Apparatus and method for recycling an ionic liquid used to purify a Bayer process stream.

Abstract

METHOD AND APPARATUS FOR PURIFYING A BAYER PROCESS STREAM. The present invention relates to an apparatus and a method for purifying a Bayer process stream that includes a FILTER stage, comprising at least one filter configured to filter particulate matter from at least one ionic liquid stream from the EXTRACT, SEPARATE, and REGENERATE stages. Filtering particulate matter from at least one of the ionic liquid streams reduces the amounts of circulating particulate matter and reduces the potential for residue formation.

Description

1 / 40 APPARATUS AND METHOD FOR RECYCLING AN IONIC LIQUID USED TO PURIFY A BAYER PROCESS STREAM FIELD OF THE INVENTION

[001] The present invention relates generally to a method and apparatus for purifying a Bayer process stream.

[002] In particular, though not exclusively, the present invention relates to a method and apparatus for purifying a Bayer process stream using an ionic liquid to remove impurities. BACKGROUND OF THE INVENTION

[003] The Bayer Process is used for the manufacture of alumina from bauxite ore.

[004] Bauxite ore generally contains organic and inorganic impurities, the quantities of which are specific to the bauxite source.

[005] Part of the process involves purifying the aluminate lye to remove various impurities, both dissolved and undissolved, to form a purified filtrate. Alumina is then precipitated from the filtrate as alumina trihydrate crystals.

[006] The purification step is important because alumina trihydrate containing high levels of organic impurities tends to produce a final product with an undesirably high level of coloration.

[007] The remaining liquid phase or spent leach can be concentrated to form strong leach. Spent leach streams are typically returned to the initial digestion stage and used as an additional ore digester after being reconstituted with additional caustics.

[008] Because the Bayer process is a closed loop, impurities entering the process stream tend to accumulate with each cycle. Petition 870260066690, dated 06 / 07 / 2026, page 10 / 120 2 / 40 of the process. These impurities can have a negative impact on the process.

[009] Ionic liquids can be used to remove impurities from the Bayer process. However, these liquids are typically expensive and toxic.

[0010] As such, it would be desirable to provide a method and apparatus for purifying a Bayer process stream that would allow for the recycling of these ionic liquids.

[0011] The above description should not be considered an admission of common general knowledge in Australia or elsewhere. SUMMARY OF THE INVENTION

[0012] The present invention relates to a method and apparatus for purifying a Bayer process stream using an ionic liquid as an impurity extractor in a liquid / liquid extraction method and apparatus for removing impurities from a Bayer process stream.

[0013] A Bayer process stream, in one embodiment, is a liquid stream generated during the Bayer process and may be one or more overflow streams of thickener, caustic lye, spent lye and strong lye streams.

[0014] The term impurities is understood to mean compounds that can contaminate a Bayer process stream. Impurities include, but are not limited to, organic and / or inorganic species. A particularly relevant class of impurity is that of non-oxalate organic compounds (NOOCs) generically and empirically represented as Na2C5O7. However, it can be observed that customized selection of the ionic liquid would allow the removal of other classes of impurities from the Bayer process stream. Petition 870260066690, dated 06 / 07 / 2026, page 11 / 120 3 / 40

[0015] More particularly, the invention relates to a method and apparatus for purifying a Bayer process stream using an ionic liquid that can reversibly associate with impurities in the Bayer process stream. The method / apparatus controls the operating parameters so that impurities can associate with the ionic liquid to remove impurities from the Bayer process stream and so that impurities can dissociate from the ionic liquid to remove impurities from the ionic liquid and regenerate the ionic liquid for recycling in the method / apparatus.

[0016] The invention was made following small-scale pilot plant work (hereinafter referred to as bench-scale pilot or BTP) by the applicant using ionic liquids for the method / apparatus. The BTP work was carried out after successful small-scale laboratory experiments on the method / apparatus.

[0017] During the BTP work, the applicant encountered a number of problems that were not present in the small-scale laboratory experiments.

[0018] One of these problems was the impact of particulate matter circulating in an ionic liquid recycling circuit.

[0019] More specifically, the applicant found that an emulsion, stabilized by particulate matter, formed between the ionic liquid and the aqueous solutions when a threshold concentration of particulate matter in the circuit was reached, rendering the recycling circuit inoperable.

[0020] This was a surprising discovery, as it was not previously known that particulate matter, particularly, but not limited to, particulate matter originating from Bayer bleach, would behave in such a detrimental manner when the method / apparatus was designed to operate with substantially industrial process streams. Petition 870260066690, dated 06 / 07 / 2026, page 12 / 120 4 / 40

[0021] In order to find a solution to this problem, the applicant carried out a series of experiments to determine the nature of the particulate matter.

[0022] In an experiment, particulate matter was isolated and analyzed using XRD, and it was determined that the particulate matter comprised: • Al(OH)3 (Gibbsite) - main component • CaCO3 - component • Al(OH)3 (Bayerite) - trace • Na3H(CO3)2.2H2O (trona) - trace • Na2C2O4 (sodium oxalate) - trace • Ca3Al2(SiO4)(OH)8 - trace • Various other minor components

[0023] Compositional analysis suggested that the particulate matter originated from Bayer bleach. However, it can be observed that the particulate matter is not confined to this source and may originate from other sources, such as NaCl brine impurities, or be externally derived particulate matter.

[0024] It was also determined that the particulate matter was insoluble in either of the aqueous streams in the method / apparatus and remained trapped in the ionic liquid.

[0025] Without being limited by theory, it is believed that particulate matter stabilizes the emulsions formed between the ionic liquid used and any of the aqueous streams used in the recycling process. These stabilized emulsions are described herein as a crude. It is further believed that various ions present in the aqueous streams of the process being purified combine to form precipitates, which, together with any retained foreign particles (such as fugitive dust), are described herein as particulate matter and are transported around the circuit. Petition 870260066690, dated 06 / 07 / 2026, page 13 / 120 5 / 40 in ionic liquid.

[0026] Subsequent analyses revealed that crude forms at the ionic (organic) liquid phase / aqueous phase interface and subsequently coalesces at this interface, separating the aqueous and ionic liquid phases. The resulting coalesced crude layer between the ionic liquid and aqueous phases can impede further separation of fresh mixed phases from the mixers, causing a loss of efficiency and a loss of ionic liquid to the aqueous stream exiting the decanter(s). This hinders the separation of the organic ionic liquid phase and the aqueous phase. Crude in the organic phase also accumulates and concentrates in the process. This affects the efficiency of the liquid / liquid extraction that occurs at each of the stages. It is observed that a decanter can be completely filled with crude, so that no other process stream can be pumped into the decanter, rendering the entire recycling circuit inoperable.

[0027] During troubleshooting, it was observed that after the equivalent of approximately 35 to 40 hours of plant operating time, the decanters used at BTP were clogged with crude oil.

[0028] It was observed that crude oil can form independently in each of the aqueous and organic phases and crude oil formation can occur at all stages of the process.

[0029] It was observed that crude formation was more pronounced in the EXTRACT stage when the ionic liquid feed stream to that stage interacts with the Bayer process stream.

[0030] In some BTP studies, it was also observed that once the precipitates derived from NaCl impurities reached a limit concentration, the focal point of crude formation shifted to the REGENERATE stage, in which crude formation increased to the point where entire sediments became non-operational. Petition 870260066690, dated 06 / 07 / 2026, page 14 / 120 6 / 40

[0031] The applicant tested the following methods which the applicant thought would be successful in removing dirt from the circuit, with limited or no success.

[0032] 1. Mixing or decanting the ionic liquid, heating the ionic liquid, dissolving it in water and salting the ionic liquid solution. This method was unsuccessful. The salting process investigated by the applicant involved adding a saline solution such as sodium hydroxide to the ionic liquid solution, allowing the separation of the ionic liquid and the saline solution, which allows the recovery of the ionic liquid.

[0033] 2. For this reason, purging the crude oil was not a viable solution due to the rapid accumulation of crude oil.

[0034] 3. Filter the ionic liquid streams from one or more of the EXTRACT, SEPARATE, and REGENERATE stages to determine whether controlling the concentration of particulate matter in the regenerated ionic liquid would affect crude formation. Initial filtration options tested by the applicant were unsuccessful.

[0035] Ultimately, further filtration tests led to the development of the present invention.

[0036] As a consequence of further testing, the invention provides an apparatus for purifying a Bayer process stream comprising: an EXTRACT stage comprising at least one contact / separation device configured to receive and mix a Bayer process stream containing impurities and an ionic liquid stream including a quaternary organic cation to form a purified Bayer process stream and an impurity-laden ionic liquid stream; a SEPARATE stage comprising at least one contact / separation device configured to receive and mix the Petition 870260066690, dated 06 / 07 / 2026, page 15 / 120 7 / 40 a stream of ionic liquid loaded with impurities and a stream of salt containing halide to form a stream of ionic liquid containing halide and a stream of salt loaded with impurities; a REGENERATE stage comprising at least one contact / separation device configured to receive and mix the halide-containing ionic liquid stream and a caustic stream to form a regenerated ionic liquid stream and a halide-containing caustic effluent stream, wherein the EXTRACT stage is configured to be in fluid communication with the REGENERATE stage via a recycling circuit to receive at least part of the regenerated ionic liquid stream to form the ionic liquid feed stream, and a FILTER stage comprising at least one filter configured to filter particulate matter from at least one of the ionic liquid streams of the EXTRACT, SEPARATE and REGENERATE stages.

