Carbon dioxide mineralisation

Abstract

The present disclosure relates to a method of carbon dioxide mineralisation, the method comprising: treating a material, such as a mineral, with carbon dioxide and a base, wherein the treatment occurs in solution phase, the material comprising: a first cation that is Ca or Mg; a second cation which is not Ca and or Mg; and one or more anions which are not carbonate; such that a product solution comprising an acid or a salt of the base and one of the one or more anions and a salt of the second cation and one of the one or more anions is formed, and a carbonate salt of the first cation is caused to precipitate.

Description

Carbon dioxide mineralisation

[0001] The present application claims priority to Australian Provisional Patent Application No.2024902618 filed 22 August 2024. Technical field

[0002] The present disclosure relates to a carbon dioxide mineralisation process. Background art

[0003] Carnallite is a potash-containing mineral. However, due to carnallite's relatively low K2O content, high solubility, and high magnesium content, it has been regarded as inferior and uneconomic compared to alternatives such as sylvite and sylvinite. The presence of high levels of magnesium in process streams in fertiliser production operations from potash-containing minerals is also known to make the production process less efficient. Full utilisation of the potassium- containing streams is not possible because the magnesium will impact product purity. As a result, when magnesium builds up to certain levels in such process streams, it is common practice to purge a portion of these streams and send the purge stream away as waste. This is a waste of resources. Separately, there is a growing requirement and market for CO2 utilisation and storage.

[0004] It would be advantageous to provide a process by which useful products can be obtained from materials, by example containing magnesium and potassium such as the evaporite mineral carnallite or the above noted process, waste or purge streams, while simultaneously providing a means of CO2 sequestration. It would also be advantageous to provide a process by which useful products can be obtained from minerals and materials that are similar to carnallite while simultaneously providing a means of CO2 sequestration.

[0005] In this specification, unless the contrary is expressly stated, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge; or known to be relevant to an attempt to solve any problem with which this specification is concerned. Summary

[0006] Disclosed herein is a method of carbon dioxide mineralisation. The method may comprise treating a material with carbon dioxide and a base, wherein the treatment occurs insolution phase. For example, the method may comprise: (i) treating a material with carbon dioxide, a base and water. The material may comprise a first cation that is Ca or Mg; a second cation that is different from the first cation, more specifically, a second cation which is not Ca or Mg; and one or more anions which are not carbonate. The treating is such that a product solution comprising an acid or a salt of the base and one of the one or more anions and a salt of the second cation and one of the one or more anions may be formed, and a carbonate salt of the first cation may be caused to precipitate.

[0007] In a first aspect of the disclosure, there is provided a method of carbon dioxide mineralisation comprising: (i) treating a material with carbon dioxide and a base, wherein the treatment occurs in solution phase, the material comprising: a first cation that is Ca or Mg; a second cation which is not Ca or Mg; and one or more anions which are not carbonate; such that a product solution comprising an acid or a salt of the base and one of the one or more anions and a salt of the second cation and one of the one or more anions may be formed, and a carbonate salt of the first cation may be caused to precipitate.

[0008] In some forms, step (i) may comprise treating the material as a solid with gaseous carbon dioxide, a base and water, treating the material as an aqueous solution with gaseous carbon dioxide and a base, treating the material as a solid with supercritical carbon dioxide, a base and water, treating the material as a solid with gaseous carbon dioxide, an aqueous solution comprising a base and water, or treating the material as a solid with an aqueous solution comprising carbon dioxide and a base. The material may be initially provided as a solid or in aqueous solution, however it is ultimately present in solution phase during the step of treating with carbon dioxide and a base.

[0009] In some forms, the water may not contain any additional dissolved salts. In some forms, the water may contain additional dissolved salts. In some forms the aqueous solution is a saturated salt solution, such as a saturated sodium chloride solution or other such salt solution.

[0010] In some forms, the method may further comprise: (ii) separating the product solution and the carbonate salt of the first cation.

[0011] In some forms, the material may be a mineral, a mineral solution, a waste stream, a rock or an orebody.

[0012] In some forms, the mineral may be an evaporite mineral.

[0013] In some forms, the mineral solution, the rock or the orebody may contain an evaporite mineral.

[0014] In some forms, the evaporite mineral may comprise the first cation and the second cation.

[0015] In some forms, the waste stream may be the product of a mineral processing step that comprises the first cation, the second cation, and the one or more anions.

[0016] In some forms, the second cation may be selected from Li, Na, and K.

[0017] In some forms, the one or more anions may be selected from chloride, bromide, iodide, nitrate, and sulfate.

[0018] In some forms, the mineral may be selected from the group consisting of carnallite (KMgCl3•6H2O), kainite (KMg(SO4)Cl•3H2O), langbeinite (K2Mg2(SO4)3), polyhalite (K2Ca2Mg(SO4)6•H2O), bloedite (Na2Mg(SO4)2•4H2O, glauberite (Na2SO4•CaSO4), schoenite (K2SO4•MgSO4•6H2O), leonite (K2SO4•MgSO4•4H2O), and lithium carnallite (LiMgCl3•7H2O).

[0019] In some forms, the mineral may be carnallite or lithium carnallite.

[0020] In some forms, a concentration of the base in step (i) may be from about 5% (w / w) to about 80% (w / w).

[0021] In some forms, the method may comprise: (i) treating the material with an aqueous solution comprising carbon dioxide and / or a base. The concentration of the base in the aqueous solution may be from about 5% (w / w) to about 80% (w / w).

[0022] In some forms, the temperature of the aqueous solution comprising carbon dioxide and a base may be from ambient temperature to about 200°C.

[0023] In some forms, the base may be selected from ammonia, MgO, NaOH, KOH, and KHCO3. In some forms, the base may be ammonia.

[0024] In some forms, the material may be a mineral in an underground mineral deposit and step (i) may comprise injecting carbon dioxide, a base and water or aqueous solution into the underground mineral deposit, such that the product solution and the carbonate salt of the first cation may be formed in the underground deposit. In some forms, in step (i) the mineral may be in solid form.

[0025] In some forms, the method may further comprise: (ii.a) extracting the product solution above-ground from the underground deposit, wherein the carbonate salt of the first cation remains in the underground deposit.

[0026] In some forms, where the base is ammonia, the method may further comprise: (iii.aa) separating ammonia from the product solution.

[0027] In some forms, the base used in step (i) may comprise ammonia obtained in step (iii.aa).

[0028] In some forms, following step (iii.aa) the product solution may comprise an acid of one of the one or more anions and a salt of the second cation and one of the one or more anions.

[0029] In some forms, the method may further comprise: (iv.ab) separating the acid of one of the one or more anions from the product solution.

[0030] In some forms, the method may further comprise: (v.ab) separating the salt of the second cation and one of the one or more anions from the product solution.

[0031] In some forms, separating the salt of the second cation and one of the one or more anions from the product solution may comprise heating and / or cooling the product solution to provide the salt of the second cation and one of the one or more anions in solid form and, if heating, steam.

[0032] In some forms, steps (iii.aa), (iv.ab) and / or (v.ab) may comprise heating the product solution, and steam obtained in step (v.ab) is utilised to provide heat in steps (iii.aa) and / or (iv.ab).

[0033] In some forms, step (iii.aa) may further comprise adding a second base to the product solution to provide a basified product solution.

[0034] In some forms, the second base may be selected from calcium oxide or calcium hydroxide, or a mixture thereof, magnesium oxide or magnesium hydroxide, or a mixture thereof, KOH, and NaOH.

[0035] In some forms, following step (iii.aa) the basified product solution may comprise a salt of the second base and one of the one or more anions.

[0036] In some forms, the basified product solution may further comprise a salt of the second cation and one of the one or more anions.

[0037] In some forms, the method may comprise step (iv.ac) separating the salt of the second base and one of the one or more anions from the basified product solution.

[0038] In some forms, the method may comprise step (v.ac) separating the salt of the second cation and one of the one or more anions from the basified product solution.

[0039] In some forms, the second base may be magnesium oxide, magnesium hydroxide, or a mixture thereof.

[0040] In some forms, step (i) may further comprise treating the mineral with a salt of magnesium and one of the one or more anions obtained following step (iv.ac) and / or step (v.ac).

[0041] In some forms, the method may comprise (iii.c) evaporating the product solution to provide a solid mixture of the salt of the base and one of the one or more anions and the salt of the second cation and one of the one or more anions.

[0042] In some forms, the method may comprise (iv.c) separating the salt of the base and one of the one or more anions and the salt of the second cation and one or more anions.

[0043] In some forms, the method may comprise (ii.d) separating the carbonate salt of the first cation from the product solution.

[0044] In some forms, the method may comprise (iii.d) separating ammonia from the product solution.

[0045] In some forms, the base used in step (i) may comprise ammonia obtained in step (ii.d).

[0046] In some forms, following step (iii.d) the product solution may comprise an acid of one of the one or more anions and a salt of the second cation and one of the one or more anions.

[0047] In some forms, the method may comprise step (iv.d) separating the acid of one of the one or more anions from the product solution.

[0048] In some forms, the method may comprise step (v.d) separating the salt of the second cation and one of the one or more anions from the product solution.

[0049] In some forms, separating the salt of the second cation and one of the one or more anions from the product solution may comprise heating or cooling the product solution to provide the salt of the second cation and one of the one or more anions in solid form and, if heating, steam.

[0050] In some forms, steps (iii.d), (iv.d) and / or (v.d) may comprise heating the product solution and steam obtained in step (vi.d) is utilised to provide heat in steps (iii.d) and / or (iv.d).

[0051] In some forms, the base in step (i) may be introduced in solution at a concentration of about 5% to about 80%. This may cause the carbonate salt of the first cation to preferentially precipitate in the form XCO3, or hydrates thereof, with X denoting the first cation. The concentration of the base in solution may be about 5% to about 28%.

[0052] In some forms, the carbonate salt of the first cation that is caused to precipitate is hydrated. In step (i) a concentration of the salt of the second cation and one of the one or more anions in the product solution is less than about 90% of its saturation concentration. This may inhibit co-precipitation of salts of the second cation with the carbonate salt of the first cation.

[0053] In a second aspect of the disclosure, there is provided a method of carbon dioxide mineralisation. The method comprises: (i) treating a material with carbon dioxide and a base, wherein the treatment occurs in solution phase, wherein the material comprises a first cation which is Ca or Mg and one or more anions which are not carbonate, such that a product solution comprising an acid and / or a salt of the base and one of the one of the one or more anions is formed, and a carbonate salt of the first cation is caused to precipitate.

[0054] The method may comprise: (i) treating a material with carbon dioxide and a base, wherein the treatment occurs in solution phase, the material comprising: a first cation which is Ca or Mg and one or more anions which are not carbonate, such that a product solution comprising an acid and / or a salt of the base and one of the one of the one or more anions is formed, and a carbonate salt of the first cation is caused to precipitate.

[0055] In some forms, the material may not consist of CaSO4, MgSO4, MgCl2, CaCl2, or hydrates thereof.

[0056] In some forms, the material may further comprise a second cation which is not Ca or Mg.

[0057] In some forms, the second cation may be selected from Li, Na, and K. In some forms, the product solution may further comprise a salt of the second cation and one of the one or more anions.

[0058] The material may be a mineral selected from carnallite, lithium carnallite, and bischofite.

[0059] In some forms, the material may further comprise a second cation and following step(i) the product solution may comprise a salt of the base and one of the one or more anions and asalt of the second cation and one of the one or more anions.

[0060] The method may be as otherwise disclosed above.

