, Mn, Sr or a combination of any two or more thereof to produce a lithium rich solution comprising a ratio of the one or more impurity / Li less than about 0.1. In some embodiments, step (v) comprises removing one or more impurities comprising Ba, Ca, Mg, Mn, Sr or a combination of any two or more thereof to produce a lithium rich solution comprising a ratio of the one or more impurity / Li less than about 0.01. In some embodiments, step (v) comprises removing one or more impurities comprising Ba, Ca, Mg, Mn, Sr or a combination of any two or more thereof to produce a lithium rich solution comprising a ratio of the one or more impurity / Li less than about 0.001. In some embodiments, step (v) comprises removing one or more impurities comprising Ba, Ca, Mg, Mn, Sr or a combination of any two or more thereof to produce a lithium rich solution comprising a ratio of the one or impurity / Li less than about 0.0001.

[0082] In some embodiments, the ion exchange resin is packed into a column. In some embodiments, the ion exchange resin is mixed with the treated concentrated lithium eluate solution and separated using a solid / liquid separation methods (e.g. filter press, vacuum filtration, centrifuge, density separation, decantation).

[0083] In some embodiment, the process further comprises:(vi) treating the lithium rich solution to produce a solid lithium salt and a spent mother liquor, and(vii)separating the solid lithium salt from the spent mother liquor.

[0084] In some embodiments, step (vi) comprises adding base to the lithium rich solution to cause precipitation of the solid lithium salt.

[0085] In some embodiments, the amount of base added in step (vi) is equivalent to the total lithium ions in the solution, at the stoichiometric ratio. In some embodiments, the base is added under the stoichiometric ratio to prevent the precipitation of all the lithium ions in the solution. In some embodiments, the concentration of lithium in the spent mother liquor is about 1,500 mg / L. In some embodiments, the concentration of lithium in the spent mother liquor is about 1,000 mg / L. In some embodiments, the concentration of lithium in the spent mother liquor is about 500 mg / L. In some embodiments, the concentration of lithium in the spent mother liquor is less than about 1,500 mg / L. In some embodiments, the concentrationof lithium in the spent mother liquor is less than about 1,000 mg / L. In some embodiments, the concentration of lithium in the spent mother liquor is less than about 500 mg / L

[0086] In some embodiments, at least part of the spent mother liquor from step (vii) is recycled in steps (i and / or v). In some embodiments, the spent mother liquor from step (vii) is recycled in steps (i and / or v). In some embodiments, substantially all of the spent mother liquor from step (vii) is recycled in steps (i and / or vi).

[0087] In some embodiments, step (vi) comprises evaporating the lithium rich solution to cause precipitation of the solid lithium salt (e.g. anhydrous LiCI and / or IJ2SO4).

[0088] In some embodiments, the solid lithium salt is a lithium carbonate, a lithium hydroxide, a lithium chloride or a combination of any two or more thereof. In some embodiments, the solid lithium salt is lithium carbonate. In some embodiments, the solid lithium salt is lithium hydroxide monohydrate. In some embodiments, the solid lithium salt is lithium chloride monohydrate, anhydrous lithium chloride or a mixture thereof.

[0089] In some embodiments, the base used in steps (v) and (vi) is of analytical grade purity. In some embodiments, the diluted base solution is of low grade, and it is polished using cationic ion exchange resins to remove contaminants prior to steps (v) and (vi).

[0090] In some embodiments, the base used in steps (v) is the spent mother liquor produced in step (vi) containing lithium ions and carbonate ions that can be recycled back in the process. In some embodiments, the base used in step (v) does not significantly increase the sodium contamination in the lithium eluate solution. In some embodiments, the base used in steps (v) is of high-grade purity. In some embodiments, the base used in steps (v) is of low-grade purity. In some embodiments, the base used in step (vi) is polished, the polishing process undertaken prior to its use in step (vi) using cationic ion exchange resins to remove contaminants.

[0091] In some embodiments, the precipitated solids in step (vii) are washed with a hot washing solution to displace the spent mother liquor with remaining dissolved impurities. In some embodiments, the hot wash solution is at temperature of at least 60 °C. In some embodiments, the hot wash solution is at temperature of at least 80 °C. In some embodiments, the hot wash solution is at temperature of at least 100 °C. In some embodiments, the hot wash solution comprises deionized water. In some embodiments, the hot wash solution comprises a dilute lithium carbonate solution. In some embodiments, the hot wash solution comprises a dilute analytical grade lithium carbonate solution. In some embodiments, the hot washsolution comprises a dilute battery grade lithium carbonate solution. In some embodiments, the hot wash solution comprises a dilute technical grade lithium carbonate solution.

[0092] In some embodiments, the spent mother liquor comprises a tail lithium solution and a washing solution. In some embodiments, the tail lithium solution comprises lithium, base (e.g. COs2-, OH ), and impurities (e.g. Na+, K+, Ca2+, etc). In some embodiments, the spent mother liquor is a liquid phase. In some embodiments, the spent mother liquor comprises liquid and solid phases. In some embodiments, the spent mother liquor is filtered to remove the precipitated solids.

[0093] In some embodiments, the spent mother liquor is recycled in step (i). In some embodiments the spent mother liquor is recycled in step (i) to control the pH of the lithium solution. In some embodiments, the spent mother liquor is filtered prior to recycling in step (i)

[0094] In some embodiments, the spent mother liquor is recycled in step (v). In some embodiments, the spent mother liquor is recycled in step (v) to treat the lithium eluate. In some embodiments the spent mother liquor is filtered prior to recycling in step (v).In some embodiments, the spent mother liquor is added to the aqueous solution in step (i) to reduce waste streams. In some embodiments, the spent mother liquor is added in step (i) as pH control agent to maintain the pH during step (i).

[0095] In some embodiments, the by-products are added to the aqueous solution in step (i) to reduce waste streams. In some embodiments, the by-products are added in step (i) as pH control agent to maintain the pH during the lithium upload step (i).

[0096] In some embodiments, the solid lithium salt is separated using a filtration process. In some embodiments, the solid lithium salt is dried to remove excess moisture.

[0097] In some embodiments, the system further comprises a third reactor comprising one or more means for concentrating and / or purifying the lithium eluate to produce a lithium rich solution,

[0098] In some embodiments, the system further comprises means for treating the lithium rich solution to produce a solid lithium salt and a spent mother liquor. In some embodiments, the means for treating the lithium rich solution to produce a solid lithium salt and a spent mother liquor is a base.

[0099] In some embodiments, the system further comprises a third separating device to separate the solid lithium salt and the spent mother liquor. In some embodiments, the systemfurther comprises a third separating device and a fourth separating device to separate the solid lithium salt and the spent mother liquor.

[0100]

[0101] In some embodiments, the system further comprises means for conveying at least part of the spent mother liquor from the third separating device to the first reactor and / or the third reactor.

[0102] Any of the aforementioned features or embodiments or aspects may be combined with one or more of the other features or embodiments or aspects as described herein.

[0103] The term "comprising" as used in this specification and claims means "consisting at least in part of". When interpreting each statement in this specification and claims that includes the term "comprising", features other than that or those prefaced by the term may also be present. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner.

[0104] It is intended that reference to a range of numbers disclosed herein (for example, 1 to 10) also incorporates reference to all rational numbers within that range (for example, 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9 and 10) and also any range of rational numbers within that range (for example, 2 to 8, 1.5 to 5.5 and 3.1 to 4.7) and, therefore, all sub-ranges of all ranges expressly disclosed herein are hereby expressly disclosed. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner.

[0105] As used herein the term "and / or" means "and" or "or", or both.

[0106] As used herein "(s)" following a noun means the plural and / or singular forms of the noun.

[0107] To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting.

[0108] The disclosure consists in the foregoing and also envisages constructions of which the following gives examples only. Features disclosed herein may be combined into new embodiments of compatible components addressing the same or related inventive concepts.BRIEF DESCRIPTION OF THE FIGURES

[0109] Preferred embodiments of the disclosure will be described by way of example only and with reference to the following drawings.

[0110] Figure 1 shows a DLE process flow sheet for a process according to the invention.

[0111] Figure 2 shows a DLE and lithium refining process flow sheet with the recycling circuits according to the invention.

[0112] Figure 3 shows a graph of lithium upload efficiency fora plug flow reactor (PFR) upload according to the invention.

[0113] Figure 4 shows a graph of lithium upload efficiency for a plug flow reactor (PFR) elution according to the invention.

[0114] Figure 5 shows a graph of lithium upload efficiency for a DLE process with lithium eluate recycling according to the invention.

[0115] Figure 6 shows a graph of lithium eluate composition in the purification process with the addition of NazCOs 10 wt%.