[0037] Filtering particulate matter from at least one of the ionic liquid streams reduces the amounts of circulating particulate matter and reduces the potential for residue formation.

[0038] The invention also provides an apparatus for recycling an ionic liquid used to purify a Bayer process stream comprising: a SEPARATE stage comprising at least one contact / separation device configured to receive and mix an impurity-laden ionic liquid stream and a separation solution stream to form a reduced-impurity ionic liquid stream and an impurity-laden separation solution stream; a REGENERATE stage comprising at least one contact / separation device configured to receive and mix the Petition 870260066690, dated 06 / 07 / 2026, page 16 / 120 8 / 40 ionic liquid stream with reduced impurities and a caustic solution stream to form a regenerated ionic liquid stream and a caustic effluent stream; wherein at least one contact / separation device of the REGENERATE stage is configured to recycle at least part of the regenerated ionic liquid stream and form an ionic liquid feed stream to purify a Bayer process stream, and a FILTER stage comprising at least one filter configured to filter particulate matter from at least one of the ionic liquid streams of the EXTRACT, SEPARATE and REGENERATE stages.

[0039] The term particulate matter is understood here to mean any particulate matter that is in one of the ionic liquid streams. Particulate matter may be particulate matter in the Bayer process stream. Particulate matter may be any solid that interacts with 'ionic' species in the circuit and forms a material, such as a crude that interferes in a purification or recycling circuit.

[0040] The term filter is understood here as any device suitable for separating particulate matter from the ionic liquid feed stream.

[0041] The contact / separation device for the stages Extract, separate, and regenerate can be selected from mixer-decanters, columns, centrifuges, static mixers, reactors, or other equipment suitable for mixing and separating two liquid streams that are at least partially immiscible. A preferred contact / separation device is a mixer-decanter, as is commonly used in solvent extraction circuits.

[0042] The ionic liquid can be any suitable ionic liquid. Petition 870260066690, dated 06 / 07 / 2026, page 17 / 120 9 / 40

[0043] By way of example, the ionic liquid may comprise an alkyl phosphonium salt that exists in three forms, depending on the bonding of the molecule with the phosphonium ion. These forms are: detached (Cl-), regenerated (OH-) and charged (NOOC-). The transition between these forms allows the ionic liquid to reversibly associate with impurities.

[0044] At least one of the operating units containing ionic liquid for the EXTRACT, SEPARATE and REGENERATE stages may include a FILTER stage filter to remove particulate matter, particularly colloidal solids, from the ionic liquid stream to control the concentration of particulate matter in the regenerated ionic liquid.

[0045] In other words, the FILTER stage can be part of the EXTRACT, SEPARATE, and REGENERATE stages. For example, the FILTER stage can be part of a storage tank, a fluid conduit, or the contact / separation device for the EXTRACT, SEPARATE, and REGENERATE stages.

[0046] The FILTER stage can also be a separate operational unit from the operational units that make up the EXTRACT, SEPARATE and REGENERATE stages.

[0047] The FILTER stage may be located after the stage SEPARATE. In one embodiment, filtration in the FILTER stage is performed on the ionic liquid stream after the SEPARATE stage.

[0048] It should be emphasized that the invention is not limited to this embodiment.

[0049] As is evident from what has been said, the ionic liquid stream transferred to the FILTER stage is typically an ionic liquid containing particulate matter with the potential for crude formation.

[0050] The concentration of solids, that is, the concentration of particulate matter, in the ionic liquid stream transferred to the stage Petition 870260066690, dated 06 / 07 / 2026, page 18 / 120 10 / 40 FILTER, it can contain up to 0.3g / L of solids.

[0051] The applicant tested solids concentrations up to 5.5 g / L and the results of the test work provided a basis for concluding that the solids concentration may be higher.

[0052] The concentration of solids can be up to 6 g / L.

[0053] The concentration of solids can be up to 10 g / L.

[0054] Typically, the concentration of solids in the ionic liquid stream transferred to the FILTER stage is less than 3 g / L within the ionic liquid stream.

[0055] The ionic liquid stream may include a stabilized emulsion that includes an aqueous phase and an ionic liquid phase.

[0056] The aqueous phase can be up to 50% by volume of the stabilized emulsion. More appropriately, the aqueous phase of the stabilized emulsion is < 10% by volume.

[0057] Typically, filtration in the FILTER stage breaks up the emulsion stabilized in the aqueous and ionic liquid phases.

[0058] The FILTER stage can be carried out using any suitable filter that is capable of separating solid material, i.e., particulate matter, from the ionic liquid stream transferred to the FILTER stage.

[0059] The filter can be configured to use differential pressure as the driving force for filtration.

[0060] The filter can be a positive pressure filter.

[0061] The filter can be a candle filter.

[0062] The FILTER stage may include a candle filter with a perlite filtration aid.

[0063] Any suitable filter medium can be used in the filter.

[0064] Properly, the filter medium is compatible with the ionic liquid.

[0065] Polypropylene (PP) and polytetrafluoroethylene (PTFE) were deemed suitable by the applicant based on test work. Petition 870260066690, dated 06 / 07 / 2026, page 19 / 120 11 / 40 short term.

[0066] The filter medium can be of multi- or monofilament construction.

[0067] The filter medium may have an air permeability between 3200 L / dm2 / min.

[0068] The FILTER stage may include the use of a filter aid, such as ceramic material, tricalcium aluminate hexahydrate (TCA), and a flocculant.

[0069] The filter aid can be selected for higher yield and longevity of the filter medium.

[0070] The auxiliary filter material may be any suitable chemical-resistant material that does not react with the ionic liquid.

[0071] The auxiliary filter material may be expanded perlite.

[0072] The filter aid material may have an average particle size between 10-100 µm. Ideally, the average particle size of the filter aid is between 50-85 µm. Most appropriately, a filter aid with an average particle size of 68 µm is used for filtration.

[0073] The filter aid can be introduced into the ionic liquid stream transferred to the FILTER stage by direct addition to the ionic liquid stream.

[0074] More appropriately, the filter aid is pre-dosed with an aqueous solution at a temperature between 20-80°C before being added to the ionic liquid stream. More appropriately, the filter aid is mixed with a water solution at a temperature of 55°C.

[0075] The pre-dosing solution of the filter aid can be prepared for a solids concentration between 10-200 g / L. More appropriately, the solids concentration is between 40-100 g / L. More Petition 870260066690, dated 06 / 07 / 2026, p. 20 / 120 12 / 40 appropriately, the solids concentration is 60 g / L.

[0076] The filter aid can be added to the ionic liquid stream transferred to the FILTER stage in a solids ratio between 1:0.1 and 1:5 (solids in stabilized emulsion feed: filter aid solids). More appropriately, the addition ratio is between 1:1 and 1:2.

[0077] The FILTER stage can be configured to operate within a temperature range of 20-70°C. More appropriately, the FILTER stage operates in a temperature range of 55-60°C.

[0078] When operating with pressure filters, the FILTER stage can operate within a differential pressure range between 200 - 800 kPa (2-8 bar). More accurately, the pressure is between 400 - 600 kPa (4-6 bar). More accurately, the operating pressure is 600 kPa (6 bar).

[0079] The FILTER stage can be configured to operate with a filtration flow rate between 10-700 L / m2 / h. More appropriately, the filtration process operates at a flow rate between 50-200 L / m2 / h. More appropriately, the filtration process operates at a flow rate between 100-150 L / m2 / h.

[0080] The FILTER stage may include a cleaning process to remove the ionic liquid trapped inside the filter aid and a filter cake of solids.

[0081] The cleaning process may include filter cake washing steps, typically with the recovered ionic liquid being returned to the method.

[0082] The subsequently washed and cleaned cake can be discarded as a paste or as dry cake for disposal.

[0083] The filter can be a filter with a pore size ranging from 5 to 100 μm. Ideally, a filter with a pore size ranging from 10-0 μm is used for the filtration step. More Petition 870260066690, dated 06 / 07 / 2026, page 21 / 120 13 / 40 appropriately, a filter with a pore size of 10-30 μm is used for filtration. The filter can be any device capable of solid-liquid separation, such as a Büchner funnel or a centrifuge.

[0084] A positive pressure filtration system, a vacuum filtration system, or a centrifuge can be used to facilitate filtration.

[0085] The apparatus may include a controller to control the parameters of the caustic current, such as flow rate and concentration, to take into account the dilution of the ionic liquid containing the halide.