[0061] Also disclosed herein is a method of obtaining and separating a first product comprising a first cation and a second product comprising a second cation from a material comprising the first cation, the second cation and one or more anions. The method may comprise: (i) treating the material with carbon dioxide and a base, wherein the treatment occurs in solution phase, such that the first product comprising a carbonate salt of the first cation is caused to precipitate and the second product comprising a product solution comprising a salt of the second cation and one of the one or more anions and a salt of the base and one of the one or more anions is formed; and (ii) separating the first product and the second product; wherein the second cation is different to the first cation and the one or more anions is not carbonate. The method may be as otherwise disclosed above. Brief description of drawings

[0062] Various embodiments / aspects of the disclosure will now be described with reference to the following figures.

[0063] Fig.1a shows a flow sheet of a first embodiment of the present disclosure;

[0064] Fig.1b shows the flow sheet of the first embodiment of Fig.1a, but with the filtrate / solution from the KCl crystallisation and separation (Xtaln) recycled to carnallite dissolution, with introduction of a base (such as KOH) as opposed to MgO to reactive extraction and without recovery of HCl from reactive extraction;

[0065] Fig.1c also shows the flow sheet of the first embodiment of Fig.1a, but with the filtrate / solution from the KCl crystallisation and separation (Xtaln) recycled to carnallite dissolution;

[0066] Fig.2a shows a flow sheet of a second embodiment of the present disclosure;

[0067] Fig.2b shows the flow sheet of the second embodiment of Fig.2a, but with the filtrate / solution from the KCl crystallisation and separation (evaporation) recycled to carnallite dissolution;

[0068] Fig.3a shows a flow sheet of a third embodiment of the present disclosure;

[0069] Fig.3b shows the flow sheet of the third embodiment of Fig.3a, but with recycled ammonia / liquor recycled from halite removal to carnallite dissolution as opposed to its introduction in the ammonia recycle from ammonia recovery to carbonation;

[0070] Fig.4a shows a flow sheet of a fourth embodiment of the present disclosure;

[0071] Fig.4b shows the flow sheet of the fourth embodiment of Fig.4a, but with recycled ammonia / solution recycled from HCl distillation to carnallite dissolution as opposed to its introduction in the ammonia recycle from ammonia recovery to carbonation;

[0072] Fig.5a shows a flow sheet of a fifth embodiment of the present disclosure;

[0073] Fig.5b shows the flow sheet of the fifth embodiment of Fig.5a, but with recycled solution recycled from Ca removal to carnallite dissolution as opposed to ammonia recovery;

[0074] Fig.6 shows a flow sheet of a sixth embodiment of the present disclosure;

[0075] Fig.7 shows a flow sheet of a seventh embodiment of the present disclosure;

[0076] Fig.8 shows a quantitative XRD characterisation of the product of carbonation of synthetic evaporites according to Example 2: (a) product of carbonation of synthetic carnallite,(b) product of carbonation of synthetic bischofite; and

[0077] Fig.9 shows a bench scale apparatus for distillation of ammonia from a product solution obtained by treatment of carnallite with ammonium carbonate.Detailed description

[0078] The Applicant has determined that by treating, in solution phase, a material comprising a first cation and a second cation (for example, an evaporite mineral such as carnallite which comprises potassium and magnesium) with carbon dioxide and a base, it is able to sequester carbon dioxide while simultaneously providing one or more useful products, such as, in the case of carnallite, magnesium carbonate, potash, and ammonium chloride and / or hydrochloric acid. The evaporite mineral may be from an evaporite deposit, an orebody, or a rock, each of which may also contain other minerals (for example carbonates such as calcite, dolomite, magnesite, and aragonite, sulfates such as anhydrite and gypsum, chlorides such as halite, sylvite, and carnallite, as well as borates, silicates, nitrates, and sulfocarbonates).

[0079] The Applicant has also determined that the material may be a waste stream of a mineral processing step, where the waste stream comprises a first cation and a second cation. The waste stream may be an aqueous solution which is treated with carbon dioxide and a base so as to sequester carbon dioxide while simultaneously providing one or more saleable products.

[0080] According to a first aspect of the present disclosure, there is provided a method of carbon dioxide mineralisation. The method comprises: (i) treating a material with carbon dioxide and a base, wherein the treatment occurs in solution phase, wherein the material comprises a first cation which is Ca or Mg and one or more anions which are not carbonate, such that a product solution comprising an acid and / or a salt of the one of the one or more anions is formed, and a carbonate salt of the first cation is caused to precipitate.

[0081] In step (i) of the method of the first aspect of the disclosure, the material is treated with carbon dioxide and a base in solution phase. That is, the material is contacted with carbon dioxide and a base in a solution, such as an aqueous solution. The material may be initially provided as a solid or in solution phase, however it is ultimately present in solution phase when treated with carbon dioxide and a base. As such, both the treatment of a solid material with carbon dioxide, a base and water, as well as the treatment of a solution of the solid material, such as an aqueous solution, with carbon dioxide and a base are understood to be encompassed by this method.

[0082] As described further below in relation to specific embodiments, where the material is a mineral that is located in an underground deposit, this may involve injecting carbon dioxide, a base and water into the deposit such that it contacts the mineral. Alternatively, where the material is a mineral, mineral-derived solution or a waste stream that is located above ground (for examplein a pit or a reactor), the mineral, mineral-derived solution, carbon dioxide and a base may be mixed together (with optional addition of water, by non-limiting example where the material is a mineral in solid form). In some cases the mineral may be dissolved or partially dissolved underground and pumped above ground in a solution or slurry (for example an aqueous solution of the mineral from solution mining). In this example, the material as an aqueous mineral solution may be contacted with carbon dioxide and a base above ground. In another example, the mineral may be contacted with carbon dioxide and water underground and treated with a base above ground. It will be appreciated by those skilled in the art that step (i) of the method need not necessarily be performed as a single operation and may comprise various sequential and / or concurrent operations so as to form the product solution. Furthermore, it will be appreciated that step (i), including any operations forming part of step (i), may be performed in a batch, semi- batch and / or continuous fashion.

[0083] Treating the material with carbon dioxide, a base and optionally water may occur separately or simultaneously. In one example, if the carbon dioxide is in the form of gaseous carbon dioxide or supercritical carbon dioxide, the material may be separately treated with carbon dioxide and an aqueous solution of the base. More specifically, gaseous or supercritical carbon dioxide and water may be separately, simultaneously or sequentially injected into an underground mineral deposit, or added to a pit or a reactor, and the resulting solution is subsequently treated with a base or an aqueous solution of the base. If the base is a gaseous base, such as ammonia, the gaseous base and the carbon dioxide may be separately, simultaneously or sequentially injected into an underground mineral deposit or added to a pit or a reactor. In another example, the mineral may be simultaneously treated with an aqueous solution comprising carbon dioxide and the base. An aqueous solution comprising carbon dioxide may be in the form of water in which carbon dioxide is dissolved, some of which may be present in the form of dissolved molecules of gaseous carbon dioxide, and some of which may be present in the form of carbonic acid. In some cases, the dissolved carbon dioxide may react with the base when the carbon dioxide and the base are dissolved in water. For example, where the base is ammonia or ammonium hydroxide, it may react with the carbon dioxide to form ammonium carbonate and the material may be treated with the resulting ammonium carbonate solution.

[0084] Further, and in some embodiments, in step (i) of the first aspect of the disclosure, the material may be first treated with carbon dioxide and then treated with the base. The carbon dioxide and base may be provided in any suitable form or combination of forms (e.g. gaseous, supercritical, aqueous solution). For example in one embodiment, step (i) may comprise firsttreating the material with an aqueous solution of carbon dioxide to form a mixture, then treating the mixture with an aqueous solution of the base. In another embodiment, step (i) may comprise starting with the material as an aqueous solution, or treating a solid material with water to form a first mixture, then bubbling carbon dioxide gas through the first mixture to form a second mixture, then treating the second mixture with an aqueous solution of the base. In yet another embodiment, step (i) may comprise starting with the material as an aqueous solution, or treating a solid material with water to form a first mixture, then bubbling carbon dioxide gas through the first mixture to form a second mixture, then (where the base is a gaseous base such as ammonia) bubbling the base through the second mixture.

[0085] For the avoidance of doubt, treating the material with gaseous carbon dioxide, a base and water, treating the material with supercritical carbon dioxide, a base and water, treating the material with an aqueous solution comprising carbon dioxide and a base, or treating the material which is an aqueous solution or waste stream with carbon dioxide and a base, refers to the optional active steps taken by the skilled addressee when implementing the method disclosed herein, and the form in which the carbon dioxide, the base and the material is initially provided. Regardless of the form of the material, the carbon dioxide or the base, it will be evident to the skilled addressee that if water is present, then an aqueous solution comprising the material, carbon dioxide and the base will ultimately form in situ.

[0086] In general in step (i) of the first aspect of the disclosure, if the material is treated with carbon dioxide and water (and no base), the material may dissolve and react with the carbon dioxide. This results in the formation of a product solution comprising an acid of the one or more anions. If the material comprises more than one anion, a mixture of different acids may be formed. Additionally, a carbonate salt of the first cation is formed and a base is added to the system to maintain the pH in the alkaline range to cause the carbonate salt of the first cation to precipitate (as Ca and Mg carbonate salts are insoluble under these conditions).

[0087] According to the present disclosure, there is provided a method of carbon dioxide mineralisation. The method comprises: (i) treating a material with carbon dioxide and a base, wherein the treatment occurs in solution phase, wherein the material comprises a first cation, a second cation and one or more anions, such that a product solution comprising a salt of the second cation and one of the one or more anions and an acid and / or a salt of one of the one or more anions is formed, and a carbonate salt of the first cation is caused to precipitate, wherein the second cation is different to the first cation and the one or more anions is not carbonate.

[0088] In some embodiments, the material comprises a first cation in the form of a divalent cation, and a second cation in the form of a monovalent cation. In some embodiments, the material comprises a first cation, in the form of an alkaline earth metal, and a second cation in the form of an alkali metal. In some embodiments, the first cation may be selected from Ca or Mg. In some embodiments, the second cation may be selected from Li, Na and K. In some embodiments the second cation is K. In some embodiments, the material comprises a first cation which may be selected from Ca or Mg and a second cation which may not be Ca or Mg. In some embodiments, the material comprises a first cation which may be selected from Ca or Mg and a second cation which may be selected from Li, Na and K. Thus, the material may comprise a first cation in the form of Ca and a second cation which is selected from Li, Na and K. The material may comprise a first cation in the form of Mg and a second cation which is selected from Li, Na and K. The material may comprise one or more anions that are not carbonate, and may be selected from chloride, bromide, iodide, nitrate, and sulfate. The material may comprise a first cation in the form of Mg and one or more anions selected from chloride, bromide, iodide, nitrate, and sulfate. The material may comprise a first cation in the form of Ca and one or more anions selected from chloride, bromide, iodide, nitrate, and sulfate. The material may comprise a first cation in the form of Mg, a second cation which is selected from Li, Na and K, and one or more anions selected from chloride, bromide, iodide, nitrate, and sulfate. The material may comprise a first cation in the form of Ca, a second cation which is selected from Li, Na and K, and one or more anions selected from chloride, bromide, iodide, nitrate, and sulfate.