[0116] Figure 7 shows a graph of the concentration of a lithium eluate concentrated with forward osmosis.DETAILED DESCRIPTION OF THE INVENTION

[0117] Described herein is a process for extracting lithium from an aqueous solution containing lithium, the process comprising, (i) contacting an aqueous solution containing lithium with a lithium sorbent to absorb the lithium to produce a mixture of a lithium loaded sorbent and lithium depleted solution, (ii) separating the lithium loaded sorbent and the lithium depleted solution, and (iii) treating the lithium loaded sorbent to produce a mixture of a lithium eluate and a regenerated sorbent and, (iv) separating the lithium eluate and the regenerated sorbent.

[0118] Also described herein is a system for extracting lithium from an aqueous solution containing lithium, the system comprising, a first reactor for bringing an aqueous solution containing lithium into contact with a lithium sorbent to absorb the lithium to produce a lithium loaded sorbent and lithium depleted solution, means to separate the lithium loaded sorbent and the lithium depleted solution, a second reactor for treating the lithium loaded sorbent to produce a lithium eluate and regenerated sorbent. In the system described hereinthe first and / or second reactors are preferably a plug flow reactor. The system may be configured to be operated as a continuous process.

[0119] The inventors have discovered that utilizing one or more plug flow reactors is advantageous for scaling up the lithium extraction process towards commercialization as compared to batch reactors. The main advantages are the lower capital cost of the equipment and maintenance required as compared to tank reactors. The use of plug flow reactors also allows the process to be carried out continuously as compared to batch reactors. The plug flow reactor process also shows significant advantages with improved extraction rate and reaction time as compared to continuous stirred tank reactor process. The process improvements are a result of the high conversion rates achieved using a plug flow reactor in the DLE process, by maintaining the concentration gradients with a constant flow rate applied to avoid back-mixing of the sorbent in the reaction (e.g. lithium loaded sorbent is not back mixed with the lithium brine as the reaction progresses along the PFR). The sorbent and lithium solution can be flowed in a plug flow reactor process until the desired absorption / upload is obtained. The same concept is applied for the lithium elution, with lithium loaded sorbent flowed in a plug flow reactor. Acid can be added until the desired lithium release (elution) is obtained. It was found that the sorbent dose rate may be optimized to tune the plug flow reactor process time and for the design of the pipe length for the required residence time. The plug flow reactor also allows the pH and sorbent dose to be altered as the absorption reaction progresses along the reactor, e.g., by addition of an acid, a base or sorbent through feed ports along the plug flow reactor.

[0120] The inventors have also developed multiple optional recycling streams in the lithium extraction process to minimize waste and process cost. The recycling streams described herein comprise the excess acid, one or more by-products and the spent mother liquor.

[0121] The lithium eluate obtained in step (iv) with excess acid may be recycled to elute further lithium loaded sorbent with the benefit of recycling excess acid and increasing the lithium eluate concentration. For example, the lithium eluate obtained in step (iv) may be contacted with a further lithium loaded sorbent. Effectively, recycling the lithium eluate reduces the requirements for concentrating the lithium eluate (e.g. reverse osmosis process, evaporation, forward osmosis, etc.) to produce a lithium rich solution. This process may provide multiple advantages compared to a process without the recycling step, including (1) reduced water usage; (2) reduced usage of means for eluting lithium from sorbent, such as the acid; (3)increased concentration of lithium in the lithium eluate; and (4) reducing the use of membrane concentration systems or evaporation process to concentrate the lithium eluate solution for further processing.

[0122] Preferably, the lithium eluate solution is recycled until the solution has a lithium concentration of at least 1,000 mg / l. More preferably, the lithium eluate solution is recycled until the solution has a lithium concentration of at least 1,200, 1,400, 1,600, 1,800 or 10,000 mg / l

[0123] Certain by-products of the DLE process can also be recovered and used as a pH control aid in the DLE process. The advantages of recycling the by-products are the recovery of the base ions and reduce the waste produced in the process. The spent mother liquor can also be recycled in the process to recover both the base ions and lithium ions back into the process.

[0124] Step (i), bringing an aqueous solution containing lithium into contact with a sorbent, can be referred to as the upload step. The sorbent selectively absorbs lithium into or onto its porous structure and releases hydrogen ions. The lithium sorbent is usually a powder or slurry; although the sorbent could be in the form of a pellet or bead.

[0125] The amount of sorbent used in step (i) is preferably in excess dose to the amount of lithium in the aqueous solution. For example, the sorbent dose may be based on a 10 mg / g capacity (mg of lithium / grams of sorbent). Preferably, the sorbent in step (i) is about over 1 to 3 times the dose capacity to the amount of lithium in the in the aqueous solution. As an example of the sorbent being added in a slight excess to the amount needed to absorb the lithium, for an aqueous solution containing 200 mg / l lithium, a sorbent with a capacity of 10 mg / g Li may be added at a rate > 20 g / l to be in excess.

[0126] The upload step is preferably performed in a plug flow reactor. Those persons skilled in the art will appreciate that various parameters of the system may be altered to achieve, e.g., the desired lithium absorption. One parameter is residence time, i.e. the amount of the time mixture (e.g. aqueous solution and sorbent) remains in the plug flow reactor. The sorbent and aqueous solution containing lithium are preferably pumped at a constant rate in the plug flow reactor until the lithium absorbs into the sorbent. This process typically takes about 2 minutes although it can take minutes to hours depending on the sorbent particle size, excess sorbent dose, temperature, pH, lithium concentration etc. For example, the aqueous solution and the lithium sorbent may be flowed through the plug flow reactor with a residence time ranging from about 1 to 120 minutes. Preferably, the residence time is about 1 to 10 minutes.

[0127] Another parameter is the flow velocity. The flow velocity may be set to maintain constant plug flow and to achieve the desired residence time. If the flow velocity is too slow, it can cause sedimentation and / or blockage. If the flow velocity is too fast, it can lead to a short residence time and, consequently, insufficient lithium absorption. In some embodiments, the plug flow in the plug flow reactor comprises an axial flow. Accordingly, the aqueous solution and the sorbent may be transferred into the plug flow reactor with a minimum velocity to suspend the sorbent particles (i.e. avoid sedimentation and / or blockage). This may be a high axial velocity with turbulent flow is applied to suspend the sorbent particles. For example, the flow velocity of the aqueous solution in the plug flow reactor may be 1 -10 m / s. Preferably, the flow velocity of the aqueous solution in the plug flow reactor is 1-3 m / s.

[0128] The sorbent dose flow in the plug flow reactor may be calculated based on the lithium concentration in the aqueous solution and the aqueous solution flow rate. For example, the sorbent may be dosed in the plug flow reactor at about 0.01 to 100 g / s flow rate. Alternatively, the sorbent may be dosed as a slurry with solids concentration ranging from 0.1 to 99 wt%. For example, the sorbent may be suspended in water at 30wt% slurry concentration with the flow rate dose ranging from 0.1 to 353 g / s.

[0129] The preferred flow velocity may vary with other parameters of the system, e.g., pipe length and diameter. When the plug flow reactor has a shorter pipe length, a lower flow velocity may be used to achieve sufficient residence time. Conversely, when the plug flow reactor has a longer pipe length, a higher flow velocity may be used. For example, the length of the plug flow reactor may be about 50 to 1500 m, about 50 to 800 m. about 50 to 600 m, about 100 to 400 m, about 100 to 300 m or about 100 to 200 m. Preferably, the length of the plug flow reactor is about 100 to 200 m.

[0130] The diameter of the pipe is also relevant for flow characteristics. Preferably, the plug flow reactor is operated to achieve substantially axial flow of the aqueous solution and sorbent mixture though the reactor. Because there is no axial mixing, a concentration gradient forms along the length of the reactor, with the concentration of the aqueous solution and sorbent mixture changing continuously in a unidirectional flow, exclusively in a forward direction along the reactor's length. Without wishing to be bound by theory, it is believed the mixture flows through the reactor in an axial direction with minimal forward or backward mixing, which provides a consistent residence time for the mixture flowing through reactor. For example, the plug flow reactor may have a diameter of about 5 to 155 mm, about 10 to 140 mm, about 10to 120 mm, about 15 to 100 mm, about 15 to 80 mm, about 15 to 60 mm, about 20 to 40 mm or about 20 to 30 mm. Preferably, the plug flow reactor has a diameter of about 20 to about 30 mm.

[0131] The plug flow reactor may comprise one or more feed ports to allow addition of components at multiple points along the plug reactor. For example, additional sorbent (such as freshly activated sorbent) may be added at multiple points along the plug flow reactor via one or more feed ports. Additionally, or alternatively, an acid or a base may be added along the plug flow reactor via feed ports to maintain the pH of mixture within a desired range. Those persons skilled in the art will appreciate the number and location of feed ports will be system dependent, e.g. to achieve desired lithium absorption, pH, etc.