[0086] The apparatus may comprise at least three mixing decanters. Properly, the apparatus comprises ten mixing decanters.

[0087] In the EXTRACT stage, at least one mixer-settler may be configured to receive and mix a Bayer process stream containing impurities and an ionic liquid feed stream to form a purified Bayer process stream and an ionic liquid stream loaded with impurities, respectively. Appropriately, the EXTRACT stage comprises three mixer-settlers arranged in series.

[0088] In the SEPARATE stage, at least one mixer-decanter may be configured to receive and mix the impurity-laden ionic liquid stream with a halide-containing salt stream to form a halide-laden ionic liquid stream and an impurity-laden salt stream, respectively. Appropriately, the SEPARATE stage comprises three mixer-decanters arranged in series.

[0089] In the REGENERATE stage, at least one mixer / decanter may be configured to receive and mix the halide-containing ionic liquid stream with a caustic stream to form a regenerated ionic liquid stream and an effluent stream. Petition 870260066690, dated 06 / 07 / 2026, page 22 / 120 14 / 40 caustic containing halide, respectively. Properly, the REGENERATE stage comprises four mixer-settlers arranged in series.

[0090] The first mixer-decanter in the EXTRACT stage can be configured to be in fluid communication with the final mixer-decanter in the REGENERATE stage via a recycling circuit to receive at least part of the regenerated ionic liquid stream to form the ionic liquid feed stream.

[0091] In one embodiment, in use, within the mixer-decanter of the EXTRACT stage, the hydroxyl ions within the ionic liquid feed stream are replaced by NOOC ions in the Bayer process stream containing impurities to form the purified Bayer process stream and the impurity-laden ionic liquid stream (forms NOOC). The impurity-laden ionic liquid stream exiting the third mixer-decanter of the EXTRACT stage then flows to the first mixer-decanter of the SEPARATE stage.

[0092] In one embodiment, in use within SEPARATE stage mixer-decanters, NOOC ions are transferred from the impurity-laden ionic liquid stream to the halide-containing salt stream. The NOOC ions in the impurity-laden ionic liquid stream are replaced by chloride ions from the halide-containing salt stream to form a halide-containing ionic liquid stream (forms Cl) and an impurity-laden salt stream. Mass transfer is driven by a high concentration of chloride ions in the aqueous phase.

[0093] The separated ionic liquid that exits the third mixer-decanter of the SEPARATE stage then flows to the first mixer-decanter of the REGENERATE stage.

[0094] In one embodiment, in use, within mixers Petition 870260066690, dated 06 / 07 / 2026, page 23 / 120 In the 15 / 40 REGENERATE stage decanters, the separated ionic liquid is converted into regenerated ionic liquid (OH form) upon contact with a caustic stream to form a regenerated ionic liquid stream and a caustic effluent stream containing halide. The regenerated ionic liquid stream exiting the fourth mixer-decanter of the REGENERATE stage is then recycled to the first mixer-decanter of the EXTRACT stage. The caustic effluent stream containing halide is pumped to a salt separation unit.

[0095] The apparatus can be installed after the alumina trihydrate precipitation step to treat spent Bayer lye.

[0096] The FILTER stage can be configured so that the concentration of particulate matter in the regenerated ionic liquid stream falls below a predetermined limit concentration before the regenerated ionic liquid returns to the EXTRACT stage as at least part of the ionic liquid feed stream.

[0097] The predetermined limit concentration may be any suitable concentration, taking into account any one or more of the following factors: the Bayer process lye being processed, the particular ionic liquid and the processing conditions.

[0098] Appropriately, the filtrate solids are less than 3 g / L of particulate matter. More appropriately, the filtered solids are less than 0.5 g / L of particulate matter. More appropriately, the filtered solids are less than 0.1 g / L of particulate matter.

[0099] The filter stage can provide multi-stage filtration.

[00100] The invention also provides a method for purifying a Bayer process stream comprising: to provide an ionic liquid feed stream that includes a quaternary organic cation, wherein the feed stream Petition 870260066690, dated 06 / 07 / 2026, page 24 / 120 16 / 40 of the ionic liquid is at least partially immiscible with the Bayer process stream; Mix the Bayer process stream with the ionic liquid feed stream and form an aqueous phase comprising purified Bayer process lye and an organic phase comprising impurity-laden ionic liquid, wherein the mixing reduces the impurity concentration in the Bayer process lye; to separate at least partially the aqueous phase from the organic phase and form a purified Bayer process stream and an ionic liquid stream loaded with impurities; Mixing an impurity-laden ionic liquid stream and a halide-containing salt stream to form an aqueous phase comprising an impurity-laden salt and an organic phase comprising a halide-containing ionic liquid, wherein the mixing reduces the impurity concentration in the impurity-laden ionic liquid stream; to at least partially separate the aqueous phase from the organic phase and form a stream of ionic liquid containing halide and a stream of salt loaded with impurities; to mix the ionic liquid stream containing halide and a caustic solution and form an aqueous phase comprising a caustic solution containing halide and an organic phase comprising a regenerated ionic liquid, wherein the mixture replaces at least some of the halide groups in the ionic liquid halide-containing solution with hydroxyl groups from the caustic solution; to separate at least partially the aqueous phase from the organic phase and form a salt stream containing halide and a regenerated ionic liquid vapor; filter at least one of the ionic liquid streams from Petition 870260066690, dated 06 / 07 / 2026, page 25 / 120 17 / 40 stages EXTRACT, SEPARATE and REGENERATE and remove particulate matter; and recycle at least part of the regenerated ionic liquid stream and form at least part of the ionic liquid feed stream.

[00101] The invention also provides a method for recycling an ionic liquid used to purify a Bayer process stream, comprising: to mix a stream of ionic liquid loaded with impurities with a stream of separating solution and to form an aqueous phase comprising a separating solution loaded with impurities and an organic phase comprising an ionic liquid of reduced impurities; to separate at least partially the aqueous phase from the organic phase and form a stream of ionic liquid with reduced impurities and a stream of removal solution loaded with impurities; Mix the ionic liquid stream with reduced impurities and a caustic solution stream to form an aqueous phase comprising a spent caustic solution and an organic phase comprising a regenerated ionic liquid; Filter at least one of the ionic liquid streams from the EXTRACT, SEPARATE, and REGENERATE stages and remove particulate matter; and recycle at least part of the regenerated ionic liquid stream to form the ionic liquid feed stream.

[00102] The filtration step may include the removal of particulate matter so that the concentration of particulate matter in the regenerated ionic liquid stream is below a predetermined limit concentration. Petition 870260066690, dated 06 / 07 / 2026, page 26 / 120 18 / 40

[00103] In one embodiment, the ionic liquid comprises an alkyl phosphonium salt that exists in three forms, depending on the molecule's bonding with the phosphonium ion. These forms are: detached (Cl-), regenerated (OH-), and charged (NOOC-). The transition between these forms allows the ionic liquid to reversibly associate with the impurity.

[00104] The method may include providing an ionic liquid feed stream that is at least partially immiscible with the Bayer process stream. The ionic liquid feed stream may include an ionic liquid comprising a quaternary organic cation.

[00105] Australian patent 2010337293 in the name of Cytec Technology Corp. discloses ionic liquids comprising a quaternary organic cation and methods and compositions for removing impurities from ionic liquids loaded with impurities.

[00106] The reference here to the Australian patent Cytec is not an admission that the description in the patent is part of common general knowledge in Australia or elsewhere.

[00107] The following description of the quaternary organic cation is based closely on the description in the Australian Cytec patent.

[00108] As reported in the Australian Cytec patent, the quaternary organic cation can be selected from the group consisting of phosphonium, ammonium, sulfonium, pyridinium, pyridazinium, pyrimidine, pyrazine, pyrazolium, imidazole, thiazole, oxazole, pyrrolidine, quinoline, isoquinoline, guanidine, piperidine and methylmorpholine.

[00109] Appropriately, the quaternary organic cation is selected from the group consisting of: Petition 870260066690, dated 06 / 07 / 2026, page 27 / 120 19 / 40 wherein Ra, Rb, Rc, Rd, Re, Rf may be selected independently from hydrogen, or a substituted C1-C50 alkyl group, wherein the substituents include one or more selected from alkyl, cycloalkyl, alkenyl, cycloalkynyl alkynyl, alkoxy, alkoxyalkyl, aldehyde, ester, ether, ketone, carboxylic acid, alcohol, carboxylate, hydroxyl, nitro, silyl, aryl and halide functionalities. Raa Rf molecules can individually comprise approximately 1 to 50 carbon atoms. It can be observed that two or more Raa Rf molecules can form a ring structure. R1 to R7 can each be selected independently from hydrogen, halogen, or a substituted C1-C50 alkyl group, wherein the substituents include one or more selected from alkyl, cycloalkyl, alkenyl, cycloalkynyl, alkynyl, alkoxy, Petition 870260066690, dated 06 / 07 / 2026, p. 28 / 120 20 / 40 alkoxyalkyl, aldehyde, ester, ether, ketone, carboxylic acid, alcohol, carboxylate, hydroxyl, nitro, silyl, aryl, and halide functionalities. R1 to R7 may individually comprise about 1 to 50 carbon atoms. It will be observed that two or more of R1 to R7 may form a ring structure.