[0089] The material may be a mineral, a mineral solution, a waste stream, a rock or an orebody. In some embodiments, the material may contain an evaporite mineral. The evaporite mineral may be selected from the group consisting of carnallite (KMgCl3•6H2O), kainite (KMg(SO4)Cl•3H2O), langbeinite (K2Mg2(SO4)3), polyhalite (K2Ca2Mg(SO4)6•H2O), bloedite (Na2Mg(SO4)2•4H2O, glauberite (Na2SO4•CaSO4), schoenite (K2SO4•MgSO4•6H2O), leonite (K2SO4•MgSO4•4H2O), tachyhydrite (CaMg2Cl6•12H2O), kieserite (MgSO4•H2O), bischofite (MgCl2•6H2O), epsomite (MgSO4•7H2O), hexahydrite (MgSO4•6H2O), and lithium carnallite (LiMgCl3•7H2O). The mineral may be selected from the group consisting of carnallite (KMgCl3•6H2O), kainite (KMg(SO4)Cl•3H2O), langbeinite (K2Mg2(SO4)3), polyhalite (K2Ca2Mg(SO4)6•H2O), bloedite (Na2Mg(SO4)2•4H2O, glauberite (Na2SO4•CaSO4), schoenite (K2SO4•MgSO4•6H2O), leonite (K2SO4•MgSO4•4H2O), tachyhydrite (CaMg2Cl6•12H2O), and lithium carnallite (LiMgCl3•7H2O). The mineral may be selected from the group consisting of carnallite (KMgCl3•6H2O), kainite (KMg(SO4)Cl•3H2O), langbeinite (K2Mg2(SO4)3), polyhalite (K2Ca2Mg(SO4)6•H2O), bloedite (Na2Mg(SO4)2•4H2O, glauberite (Na2SO4•CaSO4), schoenite(K2SO4•MgSO4•6H2O), leonite (K2SO4•MgSO4•4H2O), and lithium carnallite (LiMgCl3•7H2O). The mineral may be selected from carnallite, lithium carnallite, and bischofite. The mineral may be carnallite or lithium carnallite. The mineral may be carnallite.

[0090] In some embodiments, the material may be a waste stream that comprises a first cation, a second cation, and one or more anions. The waste stream may be the product of a mineral processing step, and the present method may be used to isolate saleable products from the waste stream, such as potassium chloride, hydrochloric acid, ammonium chloride, lithium, magnesium carbonate and calcium carbonate. For example, in potash processing, the magnesium concentration is controlled by bleeding a portion of the processing stream and discarding this bleed fraction. By discarding, this stream is considered a waste stream.

[0091] Whether the material is a mineral, a mineral-derived solution, a waste stream, a rock or an orebody, the material will contain at least a first cation, a second cation, and one or more anions. In some embodiments, the material may be a mixture or combination of a material containing a first cation and a material containing a second cation, such as a deposit, rock or orebody that contains a mixture of sylvite and bischofite or a waste stream that contains a mixture of potassium chloride and magnesium sulfate. In other embodiments, the material may be a deposit, rock or orebody that contains multiple minerals containing a first cation, a second cation, and one or more anions within their structure, such as a carnallite deposit.

[0092] The material may be a single chemical entity, for example a single mineral or solution comprising a single mineral, or it may be a mixture of two or more chemical entities, for example a mixture of two or more minerals or a solution comprising two or more minerals.

[0093] Where the material is treated with a base in step (i), the base may be any suitable base. The base may be an inorganic base. The base may be a metal oxide or hydroxide, such as an alkali metal or alkaline earth metal oxide or hydroxide. The base may be selected according to the elemental composition of the material to be treated so as not to introduce any new elements that subsequently need to be removed from the product solution or the precipitate. The base may be selected from ammonia, MgO, NaOH, KOH, CaO, Ca(OH)2 and KHCO3. The base may be selected from ammonia and KOH. The base may be ammonia. Where the base is ammonia, the product solution may comprise an ammonium salt with one of the one or more anions. Where the base is a metal oxide or hydroxide, the product solution may comprise a metal salt with one of the one or more anions.

[0094] Where step (i) comprises treating the material with an aqueous solution comprising carbon dioxide and a base and the base is ammonia or ammonium hydroxide, this may comprise treating the material with an aqueous solution of ammonium carbonate.

[0095] In some embodiments, the water utilised in the process does not contain any additives. Additives may include organic compounds, surfactants, and additional dissolved salts. In some embodiments, the water utilised in the process may not contain any additional dissolved salts. For the avoidance of doubt, this refers to water with which the material is initially treated by the operator of the method, and not the product solution. That is, step (i) may not comprise treating the material with any additives or, in other words, step (i) may consist of treating the material with carbon dioxide, water, and a base. In some embodiments, the material may be in a solution (such as where the material is a waste stream) and the solution may already contain organic compounds, surfactants, and additional dissolved salts.

[0096] In some embodiments, treating the material with carbon dioxide comprises treating the material with carbon dioxide of any purity. The purity of the carbon dioxide used may vary from about 1% to 100% pure carbon dioxide. The carbon dioxide may, for example, be provided from a gas or coal-fired power plant, an aluminium smelter, via direct air capture, an ethanol production plant or any other source.

[0097] In some embodiments, treating the material with carbon dioxide comprises adding the carbon dioxide until the level of the first cation present in solution decreases. In some embodiments, up to about 100% of the first ion would be removed from solution, such as up to about 99%, up to about 95%, up to about 90%, up to about 85%, up to about 80%, or up to about 75%. It will be appreciated by the skilled addressee that the ideal target extent of the removal of the first ion is determined by the downstream potash processing step requirements. The level of the first cation in solution may be monitored by inductively coupled plasma or atomic absorption spectroscopy or by any other suitable analytical technique. In some embodiments, treating the material with carbon dioxide comprises adding the carbon dioxide until the pH of the mixture is about 8 or above. In some embodiments, the carbon dioxide is added until the pH of the mixture is in the range of about 8 to about 9.

[0098] Where step (i) comprises treating the material with an aqueous solution comprising carbon dioxide, the carbon dioxide is added in excess. In some embodiments, concentration of the carbon dioxide may be between about 1 – 20 g CO2 / kg solution.

[0099] Where step (i) comprises treating the material with a base, and the base is provided in an aqueous solution, the concentration of the base may be between about 5% (w / w) to about 75% (w / w). In some embodiments, the concentration of the base may be between about 5% (w / w) to about 50% (w / w). In some embodiments, the concentration of the base is between about 5% (w / w) and about 45% (w / w), about 5% (w / w) and about 40% (w / w), about 5% (w / w) and about 35% (w / w) or about 5% (w / w) and about 30% (w / w).

[0100] Where step (i) comprises treating the material with an aqueous solution of ammonium carbonate, the concentration of the ammonium carbonate that is added may be between about 0.1M to about 5M. In some forms, the concentration of the ammonium carbonate is between about 0.1M and about 3M, about 0.5M and about 4M, about 0.5M and about 3M, about 1M and about 3M, about 1M and about 2M, or about 0.5M and about 2M. In some embodiments, the final concentration of ammonium carbonate when the material is treated is from about 0.02 to about 3M, from about 0.05 to about 1M or about 0.1 to about 0.5M.

[0101] Where step (i) comprises treating the material with an aqueous solution of ammonium carbonate, the temperature of the aqueous solution may be from about ambient temperature to about 80°C. In some forms, the temperature of the aqueous solution is from about 10°C to about 60°C, about 10°C to about 50°C, about 15° to about 60°C, about 15°C to about 50°C, about 15° to about 60°C or about 15°C to about 50°C.

[0102] In some embodiments, the step of treating, in solution, the material with carbon dioxide and a base may be performed such that the concentration of the material is controlled and / or the concentration of the salt of the second cation and one of the one or more anions in the product solution is controlled. This may be particularly relevant where the carbonate salt of the first cation precipitates as a hydrate as this removes water from the product solution, increasing the concentration of the salt of the second cation and one of the one or more anions in the product solution. In one example, the material is provided as an aqueous solution and is then treated with carbon dioxide and a base, the material may be provided as solution containing from about 1% (w / w) to about 80% (w / w) of the material, from about 1% (w / w) to about 60% (w / w) of the material or from about 10% (w / w) to about 50% (w / w) of the material. In another example, sufficient water is used in the step of treating, in solution, the material with carbon dioxide and a base to ensure that the concentration of the salt of the second cation and one of the one or more anions in the product solution is, for example where the salt of the second cation and one of the one or more anions is KCl, from about 1 g / L KCl to about 200 g / L KCl, from about 1 g / L KCl to about 150 g / L KCl, from about 20 g / L KCl to about 120 g / L KCl or from about 40 g / L KCl toabout 115 g / L KCl of the salt of the second cation. Put another way, sufficient water is used in the step of treating, in solution, the material with carbon dioxide and a base to ensure that the concentration of the salt of the second cation and one of the one or more anions in the product solution is less than about 90% of its saturation concentration, or less than about 80, 70, 60, 50, 40, 30, 20 or 10% of its saturation concentration. In some embodiments, the concentration of the salt of the second cation and one of the one or more anions in the product solution is between about 10% and about 90% of its saturation concentration, or between about 10-20, 10-30, 10-40, 10-50, 10-60, 10-70, 10-80, 20-30, 20-40, 20-50, 20-60, 20-70, 20-80, 20-90, 30-40, 30-50, 30- 60, 30-70, 30-80, 30-90, 40-50, 40-60, 40-70, 40-80, 40-90, 50-60, 50-70, 50-80, 50-90, 60-70, 60-80, 60-90, 70-80, 70-90, or between about 80% and 90% of its saturation concentration. The skilled addressee can readily determine the saturation concentration of a given salt, which may depend on factors such as the pH and / or temperature of the solution. For example, the saturation concentration of KCl at 20 °C is about 340 g / L.

[0103] In one embodiment, there is provided a method of carbon dioxide mineralisation, the method comprising (i) treating a material with an aqueous solution comprising carbon dioxide and a base, wherein the material comprises a first cation which is Ca or Mg and one or more anions which are not carbonate, such that a product solution comprising an acid and / or a salt of the base and one of the one or more anions is formed, and a carbonate salt of the first cation is caused to precipitate.

[0104] In another embodiment, there is provided a method of carbon dioxide mineralisation, the method comprising (i) treating a material with an aqueous solution comprising carbon dioxide and a base, wherein the material comprises a first cation which is Ca or Mg, a second cation which is not Ca or Mg, and one or more anions which are not carbonate, such that a product solution comprising an acid and / or a salt of the base and one of the one or more anions and a salt of the second cation and one of the one or more anions is formed, and a carbonate salt of the first cation is caused to precipitate.

[0105] In a third aspect of the present disclosure, there is provided a method of obtaining and separating a first product comprising a first cation and a second product comprising a second cation from a material comprising the first cation, the second cation and one or more anions, the method comprising: (i) treating the material with carbon dioxide and a base, wherein the treatment occurs in solution phase, such that the first product comprising a carbonate salt of the first cation is caused to precipitate and the second product comprising a product solution comprising a salt of the second cation and one of the one or more anions and an acid and / or a saltof the base and one of the one or more anions is formed; and (ii) separating the first product and the second product; wherein the second cation is different to the first cation and the one or more anions is not carbonate.

[0106] In a fourth aspect of the disclosure there is provided a use of carbon dioxide and a base for obtaining and separating a first product comprising a first cation and a second product comprising a second cation from a material comprising the first cation, the second cation and one or more anions, wherein in said use: (i) the material is treated with carbon dioxide and a base, wherein the treatment occurs in solution phase, such that the first product comprising a carbonate salt of the first cation is caused to precipitate and the second product comprising a product solution comprising a salt of the second cation and one of the one or more anions and an acid and / or a salt of the base and one of the one or more anions is formed; and (ii) the first product and the second product are separated; wherein the second cation is different to the first cation and the one or more anions is not carbonate.