[0132] Flow of the aqueous solution and sorbent through the plug flow reactor will typically be driven by a pump. Accordingly, the DLE system may comprise a pump connected to the plug flow reactor to facilitate flow. Additionally or alternatively, gravity may be utilized in some circumstances. For example, the plug flow reactor input flow may occur at a higher elevation to the output flow to facilitate the flow of the aqueous solution and lithium sorbent along the plug flow reactor.

[0133] The progress of the upload / adsorption may be monitored, for example via Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Flame atomic absorption spectroscopy (FAAS) or Ion Chromatography (IC), to see when the desired absorption / upload is obtained. Preferably the pH of step (i) is maintained at 3 to 10 while the lithium is being absorbed as desired and / or absorption step is stopped and / or just prior to the next step.

[0134] A base may be added continuously to maintain the pH while the lithium is being absorbed, for example bases that may be used are NaOH, Ca(OH)2, CaCOs, NazCOs, NHsOH and / or NaHCOs. The addition of the base if not controlled may cause localized precipitation, it is therefore preferred that the base is added gradually and / or a dilute base is used such that localized precipitation is reduced when compared to addition of the base in a single load. In a continuous system, the pH may be maintained at different pipe lengths with the use of feed ports. Accordingly, the plug flow reactor may have one or more feed ports located along the reactor for dosing a base into the aqueous solution and sorbent flow. The location of the feed ports may be determined based on the requirements of the system. For example, it may be preferable to have feed points located at the halfway point or after to allow dosing of base to counteract pH decrease due to the release of hydrogen ions from the sorbent. A combinationof bases may also be added along the plug flow reactor. For example, Ca(OH)2 may be added early in the process followed by a NazCOs towards the end of the absorption process.

[0135] Additionally or alternatively, the aqueous solution may comprise a natural buffer capacity to maintain the pH while the lithium is being absorbed. For example, the aqueous solution may contain a buffer such as borate or bicarbonate.

[0136] The sorbent is preferably dosed into the aqueous solution containing lithium in the plug flow reactor with no mixing device. Advantageously, the use of a plug flow reactor avoids the needs for a mixing device or process. For example, the reactor does not need baffle mixers, static mixers or changing flow directions.

[0137] Once the lithium has been absorbed, the lithium loaded sorbent is separated from the lithium depleted solution in step (ii). This can be achieved using physical separation methods, such as a filter press or an ultrafiltration membrane, as the lithium loaded sorbent largely remains a solid. Other means of separating the solid lithium loaded sorbent and the lithium depleted solution will be apparent to a person skilled in the art. When the sorbent is at low concentrations, a pre-concentration filtration method or settling can be used to concentrate the sorbent before it is further concentrated with another method. In some cases, the sorbent can be concentrated to a slurry and eluted as a slurry. Once separated, the lithium depleted solution may be disposed of or, may be further processed or, particularly when the aqueous solution containing lithium came directly or indirectly from a ground water (for example a geothermal water) can be reinjected into the ground. The physical separation method can be continuous to match the continuous absorption process.

[0138] The mixture of loaded lithium sorbent and depleted lithium solution may be transferred to a tank for storage and / or separation. For example, after the upload step in the plug flow reactor, the mixture may be transferred to a tank, preferably a stirred tank, for separation. The sorbent mixture may be stored in a tank and recirculated into a UF membrane for a dewatering process. Once the sorbent concentration is >30wt%, the sorbent may be further concentrated with a dialysis process using a UF membrane and recirculation tank. Once the sorbent is sufficiently concentrated, it may be transferred to a tank or plug flow reactor for elution.

[0139] In order to recover the lithium from the lithium loaded sorbent, the sorbent is brought into contact with an acid (for example washed with acid or the acid is dosed into the plug flow reactor with the sorbent). This may be referred to as the elution step or unload step. Thehydrogen ions exchange for lithium in the porous structure releasing the lithium and regenerating the sorbent.

[0140] The elution step may be performed, e.g., in a tank or in a plug flow reactor. Details of the design and operation of the plug flow reactor mentioned above for the upload step, where appropriate, will also apply to the elution step. Preferably, the elution step is performed in a plug flow reactor.

[0141] The lithium loaded sorbent may be dosed in water or, alternatively dosed in lithium eluate solution at 1 to 1000 g / L, preferably around 700 g / l. Sorbent may then be added to the acid solution to release the lithium. Acid may also be added to the lithium eluate liquor before contacting with the sorbent. HCI is the preferable acid although other acids such as H2SO4, HBr, HI and phosphoric acid may be used. Some organic acids may be used although some, such as oxalic acid or citric acid, may dissolve the sorbent so would be less preferred. The acid may be added all at once or preferably slowly (i.e. over 2 minutes, or added gradually along the PFR length), the acid may be added in excess or at a 1 :1 stoichiometric ratio to the lithium held by the sorbent or until a stable pH around 1 -2 is achieved to produce a lithium eluate with excess acid and regenerated sorbent. The acid may be added in excess and / or all at once to the recycled / re-used lithium eluate for multiple elution cycles (e.g. 4 times excess acid is added to be used for 4 consecutive elution cycles). The recovery of the lithium from the lithium loaded sorbent may also be done in a plug flow reactor. Sorbent and acid are continuously dosed into the plug flow reactor. Dosing points along the plug flow reactor, e.g. via feed ports, may be used to add sorbent or acid at different stages along the reactor.

[0142] The lithium eluate and regenerated sorbent may be separated, for example by filtration (such as with a filter press, microfiltration or an ultrafiltration membrane) or other means.

[0143] The process may comprise one or more steps to concentrate and / or purify the lithium eluate to produce a lithium rich solution. For example, the process may comprise recycling the lithium eluate in steps (iii) and (iv) to increase the lithium concentration, treating the lithium eluate to remove one or more impurities (e.g., by precipitating the impurities as one or more by-products), concentrating the lithium eluate, e.g., with osmosis, evaporating the lithium eluate or a combination of any two or more thereof.

[0144] The lithium eluate may be re-used in the process, e.g. recycled in elution step (iii). For example, the lithium eluate may be recycled in the elution step to further contact the lithium loaded sorbent and increase the concentration of lithium in the lithium eluate. Further lithiumloaded sorbent (i.e. fresh lithium loaded sorbent) may also be added in the elution step when recycling the lithium eluate. Accordingly, when recycling the lithium eluate, the elution step may be carried out with the same lithium loaded sorbent, further lithium loaded sorbent, or a combination thereof. In some instances, the process may be a continuous process in which lithium eluate is continuously recycled into the elution step with fresh lithium loaded sorbent.

[0145] Some or all of the lithium eluate may be recycled in the elution step. For example, at least about 10% v / v of the lithium eluate from step (iv) may be recycled to step (iii). In some embodiments, at least about 30% v / v, 50% v / v, 70% v / v or 90% v / v of the lithium eluate from step (iv) is recycled to step (iii). In some embodiments, about 100% v / v of the lithium eluate from step (iv) is recycled to step (iii).

[0146] The lithium eluate may be recycled in the elution step until a predetermined lithium concentration is achieved. For example, the lithium eluate may be recycled in the elution step until a lithium concentration of at least about 1,000 mg / l, 1,200 mg / l, 1,400 mg / l, 1,600 mg / l, 1,800 mg / l is achieved. In some embodiments, the lithium eluate solution from step (iv) is recycled to step (iii) until the lithium eluate solution has a lithium concentration of at least about 10,000 mg / l.

[0147] The lithium eluate may be further processed and refined into battery grade (e.g. LizCOs, LiOH) when the concentration of lithium is at least 1,000 mg / l. The inventors have found that recycling the lithium eluate in the process is particularly relevant when processing medium to low grade lithium bines to build up the lithium concentration in the elution step reducing or eliminating the need to use reverse osmosis systems or evaporation process. The regenerated sorbent may be reused in the process, i.e. recycled in the upload step (i).

[0148] Advantageously, elution of a lithium loaded sorbent with the lithium eluate may not require the addition of more water and acid since these components will already be present from the first elution step. In some cases, it is preferable to add more acid to the lithium eluate, to maintain an excess or at least a 1 :1 stoichiometric ratio to the lithium held by the sorbent or until a stable pH around 1 -2 is achieved to produce a lithium eluate with excess acid and regenerated sorbent.