[00110] Examples of quaternary organic cations include, but are not limited to, tributyloctylphosphonium, tributyl(methyl)phosphonium, tributyl-8-hydroxyoctylphosphonium, tetrabutylphosphonium, tetrapentylphosphonium, tetrahexylphosphonium, tetraoctylphosphonium, octyl(tributyl)phosphonium, tetradecyl(tributyl)phosphonium, tetradecyl(trihexyl)phosphonium, tributyl(methyl)ammonium, tetrabutylammonium, tetrapentylammonium, tetrahexylammonium, tetraoctylammonium, tetradecyl(tributyl)ammonium, tetradecyl(trihexyl)ammonium, dimethyl dicoco quaternary ammonium, stearamidopropyldimethyl-2-hydroxyethylammonium, ethyl(tetradecyldiundecyl)ammonium, seboalkyltrimethylammonium, N,N,N-trimethyl1-dodecanammonium, benzyldimethylcocoalkylammonium, N,N-dimethylN-dodecylglycine, butylmethylpyrrolidinium, l-octyl-2,3-dimethylimidazole, l-butyl-3-methylimidazole, sulfonium and guanidine. The term coco refers to the alkyl group derived from the mixture of fatty acids found in coconut oil, which are generally saturated fats with about 12 carbon atoms.

[00111] A preferred quaternary organic cation is tributylotylphosphonium.

[00112] The quaternary organic cation is typically associated with a counter-ion or anionic anion. The anion can be a chaotropic anion or a cosmotropic anion.

[00113] Examples of suitable anions include, but are not limited to, halide (e.g., fluoride, chloride, bromide, iodide), hydroxyl, alkyl sulfate (e.g., methyl sulfate, ethyl sulfate, octyl sulfate), dialkyl phosphate, sulfate, nitrate, phosphate, sulfite, phosphite, nitrite, hypochlorite, Petition 870260066690, dated 06 / 07 / 2026, page 29 / 120 21 / 40 chlorite, chlorate, perchlorate, carbonate, bicarbonate, carboxylate (e.g., formate, acetate, propionate, butyrate, hexanoate, fumarate, maleate, lactate, oxalate, pyruvate), bis(trifluoromethyl)sulfonylimide ([NTF2]), tetrafluoroborate, hexafluorophosphate, CN-, SCN- and OCN.

[00114] The group of halides and compounds containing halogens may include, but is not limited to: F-, Cl-, Br-, I-, BF4-, ClOs, ClO4-, BrO3-, BrO4-, IO3-, IO4-. PF6-, AlCk, AbCl-, AlsClio-, AlBr<, FeCk, BCk, SbF6-, AsFe, ZnCl3-, SnCl3-, CuCk, CF3SO3-, (CFsSOs^N-, CF3CO2- and CCbCO2-.

[00115] A preferred class of anions is halides. A preferred anion is chloride.

[00116] The ionic liquid may include any pairing of any of the quaternary organic cations and anions.

[00117] The ionic liquid may be selected from the group consisting of tributyloctylphosphonium chloride, trihexyltetradecylphosphonium chloride, tetrabutylphosphonium chloride, tetradecyl(tributyl)phosphonium chloride, tributyl(8-hydroxyoctyl)phosphonium chloride and octyl(tributyl)phosphonium chloride.

[00118] The ionic liquid may be selected from the group consisting of tetrabutylammonium hydroxide, tetrabutylammonium chloride, stearamidopropyldimethyl-2-hydroxyethylammonium nitrate, ethyltetradecyldiundecylammonium chloride, tetrahexylammonium bromide, dodecyltrimethylammonium chloride, benzyldimethylcoco chloride, N,N-dimethyl-N-dodecylglycine betaine, Adogen 462®, Aliquat® HTA-1 and seboalkyltrimethylammonium chloride.

[00119] The ionic liquid can be a phosphonium salt that exists in three forms, depending on the molecule's bond with the phosphonium ion. These forms are: detached (Cl-), regenerated (OH-) and charged (NOOC-).

[00120] The ionic liquid may be a tributylotylphosphonium salt that exists in the following three forms: detached (Cl-), regenerated (OH-) and charged (NOOC-). Petition 870260066690, dated 06 / 07 / 2026, page 30 / 120 22 / 40

[00121] The ionic liquid feed stream may include a diluent. The diluent may be alcohols (e.g., isopropanol), polyols, and / or polyethylene oxide. Such diluents may facilitate phase separation.

[00122] The ionic liquid feed stream may include at least 1% by weight of ionic liquid. Properly, the ionic liquid feed stream includes at least about 10% by weight of ionic liquid. More properly, the ionic liquid feed stream includes at least about 50% by weight of ionic liquid. Still more properly, the ionic liquid feed stream comprises about 70% by weight of ionic liquid.

[00123] The method involves mixing the ionic liquid feed stream with the Bayer process stream.

[00124] Although the ionic liquid stream and the Bayer process stream may be mutually soluble to some extent, typically the two phases are at least partially immiscible with each other to form a liquid / liquid mixture in an EXTRACT stage.

[00125] The ionic liquid entering the EXTRACT stage may be in its regenerated form. Appropriately, the ionic liquid entering the EXTRACT stage is tributyl ctyl phosphonium hydroxide.

[00126] In the EXTRACT stage, the external O / W ratio can vary from 0.5 to 2. Ideally, the external O / W ratio varies from 0.67 to 1: More ideally, the external O / W ratio varies from 0.75 to 0.85.

[00127] The external O / A ratio defines the O / A ratio of each stage. This is in contrast to the internal O / A ratio which defines the O / A ratio of each mixer-settler within each stage.

[00128] During mixing, the impurity, for example NOOC, is extracted from the used lye and transferred to the ionic liquid. This reduces the Petition 870260066690, dated 06 / 07 / 2026, page 31 / 120 23 / 40 impurity concentration in the Bayer process stream and forms an aqueous phase comprising purified Bayer process lye and an organic phase comprising impurity-laden ionic liquid.

[00129] The aqueous and organic phases are then at least partially separated to form a purified Bayer process stream and an impurity-laden ionic liquid stream.

[00130] The purified Bayer process stream from the EXTRACT stage is sent for further processing, for example, to a refinery, while the ionic liquid stream loaded with impurities is directed to a SEPARATE stage.

[00131] The ionic liquid entering the SEPARATE stage may be in its charged form. Properly, the ionic liquid entering the EXTRACT stage is the tributyl ethyl phosphonium salt associated with NOOC.

[00132] In the SEPARATE stage, the external O / W ratio can vary from 0.5 to 3. Appropriately, the external O / W ratio varies from 0.67 to 2.5: Most appropriately, the external O / W ratio is 1.89.

[00133] The internal O / A ratio can vary from 0.5 to 2. Ideally, the internal O / A ratio varies from 0.8 to 1.2.

[00134] In the SEPARATE stage, the ionic liquid stream loaded with impurities is mixed with a separating solution. Appropriately, the separating solution is a salt stream containing halide. More appropriately, the salt stream containing halide is a brine solution (sodium chloride).

[00135] During mixing, ion exchange occurs between the ionic liquid and the salt, which contains a halide, where the anionic impurity of the ionic liquid is exchanged with the halide group of the salt to reduce the concentration of impurities in the impurity-laden ionic liquid stream. This forms a mixture comprising an aqueous phase containing an impurity-laden salt and an organic phase comprising Petition 870260066690, dated 06 / 07 / 2026, page 32 / 120 24 / 40 an ionic liquid containing a halide.

[00136] The aqueous and organic phases are then at least partially separated to form a salt stream laden with impurities and an ionic liquid stream containing halide.

[00137] The impurity-laden salt stream is processed to remove residual ionic liquid before discharge into the environment. A certain level of ionic liquid entrapment is expected in the impurity-laden salt stream due to the nature of the mixing / decantation process, typically ranging from 300-400 ppm. As such, the impurity-laden salt stream is passed through a coalescer designed to agglomerate and collect the residual ionic liquid for recovery back into the circuit.

[00138] The salt stream loaded with impurities can also pass through at least one activated carbon column to further reduce the final concentration of ionic liquid before being discharged into the environment. At least some of the salt in the stream can be recycled back to the SEPARATE stage.

[00139] The final concentration of ionic liquid in the salt stream can be < 1 ppm.

[00140] The ionic liquid stream containing halide is directed to a REGENERATE stage.

[00141] The ionic liquid that enters the REGENERATE stage may be in its separate form. Properly, the ionic liquid that enters the REGENERATE stage is tributyltylphosphonium chloride.