[0107] According to the fourth aspect of the present disclosure, step (i) of treating a material (e.g. mineral) with carbon dioxide and a base, wherein the treatment occurs in solution phase, may be followed by step (ii) of separating the resulting product solution and the carbonate salt of the first cation. This is described more specifically below in respect of the embodiments depicted in the Figures, i.e. Figures 1a, 1b, 1c, 2a, 2b, 3a and 3b. In general, the product solution and the carbonate salt of the first cation can be separated by any suitable means known to the skilled addressee for separating a solid from a solution, such as filtration, settling or sedimentation of the precipitate and removal of the supernatant solution (including by centrifugation), and flocculation. The skilled addressee will appreciate that step (ii) of separating the resulting product solution and the carbonate salt of the first cation includes the product solution containing up to about 10% by weight of the carbonate salt of the first cation and / or the carbonate salt of the first cation containing up to about 10% by weight of the components of the product solution, up to about 10% by weight of the salt of the second cation and / or up to about 10% by weight of the acid and / or the salt of one of the one or more anions.

[0108] In the third and fourth aspects of the present disclosure, the material, first cation, second cation, the step of treating the material with carbon dioxide, a base and water, the carbon dioxide, the water, and other features, are as described in relation to the first and second aspects of the present disclosure. Embodiments of the step of separating the product solution from the carbonate salt of the first cation are described further below.Underground deposit processes

[0109] In some embodiments of the first, second, and third aspects of the disclosure, such as those depicted in Figs.1 to 5, the material may be a mineral, an orebody or a rock, and may be located in an underground deposit. In this example, the material may be in solid form (e.g. it is not dissolved in an aqueous solution or caused to react with any chemical agent prior to step (i) of the method of the first aspect of the disclosure).

[0110] Thus in step (i) treating the material with carbon dioxide and a base, wherein the treatment occurs in solution phase, may comprise injecting carbon dioxide, a base and water or aqueous solution into the underground deposit, such that the product solution and the carbonate salt of the first cation are formed in the underground deposit. As described above, the treatment may comprise adding the carbon dioxide, the base and water or aqueous solution separately, sequentially or simultaneously. In some embodiments, the water or aqueous solution and the carbon dioxide may be injected into the underground mineral deposit, followed by the base (which may be ammonia). The water may be injected into the underground deposit at a temperature of from about ambient temperature to about 80°C. In some forms, the temperature of the resulting aqueous solution may be from about 10°C to about 60°C, about 10°C to about 50°C, about 15° to about 60°C, about 15°C to about 50°C, about 15° to about 60°C or about 15°C to about 50°C.

[0111] In some embodiments, step (i) may comprise injecting an aqueous solution comprising carbon dioxide and a base into the underground mineral deposit. The base may be ammonia, such that the aqueous solution comprising carbon dioxide and a base is an aqueous solution of ammonium carbonate. In this case, the aqueous solution comprising carbon dioxide and a base may be injected into the underground mineral deposit at a pressure of between about 1 – 200 bar. The aqueous solution comprising carbon dioxide and a base may be injected into the underground deposit at a temperature of from about ambient temperature to about 300°C. In some forms, the temperature of the aqueous solution may be from about 10°C to about 60°C, from about 10°C to about 60°C, about 10°C to about 50°C, about 15° to about 60°C, about 15°C to about 50°C, about 15° to about 60°C or about 15°C to about 50°C.

[0112] Following step (i), the method of this embodiment may further comprise a step (ii.a) of extracting the product solution above-ground from the underground deposit, wherein the carbonate salt of the first cation remains underground. Thus carbon dioxide may be sequesteredunderground while the product solution, containing commercially useful products, is extracted. Step (ii.a) is equivalent to the separation step (ii) of the third aspect of the disclosure.

[0113] In this embodiment, steps (i) and (ii.a) may be carried out using conventional techniques for solution mining. Broadly speaking, at least two boreholes are drilled to access the underground deposit, one lined with an injection pipe and one lined with a production pipe. A solvent (in this case, carbon dioxide, a base and water) is injected into the deposit via an injection pipe using a pump. Dissolved mineral (in this case, the product solution) is pumped to the surface via a production pipe, where it may be further processed. In one embodiment, water is injected into the deposit via an injection pipe to dissolve the deposit, carbon dioxide is injected into the solution and then the base is added. The first product comprising a carbonate salt of the first cation is caused to precipitate so that the second product comprising a product solution comprising a salt of the second cation and one of the one or more anions and a salt and / or an acid of the base and one of the one or more anions is pumped to the surface via the production pipe for further processing.

[0114] In some embodiments, such as those depicted in Figs.1 and 3 to 5, step (i) comprises injecting ammonia into the underground mineral deposit, which may be in the form of injecting an ammonium carbonate solution into the underground mineral deposit, or carbon dioxide, ammonia and water may be injected separately or in any combination. In this case, the method may further comprise a step (iii.aa) of separating ammonia from the product solution. This may be achieved by, for example, distillation of ammonia from the product solution. The ammonia obtained in step (iii.aa) may then be recycled by re-injecting it into the underground mineral deposit, such that the base used in step (i) comprises ammonia obtained in step (iii.aa).

[0115] Following step (i), the product solution comprises an ammonium salt of one of the one or more anions. Under distillation conditions, as ammonia is removed, the product solution following step (iii.aa) comprises an acid and / or a salt of one of the one or more anions. Where the mineral further comprises a second cation as defined above (such as in embodiments of the first aspect of the disclosure, or in the second or third aspects of the disclosure), the product solution following step (iii.aa) comprises an acid and / or a salt of one of the one or more anions and a salt of the second cation and one of the one or more anions.

[0116] In some embodiments of the first aspect of the disclosure, or in the second or third aspects of the disclosure, such as that depicted in Fig.1a, the mineral further comprises a second cation as defined above, and the product solution following step (iii.aa) comprises an acid and / ora salt of one of the one or more anions and a salt of the second cation and one of the one or more anions. In this case, the method may further comprise a step (iv.ab) of separating the acid and / or the salt of one of the one or more anions from the product solution. This may be achieved by, for example, distillation of the acid of one of the one or more anions from the product solution. Steps (iii.aa) and (iv.ab) may be carried out in concert, for example in a fractional distillation whereby ammonia and the acid of one of the one or more anions are distilled and separated from one another and from the product solution.

[0117] Following step (iv.ab) the product solution comprises the salt of the second cation and one of the one or more anions, and is free from, or substantially free from, the base and the acid and / or the salt of one of the one or more anions. The salt of the second cation and one of the one or more anions may be separated from the product solution, that is, isolated or substantially isolated from the remaining components of the product solution such as water. Thus the method may further comprise a step (v.ab) of separating the salt of the second cation and one of the one or more anions from the product solution. This may be achieved by, for example, heating the product solution to provide the salt of the second cation and one of the one or more anions in solid form and steam. This may involve heating the product solution such that it is evaporated to dryness, leaving a solid salt of the second cation and one of the one or more anions. Alternatively, the product solution may be heated such that sufficient water evaporates to cause the solid salt of the second cation and one of the one or more anions to crystallise, which may be followed by filtration of the resulting mixture to isolate the solid salt of the second cation and one of the one or more anions. The resulting solution (centrate) may be re-used in the method, for example forming part of the water used in step (i). The steam produced in the course of heating the product solution may be utilised to provide heat in steps (iii.aa) and / or (iv.ab).

[0118] In some embodiments, such as those depicted in Figs.3 to 5, step (iii.aa) may further comprise adding a second base to the product solution to provide a basified product solution. This may assist in recovery and recycling of ammonia, when used as the base in step (i). The second base may be any suitable inorganic base, such as a hydroxide, for example a metal hydroxide, for example an alkali metal or alkali earth metal hydroxide. The second base may be selected from calcium oxide or calcium hydroxide, or a mixture thereof, magnesium oxide or magnesium hydroxide, or a mixture thereof, KOH, and NaOH.

[0119] The second base may be added to the product solution in a concentration of from about 0.05M to about 1M. In some cases the second base may be added in a concentration of from about 0.11M to about 0.3M. Thus, prior to step (iii.aa), the product solution comprises anammonium salt of one of the one or more anions, and, if the mineral comprises a second cation as defined above, the product solution further comprises a salt of the second cation and one of the one or more anions. Following the addition of the second base in step (iii.aa), the basified product solution comprises ammonia (as dissolved ammonia and / or ammonium hydroxide), a salt of the second base and one of the one or more anions, and if the mineral comprises a second cation as defined above, the basified product solution further comprises a salt of the second cation and one of the one or more anions.

[0120] In this case, step (iii.aa) may comprise separating ammonia from the basified product solution, for example by distillation as described above. This may be followed by a step (iv.ac) of separating the salt of the second base and one of the one or more anions from the basified product solution and / or a step (v.ac) of separating the salt of the second cation and one of the one or more anions from the basified product solution. Steps (iv.ac) and / or (v.ac) may involve heating the basified product solution such that the salt of the second base and one of the one or more anions and / or the salt of the second cation and one of the one or more anions crystallises. Steps (iv.ac) and (v.ac) may be carried out in concert, for example in a fractional crystallisation. Heating the basified product solution may generate steam, which may be recycled and used to heat the basified product solution in step (iii.aa).

[0121] Where the second base is magnesium oxide or magnesium hydroxide, or a mixture thereof, following steps (iv.ac) and / or (v.ac) the magnesium may be used to mineralise further carbon dioxide. In this case, the salt of the second base and one of the one or more anions is a magnesium salt of one of the one or more anions. Thus for example, step (iv.ac) may comprise heating the basified product solution such that the magnesium salt of one of the one or more anions crystallises. The magnesium salt of one of the one or more anions may then be isolated by filtration, re-dissolved in water, and injected into the underground mineral deposit in step (i). In another example, step (iv.ac) is omitted and step (v.ac) comprises heating the basified product solution such that the salt of the second cation and one of the one or more anions crystallises. The salt of the second cation and one of the one or more anions may then be isolated by filtration, such that the filtrate comprises the magnesium salt of one of the one or more anions. The water injected into the underground mineral deposit in step (i) may then comprise the filtrate comprising the magnesium salt of one of the one or more anions.

[0122] Where the second base is calcium oxide or calcium hydroxide, or a mixture thereof, further steps may be undertaken to remove calcium salts from the basified product solution, as depicted in Figs.3 to 5. In this case, step (iii.aa) may be followed by a step (v.ac) of separatingthe salt of the second cation and one of the one or more anions from the basified product solution, for example by crystallisation. The resulting basified product solution (i.e. the filtrate from the crystallisation) comprises a calcium salt of one of the one or more anions. This resulting basified product solution may be treated with a metal carbonate salt, such as sodium carbonate. This results in the formation of insoluble calcium carbonate (which may be isolated by filtration) and a solution of the metal salt of one of the one or more anions, which may be isolated from solution, for example by crystallisation. Alternatively, this resulting basified product solution may be treated with a source of sulfate, such as a metal sulfate salt, such as potassium sulfate, or with sulfuric acid. If treated with sulfuric acid, this results in the formation of insoluble calcium sulfate (which may be isolated by filtration) and an acid of one of the one or more anions, which may be isolated by, for example, distillation. If treated with a metal sulfate salt, this results in the formation of insoluble calcium sulfate (which may be isolated by filtration) and a metal salt of one of the one or more anions, which may be isolated by, for example, crystallisation. If the metal coincides with a second cation comprised in the mineral, the metal salt of one of the one or more anions may be fed back in to, for example, the basified product solution at step (iii.aa).

[0123] In some embodiments, such as that depicted in Fig.2a, the mineral further comprises a second cation as defined above, and following step (i) the product solution comprises a salt of a base and one of the one or more anions and a salt of the second cation and one of the one or more anions. In this case, step (ii.a) may be followed by a step (iii.c) of evaporating the product solution to provide a solid mixture of the salt of the base and one of the one or more anions and the salt of the second cation and one of the one or more anions. Water recovered from the evaporation in step (iii.c) may be recycled such that the water in step (i) comprises water recovered from the evaporation in step (iii.c).

[0124] Step (iii.c) may be followed by a step (iv.c) of separating the salt of the base and one of the one or more anions and the salt of the second cation and one or more anions. For example, the salt of the second cation and one or more anions may be sublimed, leaving a residue of the salt of the base and one of the one or more anions.