[0149] Advantageously, the lithium absorption step (i) and / or recovering the lithium from the loaded sorbent step (iii) in a plug flow reactor prevents backwards mixing of sorbent in different states i.e. the state of the sorbent progresses linearly along the reactor. This allows the pH and dose of sorbent to be adjusted as the desired reaction proceeds. An example maybe a slower base addition rate at the end of the reactor compared to the start of the reactor due to the slower absorption kinetics of the brine. Another example may be the addition of fresh sorbent to the end of the reactor to scavenge the low lithium levels to improve upload efficiency. In another example, loaded sorbent may be added to the end of the reactor to partly neutralize any excess acid. Alternatively, the acid dose rate may be slower at the end of the reactor compared to the start of the reactor due to the slower release kinetics of the lithium from the sorbent.

[0150] The lithium eluate may be treated to remove one or more impurities. The impurities may be removed by selective precipitation, absorption on an ion exchange resin or a combination thereof. For example, the impurities in the lithium eluate may be selectively precipitated as one or more by-products and separated based on the solubility limit of the impurities. The solubility limit of the by-products typically decreases with the increase on the pH of the solution and / or the temperature of the solution. Therefore. By-products may be selectively precipitated by increasing the pH and / or temperature of the lithium concentrated eluate to decrease the solubility limit of a specific impurity or a combination of impurities. The amount of base to be added to the solution may also be calculated relative to the amount of impurity to be precipitated. In these embodiments, the base may be added in stoichiometric dose or stoichiometric excess (e.g. 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0 times the stoichiometric dose) relative to the amount of impurity to be removed. For example, in some embodiments, the one or more by-products are precipitated with the addition of a base (e.g. NazCOs, NaOH) equivalent to the mols of the impurity as exemplified in Equations 1 and 2 with calcium ions as an example of impurity. Preferably, step (v) is performed at a temperature of about 50 to 100°C, about 60 to 100°C, about 70 to 100°C or about 80 to 100°C.2NaOH + Ca2+-> Ca(0W)2+ 2Na+Equation 1Na2CO3+ Ca2+-> CaC03+ 2Na+Equation 2

[0151] The precipitated by-products may be separated from the lithium eluate by conventional solid / liquid separation methods known in the art. For example, the solid byproducts may be separated from the lithium eluate by a filtration process (such as filter press, centrifuge, microfiltration, ultrafiltration, nanofiltration and a combination of any two or more thereof), density separation and / or decantation.

[0152] The one or more impurities may be removed sequentially and / or concomitantly. For example, a first by-product may be precipitated and separated from the concentrated lithium eluate, followed by precipitation and separation of a second by-product, and repeated as required. This may be achieved, e.g., by adding the base equivalent to precipitate the byproduct with the lowest solubility limit present in the lithium eluate to precipitate the first byproducts, separating the first by-product from the solution then further adding base to the solution to precipitate a second by-product and separating the second by-product from the solution, and so on. The one or more by-products may be removed sequentially by a combination of precipitation and separation steps and polishing steps. The one or more byproducts may be removed concomitantly by a combination of precipitation and separation steps and polishing steps. For example, one or more by-products may be removed in one or more steps precipitation and separation steps and further dissolved impurity may be separated by one or more polishing steps involving contacting the lithium rich solution with an ion exchange resin.

[0153] Preferably, the one or more by-products removed in step (v) may be recycled in the process. For example, the separated by-product may be recycled in step (i) to control the pH of the solution (as a base). Advantageously, recycling the by-products reduces waste produced by the process and reduces the amount of new reagents that must be added to the process. Advantageously the by-products may be used as one or more by-products combined.

[0154] Optionally, one or more remaining dissolved impurities in the lithium eluate, may be removed by polishing, i.e., contacting the lithium eluate with an ion exchange resin for a sufficient period of time to adsorb the one or more dissolved impurities. A suitable ion exchange resin may be selected based on the desired dissolved impurities to be removed. Suitable ion exchange resins include, but are not limited to, commercially available resins such as a cationic ion exchange resin. For example, Purolite™ S940 may be used to purify the lithium eluate to decrease the amount of the dissolved impurities down to <5 mg / l or trace levels. Some of the dissolved impurities that can be removed with the Purolite™ S940 are Ba, Ca, Mg, Sr. Purolite™ S108 can be used to remove boron to < 5 mg / l. In some embodiments, the ion exchange resin is packed into a column. In some embodiments, the ion exchange resin is mixed with the concentrated lithium eluate liquor and separated using a solid / liquid separation method (e.g. filter press, vacuum filtration, centrifuge, density separation, decantation). Optionally, the dissolved impurity may be recovered from ion exchange resin, e.g., by washingthe resin with an acidic solution. The dissolved impurity may be disposed of as a liquid waste, a solid waste, and / or mixed with the spent brine for reinjection.

[0155] Additionally or alternatively, the lithium eluate may be filtered through a nanofiltration membrane to remove one or more impurities, e.g. a divalent ion such as Ca, Mg, or Fe.

[0156] Optionally, the lithium eluate may be concentrated by, e.g., evaporation and / or a lithium concentration membrane system. The lithium concentration membrane system may utilize concentration processes, such as a low-pressure reverse osmosis membrane, a high- pressure reverse osmosis membrane, a forward osmosis membrane, a reverse osmosis membrane or a combination of any two or more thereof. A draw solution may be used in combination with a forward osmosis membrane in the lithium concentration process to create an osmotic pressure difference, drawing water from a feed solution across a semi-permeable membrane. The draw solution may have a higher osmotic pressure than the feed solution. The draw solution may be a high TDS solution. Examples of suitable draw solutions include, but are not limited to a solution of a high molecular weight salt such as ammonium bicarbonate or trimethyl ammonium bicarbonate; a polymer based draw solution such as PAA, PEG or coblock polymers; a brine; spent brine; lithium depleted brine; lithium depleted brine after DLE process; sea water; saline water or combination of any two or more thereof. When certain osmosis processes are utilized, e.g. reverse osmosis, a concentrated lithium solution (i.e. a lithium rich solution) and a permeate are produced. Advantageously, the permeate may be recycled in the DLE process. For example, when the lithium eluate is acidic, an acidic permeate may be produced, which can subsequently be cycled into the elution step of the process, or any other step in which an acid is required.

[0157] Those persons skilled in the art will appreciate the concentration and purification steps may be performed in any order as appropriate and repeated as necessary.

[0158] Advantageously, the lithium rich solution may be sufficiently pure for certain applications. However, optionally, the lithium rich solution may be further treated to produce a solid lithium salt and spent mother liquor. For example, the pH of the treated lithium rich solution may be increased until the lithium salt precipitates from the solution with the addition of a base. The solubility limit of lithium in solution may be dependent on the temperature of the solution. The amount of base to be added to the solution may also be calculated relative to the amount of lithium in the solution. In these embodiments, the base may be added in stoichiometric dose or stoichiometric excess (e.g. 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0times the stoichiometric dose) relative to the amount of lithium. The lithium salt may be separated from the spent mother liquor by liquid / solid separation methods as described above. Advantageously, the separated lithium salt may provide a high purity lithium, e.g., battery grade lithium. The spent mother liquor may be recycled in the DLE process to recover the lithium and base ions and reduce waste streams in the process. For example, the spent mother liquor may be recycled in step (i) and / or in step (v).

[0159] In one aspect, the invention provides a process for extracting lithium from an aqueous solution containing lithium, the process comprising: i) contacting an aqueous solution containing lithium with a lithium sorbent to produce a mixture of a lithium loaded sorbent and a lithium depleted solution; ii) separating the lithium loaded sorbent and the lithium depleted solution; iii) treating the lithium loaded sorbent with an acid to produce a lithium eluate and a regenerated sorbent; iv) separating the lithium eluate and the regenerated sorbent; v) concentrating and / or purifying the lithium eluate to produce a lithium rich solution, wherein concentrating and / or purifying the lithium eluate comprises one or more of the following steps: a. repeating steps (iii) and (iv) with the lithium eluate from step (iv), b. treating the lithium eluate with a base to precipitate one or more impurities as one or more by-products and separating the by-products from the lithium eluate, wherein at least part of the by-products is recycled in step (i), c. removing one or more impurities, e.g. by contacting the lithium eluate with an ion exchange resin for a sufficient period of time to adsorb the one or more impurities and / or filtering the lithium eluate through a nanofiltration membrane, and / or d. concentrating the lithium eluate by an osmosis or evaporation process; vi) treating the lithium rich solution to produce a solid lithium salt and a spent mother liquor; and vii) separating the solid lithium salt from the spent mother liquor; wherein at least part of the spent mother liquor from step (vii) is recycled in steps (i and / or v- b).