[00142] At this stage, the external O / A ratio can vary from 0.5 to 2. Ideally, the external O / A ratio varies from 0.67 to 1.5: More ideally, the external O / A ratio varies from 1.13

[00143] The internal O / A ratio can vary from 0.5 to 2. Ideally, the internal O / A ratio varies from 0.8 to 1.2.

[00144] In the REGENERATE stage, the ionic liquid stream that Petition 870260066690, dated 06 / 07 / 2026, page 33 / 120 25 / 40 contains halides and is mixed with a caustic stream.

[00145] The caustic concentration may be less than 50% by weight. Appropriately, the caustic concentration is less than 30% by weight. More appropriately, the caustic concentration is less than 20% by weight. More appropriately, the caustic concentration is 10% by weight.

[00146] The caustic stream may contain sodium hydroxide.

[00147] During mixing, the halide group of the halide-containing ionic liquid is replaced by the hydroxyl group of the caustic stream. This forms a liquid / liquid mixture comprising an aqueous phase comprising regenerated ionic liquid and a halide-containing caustic solution.

[00148] The aqueous and organic phases are then at least partially separated to form a regenerated ionic liquid stream and a caustic stream containing halide.

[00149] The caustic stream containing halides is processed for discharge into the environment.

[00150] At least part of the regenerated ionic liquid stream must be recycled to the EXTRACT stage to form the ionic liquid feed stream.

[00151] The ionic liquid stock is gradually degraded or lost in the circuit, mainly in the EXTRACT and REGENERATE stages which have a high concentration of caustic substances. To maintain the ionic liquid concentration in the circuit, fresh ionic liquid can be added to the process, appropriately in the REGENERATE stage. Ideally, the fresh ionic liquid is in its separated form. Most appropriately, the fresh ionic liquid is tributyl ctyl phosphonium chloride.

[00152] Properly, one or both of the organic ionic liquids entering and leaving REGENERATE are filtered. Petition 870260066690, dated 06 / 07 / 2026, page 34 / 120 26 / 40

[00153] Because the viscosity of the ionic liquid at room temperature is too high to allow efficient filtration of the pure ionic liquid, the ionic liquid may be diluted before filtration to facilitate the filtration process. Suitablely, the ionic liquid is diluted with water in a ratio ranging from 0.5 (1:2) to 2 (2:1). Suitablely, the ratio of ionic liquid to water is 1 (1:1).

[00154] The parameters of the caustic solution stream, such as flow rate and concentration, can be adjusted to take into account the dilution of the ionic liquid.

[00155] Dilution of the ionic liquid can occur in the stream entering the REGENERATE stage. Water is appropriately added to the stream entering the REGENERATE stage to dilute the ionic liquid stream.

[00156] Once the colloidal solids are filtered, at least part of the resulting filtered stream can be recycled to the ionic liquid feed stream.

[00157] The filtered stream can be mixed with a metal halide salt and / or a caustic solution to recover the ionic liquid. The recovered ionic liquid is then appropriately recycled back into the circuit. The recovered ionic liquid can be decanted before being recycled back into the circuit.

[00158] The regenerated ionic liquid stream can be diluted with water before the filtration step.

[00159] In each of the EXTRACT, SEPARATE, and REGENERATE stages, the aqueous stream can flow countercurrently to the stream containing organic ionic liquid. Countercurrent operation increases the transfer of impurities from the stream containing impurities to the extraction stream, maintaining a nearly constant concentration gradient between the two streams throughout. Petition 870260066690, dated 06 / 07 / 2026, page 35 / 120 27 / 40 the contact length.

[00160] In each of the EXTRACT, SEPARATE and REGENERATE stages, the flow rate of each stream can vary from 244m3 / h.

[00161] The organic ionic liquid stream in the EXTRACT stage can have a flow rate ranging from 10-26 m3 / h.

[00162] The aqueous stream in the EXTRACT stage can be any suitable flow rate.

[00163] The aqueous stream in the SEPARATE stage can have a flow rate ranging from 4-14 m3 / h.

[00164] The aqueous stream in the REGENERATE stage can have a flow rate that varies from 6-23 m3 / h.

[00165] In each of the EXTRACT, SEPARATE and REGENERATE stages, the mixing step can be carried out in several ways, including batch, semi-continuous or continuous methods. Properly, the mixing step is a continuous process.

[00166] Each mixing step may involve feeding the organic and aqueous streams into any suitable apparatus that can be used for mixing and phase separation or sedimentation. Examples of suitable mixing and phase separation or settling apparatus include, but are not limited to, continuous mixer / settler units, static mixers, in-line mixers, columns, centrifuges, and hydrocyclones. A preferred apparatus is a mixer-settler.

[00167] In each of the EXTRACT, SEPARATE and REGENERATE stages, the operating temperature can reach 100°C. The operating temperature can be varied to control the rate of phase separation.

[00168] The operating temperature of each of the stages Petition 870260066690, dated 06 / 07 / 2026, page 36 / 120 28 / 40 Extracting, separating, and regenerating temperatures can vary from 50-80°C, ideally 65-75°C, and most ideally 60-65°C.

[00169] The method may include controlling the internal and / or external O / W ratios of each of the EXTRACT, SEPARATE, and REGENERATE stages. The O / W ratios may vary from 0.001 (1:1000) to 100 (100:1). In one embodiment, the O / W ratios vary from 0.01 to 100. In another embodiment, the ratios vary from 0.1 to 10. In another embodiment, the ratios vary from 0.25 to 6.67. In yet another embodiment, the ratios vary from 0.25 to 2. BRIEF DESCRIPTION OF THE DRAWINGS

[00170] One embodiment of the invention is described below by way of example with reference only to the accompanying drawings, in which:

[00171] Figure 1 is a flow diagram of one embodiment of a method for recycling an ionic liquid, according to the invention; and

[00172] Figure 2 is a diagram of an embodiment of an apparatus configured to recycle an ionic liquid, according to the invention. DETAILED DESCRIPTION

[00173] The embodiments described herein are embodiments of a method and apparatus for purifying a Bayer process stream using an ionic liquid to remove impurities from the Bayer process stream according to the invention.

[00174] The examples described herein focus on the application of the invention for the removal of impurities from a spent Bayer lye stream. As noted above, a particularly relevant class of impurity in the spent Bayer lye stream is NOOC.

[00175] The embodiment of the method for purifying a Bayer process stream according to the invention is marked as 10 in Figure 1. Petition 870260066690, dated 06 / 07 / 2026, page 37 / 120 29 / 40

[00176] The embodiment of the apparatus for purifying a Bayer process stream according to the invention is marked as 110 in Figure 2.

[00177] With reference to the Figures, the basic unit operations for the device are an EXTRACT stage 16, a SEPARATE stage 18 and a REGENERATE stage 20.

[00178] The EXTRACT 16 stage comprises three mixer-decanters comprising mixers 48A-C and decanters 46A-C (figure 2). The EXTRACT mixer-decanters are arranged in series with the first EXTRACT mixer-decanter E1 comprising mixer 48A and decanter 46A and the final EXTRACT mixer-decanter E3 comprising mixer 48C and decanter 46C.

[00179] The SEPARATE stage 18 comprises three mixer-decanters comprising mixers 52A-C and decanters 50A-C (figure 2). The SEPARATE mixer-decanters are arranged in series with the first SEPARATE mixer-decanter S1 comprising mixer 52A and decanter 50A and the final SEPARATE mixer-decanter S3 comprising mixer 52C and decanter 50C.

[00180] The REGENERATE 20 stage comprises four mixer-settlers comprising mixers 56A-C and settlers 54A-C (figure 2) arranged in series.

[00181] The method and apparatus of the invention are characterized by a FILTER stage comprising at least one filter configured to filter particulate matter from at least one of the ionic liquid streams of the EXTRACT, SEPARATE and REGENERATE stages 16, 18, 20.

[00182] An ionic liquid feed stream 12 comprising 70% by weight of tributylethylphosphonium hydroxide and 30% in Petition 870260066690, dated 06 / 07 / 2026, page 38 / 120 30 / 40 weight of water, and a spent Bayer lye stream 14 containing NOOC at a concentration of 22.5 g / L as carbon are fed into the EXTRACT stage 16 (Figure 1) in countercurrent at an external O / W ratio ranging from 0.67 to 1.0 and an internal O / W ratio ranging from 0.8 to 1.2 for mixing. The spent Bayer lye stream 14 enters through the final EXTRACT mixer-decanter E3, while the ionic liquid feed stream 12 enters through the first EXTRACT mixer-decanter E1.

[00183] The temperature of the spent Bayer lye stream 14 used varies from 60-80°C, while the temperature of the ionic liquid feed stream varies from 20-30°C, preferably from 20-25°C.

[00184] An operating temperature ranging from 50-80°C, preferably 60-65°C, is maintained in the EXTRACT stage.