[0125] Alternatively, and as shown in Fig.2b, instead of evaporating the product solution to provide a solid mixture as in step (iii.c), the product solution may be subject to fractional crystallisation and separation so as to sequentially isolate the salt of the base and one of the one or more anions, and the salt of the second cation and one of the one or more anions.Above-ground processes

[0126] While some of the embodiments referenced above are described with respect to a material located in an underground mineral deposit, the disclosed embodiments may equally be applied to materials that are disposed above-ground. The embodiments referenced above may also be applied to waste streams that result from a processing operation, where the method is performed above ground. While the material may originate from an underground deposit prior to the method of the first, second or third aspects of the present disclosure being carried out, above- ground processes encompass processes where the material is removed from its underground deposit in solid form, and then subjected to the method of the first, second or third aspects of the present disclosure. Above-ground processes also encompass processes where the material is removed from its underground deposit in solution form (e.g. it is dissolved underground then extracted above-ground in a conventional solution mining process), and then subjected to the method of the first, second or third aspects of the present disclosure. In another embodiment, the material is a waste stream, comprising the material in solution phase, from a processing operation and the method of the first, second or third aspects of the present disclosure may be carried out above-ground.

[0127] In such above-ground embodiments, step (ii.a) above is omitted and step (i) is followed by a step (ii.d) of separating the carbonate salt of the first cation (which is caused to precipitate in step (i)) from the product solution. This may be achieved by, for example, filtration, sedimentation, centrifugation or flotation.

[0128] In some embodiments, such as those depicted in Figs.6 and 7, the material may be located above-ground. Thus in step (i) treating the material, wherein the treatment occurs in solution phase, with carbon dioxide and a base may take place for example in a pit or a reactor. In some embodiments the material may already initially be in solution phase, such as a waste stream or a product of solution mining. In other embodiments, step (i) may comprise treating the material provided initially in solid form with an aqueous solution comprising carbon dioxide and a base. In some embodiments, step (i) may comprise immersing the material, provided initially in solid form, in water, and bubbling carbon dioxide and a gaseous base such as ammonia through the mixture. In some embodiments, step (i) may comprise immersing the material, provided initially in solid form, in an aqueous solution of a base, and bubbling carbon dioxide through the mixture. In some embodiments, step (i) may comprise treating the material, provided initially in solid form, with an aqueous solution comprising carbon dioxide and a base. The base may beammonia, such that the aqueous solution comprising carbon dioxide and a base is an aqueous solution of ammonium carbonate.

[0129] In some embodiments, step (i) may comprise first dissolving the material, provided initially in solid form, in water, and then treating it with carbon dioxide and a base (for example as depicted in Fig.7). In some embodiments, step (i) may comprise treating the material, provided initially in solid form, with water, carbon dioxide and a base (for example as depicted in Fig.6). In some embodiments, where a mineral was pumped above-ground from an underground deposit using a solution mining process, the material may be provided initially dissolved in aqueous solution. In such embodiments, step (i) may comprise treating an aqueous solution of the material with carbon dioxide and a base.

[0130] Step (i) may take place at a temperature of between about ambient temperature to about 80°C. In some forms, the temperature is from about 10°C to about 60°C, about 10°C to about 50°C, about 15° to about 60°C, about 15°C to about 50°C, about 15° to about 60°C or about 15°C to about 50°C.

[0131] Step (i) may be followed by a step (ii.d) of separating the carbonate salt of the first cation (which is caused to precipitate in step (i)) from the product solution. This may be achieved by, for example, filtration. Step (ii.d.) is equivalent to the separation step (ii) of the third aspect of the disclosure. In some embodiments, step (ii.d) of separating the carbonate salt of the first cation (which is caused to precipitate in step (i)) from the product solution may be followed by a step (ii.e) of drying the separated first cation precipitate. In some embodiments, the drying temperature is from about 40°C to about 100°C, about 45°C to about 100°C, about 40° to about 80°C, about 45°C to about 80°C, about 40° to about 60°C, about 45°C to about 60°C, about 40° to about 55°C or about 45°C to about 55°C.

[0132] The carbonate salt of the first cation may be a salt consisting of solely the first cation and carbonate, or a hydrate thereof. The carbonate salt of the first cation may comprise no other cations. Put another way, the carbonate salt of the first cation may be of the form XCO3, or hydrates thereof, with X denoting the first cation. The carbonate salt of the first cation may be obtained in following step (ii.d.) in substantially pure form, that is, it may be obtained in a purity of at least 80% (w / w), or at least 85, 90, 95, 97, or 99% (w / w). Where the first cation is Mg, the carbonate salt of the first cation may be nesquehonite (MgCO3^3H2O) and may be free from, or substantially free from, roguinite ((NH₄)₂Mg(CO₃)₂^4H₂O). The carbonate salt of the first cationmay be free from, or substantially free from, the salt of the second cation and the one or more anions. Carbonation parameter control

[0133] It will be appreciated that the co-precipitation of the second cation, such as by crystallisation during treatment of the material, and the formation of unwanted precipitates of the first cation during this treatment may be deleterious to the efficiency and / or output that may otherwise be achieved in accordance with the present disclosure. Various treatment parameters may therewith be controlled towards this purpose, including control of solution chemistry, reaction parameters, and avoidance of conditions that favour co-precipitation.

[0134] Towards mitigating co-precipitation of the second cation, a mechanism may be to control the concentration of the salt of the second cation in the product solution to remain below its saturation point while carbonation of the first cation is intended to occur. It will be appreciated that if this concentration is exceeded, such as under conditions of limited water or excessive carbonate addition, undesired crystallisation of the salt of the second cation can occur as it becomes supersaturated. In one particular form where the carbonate salt of the first cation that is caused to precipitate is hydrated (its precipitation removing water from solution), the concentration of the salt of the second cation and one of the one or more anions can be controlled by ensuring sufficient water is present such that its solubility limit in the product solution is not exceeded, inhibiting its co-precipitation with the carbonate salt of the first cation.

[0135] Example 4 exemplifies this mechanism for the carbonation of the first cation as magnesium to form a hydrated carbonate as nesquehonite [MgCO3.3H2O], showing that unintended crystallisation of KCl (as by example seen in Examples 3.1 and 3.2) can be avoided by proper KCl concentration control in the product solution as its concentration increases due to water consumption by the formation of nesquehonite.

[0136] Towards mitigating the formation of unwanted precipitates of the first cation, by example precipitates that are difficult to separate from the product solution or precipitates that pose a hazard, a mechanism may be to control a concentration of the base during precipitation so as to avoid forming a carbonate of the base, which in turn may combine with the first cation carbonate to form mixed carbonates.

[0137] Example 3 exemplifies this mechanism where the addition of the base as ammonia was done in a manner which allowed ammonium carbonate to form and which in turn combined withthe magnesium carbonate precipitate to form a final precipitate as the mixed carbonate roguinite [(NH₄)₂Mg(CO₃)₂^4H₂O]. Example 4 conversely shows how the proper control of ammonia concentration during precipitation of the magnesium carbonate allowed for the preferential precipitation of nesquehonite [MgCO3.3H2O], a stable and more readily separable form of the precipitate. Example 4 describes that the ammonia concentration was controlled by means of slowly introducing ammonia and concurrently with CO₂, although those skilled in the art will appreciate that there may be various ways in which a concentration of the base may be controlled.

[0138] A further advantage of controlling the concentration of the base during precipitation follows, and this also allows closer control of the pH, which may further encourage selective formation of a target precipitate, for example in the case of magnesium carbonate as nesquehonite.

[0139] In some embodiments, such as those depicted in Figs.6 and 7, step (i) comprises treating the material with an aqueous solution comprising carbon dioxide and ammonia, i.e. an ammonium carbonate solution. In this case, the method may further comprise a step (iii.d) of separating ammonia from the product solution. This may be achieved by, for example, distillation of ammonia from the product solution. The ammonia obtained in step (iii.d) may be recycled to form further ammonium carbonate solution, such that the base used in step (i) comprises ammonia obtained in step (iii.d).

[0140] Following step (i), the product solution comprises an ammonium salt of one of the one or more anions. Under distillation conditions, as ammonia is removed, the product solution following step (iii.d) comprises an acid of one of the one or more anions. Where the mineral further comprises a second cation as defined above, for example in embodiments of the first aspect of the disclosure, or in the second or third aspects of the disclosure, the product solution following step (iii.d) comprises an acid of one of the one or more anions and a salt of the second cation and one of the one or more anions.

[0141] Where the mineral further comprises a second cation as defined above, the product solution following step (iii.d) comprises an acid of one of the one or more anions and a salt of the second cation and one of the one or more anions. In this case, the method may further comprise a step (iv.d) of separating the acid of one of the one or more anions from the product solution. This may be achieved by, for example, distillation of the acid of one of the one or more anions from the product solution. Steps (iii.d) and (iv.d) may be carried out in concert, for example in afractional distillation whereby ammonia and the acid of one of the one or more anions are distilled and separated from one another and from the product solution.

[0142] Following step (iv.d) the product solution comprises the salt of the second cation and one of the one or more anions from the product solution, and is free from, or substantially free from ammonia and acid. The salt of the second cation and one of the one or more anions may be separated from the product solution, that is, isolated or substantially isolated from the remaining components of the product solution such as water. Thus the method may further comprise a step (v.d) of separating the salt of the second cation and one of the one or more anions from the product solution. This may be achieved by, for example, heating the product solution to provide the salt of the second cation and one of the one or more anions in solid form and steam. This may involve heating the product solution such that it is evaporated to dryness, leaving a solid salt of the second cation and one of the one or more anions. Alternatively, the product solution may be heated such that sufficient water evaporates to cause the solid salt of the second cation and one of the one or more anions to crystallise, which may be followed by filtration of the resulting mixture to isolate the solid salt of the second cation and one of the one or more anions. The resulting solution (centrate) may be re-used in the method, for example forming part of the water used in step (i). The steam produced in the course of heating the product solution may be utilised to provide heat in steps (iii.d) and / or (iv.d). Separation of the salt of the second cation and one of the one or more anions from the product solution

[0143] As discussed above, there may be various ways in which a salt of the second cation and one of the one or more anions, such as KCl, can be recovered from the product solution. Therewith, a means is provided by which a product of the second cation may be obtained from a material containing both a first cation and a second cation, such as carnallite or a carnallite- derived solution, which has to date been considered unfeasible.

[0144] By non-limiting example, the salt of the second cation and one of the one or more anions may be recovered from the product solution by means of evaporative crystallisation and / or cooling crystallisation as shown in Figs.1 through 7. In evaporative crystallisation, the product solution is heated to evaporate water (forming steam), increasing the product solution’s concentration until the salt of the second cation and one of the one or more anions begins to crystallise. The resulting crystals of the salt of the second cation and one of the one or more anions may then be separated from solution, such as by filtration or centrifugation, and optionallydried so as to form a saleable product. In cooling crystallisation, the product solution is cooled, and due to the temperature-dependent solubility of the salt of the second cation and one of the one or more anions, the salt crystallises out of product solution as the temperature drops. The remaining solution, which may still contain other salts like NaCl or MgCl₂, can be further processed or recycled as shown in Figs.1 through 5.

[0145] By further non-limiting example, flotation may be used whereby collectors (and optionally depressants) may be introduced so as to render the salt of the second cation and one of the one or more anions hydrophobic such that air bubbles in a flotation cell can cause the salt to rise in a froth and be separated, cleaned and / or dried as may be necessary to form a saleable product.