[0160] In another aspect, the invention provides a system for extracting lithium from an aqueous solution containing lithium, the system comprising, i) a first reactor for contacting an aqueous solution containing lithium with a lithium sorbent to absorb the lithium to produce a lithium loaded sorbent and a lithium depleted solution; ii) a first separating device for separating the lithium loaded sorbent and the lithium depleted solution; iii) a second reactor for contacting the lithium loaded sorbent with a means for treating the lithium loaded sorbent to produce a lithium eluate and a regenerated sorbent, iv) a second separating device for separating the lithium eluate and the regenerated sorbent; v) one or more means for concentrating and / or purifying the lithium eluate to produce a lithium rich solution selected from: a. means for conveying the lithium elute to the third second reactor, b. a third reactor for precipitating one or more impurities from the lithium eluate as one or more by products and, optionally, means for conveying the byproducts to the first reactor, and / or c. a lithium concentration system, e.g. one or more osmosis membranes and / or an evaporation device; vi) means for treating the lithium rich solution to produce a solid lithium salt and a spent mother liquor; vii) a third separating device for separating the solid lithium salt and the spent mother liquor; viii) means for conveying at least part of the spent mother liquor from the third separating device to the first reactor and / or the third reactor.

[0161] In one aspect, the invention provides a process for extracting lithium from an aqueous solution containing lithium, the process comprising: i) contacting an aqueous solution containing lithium with a lithium sorbent to produce a mixture of a lithium loaded sorbent and a lithium depleted solution; ii) separating the lithium loaded sorbent and the lithium depleted solution; iii) treating the lithium loaded sorbent with an acid to produce a lithium eluate and a regenerated sorbent;iv) separating the lithium eluate and the regenerated sorbent; v) concentrating and / or purifying the lithium eluate to produce a lithium rich solution, wherein concentrating and / or purifying the lithium eluate comprises the following steps: a. repeating steps (iii) and (iv) with the lithium eluate from step (iv), b. treating the lithium eluate with a base to precipitate one or more impurities as one or more by-products and separating the by-products from the lithium eluate, wherein at least part of the by-products is recycled in step (i), c. removing one or more impurities, e.g. by contacting the lithium eluate with an ion exchange resin for a sufficient period of time to adsorb the one or more impurities and / or filtering the lithium eluate through a nanofiltration membrane, and / or d. concentrating the lithium eluate by an osmosis and / or evaporation process; vi) treating the lithium rich solution to produce a solid lithium salt and a spent mother liquor; and vii) separating the solid lithium salt from the spent mother liquor; wherein at least part of the spent mother liquor from step (vii) is recycled in steps (i and / or v- b).

[0162] Examples of the lithium precipitation reaction are shown in equations 3 and 4. In equation 3 the mols of the base as carbonate ions (CO32) are in a 0.5 mol equivalent to lithium ions (Li+). In equation 4 the mols of the base as hydroxyl ions (OH ) are in a 1 mol equivalent to lithium ions (Li+).Na2CO3+ 2Li+-> Li2CO3+ 2Na+Equation sNaOH + Li+-> LiOH + Na+Equation 4

[0163] Lithium sorbents are described, for example in Johnson Matthey Technol. Rev., 2018, 62, (2), 161-176 "Lithium Recovery from Aqueous Resources and Batteries: A Brief Review". The lithium sorbent may be a metal oxide-based ion exchange sorbent. For example, suitable metal oxide-based ion exchange sorbents may include a hydrogen manganese oxide sorbent, a hydrogen titanium oxide sorbent, a hydrogen manganese phosphate, a hydrogen iron phosphate, a hydrogen aluminium oxide and / or a hydrogen copper oxide. Conventionalsorbents capable of absorbing lithium known in the art may be useful in the invention, e.g., LiTiC>2, Li2TiO3, Li4TiC>2, Li4TiO4, Li7Tiio024, LiMn2O4, Li1.67Mn1.67O4, Li1.33Mn1.67O4, Lix.2AI(OH)3, LiAIC , LiMnPO4, LiFePO4 and / or LiCuO2. Such sorbent precursor may be activated, if required, to form the lithium sorbent, e.g. by treatment with an acid to exchange the lithium for hydrogen. The lithium sorbent is preferably a hydrogen manganese oxide sorbent or a hydrogen titanium oxide sorbent, preferably a hydrogen manganese oxide sorbent. The sorbent is preferably lambda-phase manganese sorbents (A-MnC ) also known as lithium manganese oxide (LMO) sorbents.

[0164] For example, a hydrogen manganese oxide sorbent is made by heating (for example in a furnace) solid manganese oxide with a lithium source (for example a lithium salt) to make a lithium manganese oxide. The lithium manganese oxide is then treated with an acid to exchange the lithium for hydrogen to give a hydrogen manganese oxide sorbent.

[0165] The aqueous solution containing lithium may be obtained from a range of sources, for example, geothermal brine, salar brine, sea water, formation water, concentrates from processing seawater, a waste stream from a lithium processing facility, a waste stream from a battery recycling plants, oil well brines, other ground water. For example, geothermal brine may be used which has been processed by a silica extraction plant to remove or reduce silica content. Some sources may be naturally warm (for example 40 °C) without the need to heat the aqueous solution containing lithium, for example a geothermal source. Some sources will be cold brines and without the need to heat the aqueous solution containing lithium.

[0166] Various embodiments are described with reference to the Figures. Throughout the Figures and specification, the same reference numerals may be used to designate the same or similar components, and redundant descriptions thereof may be omitted.

[0167] A DLE preferred process according to the invention is shown in Figure 1. The system comprises two plug flow reactors 120 and 130 connected in series, containing physical separation systems 103 and 107 in between each plug flow reactor. Incoming lithium brine 101 enters the first plug flow reactor at a set velocity / flow rate through pump 121. At the same time, sorbent 102 is simultaneously pumped into the plug flow reactor at a set flow rate / velocity set through pump 122 to provide a set final concentration of lithium brine and sorbent. This sorbent / lithium brine flows through the plug flow reactor 120 as upload of lithium to the sorbent occurs. As the sorbent / lithium brine mixture enters the plug flow reactor, a base is simultaneously pumped into the plug flow reactor using one or more feeding ports109, 110, 111 along the PFR. The base is pumped into the plug flow reactor at a flow rate / velocity set to ensure a pH of the sorbent / lithium brine mixture that results in the lithium upload. Continued pH dosing may be required as lithium ions replace hydrogen ions within the sorbent as the upload progresses through the plug flow reactor with a consequent pH decrease. The residence time of the sorbent / lithium brine in the first plug flow reactor may be adjusted by changing the flow rate such that lithium upload to the sorbent will occur by the time the mixture reaches the end of the plug flow reactor, at which point sorbent will be physically separated from the lithium depleted brine 104 with a separating device 103. The separated lithium loaded sorbent is then dialyzed while being concentrated in the filtration process in 103 to form a concentrated lithium loaded sorbent slurry.

[0168] The concentrated lithium loaded sorbent slurry is then flowed into a second plug flow reactor 130 at a set flow rate / velocity through pump 123. As the concentrated lithium loaded sorbent slurry enters the plug flow reactor 130, an acid 105 is simultaneously pumped into the plug flow reactor through pump 124. Recycled acid 106 is pumped into the reactor through pump 125. The acid is pumped into the plug flow reactor at a flow rate / velocity set to ensure a pH of the loaded sorbent slurry / acid mixture that results in release of the lithium from the lithium loaded sorbent using one or more feed ports 112, 113, 114 along the PFR. As the lithium loaded sorbent / acid mixture flows through the plug flow reactor additional feed ports for acid may be provided with additional acid to the system to ensure the pH is maintained below the critical pH for efficient lithium elution. Continued pH dosing may be required as hydrogen ions replace lithium ions within the sorbent as the elution progresses through the plug flow reactor with a consequent pH increase. Addition of excess acid dose at the beginning of the plug flow reactor can result in damage to both the sorbent system and plug flow reactor componentry. Once the loaded sorbent slurry / acid mixture reaches the end of the plug flow reactor, elution will have completed forming a lithium eluate and eluted sorbent mixture. The lithium eluate is then separated from the eluted sorbent with separation device 107 and providing a separated eluted sorbent slurry and lithium eluate. Optionally, the lithium eluate is concentrated in a lithium concentration system 108 to provide a lithium rich solution and an acid 106 that is recycled in the reactor through pump 125. The eluted sorbent (regenerated sorbent) is recycled back in the process from 107 through pump 122. In further cycles for elution of lithium loaded sorbent, acid is pumped into the plug flow reactor simultaneously with the lithium loaded sorbent slurry. Alternatively, recycled acid 106 can be used. This allowsfor efficient elution of the lithium loaded sorbent reducing fresh acid usage and providing a gradual increase in the lithium concentration in the lithium eluate after each further elution cycle.