[00185] As noted above, the mixer-settlers of stage 16 of the EXTRAIR comprise mixers 48A-C and settlers 46A-C (figure 2).

[00186] The first mixer-decanter E1 is in fluid communication with the final mixer-decanter R4 comprising mixer 56C and decanter 54C in the REGENERATE stage 20 via a recycling circuit. E1 receives the regenerated ionic liquid from the REGENERATE stage to form the ionic liquid feed stream 12 and the final EXTRACT mixer-decanter E3 is in fluid communication with the first mixer-decanter S1 comprising mixer 52A and decanter 50A of the SEPARATE stage 18.

[00187] During mixing in mixers 48A-C, NOOC is extracted from the Bayer lye stream 14 and transferred to the ionic liquid feed stream 12. This reduces the NOOC concentration in the Bayer lye stream 14 and forms a spent, purified, aqueous Bayer lye and an organic ionic liquid loaded with NOOC. Petition 870260066690, dated 06 / 07 / 2026, page 39 / 120 31 / 40

[00188] The aqueous and organic phases are then separated to form a purified Bayer process stream 24 with a lower NOOC concentration than the Bayer lye stream 14, for example 6.9 g / L or lower, and an ionic liquid stream loaded with NOOC 26 exiting the EXTRACT stage.

[00189] The purified spent Bayer lye stream 24 (which exits the first mixer-decanter EXTRACT E1) is transferred for further processing in a refinery, while the NOOC-charged ionic liquid stream 26 is transferred to the SEPARATE stage 18.

[00190] As noted above, the SEPARATE 18 stage comprises three mixer-settlers comprising mixers 52A-C and settlers 50A-C (figure 2) arranged in series.

[00191] The first SEPARATE mixer-decanter S1 is in fluid communication with the final mixer-decanter E3 which comprises mixer 48C and decanter 46C of the EXTRACT 16 stage and the final SEPARATE mixer-decanter S3 is in fluid communication with the first mixer-decanter R1 which comprises mixer 56A and decanter 54A of the REGENERATE 20 stage.

[00192] In the SEPARATE stage 18, the NOOC-laden ionic liquid stream 26 flows countercurrently to a brine (sodium chloride) stream 28 at an external O / W ratio ranging from 0.67 to 2.5 and an internal O / W ratio ranging from 0.8 to 1.2 for mixing. The brine (sodium chloride) stream 28 is fed into the final SEPARATE mixer-decanter S3, while the NOOC-laden ionic liquid stream 26 enters through the first SEPARATE mixer-decanter S1.

[00193] An operating temperature ranging from 60-80°C, preferably 70-75°C, is maintained in the SEPARATE stage. Petition 870260066690, dated 06 / 07 / 2026, page 40 / 120 32 / 40

[00194] During mixing in 52A-C, ion exchange occurs between the ionic liquid and the brine in which the anionic NOOC is exchanged for the chloride group in the brine. This forms a mixture comprising an aqueous phase containing brine loaded with NOOC and an organic phase comprising ionic liquid containing chloride.

[00195] The aqueous and organic phases are then separated to form a brine stream loaded with NOOC 30 with a NOOC concentration typically of at least 20 g / L and an ionic liquid stream containing chloride 32 that exits the SEPARATE stage.

[00196] The brine stream loaded with NOOC 30 (which exits the first mixer-decanter SEPARATE S1) is transferred for further processing before discharge into the environment.

[00197] Further processing includes passing the NOOC 30-laden brine stream through a coalescer to agglomerate and collect any trapped ionic liquid, typically ranging from 300-500 ppm, for recovery back into the loop.

[00198] Further processing also includes passing the NOOC 30-laden brine stream through a series of activated carbon columns to reduce the final ionic liquid concentration to less than < 1 ppm before the clean brine stream is discharged into the environment.

[00199] Part of the clean brine stream is recycled to the REGENERATE stage.

[00200] The ionic liquid stream containing chloride 32 is directed to the REGENERATE 20 stage which comprises four mixer-settlers.

[00201] As noted above, Figure 2 shows the four REGENERAR mixer-settlers as mixers 56A-C and settlers 54A-C arranged in series. Petition 870260066690, dated 06 / 07 / 2026, page 41 / 120 33 / 40

[00202] The first mixer-decanter R1 of the REGENERATE 20 stage is in fluid communication with the mixer-decanter S3 of the SEPARATE 18 stage, and the mixer-decanter R4 of the REGENERATE 20 stage is in fluid communication with the first mixer-decanter E1 of the EXTRACT 16 stage to transfer the regenerated ionic liquid to the EXTRACT 16 stage.

[00203] In the REGENERATE stage 20, the ionic liquid stream containing chloride 32 flows countercurrently to a caustic stream (sodium hydroxide) 35 which typically has a concentration of at least 10% by weight in an external O / W ratio ranging from 0.67 to 1.5 and an internal O / W ratio ranging from 0.8 to 1.2 for mixing. The caustic stream (sodium hydroxide) 35 is fed into the final REGENERATE mixer-decanter R4, while the ionic liquid stream containing chloride 32 is fed into the first REGENERATE mixer-decanter R1.

[00204] The temperature of the caustic stream 35 varies from 10-30°C, preferably 25°C.

[00205] An operating temperature ranging from 50-80°C, preferably 60-65°C, is maintained in the REGENERATE stage.

[00206] During mixing in mixers 56A-C, the chloride group of the ionic liquid is replaced by the hydroxyl group of the caustic solution. This forms an aqueous phase comprising a regenerated ionic liquid and a caustic solution containing chloride.

[00207] The aqueous and organic phases are then separated to form a regenerated ionic liquid stream 12 and a caustic stream containing chloride 36 that exits the REGENERATE stage 20 through the first REGENERATE mixer-decanter R1.

[00208] The caustic stream containing chloride 36 is further processed in a salt separation unit 40. The stream Petition 870260066690, dated 06 / 07 / 2026, page 42 / 120 34 / 40 processed caustic generates a sodium chloride stream 42 that is fed at least in part to the brine stream 28 or generates a sodium hydroxide stream 44 that is fed at least in part to the caustic stream 35.

[00209] The stock of ionic liquid is gradually degraded or lost in the circuit.

[00210] To maintain the ionic liquid concentration, fresh ionic liquid 37 in the form of tributylethylphosphonium chloride is added to the REGENERATE stage 20.

[00211] As discussed earlier, a problem encountered during the course of BTP's work was that, once a limit concentration of particulate matter was reached in an ionic liquid recycling circuit, an emulsion (referred to above as crude), stabilized by the particulate matter, formed between the used ionic liquid and the aqueous solutions, rendering the purification or recycling circuit unusable.

[00212] To mitigate crude formation, the outgoing organic ionic liquid stream SEPARATE passes through a suitably sized filtration device to maintain a solids concentration, i.e., particulate matter, below a limit concentration in the filtered stream before being transferred to the REGENERATE stage as the chloride-containing ionic liquid stream 32.

[00213] In another embodiment, to mitigate crude formation, the outgoing organic ionic liquid stream REGENERATE passes through a suitably sized filtration device to maintain a solids concentration, i.e., particulate matter, below a limit concentration in the filtered stream before being recycled as the ionic liquid feed stream 12.

[00214] Once the colloidal solids are filtered, the resulting stream can be salted using sodium chloride and / or caustic soda. Petition 870260066690, dated 06 / 07 / 2026, page 43 / 120 35 / 40 to recover the ionic liquid, before the ionic liquid is decanted and recycled back into the circuit.

[00215] As noted above, the invention extends to filtering the organic ionic liquid stream before or after any one or more of the EXTRACT, SEPARATE and REGENERATE stages 16, 18, 20.

[00216] In order to evaluate the present invention, the benchtop pilot (BTP), mentioned above, was operated using a method and apparatus similar to that described above with the use of the operating parameters described in Table 1. Table 1: Parameters for BTP Actual Standard Parameter Units Temperature 57 65 °C Mixer tip speed 3 3 m / s Mixer dwell time approx. 130 < 120 s Composition RA 10 10% NaOH Composition SA 27 27% NaCl (saturated) Flowchart (R:E:S) 4:3:3 4:3:3 Continuity R1, E1, S1 R1, E1, S1 Organic continuous R2, R3, R4, E2, E3, S2, S3 R2, R3, R4, E2, E3, S2, S3 Aqueous continuous Petition 870260066690, dated 06 / 07 / 2026, page 44 / 120 36 / 40 Flow rates - IL 0.62:1 0.85:1 RA 0.95:1 0.75:1 SA 0.67:1 0.45:1

[00217] Measured operating parameters are listed in the Actual column, while defined parameters are listed in the Default column.