[0146] Forms of the method of the first aspect of the disclosure may be summarised as follows. Equivalent forms may be described in respect of the second aspect of the disclosure, wherein the material comprises a first cation and a second cation which are different from one another, and in respect of the third aspect of the disclosure, wherein the method is a method of producing a first product comprising a first cation and a second product comprising a second cation from a material comprising the first cation, the second cation and one or more anions, as described above. Form 1a (see, for example, Fig.1a):

[0147] A method of carbon dioxide mineralisation is disclosed herein. The method comprises: (i) treating a mineral with carbon dioxide, water and ammonia, wherein said treating comprises injecting carbon dioxide, water, and ammonia into an underground mineral deposit comprising the mineral, wherein the mineral comprises a first cation which is Ca or Mg and one or more anions which are not carbonate, such that a product solution comprising an ammonium salt of one of the one or more anions is formed, and a carbonate salt of the first cation is caused to precipitate; (ii.a) extracting the product solution above-ground from the underground deposit, wherein the carbonate salt of the first cation remains in the underground deposit; (iii.aa) separating ammonia from the product solution, wherein the ammonia used in step (i) comprises ammonia obtained in step (iii.aa); and (iv.ab) separating the acid of one of the one or more anions from the product solution.Form 1b (see, for example, Figs.6 and 7):

[0148] Another method of carbon dioxide mineralisation is disclosed herein. The method comprises: (i) treating a material with carbon dioxide and ammonia, wherein the treatment occurs in solution phase, wherein the material comprises a first cation which is Ca or Mg and one or more anions which are not carbonate, such that a product solution comprising an ammonium salt of one of the one or more anions is formed, and a carbonate salt of the first cation is caused to precipitate; (ii.d) separating the carbonate salt of the first cation from the product solution; (iii.aa) separating ammonia from the product solution, wherein the ammonia used in step (i) comprises ammonia obtained in step (iii.aa); and (iv.ab) separating the acid of one of the one or more anions from the product solution.

[0149] In Form 1a and / or Form 1b, where the material (e.g. mineral) further comprises a second cation which is not Ca or Mg, optionally wherein the second cation is selected from Li, Na, and K, the product solution comprises an ammonium salt of one of the one or more anions and a salt of the second cation and one of the one or more anions. In this case, the method may further comprise: (v.ab) separating the salt of the second cation and one of the one or more anions from the product solution. Form 2a (see, for example, Figs.3 to 5):

[0150] Another method of carbon dioxide mineralisation is disclosed herein. The method may comprise: (i) treating a mineral with carbon dioxide, water and ammonia, wherein said treating comprises injecting carbon dioxide, water, and ammonia into an underground mineral deposit comprising the mineral, wherein the mineral comprises a first cation which is Ca or Mg and one or more anions which are not carbonate, such that a product solution comprising an ammonium salt of one of the one or more anions is formed, and a carbonate salt of the first cation is caused to precipitate; (ii.a) extracting the product solution above-ground from the underground deposit, wherein the carbonate salt of the first cation remains in the underground deposit; (iii.aa) separating ammonia from the product solution, wherein said separating comprises adding a second base to the product solution to provide a basified product solution comprising a salt of the second base and one of the one or more anions, wherein the ammonia used in step (i) comprises ammonia obtained in step (iii.aa); and (iv.ac) separating the salt of the second base and one of the one or more anions from the basified product solution.Form 2b:

[0151] Another method of carbon dioxide mineralisation is disclosed herein. The method comprises: (i) treating a material with carbon dioxide, water and ammonia, wherein the material comprises a first cation which is Ca or Mg and one or more anions which are not carbonate, such that a product solution comprising an ammonium salt of one of the one or more anions is formed, and a carbonate salt of the first cation is caused to precipitate; (ii.d) separating the carbonate salt of the first cation from the product solution; (iii.aa) separating ammonia from the product solution, wherein said separating comprises adding a second base to the product solution to provide a basified product solution comprising a salt of the second base and one of the one or more anions, wherein the ammonia used in step (i) comprises ammonia obtained in step (iii.aa); and (iv.ac) separating the salt of the second base and one of the one or more anions from the basified product solution.

[0152] In Form 2a and / or Form 2b, where the material (e.g. mineral) further comprises a second cation which is not Ca or Mg, optionally wherein the second cation is selected from Li, Na, and K, the product solution comprises a salt of the base and one of the one or more anions and a salt of the second cation and one of the one or more anions. In this case, the method may further comprise: (v.ac) separating the salt of the second cation and one of the one or more anions from the product solution. Form 3a (see, for example, Fig.2a):

[0153] Another method of carbon dioxide mineralisation is disclosed herein. The method comprises: (i) treating a mineral with carbon dioxide, water and a base, wherein said treating comprises injecting carbon dioxide, water, and the base into an underground mineral deposit comprising the mineral, wherein the mineral comprises a first cation which is Ca or Mg and one or more anions which are not carbonate, such that a product solution comprising a salt of the base and one of the one or more anions is formed, and a carbonate salt of the first cation is caused to precipitate; (ii.a) extracting the product solution above-ground from the underground deposit, wherein the carbonate salt of the first cation remains in the underground deposit; (iii.c) evaporating the product solution to provide a solid form of the salt of the base and one of the one or more anions.Form 3b:

[0154] Another method of carbon dioxide mineralisation is disclosed herein. The method comprises: (i) treating a material with carbon dioxide, water and a base, wherein the material comprises a first cation which is Ca or Mg and one or more anions which are not carbonate, such that a product solution comprising a salt of the base and one of the one or more anions is formed, and a carbonate salt of the first cation is caused to precipitate; (ii.d) separating the carbonate salt of the first cation from the product solution; (iii.c) evaporating the product solution to provide a solid form of the salt of the base and one of the one or more anions.

[0155] In Form 3a and / or Form 3b, where the material (e.g. mineral) further comprises a second cation which is not Ca or Mg, optionally wherein the second cation is selected from Li, Na, and K, the product solution comprises a salt of the base and one of the one or more anions and a salt of the second cation and one of the one or more anions. In this case, step (iii.c) comprises evaporating the product solution to provide a solid mixture of the salt of the base and one of the one or more anions and the salt of the second cation and one of the one or more anions, and the method may further comprise: (iv.c) separating the salt of the base and one of the one or more anions and the salt of the second cation and one or more anions. Examples

[0156] The present disclosure is further described below by reference to the following non- limiting examples.

[0157] Percentages are w / w unless specified otherwise. Example 1 - Preparation of synthetic carnallite

[0158] Synthetic carnallite was prepared by the following method: ^Fill a hot water urn with deionised (DI) water, turn it on and set it to 90°C.^ Weigh out the required amount of magnesium chloride and potassium chloride salts into asealed bag. The stoichiometric ratios of the feed is as follows:Material Mass % KCl 27%MgCl234% H2O 39%^ Set up a 1 L Schott bottle on a magnetic heated stirrer in the fume cupboard.^ Add the required amount of hot DI water and salts to the Schott bottle and stir to dissolvewhile maintaining temperature at 90°C. ^Once dissolved, remove from the heat and allow to cool to room temperature.^ Place the Schott bottle in the fridge overnight to cool further.^ The following day, vacuum filter the solids.^ Record the mass of filtrate and subsample through a 0.45µm syringe filter for assay.^ Record the mass of the wet solids and place in oven at 40°C until dry.^ Record the dry mass of the solids and vacuum seal in a bag for assay.

[0159] XRD analysis of the prepared solids indicated that the product was composed of 95% w / w carnallite and 5% w / w bischofite.

[0160] Lithium carnallite was also generated using a method similar to the above. This was then used for CO2sequestration tests. The ratios of the feed materials are as follows: Material Mass % MgCl2.6H2O 42% LiCl 27% DI water 31%

[0161] Magnesium chloride (bischofite) was also used without further treatment in CO2 sequestration tests described below. Example 2a – Carbonation of synthetic evaporites

[0162] The synthetic carnallites prepared as described in Example 1 were carbonated by the following method towards separating magnesium, as first cation, from potassium, as second cation, by precipitating the magnesium as a carbonate: ^Prepare 3 sets of 100mL of 154 g / L (NH4)2CO3 of solution.^ Weigh 71.6g of synthetic carnallite (prepared as in Example 1) for each test.^ Maintain the pH at a range between 8 and 9 using KOH or HCl.^ Slowly add the carnallite to the ammonium carbonate solution, stirring continuously untilall carnallite has been added. ^Allow mixing for 2, 6 & 24 hours at room temperature.^ At the end of the mixing period, filter the solids.^ Rinse twice with deionised water.^ Dry solids in a low temperature oven (40°C) for at least two (2) days.Experiment Units 2a.1 2a.2 2a.3 2a.4 2a.5 2a.6 2a.7 Concentration of ammonium g / L 154 154 154 154 154 154 154 carbonate Volume added mL 100 100 100 100 100 100 100 pH - 8-9 8-9 8-9 8-9 8-9 8-9 8-9Duration of mixing hr 2 6 24 2 2 6 24Evaporite type - Carnallite *L.C BischofiteEvaporite mass g 71.6 71.6 71.6 75.4 75.4 75.4 84.4 Carbonation Products (from XRD) Nesq.Chlor. Nesq. Nesq. Sylv. Chor. Chlor. *L.C = Lithium Carnallite, Nesq. = Nesquehonite, Chlor. = Chlorartinite, Sylv. = Sylvite Quantitative XRD results are provided in Figs.8(a) and 8(b). The results showed that the major product formed from each of examples 2a.1 to 2a.7 was nesquehonite, with trace amounts of chlorartinite also formed. Nesquehonite is the preferred product due to its efficiency of carbon sequestration. Trace amounts of sylvite were present in the precipitate in each of examples 2a.1 to 2a.3. Example 2b – Carbonation of synthetic evaporites – adding ammonia to evaporite solution

[0163] In this example, the main objective was to investigate separation of magnesium, as first cation, from potassium, as second cation, while also enabling the sequestration of CO2 by simulating the activities practiced in solution mining if carnallite deposits were mined to produce potash products. Using thermodynamic models, the compositions of solutions produced from solution mining were determined. The main aim was to find the optimum solution concentrationto enable carbonation to be conducted to allow for separation of the first cation from the second cation.

[0164] For example, if solution mining was to be conducted using water at 40°C, to achieve 90% of sylvite (KCl) saturation, the following compositions were determined: KCl = 201g / L; MgCl2= 257g / L. These were then dissolved in 1L of DI water.

[0165] A similar model was used to determine various solution mining temperatures targeting various sylvite saturation levels. The procedure below was applied in this example: ^Weigh out the required potassium chloride salts into a labelled and weighed beaker.^ Separately weigh out the required magnesium chloride salts and add to the beakercontaining the potassium chloride. ^Add DI water to the beaker to ensure all salts are dissolved and record amount of DI water.Heat the solution to the required temperature. ^Prepare ammonia solutions at various concentrations (7%, 14% and 28%) by appropriatedilutions. ^Bubble CO2 to the carnallite solution at 0.8L / min through a frit to ensure gas dispersion.^ Slowly add the ammonia solution to the mixture to maintain the pH between 8 & 9.^ Allow mixing for 30 minutes to 2 hours after which solids and liquor are then separated.^ Dry the solids at 40°C until they are sufficiently dry.