[0169] A schematic diagram of a preferred process to extract lithium from brines to produce a lithium rich solution and / or a lithium salt according to the invention is shown in Figure 2. The lithium aqueous solution is contacted with the sorbent in the lithium upload step of the DLE process. At the end of the upload step the lithium depleted aqueous solution may be sent for disposal or reinjection. The lithium loaded sorbent is then directed to the elution step of the DLE process. In the elution step, acid is added to recover the lithium in the form of a lithium eluate, and the sorbent is recycled back to the upload step. The lithium eluate is optionally concentrated by recycling back into further elution cycles or by using concentration processes, for example low-pressure reverse osmosis, high-pressure reverse osmosis, forward osmosis, evaporation, or the combination of any two or more thereof, where the excess acid and remaining lithium can be recycled in the elution step while lithium is concentrated. The concentrated lithium eluate is then purified with a diluted base to precipitate by-products of the DLE process in the form of carbonates or hydroxides (e.g. Ca(OH)2, CaCOs, MgCOs). The by-products can be recycled back in the upload step of the DLE process to control the pH of the lithium aqueous solution and / or to reduce waste streams. As an alternative to the purification of the lithium eluate, nanofiltration can be used to separate divalent ions (e.g. Ca, Mg, Fe etc.), generating a divalent impurity retentate and a lithium rich solution. The lithium rich solution is filtered and optionally further processed in concentration processes that may include forward osmosis, low-pressure osmosis, high pressure osmosis, evaporation or the combination of two or more processes to further increase the lithium concentration. The purified and concentrated lithium eluate is filtered and further processed in the polishing step using IX resins to selectively remove dissolved impurities (e.g. Ca2+, Mg2+, Sr2+). The IX resin can be regenerated and re-used in the process. The polished lithium eluate may be processed in a crystallizer to precipitate a lithium salt (e.g. LiOH, LizCOs) and a tail lithium liquor (spent mother liquor). The spent mother liquor containing lithium and carbonate ions may be recycled in the lithium upload step and / or in the lithium rich solution purification step. The steps of recycling the by-products and the spent mother liquor can significantly reduce the waste streams and chemical usage in the process.

[0170] The advantages of the recycling streams include the reduction in the process operational costs and recovery of the lithium back in the process. The recycling circuits are composed of the sorbent recycling in the upload step (i) for multiple cycles, the acid recycling in the elution step (iii) with the re-use of the lithium eluate, the spent mother liquor recycling in steps (i) and (v), the by-products recycling in steps (i).

[0171] Where, in the foregoing description reference has been made to integers or components having known equivalents thereof, those integers are herein incorporated as if individually set forth.

[0172] Although the present disclosure has been described in terms of certain embodiments, other embodiments apparent to those of ordinary skill in the art also are within the scope of this disclosure. Thus, various changes and modifications may be made without departing from the spirit and scope of the disclosure. For instance, various components may be repositioned as desired. Moreover, not all of the features, aspects and advantages are necessarily required to practice the present disclosure. Accordingly, the scope of the present disclosure is intended to be defined only by the claims that follow.EXAMPLESEXAMPLE 1: PLUG FLOW REACTOR (PFR) TRIAL

[0173] The lithium upload was carried out in the PFR using a synthetic brine containing approximately 20 mg / l lithium concentration. The test was carried out at ambient temperature, with brine flow set at 1.9 m3 / h (equiv. to 0.5 l / s) and the sorbent added as a 30 wt% slurry at a constant flow rate of 3 ml / second in the PFR with a total residence time of 2 minutes. A dilute base was added in the first chemical dosing port in the PFR to control the brine pH during the upload trial to favor the lithium upload at pH> 5. Samples were taken from each of the 6 sampling ports along the PFR and the lithium upload efficiency was calculated. Once the sorbent slurry / brine mixture reached the end of the plug flow reactor, the upload was completed, forming the lithium depleted brine and a lithium loaded sorbent. The summary of the results is shown in Figure 3. The average upload efficiency of two trials was 91%, in a total residence time of 2 minutes by the samples taken at the sample point 6 in the PFR.

[0174] The lithium elution reaction was tested in a PFR after contacting the sorbent with a lithium brine. The lithium loaded sorbent slurry was at 30 wt% solids concentration and theslurry was processed in the PFR at ambient temperature with a fluid velocity of 1 m / s. The length of the PFR was 135 m which resulted in a total residence time of 2 minutes to complete the elution reaction. A total of 6 sample points were placed along the PFR to determine the rate of the kinetics reaction. As the lithium loaded sorbent slurry entered the PFR, a concentrated acid was simultaneously pumped into the PFR chemical dosing port. The acid was pumped into the PFR to ensure a pH of about 1.5 of the loaded sorbent slurry / acid mixture to result in release of lithium from the lithium loaded sorbent. Once the loaded sorbent slurry / acid mixture reached the end of the plug flow reactor, the elution was completed forming an acidified lithium eluate and eluted sorbent mixture.

[0175] The results from the PFR trials were compared with a sample tested in the laboratory where a 30 wt% sorbent slurry was contacted with strong acid at pH 1.5 under constant agitation for 24 hours to achieve the equilibrium reaction. The lithium recovery efficiencies are shown in Figure 4 for the samples taken along the PFR with a >80% recovery efficiency obtained at sample point 1 and >97% recovery efficiencies observed for the samples taken at sample points 5 and 6. The PFR have shown an effective process for recovering lithium with a reaction time completed in less than 2 minutes time under the experimental conditions tested.EXAMPLE 2: LITHIUM ELUATE RECYCLING TRIAL

[0176] The lithium eluate recycling trial was carried out to investigate the potential of recycling the excess acid in the elution step of the Direct Lithium Extraction (DLE) process in a multicycle process. Lithium chloride was used in this experiment; however, other acids can also be used (e.g. H2SO4). In this trial a lithium sorbent was contacted with a lithium brine to achieve >90% lithium upload efficiency. The lithium loaded sorbent was filtered and dialyzed to remove entrained brine. The dialyzed sorbent was contacted with fresh acid in the first DLE cycle with 2 times excess stoichiometry of Li:H ions to achieve a pH of about 1.5 to produce a lithium eluate and a regenerated sorbent. The regenerated sorbent was used in another lithium upload cycles. The lithium eluate was collected and stored for re-use in the next elution cycles. The lithium eluate was re-used in the elution process from cycles 2 to 6 as shown in Figure 5, containing excess acid and fresh acid was added to achieve at least 2 x excess stoichiometry of Li:H ions in the solution.

[0177] It was observed a continuous increase in the lithium concentration in the lithium eluate from about 840 to 1967 mg / l with a total of 6 DLE cycles completed. The average lithiumrecovery efficiency was 100% with some cycles being below 100% and other cycles slightly higher than 100% as a result of the ion exchange equilibrium reaction compensating the lithium not fully eluted in the previous cycles. One advantage of recycling the lithium eluate liquor in the DLE process was the recovery of at least part of the excess acid. Another advantage was to obtain a lithium eluate with high lithium concentration, which minimizes or eliminate the processing of the lithium eluate using concentration processes such as evaporation, Reverse Osmosis, etc., and significantly reduce operational costs in the process. The obtained lithium eluate was suitable for purification and processing into battery grade lithium salt.EXAMPLE 3: LITHIUM ELUATE PURIFICATION, POLISHING AND PRECIPITATION OF BATTERY GRADE LITHIUM SALT

[0178] This example shows the purification process of the concentrated lithium eluate. A sample of a concentrated lithium eluate was obtained in the form of lithium chloride (LiCI) containing impurities from the DLE process. This sample was incrementally treated with high grade sodium carbonate to precipitate the by-products in the form of carbonates. The byproducts in the lithium chloride sample are a result of any solids that have been precipitated in the upload step and / or any adsorbed ions that have been carried over with the sorbent to the elution step of the DLE process. The carbonates formed in the purification step are the byproducts of the DLE process and they may comprise BaCOs, CaCOs, MgCOs, MnCOs, SrCOs, and others.