[00218] Table 2 provides a summary of the analytical results of the BTP. Table 2: Summary of BTP analytical results Media p Cl TOC mg / L ppm mg / L Regenerated Aqueous (RA) 0 14.4 5390 Aqueous ex R4 (1st stage) 49 7260 4950 Aqueous ex R3 (2nd stage) 38 10900 4340 Aqueous ex R2 (3rd stage) 45 14600 3730 Aqueous ex R1 (4th stage) - SRA 10 23900 3780 DSL (Bayer feed bleach) 10 351 22900 Bayer bleach ex E3 (1st stage) 112 4700 14600 Bayer bleach ex E2 (2nd stage) 79 4370 11800 Refined ex E1 (3rd stage) 10 3560 6910 Strip Aqueous - SA 0 19300 6880 Aqueous ex S3 (1st stage) 34 164000 8950 Aqueous ex S2 (2nd stage) 30 162000 9580 Aqueous ex S1 (3rd stage) - SSA 28 145000 21700

[00219] Triplicate samples were taken from each of the three aqueous feed stock tanks (EXTRACT - DSL, SEPARATE - SA, REGENERATE - RA), as well as from each pond of Petition 870260066690, dated 06 / 07 / 2026, page 45 / 120 37 / 40 aqueous overflow from the settling tank for a total of 39 samples. Each sample was analyzed individually with respect to phosphorus, chloride, and total organic carbon content. Once the sample results were received, the median of each set of three results was calculated and is presented in Table 2 above.

[00220] Phosphorus was selected as a representative sample for the ionic liquid, since the previous P was expected, and proved to be low enough not to interfere with the analysis, and because the ionic liquid contains phosphorus.

[00221] All values ​​less than 20 ppm were reported as < 20 ppm. In the table above, where this < 20 ppm was reported for SA and RA, the value was entered in the table above as 0, since this is a pure solution before contact with any ionic lye. In all other cases where a value < 20 ppm was reported, a value of 10 ppm was entered as a working estimate of the P content of the sample.

[00222] The following observations were made based on the results in Table 2: • The purification of the Bayer 14 lye stream containing NOOCs occurred in the EXTRACT stage. This is evidenced by a decrease in TOC content from 22,900 mg / L in the spent Bayer 14 lye stream fed into E3 to 6,910 mg / L in the purified Bayer 24 process stream exiting E1. • NOOC was predominantly removed in the SEPARATE stage. This is evidenced by an increase in the TOC content of the brine stream (S3; SA) 28 supplied in S3 from 6,880 mg / L to 21,700 mg / L in the NOOC-laden brine stream (S1; SSA) 30 exiting S1. • The regeneration of the ionic liquid in the REGENERATE stage is evidenced by an increase in the Cl concentration of the caustic stream (R4; RA) supplied at R4 from 14.4 ppm to 23,900 Petition 870260066690, dated 06 / 07 / 2026, page 46 / 120 38 / 40 ppm in the caustic stream containing chloride (R1; SRA) 36 that exits R1. • A small amount of ionic liquid was removed by the caustic stream containing chloride (R1; SRA) 36 exiting the REGENERATE 20 stage. This is evidenced by an increase in the concentration of P in the caustic stream (R4; RA) 35 from 0 mg / L supplied at R4 to 10 mg / L in the caustic stream containing chloride (SRA) 36 exiting R1.

[00223] The effectiveness of filtering organic ionic liquid streams is illustrated by the following filtration experiments, summarized in Examples 1-3 below.

[00224] Example 1 - Filtration device: DrM TSD filter in 316L stainless steel with a 32 mm diameter candle filter. - No filter or dilution required. Temperature: 51°C - G11 M080 / 30 filter mesh (polypropylene) - Feed solids 1.7 g / L Maximum filtration pressure: 400 kPa (4 bar) - Solids filtered after the development of the filter cake, 0.43 g / kg. - Total flow rate of 48 L / m² / h after 240 minutes.

[00225] Example 2 - Filtration device: DrM TSD filter in 316L stainless steel with a 32 mm diameter candle filter. - Coarse perlite AP 70, undiluted feed with water. Temperature: 57°C - Filter aid body feed ratio 1:1 Petition 870260066690, dated 06 / 07 / 2026, page 47 / 120 39 / 40 - G11 M080 / 30 filter mesh (polypropylene) - Feed solids 4.3 g / L Maximum filtration pressure: 300 kPa (3 bar) - Total flow rate 89 L / m² / h after 117 minutes - No visible filtrate solids were observed (indicative of < 0.1 g / L based on correlation of visual findings with measurements from previous tests).

[00226] Example 3 - Filtration device: DrM TSD filter in 316L stainless steel with a 32 mm diameter candle filter. - Coarse AP 70 perlite, undiluted Temperature: 58°C - Filter aid body feed ratio 2:1 - G11 M080 / 30 filter mesh (polypropylene) - Feed solids 0.7 g / L Maximum filtration pressure: 300 kPa (3 bar) - Total flow rate 378 L / m² / h after 23 minutes - No visible filtrate solids were observed (indicative of < 0.1 g / L based on correlation of visual findings with measurements from previous tests)

[00227] The above observations show that the filter(s) installed in the device effectively remove(s) circulating particulate matter to prevent the formation of debris and allow the device to function.

[00228] Many modifications can be made to the embodiments of the invention described above without departing from the spirit and scope of the present invention.

[00229] As an example, mixers and decanters in the EXTRACT, SEPARATE and REGENERATE stages 16, 18, 20 can be Petition 870260066690, dated 06 / 07 / 2026, p. 48 / 120 40 / 40 any suitable mixers and decanters.

[00230] In the following and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "that which includes" is used in an inclusive sense, that is, to specify the presence of the indicated features, but not to preclude the presence or addition of other features in various embodiments of the present invention. GLOSSARY Term Definition BTP Benchtop pilot plant DSL Spent lye in digestion IL Ionic liquid NOOC Non-oxalate organic carbon compounds TOC Total organic carbon O / A Organic to aqueous ratio based on flow rates RA Regen Aqueous - solution used to convert ionic liquid from Cl- to OH- SA Strip Aqueous - solution used to remove NOOC from IL SRA Spent Aqueous Regen - aqueous regeneration solution exiting the SX SSA Strip Aqueous - aqueous separation solution exiting the SX SX Solvent extraction Petition 870260066690, dated 06 / 07 / 2026, page 49 / 120

Claims

1 / 9 CLAIMS 1. Apparatus (110) for recycling an ionic liquid used to purify a Bayer process stream, characterized in that it comprises: a SEPARATE stage (18) comprising at least one contact / separation device configured to receive and mix an impurity-laden ionic liquid stream (26) and a separation solution stream to form a reduced-impurity ionic liquid stream and an impurity-laden separation solution stream; a REGENERATE stage (20) comprising at least one contact / separation device configured to receive and mix the reduced-impurity ionic liquid stream and a caustic solution stream (35) to form a regenerated ionic liquid stream and a caustic effluent stream (36);wherein at least one contact / separation device of the REGENERATE stage (20) is configured to recycle at least part of the regenerated ionic liquid stream and form an ionic liquid feed stream to purify a Bayer process stream; and a FILTER stage comprising at least one filter configured to filter particulate matter from at least one of the ionic liquid streams of the SEPARATE and REGENERATE stages (18, 20) to control the concentration of particulate matter in the ionic liquid streams.

2. Apparatus, according to claim 1, characterized in that it includes a controller to operate the FILTER stage at a filtration flow rate between 10-700 L / m2 / h.

3. Apparatus, according to claim 1 or 2, characterized in that the FILTER stage is configured to control the viscosity of at least one ionic liquid stream of the SEPARATE and REGENERATE stages (18, 20) so that the FILTER stage operates at a filtration flow rate between 10-700 L / m2 / h.

4. Apparatus according to claim 3, characterized in that the controller is configured to control the viscosity being configured to control (a) the dilution of at least one ionic liquid stream of the SEPARATE and REGENERATE stages (18, 20) and / or (b) the FILTER stage to operate within a temperature range of 20-70°C and / or (c) the operating temperature of at least one of the SEPARATE and REGENERATE stages (18, 20) in the range of 50-80°C.

5. Apparatus, according to any one of claims 1 to 4, characterized in that it includes a controller configured to control the dilution of at least one ionic liquid stream from the SEPARATE and REGENERATE stages (18, 20).

6. Apparatus, according to any one of claims 1 to 5, characterized in that it includes a controller configured to operate the FILTER stage within a temperature range of 20-70°C.

7. Apparatus, according to any one of claims 1 to 6, characterized in that it includes a controller configured to control the operating temperature of at least one of the SEPARATE and REGENERATE stages (18, 20) to vary from 50-80°C.