[0166] In another test (Example 2b.1), a typical composition for a “bleed stream” or “purge stream” as practiced in solution mining was used. This bleed stream had the following composition: 220g / L NaCl, 160g / L KCl, 24g / L MgCl2. The objective of this test was to separate magnesium, as first cation, from potassium, as the second cation, in the solution. Experiment Units 2b.1 2b.2 2b.3Carnallite solution g 2457 2396 2012 KCl saturation (in carnallite solution) % Bleed stream 90 30 Ammonia concentration at use % 28 28 28 Ammonia solution used g 116 527 559 Mixing time hr 24 24 24 Carbonation Products (from XRD) Hal. - - Sylv.Experiment Units 2b.1 2b.2 2b.3Hydr. Dyp. Tych. Hal. = Halite; Sylv. = Sylvite; Hydr. = Hydromagnesite; Dyp. = Dypingite; Tych. = Tychite

[0167] For the above examples, some of the carbonation products were not the intended products, and this example did not result in formation of nesquehonite. For the highly concentrated solution used in some of these tests, some of the halite and sylvite precipitated in trace amounts. These tests showed that to effectively separate magnesium, as first cation, from potassium, as second cation, by carbonation of the magnesium, it may be important to control the solution composition to specific ranges. For example, control the KCl saturation to be below about 90%. It was observed that failure to do so may result in the formation of a thick viscous material which can lead to inefficient mixing and uncontrolled precipitation of unwanted salts.

[0168] The filtrate and solids that were generated from the methods described in this example were analysed by a combination of methods. Solutions were diluted appropriately prior to analysis by ICP and UV-Vis (for chloride). Solids analysed by ICP after the necessary fusions or by ion chromatography (IC). Experiment Units 2b.1 2b.2 2b.3Mg in starting solution (before carbonation) g / L 4.7 38 33.1 K in starting solution (before carbonation) g / L 60.5 60 53.1 Concentration of Mg in filtrate (after carbonation) g / L 0.16 10.7 4.2 Concentration of K in filtrate (after carbonation) g / L 54.0 55.0 35.3 Concentration of Mg in precipitate % 8.1 No data 20.3 Concentration of K in precipitate % 12.2 No data 1.6 Example 3 – One-pot carbonation of synthetic evaporites

[0169] A 14% ammonia solution was prepared by mixing equal weights of DI water and 28% ammonia solution (w / w). ^CO2 was bubbled through the prepared 14% ammonia solution until ~pH 8.5 was reached,with the formation of ammonium carbonate. CO2bubbling was stopped at this pH. ^A carnallite solution was prepared as described in Example 2.^ The carnallite solution was then slowly added to the ammonium carbonate solution usinga dosing pump with the agitator inside the reactor turned on. ^The carnallite solution was added until a pH of ~7.9-8.0 was reached.^ The mixture was stirred for two (2) hours. After this, the formed slurry was filtered toseparate the solids from the solution. ^The solids were washed with DI water and split into two separate portions. One portionwas dried at 40°C while the other was dried at 55°C. ^The solution was diluted appropriately before analysis by ICP.Experiment Units 3.1 3.2 3.3Carnallite solution g 121 351 517 KCl saturation (in carnallite solution) % 90 90 45 Ammonium carbonate solution used g 204 731 321 Start pH of ammonium carbonate solution - 8.7 8.6 8.5Mixing duration hr 2 2 0.8Final pH (after carnallite addition) - 7.9 8.0 8.0 Volume of CO2delivered to the test L 31 44 22

[0170] Quantitative XRD results are provided in the table below. As described in the procedure above, the solids from Example 3.3 was dried at two different temperatures (40°C and 50°C). The XRD results below show that the drying temperature has an influence on the final solid phases formed, for example as roguinite transforms to nesquehonite at drying temperatures greater than 40°C. 3.1 3.2 3.3 (40 °C) 3.3 (50 °C) Mineral or mineral group Mass % Quartz 1 1 1 0Nesquehonite, MgCO3.3H2O 6 7 64 100 “Roguinite”, (NH4)2Mg(CO3)2.4H2O 93 92 35 0

[0171] The filtrate and solids which were generated from the methods described in this example were analysed by a combination of methods. Solutions were diluted appropriately prior to analysis by ICP and UV-Vis (for Chloride). Solids analysed by ICP after the necessary fusions or by ion chromatography (IC).Experiment Units 3.1 3.2 3.3Mg in starting solution (before carbonation) g / L 36.1 36.1 28.7 K in starting solution (before carbonation) g / L 57.3 57.3 44.4 Concentration of Mg in filtrate (after carbonation) g / L 0.03 0.02 2.3 Concentration of K in filtrate (after carbonation) g / L 21.8 19.3 25.3 Concentration of Mg in precipitate % 20.3 11.7 ND Concentration of K in precipitate % 1.6 0.3 ND* ND = No data

[0172] Analysis of the results showed that in Examples 3.1 and 3.2, the major carbonation product formed was roguinite , (NH4)2Mg(CO3)2.4H2O, with minor amounts of nesquehonite, MgCO3.3H2O. This formation of roguinite may be undesirable for two main reasons: 1) it leads to ammonia loss to the solid phase, which may lead to unfavourable economic outcomes; and 2) the roguinite is not stable, meaning that over time it may break down and evolve ammonia, which may pose a health and environmental hazard. Test 3.3 again showed that the major carbonation product formed was roguinite with minor amounts of nesquehonite, while drying at 50°C resulted in an increase in the amount of nesquehonite. From these tests it was concluded that the initial formation of ammonium carbonate may not the optimum way for the separation of magnesium, as first cation, from potassium, as second cation, by carbonation of the magnesium. This is because there is a possibility of forming the mixed carbonate, roguinite. Avoiding the formation of roguinite may therewith involve controlling the ammonia concentration in solution, such as by adding ammonia slowly to the carbonation process, to mitigate initial ammonium carbonate formation which in turn enabled roguinite formation.

[0173] A reason for this may be that, as the solution is carbonated, the pH is decreased due to formation of carbonic acid (H2CO3) / bicarbonate (HCO3-). The hydration of dissolved CO2 generates carbonic acid with eventual formation of bicarbonate and carbonate (CO32-). It is preferable that the Mg2+cation interacts with the CO32-anion. However, if the ammonia (NH3) is available in excess, NH4+can become a significant cation in solution, which in turn can result in the formation of ammonium carbonate in addition to magnesium carbonate. The ammonium carbonate and magnesium carbonate may therewith allow for the formation of the double carbonate, roguinite. Consequently, it may be that by controlling or limiting the addition of ammonia (NH3) to the solution, the preferential formation of the magnesium carbonate may be promoted. In this manner, the ammonia may only serve to regulate the pH by the OH- (formed with NH4+as reaction products of the dissolution of the ammonia in water) reacting with hydronium ions (H3O+) formed during the formation of carbonic acid / bicarbonate as describedabove. In turn, the ammonium ion (NH4+) can combine with free Cl from the dissolution of the carnallite so as to form ammonium chloride (NH4Cl). Example 4 – Carbonation of synthetic evaporites

[0174] It was recognised from the tests in Example 3 that the process of forming an ammonium carbonate solution followed by mixing this with the carnallite can result in the formation of the undesirable “roguinite”, as discussed above and seen in Test 3.1, Test 3.2 and Test 3.3 (40°C). As further described, a way to prevent the formation of roguinite was to avoid forming ammonium carbonate in the first place. Further, in examples 3.1 and 3.2, the initial carnallite solution concentration may have been too high as sylvite (KCl) was present in the precipitate.

[0175] To address this, in Example 4.1, CO2and a carnallite solution was dosed simultaneously into a 14% ammonia solution while in Example 4.2, ammonia solution and CO2were dosed simultaneously to a carnallite solution. In both tests, the diluted ammonia (14%, 7%) provided additional control over the initial concentrations. Furthermore, the dilution provided sufficient water of hydration for the target magnesium carbonate precipitate (nesquehonite). It will be appreciated that as the formation of a hydrated carbonate precipitate progresses, water is consumed which causes the KCl concentration in solution to increase. If there is insufficient water, this may lead to the KCl in solution exceeding its solubility limit, which in turn would cause the KCl to crystallise out of solution as it is supersaturated in KCl. Therefore, it was discovered that to efficiently separate magnesium, as first cation, from potassium, as second cation, control of the concentration of the second cation in solution may be important so as to limit KCl crystallisation in the carbonation step. The duration of mixing was varied depending on the rheology of the formed slurry.

[0176] Example 4.1 was carried out as described below to target not more that 45% sylvite saturation: ^Carnallite solution was prepared as described in Example 2.^ Calculations were done to determine the amount of 14% ammonia solution required toachieve the target concentration calculations. ^The required ammonia solution was placed in a suitable glass reactor with an overheadstirrer.^ A CO2 line was attached to gas dispersing frit which was positioned inside the reactor andsubmerged by the solution. ^CO2 was delivered at 0.8L / minute.^ The required carnallite solution was delivered slowly using a dosing pump until all of it wasdelivered. ^Mixing was allowed to progress until a change in the slurry behaviour was observed, atwhich point the test was stopped. In these cases, the slurry was seen to start thickening with the formation of a thick paste.

[0177] Example 4.2 was carried out as described below: ^Carnallite solution was prepared as described in Example 2.^ The required carnallite solution was placed in a suitable glass reactor with an overheadstirrer. ^A CO2 line was attached to gas dispersing frit which as positioned inside the reactor andsubmerged by the solution. ^CO2 was delivered at 0.8L / minute.^ Calculations were done to determine the amount of 7% ammonia solution required toachieve the target concentration calculations. ^The determined ammonia solution was delivered slowly using a dosing pump until all ofthe 7% ammonia solution was delivered. ^Mixing was allowed to progress until a change in the slurry behaviour was observed, atwhich point the test was stopped. In these cases, the slurry was seen to start thickening with the formation of a thick paste. ^After this, the formed slurry was filtered to separate the solids from the solution.^ The solids were washed with DI water and split into two separate portions. One portionwas dried at 40 °C while the other was dried at 55 °C. ^The solution was diluted appropriately before analysis by ICP.Experiment Units 4.1 4.2Mass of carnallite solution g 519 516 Concentration of ammonia solution used % 14 7Mass of ammonia solution added g 299 162 Volume of CO2L 37 14 Duration of mixing min 46 17

[0178] Quantitative XRD results for the solids formed in Test 4.1 and Test 4.2 are provided in the table below. Test 4.1 Test 4.1 Test 4.2 Test 4.2 (40 °C) (50 °C) (40 °C) (50 °C) Mineral or mineral group Mass % Quartz 1 0 - - Sylvite, KCl 0 0 1 1 Nesquehonite, MgCO3.3H2O 36 100 95 97 “Roguinite”, (NH4)2Mg(CO3)2.4H2O 63 0 - - Chlorartinite Mg 0 0 4 2 2(CO3)Cl(OH).3(H2O)

[0179] The filtrate and solids which were generated from the methods described in this example were analysed by a combination of methods. Solutions were diluted appropriately prior to analysis by ICP and UV-Vis (for Chloride). Solids analysed by ICP after the necessary fusions or by ion chromatography (IC). Experiment Units 4.1 4.2Mg in starting solution (before carbonation) g / L 26.8 33.1 K in starting solution (before carbonation) g / L 45.9 55.8 Concentration of Mg in filtrate (after carbonation) g / L 2.1 14.9 Concentration of K in filtrate (after carbonation) g / L 31.4 35.3 Concentration of Mg in precipitate % 12.2 (40 °C) 16.8 (40 °C) 20.8 (50 °C) 16.6 (50 °C) Concentration of K in precipitate % 0.5 (40 °C) 0.4 (40 °C) 1.0 (50 °C) 0.4 (50 °C)

[0180] Analysis of the results showed that in Examples 4.1 the major carbonation product formed was roguinite with minor amounts of nesquehonite, while drying at 50°C resulted in an increase in the amount of nesquehonite. Test 4.2 resulted in a major product of nesquehonite regardless of the drying temperature, with trace amounts of sylvite and chlorartinite present. Example 5 – Preparation of ammonium carbonate solution