[0179] The composition of the lithium rich solution before and after the purification process is shown in Table 1. The lithium rich solution was heated up to 60 °C prior to the purification process to decrease the solubility of the by-products. The required sodium carbonate dose was calculated based on the chemical reaction of the by-products present in the concentrated lithium eluate with sodium carbonate. The total dose was calculated based on the total mols of the dissolved impurities and the equivalent carbonate stoichiometric mol rate. The sodium carbonate was then added slowly as a diluted solution of 10 wt%. Samples were taken during the purification process to determine the impurity removal versus the mols of sodium carbonate added and the corresponding pH, as summarized in Table 1. The concentration of the dissolved impurities in the lithium rich solution is shown in mg / l and they were precipitated in the purification step in the form of carbonates as the by-products and separated byfiltration. In this example one single filtration process was carried out at the end of the impurity removal step. Alternatively, the filtration step can be performed in multiple steps during the precipitation step based on their solubility limit to selectively separate the by-products. In Figure 6 the concentration of the elements in the lithium rich solution is shown with the addition of NazCOs. It is observed a decrease on the concentration of the elements due to dilution factor as a result of the addition of the 10wt% NazCOs solution. Manganese is the first dissolved impurity to precipitate in the example shown in Table 1 and Figure 6, followed by calcium and magnesium. Barium and Strontium also precipitates along with calcium and magnesium, and the remaining amount precipitates after calcium and magnesium are completely precipitated out of solution. These by-products may be recycled in the DLE process as pH control aid to minimize the waste generated in the DLE process.

[0180] The lithium rich solution was then polished using a cationic IX resin Purolite™ S940. The treated concentrated lithium eluate was processed further to obtain a lithium salt in the crystallization step was using sodium carbonate. The required sodium carbonate dose was calculated based on the concentration of lithium in solution and the required mols of carbonate ions. Table 2 shows examples of LizCOs compositions obtained after the polishing and crystallization processes. The LizCOs reference from Albemarle and SQM with the main elements listed in the battery grade specifications is also shown for comparison. The H2CO3 was of battery grade purity as compared with the reference samples.Table 1. Concentrated lithium eluate composition in the purification process.Table 2. Example of the composition of the concentrated lithium eluate in the crystallization process and the final product of the crystallization process. The grade of the final product was compared with commercially available products for reference.EXAMPLE 4: RECYCLING THE EXCESS ACID AND LITHIUM IN THE LITHIUM CONCENTRATION STEP OF THE DLE PROCESS USING REVERSE OSMOSIS

[0181] In this example is shown the lithium concentration step which includes a reverse osmosis system to increase the lithium eluate liquor concentration and to recover excess acid used in the elution process. The acid recovery is critical as it is the biggest contributor to OPEX per ton of LCE in the DLE process. This trial was carried out as an alternative to recover the excess acid in the DLE process.

[0182] To demonstrate the excess acid recovery process, a tote of lithium eluate liquor was concentrated using a low-pressure reverse osmosis membrane. As shown in Table 3, the tote of lithium eluate liquor was initially at 1100 L with a total of 750 L of the filtrate produced. This increased the Li concentration from 134 mg / L to 490 mg / L. More importantly, 85% of the excess acid in the lithium eluate liquor (approximately 2 L of 33 wt% HCI) passed though the membrane system to the filtrate. The acidic filtrate can be used directly in the elution cycle as the eluent, thus reusing the excess acid. Furthermore, any lithium that passed through to the filtrate would also be recycled into the next elution cycle of the DLE process. The reverse osmosis concentration can be processed further in a commercial scale project to potentially recover more acid and improve the OPEX of the overall process.Table 3. Example of acid recovery in the lithium concentration step using low pressure Reverse osmosis system.EXAMPLE 5: USE OF FORWARD OSMOSIS (FO) MEMBRANE TO CONCENTRATE THE LTHIUM ELUATE

[0183] The forward osmosis membrane used in this trial consisted of a polyamide thin film composite membrane. A draw solution is used in combination with a forward osmosis membrane in the lithium eluate concentration process to create an osmotic pressure difference, drawing water from the lithium eluate across a semi-permeable membrane. The draw solution must have higher osmotic pressure than the feed solution. In this example, the draw solution used was an original lithium depleted brine with an average start conductivity of 145.8 mS / cm2. The advantage of using a lithium depleted brine is to reduce process costs and recycle the lithium depleted brine before reinjection. In Table 4 and Figure 7 is the summary of the results with the lithium eluate concentration increased from 635 mg / l to > 10000 mg / l. The results show that this process was able to significantly increase the concentration of lithium in the lithium eluate, and the relative concentration rate of the nontarget solutes indicates that no significant reverse salt flux was encountered by the high TDS brine used as the draw solution. The results from this experiment validate the use of brine as the draw solution in the forward osmosis process for the concentration of lithium eluate with no significant reverse salt flux contamination into the final concentrated lithium eluate. The concentration of the lithium eluate facilitates the purification process of the lithium eluate and also the transportation costs of the lithium eluate as the final product of the DLE process.Table 4. The concentration of the lithium eluate versus the volume processed using a forward osmosis membrane and a lithium depleted brine as the draw solution.

Claims

CLAIMS1. A process for extracting lithium from an aqueous solution containing lithium, the process comprising:(i) contacting an aqueous solution containing lithium with a lithium sorbent to produce a mixture of a lithium loaded sorbent and a lithium depleted solution,(ii) separating the lithium loaded sorbent and the lithium depleted solution,(iii) treating the lithium loaded sorbent to produce a lithium eluate and a regenerated sorbent,(iv) separating the lithium eluate and the regenerated sorbent, wherein step (i) and / or (iii) are performed in a plug flow reactor.

2. The process of claim 1, wherein the lithium sorbent is a metal oxide-based ion exchange sorbent, preferably a hydrogen manganese oxide sorbent or hydrogen titanium oxide sorbent.

3. The process of claim 1 or 2, wherein the aqueous solution is contacted with the sorbent for about 1 to 120 minutes.

4. The process of any one or claims 1 to 3, wherein the sorbent is brought into contact with the aqueous solution containing lithium at about 1 to 700 g / L, 1 to 500 g / L, 1 to 200 g / L, 1 to 100 g / L or 1 to 50 g / L; optionally wherein the sorbent is added continuously to match the continuous incoming flow of aqueous solution containing lithium.

5. The process of any one of claims 1 to 4, wherein the sorbent is added along the plug flow reactor, e.g. wherein freshly activated sorbent is added at one or multiple points along the plug flow reactor via feed ports.

6. The process of any one of claims 1 to 5, wherein a base is continuously added to the aqueous solution containing lithium to maintain the pH at an average pH of about 3 to 7 when the lithium is being absorbed along the plug flow reactor via feed ports;optionally, wherein the base is added at multiple points along the plug flow reactor or at one single point along the plug flow reactor via feed ports.

7. The process of any one of claims 1 to 6, wherein the aqueous solution containing lithium comprises a buffer to maintain the pH when the lithium is being absorbed and / or the pH of the aqueous solution containing lithium is maintained at an average pH of about 3 to 10 when the lithium is being absorbed.

8. The process of any one of claims 1 to 7, wherein (wherein the sorbent is dialysed to remove entrained lithium depleted solution,9. The process of any one of claims 1 to 8, wherein the separating step (ii) and / or the separating step (iv) comprises filtering the mixture using a physical separation method, e.g. a filter press or an ultrafiltration membrane.

10. The process of claim 9, wherein the ultrafiltration membrane is a hollow fiber or spiral wound membrane and / or the filtration is cross flow filtration.

11. The process of any one of claims 1 to 1 -, wherein the amount of lithium sorbent contacted with the aqueous solution containing lithium is in excess dose to the amount of lithium in the aqueous solution; preferably, wherein the amount of the lithium sorbent is over about 1 to 3 times the dose to the amount of lithium in the aqueous solution.

12. The process of any one of claims 1 to 11, wherein the treatment in step (iii) comprises contacting the lithium loaded sorbent with an acid to produce a mixture of a lithium eluate and a regenerated sorbent, e.g., wherein the acid is selected from one or more mineral acids and / or organic acids such as HCI, H2SO4, HBr, HI and phosphoric acid or a combination of any two or more thereof.

13. The process of any one of claims 1 to 12, wherein the process further comprises: (v) concentrating and / or purifying the lithium eluate to produce a lithium rich solution.

14. The process of claim 13, wherein concentrating and / or purifying the lithium eluate comprises one or more of the following steps: a. repeating steps (iii) and (iv) with the lithium eluate from step (iv), b. treating the lithium eluate with a base to precipitate one or more impurities as one or more by-products and separating the by-products from the lithium eluate, wherein at least part of the by-products is recycled in step (i), c. removing one or more impurities, e.g. by contacting the lithium eluate with an ion exchange resin for a sufficient period of time to adsorb the one or more impurities and / or filtering the lithium eluate through a nanofiltration membrane, and / or d. concentrating the lithium eluate by an osmosis or evaporation process.

15. The process of claim 13 or 14, wherein step (v) comprises concentrating the lithium eluate to produce a lithium rich solution with a lithium ion concentration of at least about 1,000 mg / l, 1,200 mg / l, 1,400 mg / l, 1,600 mg / l, 1,800 mg / l or 10,000 mg / l, 50,000 mg / l.