8. Apparatus (110) for purifying a Bayer process stream including the apparatus for recycling the ionic liquid used to purify the Bayer process stream, as defined in claim 1, characterized in that the apparatus (110) for purifying the Bayer stream comprises: an EXTRACT stage (16) comprising at least one contact / separation device configured to receive and mix a Bayer process stream (14) containing impurities and an ionic liquid stream (12) including a quaternary organic cation to form a purified Bayer process stream (24) and an impurity-laden ionic liquid stream (26),wherein the SEPARATE stage (18) is configured to receive and mix the ionic liquid stream loaded with impurity (26) and a salt stream containing halide (28) to form an ionic liquid stream containing halide (32) and a salt stream loaded with impurity (30); the REGENERATE stage (20) is configured to receive and mix the ionic liquid stream containing halide (32) and a caustic stream (35) to form a regenerated ionic liquid stream and a caustic effluent stream containing halide (36), wherein the EXTRACT stage (16) is configured to be in fluid communication with the REGENERATE stage (20) through a recycling circuit to receive at least part of the regenerated ionic liquid stream; and the FILTER stage is configured to filter particulate matter from at least one of the ionic liquid streams of the EXTRACT, SEPARATE and REGENERATE stages (16, 18,20) to control the concentration of particulate matter in ionic liquid streams.

9. Apparatus, according to claim 8, characterized in that the FILTER stage is configured so that the concentration of particulate matter in the regenerated ionic liquid stream falls below a predetermined limit concentration before the regenerated ionic liquid is returned to the EXTRACT stage (16).

10. Apparatus, according to claim 8 or 9, characterized in that at least one operating unit containing ionic liquid for the EXTRACT, SEPARATE and REGENERATE stages (16, 18, 20) includes the FILTER stage filter to control the concentration of particulate matter in the regenerated ionic liquid. Petition 870260066690, dated 06 / 07 / 2026, page 52 / 120 4 / 9 11. Apparatus, according to claim 8 or 9, characterized in that the FILTER stage is an operating unit separate from the operating units that form the EXTRACT, SEPARATE and REGENERATE stages (16, 18, 20).

12. Apparatus, according to any one of claims 8 to 11, characterized in that the FILTER stage is after the SEPARATE stage (18).

13. Apparatus, according to any one of claims 8 to 12, characterized in that it includes a controller configured so that the FILTER stage operates at a filtration flow rate between 10-700 L / m2 / h; 14. Apparatus, according to claim 13, characterized in that the controller is configured to control the viscosity of at least one ionic liquid stream from the EXTRACT, SEPARATE and REGENERATE stages (16, 18, 20), so that the FILTER stage operates at a filtration flow rate between 10-700 L / m2 / h.

15. Apparatus according to claim 14, characterized in that the controller is configured to control viscosity, being configured to control (a) the dilution of at least one ionic liquid stream of the EXTRACT, SEPARATE and REGENERATE stages (16, 18, 20) and / or (b) the FILTER stage to operate within a temperature range of 20-70°C and / or (c) the operating temperature of at least one of the EXTRACT, SEPARATE and REGENERATE stages (16, 18, 20) to vary from 50-80°C.

16. Apparatus, according to any one of claims 8 to 15, characterized in that it includes a controller configured to control the dilution of at least one ionic liquid stream from the EXTRACT, SEPARATE and REGENERATE stages (16, 18, 20).

17. Apparatus according to any one of claims 8 to 16, characterized in that the filter is configured to use differential pressure as the driving force for filtration.

18. Apparatus according to any one of claims 8 to 17, characterized in that the filter includes filter media with an air permeability between 3-200 L / dm2 / min.

19. Apparatus according to any one of claims 8 to 17, characterized in that the FILTER stage includes a filter aid and a flocculant.

20. Apparatus, according to any one of claims 8 to 19, characterized in that it includes a controller configured to control the FILTER stage to operate within a temperature range of 20-70°C.

21. Apparatus, according to any one of claims 8 to 20, characterized in that it includes a controller configured to control the operating temperature of at least one of the ionic liquid streams of the EXTRACT, SEPARATE and RENEGEREN stages (16, 18, 20) to a range of 50-80°C.

22. Method for recycling an ionic liquid used to purify a Bayer process stream, characterized in that it comprises: mixing an impurity-laden ionic liquid stream (26) with a separation solution stream and forming an aqueous phase comprising an impurity-laden separation solution and an organic phase comprising a reduced-impurity ionic liquid; at least partially separating the aqueous phase from the organic phase and forming an impurity ionic liquid stream. Petition 870260066690, dated 06 / 07 / 2026, page.54 / 120 6 / 9 reduced and a stream of removal solution loaded with impurities; mix the ionic liquid stream with reduced impurities and a stream of caustic solution (35) and form an aqueous phase comprising a spent caustic solution (36) and an organic phase comprising a regenerated ionic liquid; filter at least one of the ionic liquid stream loaded with impurities (26), ionic liquid stream with reduced impurities and regenerated ionic liquid stream and remove particulate matter to control the concentration of particulate matter in the ionic liquid streams; and recycle at least part of the regenerated ionic liquid stream to form an ionic liquid feed stream (12) to purify a Bayer process stream.

23. Method (10) for purifying a Bayer process stream using an ionic liquid, including the method of recycling the ionic liquid used for purifying the Bayer process stream as defined in claim 22, characterized in that the method of purifying the process stream using an ionic liquid comprises: providing an ionic liquid feed stream (12) that includes a quaternary organic cation, wherein the ionic liquid feed stream (12) is at least partially immiscible with the Bayer process stream (14); mixing the Bayer process stream (14) with the ionic liquid feed stream (12) and forming an aqueous phase comprising purified Bayer process lye and an organic phase comprising impurity-laden ionic liquid, wherein the mixing reduces the impurity concentration in the Bayer process lye (14); Petition 870260066690, dated 06 / 07 / 2026,pg. 55 / 120 7 / 9 separate at least partially the aqueous phase from the organic phase and form a purified Bayer process stream (24) and an impurity-laden ionic liquid stream (26), wherein the mixing of the impurity-laden ionic liquid stream (26) with a separation solution stream comprises mixing the impurity-laden ionic liquid stream (26) and a halide-containing salt stream (28) to form an aqueous phase comprising an impurity-laden salt and an organic phase comprising a halide-containing ionic liquid,wherein the mixture reduces the concentration of impurities in the ionic liquid stream loaded with impurities (26); the separation at least partially of the aqueous phase from the organic phase comprises separating at least partially the aqueous phase from the organic phase and forming an ionic liquid stream containing halide (32) and a salt stream loaded with impurities (30); the mixing of the ionic liquid stream with reduced impurities and a caustic solution stream (35) comprises mixing the ionic liquid stream containing halide (32) and a caustic solution (35) and forming an aqueous phase comprising a caustic solution containing halide and an organic phase comprising a regenerated ionic liquid, wherein the mixture replaces at least some of the halide groups in the ionic liquid halide-containing solution with hydroxyl groups from the caustic solution,the method further comprising: separating at least partially the aqueous phase from the organic phase and forming the salt stream containing halide (28) and a regenerated ionic liquid stream, wherein the filtration of at least one of the ionic liquid stream loaded with impurities (26), ionic liquid stream with reduced impurities and regenerated ionic liquid stream comprises filtering at least one of the feed stream of Petition 870260066690, dated 06 / 07 / 2026, page 56 / 120 8 / 9 ionic liquid (12), ionic liquid stream loaded with impurities (26), ionic liquid stream containing halide (32) and the regenerated ionic liquid stream,and removing particulate matter to control the concentration of particulate matter in the ionic liquid streams; and recycling at least part of the regenerated ionic liquid stream comprises recycling at least part of the regenerated ionic liquid stream and forming at least part of the ionic liquid feed stream (12).

24. Method, according to claim 22 or 23, characterized in that it includes filtering at least one of the ionic liquid streams at a filtration flow rate between 10-700 L / m2 / h.

25. A method according to any one of claims 22 to 24, characterized in that it includes controlling the viscosity of at least one of the ionic liquid streams to provide a filtration flow rate between 10-700 L / m² / h.

26. Method according to claim 25, characterized in that it includes viscosity control by (a) diluting at least one ionic liquid stream and / or (b) performing the filtration step within a temperature range of 20-70°C and / or (c) controlling the operating temperature of at least one of the ionic liquid streams to vary from 50-80°C.

27. A method according to any one of claims 22 to 26, characterized in that it includes diluting at least one of the ionic liquid streams before the filtration step.

28. Method according to claim 27, characterized in that at least one of the ionic liquid streams is diluted with water in a ratio ranging from 0.5 (1:2) to 2 (2:1).

29. Method, according to any of the claims in Petition 870260066690, dated 06 / 07 / 2026, pages 57 / 120 9 / 9 22 to 28, characterized in that it includes carrying out the filtration step within a temperature range of 20-70°C.

30. A method, according to any one of claims 22 to 29, characterized in that it includes controlling the operating temperature of at least one of the ionic liquid streams to vary from 50-80°C.

31. A method according to any one of claims 22 to 30, characterized in that the filtration step includes the direct addition of a filtration aid to at least one of the ionic liquid streams.

32. Method according to claim 31, characterized in that it includes pre-dosing the filter aid with a water solution at a temperature between 20-80°C before it is added to at least one of the ionic liquid streams. Petition 870260066690, dated 06 / 07 / 2026, p. 58 / 120

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