[0181] Ammonium carbonate solution was prepared by the following method: ^Prepare 500mL of ammonium hydroxide solution by diluting 28% ammonia solution to a14% solution in the following way: oMeasure 250mL of 28% ammonium hydroxide solution and pour into a beaker.o Measure 250mL of DI water and pour into the beaker containing the beakercontaining the ammonia solution and mix well. oMeasure the pH and density of the solution.o Collect a sample of the diluted solution which will be used as the starting solutiono Transfer 200mL of the diluted ammonium hydroxide solution to a fritted gasbubbler. ^Connect a CO2 bottle via a regulator so that it enters the bubbler via the frit.^ Connect flexible tubing to the open end of the bubbler.^ Position the bubbler such that the open-ended tube is directed to a small beaker containingpH 2-3 solution to absorb any ammonia that is given off from the bottle. ^Bubble CO2 at a low flow rate (e.g. 10mL / min) through the frit into the solution.^ Record the starting time^ Bubble the CO2 for 30 minutes after which all the solution is then placed into a labelledbottle and sealed tightly. ^Measure the pH and density of the solution.^ Collect a sample from each test for assay.^ Repeat the above test i.e., total number of tests = two (2).Example 6 – Ammonia recovery

[0182] Ammonia was recovered from the filtrate obtained in Example 4 as follows: ^Combine filtrates obtained in Example 4 to provide a single solution.^ Mix well and obtain a sample for assay.^ Transfer 200mL of the solution to the pre-weighed round bottomed vessel heated by aheating mantle connected to a first water-filled gas bubbler (see Figure 9). ^The vapour from the first water-filled gas bubbler (may contain some condensed water) isdirected to a pre-weighed second water-filled gas bubbler. ^Record the starting masses for the round bottom vessel and both gas bubblers to enablemass balance calculations at the end of the test. ^Allow boiling for 4 hours then turn off the heating to allow cooling down.^ Weigh the final mass of each vessel after four hours of boiling.^ Collect a sample from the round bottomed vessel as well as the gas bubblers for assay.^ Measure the pH and density of each sample.^ Submit for assay.

[0183] Ammonia recovery was determined to be 39%. Example 7 – Ammonia recovery using magnesium oxide

[0184] In this example, magnesium oxide (MgO) powder was added to the reaction vessel to act as a catalyst for ammonia recovery. The MgO used varied between 7 and 17% of the solution being subjected to ammonia recovery. Ammonia was recovered from the filtrate obtained in Examples 3 & 4 as follows: ^Weigh the required magnesium oxide and place in a sealed bag.^ Place a weighed amount of filtrate from the carbonation process into round bottom flaskand onto a heating mantle.^ Add glass lid with minimum number of openings and secure the lid.^ Connect three containers with a known weight of DI water to the reaction flask such thatno gas escapes without contacting the water in these containers as they serve as ammonia traps.^ Add pressure resistance column that has approximately 10cm column of DI water betweensecond and third trap.^ Connect a condenser to the reaction flask (round bottom flask) containing the solutions.^ Connect a gas line so that any released gas gets bubbled through the DI water and iseventually trapped.^ Allow a stream running water to pass through the condenser. The water running around thecondenser must be cooled by methods such as using a chiller or running a coil through an ice bath.^ Add magnesium oxide to solution using a funnel.^ Turn on heating mantle to heat the carbonation filtrate solution to maximum temperature(around 100°C).^ When gas bubbles start to appear in the first trap reduce heat intensity.^ Watch level in pressure resistance column, if level is rising too fast, reduce temperature ofthe heating mantle to reduce pressure on the line.^ Allow heating for 4 hours, until bubbling stops and / or pressure gets too high. If solutioncools too much, liquid in traps may siphon back towards the reactor.^ After the reaction time, turn off water tap connected to condenser, disconnect the bottles sothat there is no siphoning of the solutions, and plug all vessels with stops to ensure any ammonia does not evaporate from liquid samples.^ After the sample vessels have cooled, measure weight of water in each trap and also pH,ORP and density of the solutions in each trap and the reactor.^ Collect a sample of the solutions through a 0.45 µm syringe filter for assay.ExperimentUnit7.1 7.2 7.3 (from Ex 3) (from Ex 3) (from Ex 4) 7.4 7.5 Mass of solution usedg 1000 550 482 514 464MgO / Solution % 7 7 7 17 7NH3 Recovery % 15 41 16 35 -Trap 1 pH before - 8.1 8.1 7.6 8.9 7.0Trap 1 pH after - 11.5 11.6 11.7 11.9 11.4Trap 2 pH before - 8.1 8.1 7.3 8.9 6.5Trap 2 pH after - 8.2 8.2 7.6 9.2 7.6Example 8 – Ammonia recovery using potassium hydroxide

[0185] The recovery of ammonia from a magnesium depleted filtrate coming from the carbonation step was also tested using potassium hydroxide (KOH).

[0186] The procedure for ammonia recovery using potassium hydroxide is described below (the apparatus that was used was that as shown in Figure 9) and it will be appreciated that the same procedure may be applicable to other bases (by example, NaOH, KOH and Ca(OH)2) that may be suitable for use in the ammonia recovery process: ^The masses of the apparatus, including a round-bottomed flask and water traps(otherwise referred to as “gas traps”) were recorded. ^The required amount of 50% potassium hydroxide solution was weighed.^ A weighed amount of filtrate from the carbonation step was placed into the flask andposition on a heating mantle (the lid was tightly sealed with a metal clamp and silicone grease). ^Three containers or “water traps” with a known weight of DI water were connected tothe flask to serve as ammonia traps (the gas line inlets at the flask and water trapswere also sealed with silicone grease and clamps) with the gas lines connected so that any released gas from the flask gets bubbled through the three DI water traps and is eventually dissolved into the water contained therein. ^Potassium hydroxide solution was delivered to the flask using a funnel and the flaskopening was resealed to ensure that no ammonia gas escapes through the opening. ^The heating mantle was turned on to heat the filtrate in the flask until gentle boilingwas observed. ^When gas bubbles started to appear in a first ammonia trap, the heat intensity wasreduced, and a gentle boil was maintained by controlling the temperature settings of the heating mantle. ^After a target reaction time was reached, the water tap connected to apparatus wasturned off, the water traps were disconnected from the flask so that there was no siphoning of the solutions, and all water trap openings were plugged with stops to ensure that no ammonia evaporates from liquid samples. ^Solutions were collected from the flask and water traps and prepared for assay and NH3analysis.

[0187] The above ammonia recovery process using KOH by conversion of the ammonium chloride can be described by the reaction below. Using a different base as stated above would similarly generate ammonia in the gas phase, the only difference being that the chloride salt formed would depend on the cation of the base used.

[0188] Industrially, ammonia scrubbers, such as those using an acid, would be used as opposed to water traps. The added benefit may therewith be the formation of potassium chloride, which could be optimised to a high purity to be a sellable product, further increasing the economic viability of this process.

[0189] The results from the ammonia recovery process using potassium hydroxide are provided in the table below.NH3Test [KOH] / [NH3] pH in the gas traps recovery Number molar ratio (%) Trap 1 Trap 2 Trap 3 8.1 1.0 12.7 9.8 8.0 100.08.2 0.7 11.9 9.4 8.7 55.18.3 0.2 11.4 8.7 7.9 64.18.4 1.0 11.6 9.6 8.2 55.88.5 1.0 NA NA NA 100.08.6 1.0 NA NA NA 100.08.7 1.0 NA NA NA 91.98.8 1.0 NA NA NA 75.18.9 1.0 11.9 9.6 7.7 73.9NA – Not available

[0190] The results show that performing ammonia recovery with potassium hydroxide allows for a high recovery percentage in a range of 55.1% - 100.0%, which is higher than that seen in Examples 6 and 7, the latter with magnesium oxide.

[0191] The word ‘comprising’ and forms of the word ‘comprising’ as used in this description and in the claims does not limit the invention claimed to exclude any variants or additions.

[0192] The word ‘consisting’ and forms of the word ‘consisting’ as used in this description and in the claims limits the invention claimed to exclude any variants or additions.

[0193] Those skilled in the art will appreciate that the disclosure described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the disclosure includes all such variations and modifications. The disclosure also includes all of the steps, features, compositions and compounds referred to or indicated in this specification, individually or collectively, and any and all combinations of two or more of said steps, features, compositions and compounds.

Claims

Claims1. A method of carbon dioxide mineralisation, the method comprising:(i) treating a material with carbon dioxide and a base, wherein the treatment occurs insolution phase, the material comprising; a first cation that is Ca or Mg; a second cation which is not Ca or Mg; and one or more anions which are not carbonate; such that a product solution comprising an acid or a salt of the base and one of the one or more anions and a salt of the second cation and one of the one or more anions is formed, and a carbonate salt of the first cation is caused to precipitate.

2. The method of claim 1, wherein step (i) comprises:treating the material as a solid with gaseous carbon dioxide, a base and water, treating the material as an aqueous solution with gaseous carbon dioxide and a base, treating the material as a solid with supercritical carbon dioxide, a base and water, treating the material as a solid with gaseous carbon dioxide, an aqueous solution comprising a base and water, or treating the material with an aqueous solution comprising carbon dioxide and a base.

3. The method of claim 1 or claim 2, further comprising:(ii) separating the product solution and the carbonate salt of the first cation.

4. The method of any one of claims 1 to 3, wherein the material is a mineral, a mineralsolution, a waste stream, a rock or an orebody.

5. The method of claim 4, wherein:the mineral is an evaporite mineral comprising the first cation and the second cation;the mineral solution, the rock or the orebody comprises an evaporite mineral comprising the first cation and the second cation; or the waste stream is the product of a mineral processing step that comprises the first cation, the second cation, and the one or more anions.

6. The method of any one of claims 1 to 5 wherein the second cation is selected from Li, Na,and K.

7. The method of any one of claims 1 to 6, wherein the base is selected from ammonia,MgO, NaOH, KOH, and KHCO3.

8. The method of claim 7, wherein the base is ammonia.

9. The method of claim 8, further comprising:(iii.aa) separating ammonia from the product solution.

10. The method of claim 9, wherein the base used in step (i) comprises ammonia obtained instep (iii.aa).

11. The method of claim 9 or 10, wherein following step (iii.aa) the product solutioncomprises an acid of one of the one or more anions and a salt of the second cation and one of the one or more anions.

12. The method of claim 11, further comprising:(iv.ab) separating the acid of one of the one or more anions from the product solution.

13. The method of claim 11 or 12, further comprising:(v.ab) separating the salt of the second cation and one of the one or more anions from the product solution.

14. The method of claim 13, wherein separating the salt of the second cation and one of the one or more anions from the product solution comprises heating and / or cooling the product solution to provide the salt of the second cation and one of the one or more anions in solid form, and if heating, steam.

15. The method of claim 9, wherein step (iii.aa) further comprises adding a second base to theproduct solution to provide a basified product solution, wherein the second base is selected from calcium oxide or calcium hydroxide, or a mixture thereof, magnesium oxide or magnesium hydroxide, or a mixture thereof, KOH, and NaOH, and wherein following step (iii.aa) the basified product solution comprises a salt of the second base and one of the one or more anions.

16. The method of claim 15, further comprising:(iv.ac) separating the salt of the second base and one of the one or more anions from the basified product solution.

17. The method of claim 15 or 16, further comprising:(v.ac) separating the salt of the second cation and one of the one or more anions from the basified product solution.

18. The method of claim 1, further comprising:(iii.c) evaporating the product solution to provide a solid mixture of the salt of the base and one of the one or more anions and the salt of the second cation and one of the one or more anions.

19. The method of any one of claims 1 to 18, wherein the base in step (i) is introduced insolution at a concentration of about 5% to about 80%.

20. The method of claim 19, wherein in step (i) a concentration of the salt of the secondcation and one of the one or more anions in the product solution is less than about 90% of its saturation concentration.

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