16. The process of claim 13 or 14, wherein the lithium eluate from step (iv) is recycled to step (iii) until the lithium eluate has a lithium ion concentration of at least about 1,000 mg / l, 1,200 mg / l, 1,400 mg / l, 1,600 mg / l, 1,800 mg / l or 10,000 mg / l, 50,000 mg / l.

17. The process of any one of claims 14 to 16, wherein step (v) comprises concentrating the lithium eluate with a concentration process, e.g., wherein the concentration process is low-pressure reverse osmosis, high-pressure reverse osmosis, forward osmosis, evaporation or a combination of any two or more thereof.

18. The process of claim 17, wherein step (v) comprises concentrating the lithium eluate with an osmosis process to produce a lithium rich solution and a permeate, wherein the permeate is recycled in step (iii).

19. The process of any one of claims 13 to 18, wherein step (v) comprises filtering the lithium eluate with a nanofiltration membrane, e.g., to selectively remove multivalent ions in the lithium eluate.

20. The process of any one of claims 13 to 19, wherein the lithium eluate from step (v) comprises LiCI and / or U2SO4.

21. The process of any one of claims 13 to 20, wherein step (v) comprises purifying the lithium eluate to remove one or more impurities from the lithium eluate.

22. The process of claim 21, wherein purifying the lithium eluate to remove one or more impurities from the lithium eluate comprises precipitating the impurities as one or more by-products and separating the one or more by-products from the lithium eluate.

23. The process of claim 22, wherein the one or more by-products are selectively precipitated by increasing the pH of the lithium eluate, e.g., the pH of the lithium eluate is increased by adding a base to the solution to precipitate the one or more byproducts.

24. The process of claim 22 or 23, wherein the one or more by-products are selectively precipitated by contacting the lithium eluate with a base (e.g. a carbonate, a hydroxide, an oxide, etc.). For example the carbonate is NazCOs, NaHCOs, a waste stream containing carbonate ions (e.g. spent mother liquor) or a combination of any two or more thereof and the hydroxide is NaOH, Ca(OH)2, KOH, NH4OH, a waste stream containing hydroxyl ions (e.g. spent mother liquor) or a combination of any two or more thereof.

25. The process of any one of claims 22 to 24, wherein precipitation of the one or more by-products in step (v) is carried out in a sequence of separate precipitators at a constant pH, e.g., a first precipitator at pH 4, a second precipitator at pH 7, a third precipitator at pH 8 and / or a fourth precipitator at pH 9.

26. The process of any one of claims 22 to 25, wherein the one or more by-products precipitated from the lithium eluate are recycled in step (i) to adjust the pH of the aqueous solution.

27. The process of any one of claims 22 to 26, wherein precipitation of one or more byproducts in step (v) is performed at a temperature of about 0 to 100°C, preferably, at a temperature of about 50 to 100°C, about 60 to 100°C, about 70 to 100°C or about 80 to 100°C.

28. The process of any one of claims 22 to 27, wherein the one or more by-products are selected from MnCO3, CaCO3, MgCO3, SrCO3, Mn(OH)2, Ca(OH)2, Mg(OH)2, Sr(OH)2and a combination of any two or more thereof.

29. The process of any one of claims 13 to 28, wherein step (v) comprises contacting the lithium eluate from step (iv) with an ion exchange resin for a sufficient period of time to adsorb one or more impurities, then separating the ion exchange resin from the lithium eluate.

30. The process of any one of claims 13 to 29, wherein step (v) comprises removing one or more impurities comprising Ba, Ca, Mg, Mn, Sr or a combination of any two or more thereof, e.g., to produce a lithium rich solution comprising a concentration ratio of the one or more impurity / Li less than about 0.1.

31. The process of claim 13, wherein in step (iii) the acid is added in a first feed port along the plug flow reactor; optionally, the acid is added at multiple acid feed ports along the plug flow reactor.

32. The process of claim 33, wherein in step (iii) an acid is added to feed ports set along the length of the plug flow reactor and / or the acid dose rate is dependent on the position of the dosing point within the plug flow reactor, e.g. the acid dosing is decreased in each dosing point, along the length of the plug flow reactor.

33. The process of any one of claims 1 to 32, wherein step (iii) is performed at a temperature of about 0 to 100°C, optionally about 10 to 100°C, about 20 to 100°C, about 30 to 100°C or about 40 to 100°C.

34. The process of any one of claims 1 to 33, wherein the regenerated sorbent is reused in the process or the system.

35. The process of any one of claims 1 to 34, the process further comprises:(vi) treating the lithium rich solution to produce a solid lithium salt and a spent mother liquor, and(vii)separating the solid lithium salt from the spent mother liquor.

36. The process of claim 35, wherein step (vi) comprises adding base to the lithium rich solution to cause precipitation of the solid lithium salt and / or evaporating the lithium rich solution to cause precipitation of the solid lithium salt (e.g. anhydrous LiCI and / or IJ2SO4).

37. The process of claim 24 or 36, wherein at least part of the spent mother liquor from step (vii) is recycled in steps (i and / or v), or substantially all of the spent mother liquor from step (vii) is recycled in steps (i and / or v).

38. The process of any one of claims 35 to 37, wherein step (vi) comprises evaporating the lithium rich solution to cause precipitation of the solid lithium salt (e.g. anhydrous LiCI and / or LizSC ).

39. The process of any one of claims 35 to 38, wherein the solid lithium salt is a lithium carbonate, a lithium hydroxide, a lithium chloride, a lithium sulfate or a combination of any two or more thereof.

40. The process of any one of claims 1 to 39, wherein the plug flow reactor is operated with an axial velocity with turbulent flow sufficient to suspend the sorbent particles,e.g., wherein the flow velocity of the aqueous solution in the plug flow reactor is 0.1 - 10 m / s or 0.75-3 m / s.

41. The process of any one of claims 1 to 40, wherein the aqueous solution containing lithium is selected from a geothermal brine, salar brine, formation waters, sea water, concentrates from processing seawater, a waste stream from a lithium processing facility, a waste stream from a battery recycling plants, oil well brines, other ground water.

42. A system for extracting lithium from an aqueous solution containing lithium, the system comprising, i) a first reactor for contacting an aqueous solution containing lithium with a lithium sorbent to absorb the lithium to produce a lithium loaded sorbent and lithium depleted solution, ii) a first separating device for separating the lithium loaded sorbent and the lithium depleted solution, iii) a second reactor for contacting the lithium loaded sorbent with a means for treating the lithium loaded sorbent to produce a lithium eluate and a regenerated sorbent, iv) a second separating device for separating the lithium eluate and the regenerated sorbent, wherein the first reactor and / or the second reactor is a plug flow reactor.

43. The system of claim 42, wherein the plug flow reactor comprises a feed port; optionally wherein the plug flow reactor comprises two or more feed ports.

44. The system of claim 42 or 43, wherein the length of the plug flow reactor is about 50 to 1,500 m.

45. The system of any one of claims 42 to 43, wherein the plug flow reactor has a diameter of about 5 to 2,000 mm.

46. The system of any one of claims 42 to 45, wherein the system comprises a pump or a combination of pumps connected to the plug flow reactor to pump the aqueous solution and lithium sorbent through the plug flow reactor.

47. The system of any one of claims 42 to 46, wherein the means for treating the lithium loaded sorbent in (iii) is a source of acid, optionally the source of acid is selected from one or more mineral acids and / or organic acids such as HCI, H2SO4, HBr, HI and phosphoric acid or a combination of any two or more thereof.

48. The system of any one of claims 42 to 47, wherein the system further comprises a lithium concentration system configured to receive the lithium eluate.

49. The system of claim 48, wherein the lithium concentration system comprises a low- pressure reverse osmosis membrane, a high-pressure reverse osmosis membrane, a forward osmosis membrane, a reverse osmosis membrane, an evaporation process or a combination of any two or more thereof.

50. The system of any one of claims 42 to 49, wherein the first separating device and / or the second separating device comprises a physical separation device, e.g. a filter press or an ultrafiltration membrane.

51. The system of any one of claims 42 to 50, wherein the first reactor and the second reactor are plug flow reactors.

52. The system of any one of claims 42 to 51, wherein the system further comprises a third reactor and optionally a third separating device comprising one or more means for concentrating and / or purifying the lithium eluate to produce a lithium rich solution.

53. The system of any one of claims 42 to 52, wherein the system further comprises means for treating the lithium rich solution to produce a solid lithium salt and a spent mother liquor.

54. The system of claim 53, wherein the system further comprises a third and a fourth separating device to separate the solid lithium salt and the spent mother liquor.

55. The system of claim 54, wherein the system further comprises means for conveying at least part of the spent mother liquor from the third and / or fourth separating device to the first reactor and / or the third reactor.

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