Patent Number: 
Section: claims

1. A process for selectively separating a metallic constituent from one or more other elements and other materials accompanying the metallic constituent in a mixture, the process comprising:(a) providing the mixture in an aqueous solution such that the metallic constituent forms a complex anion selected from the group consisting of a uranyl complex anion, a vanadyl complex anion, a chromium complex anion, a transuranic complex anion, and a radionuclide complex anion in the aqueous solution and wherein the one or more other elements forms a cation or a complex cation in the aqueous solution;(b) contacting the aqueous solution with one or more additives to form layered double hydroxide (LDH) material in situ such that the complex anion is intercalated within interlayers of the LDH material to form an intercalated complex anion, and introducing additional additives comprising bicarbonates or carbonates into the aqueous solution to optimize a crystal structure or matrix of the LDH material, wherein the one or more other elements are selectively incorporated into the crystal structure or matrix of the LDH material;(c) after (b), separating the LDH material from the aqueous solution; and(d) after (c), selectively recovering the metallic constituents from the interlayers of the LDH material by subjecting the LDH material obtained from step (c) to a recovery treatment step; wherein the selectively recovering comprises:(I) subjecting the LDH material to heat treatment or thermal decomposition in an anoxic, reducing, inert or oxidizing gas, thereby forming a collapsed or metastable LDH material and resulting in formation of a first oxide material comprising the metallic constituent, a second oxide material comprising the one or more other elements, or a third material comprising the metallic constituent and the one or more other elements; or(II) subjecting the LDH material to ion exchange by adding the LDH material and at least one substituent agent to an ion-exchanging solution such that the at least one substituent agent displaces at least some of the intercalated complex anion by an ion exchange mechanism thereby resulting in the intercalated complex anion being released from the interlayers into the ion-exchanging solution, wherein the ion exchange comprises controlling pH conditions of the ion-exchanging solution. 2. A process in accordance with claim 1 wherein the metallic constituent comprises uranium, vanadium, chromium or a transuranic element or radionuclide capable of forming the complex anion in the aqueous solution and wherein the one or more other elements comprises one or more metals selected from the group consisting of Cu, Mn, Ni, Pb, Zn and rare earth metals. 3. A process in accordance with claim 1 wherein the step of contacting the solution with one or more additives to form layered double hydroxide (LDH) material in situ further comprises:(i) adding a magnesium and/or aluminium containing silicate material to the aqueous solution and dissolving at least a part of the silicate material in the solution thereby leaching at least a part of the magnesium and/or aluminium from the silicate material into the solution; and(ii) controlling reaction conditions for achieving an appropriate Mg:Al ratio in the solution for formation of the layered double hydroxide (LDH) material in situ. 4. A process in accordance with claim 3 wherein the step of controlling the reaction conditions comprises addition of at least one Mg-containing compound and/or at least one Al-containing compound for achieving the appropriate Mg:Al ratio in the solution for formation of the LDH material in situ. 5. A process in accordance with claim 4 further comprising the step of removing at least a part of the LDH material formed in situ, wherein the at least one of the said dissolved cation and/or anion species comprising magnesium and/or aluminium is incorporated in the LDH material. 6. A process in accordance with claim 3 wherein the step of controlling the reaction conditions further comprises providing substantially alkaline reaction conditions for formation of the LDH material in situ. 7. A process in accordance with claim 3 wherein the step of controlling the reaction conditions further comprises addition of alkaline or acid-neutralising material for formation of the LDH material in situ. 8. A process in accordance with claim 3 wherein the silicate material is one or more of: Attapulgite; Clinoptilolite; Sepiolite; Talc; or Vermiculite. 9. A process in accordance with claim 3 wherein at least a part of the silicate material from step (i) and the LDH material formed in situ in step (ii) form an insoluble clay material mixture wherein the insoluble clay material mixture incorporates said cation or complex cation in the solution and/or complex anion in the solution. 10. A process in accordance with claim 3 wherein undissolved parts of the silicate material comprise undissolved clay material particles from step (i) and provide nucleation sites for formation of at least a part of the LDH material formed in situ in step (ii). 11. A process in accordance with claim 3 wherein the cation or complex cation in the solution comprises magnesium and/or aluminium cations such that the magnesium and/or aluminium is incorporated into the interlayers of the LDH material formed in situ. 12. A process in accordance with claim 3 wherein step (i) further comprises adding an additional material to a mixture comprising the silicate material. 13. A process in accordance with claim 1 wherein the LDH material formed in situ comprises hydrotalcite. 14. A process in accordance with claim 1 wherein the substituent agent is selected from the group consisting of: nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), a crown ether or other organic or (complex) inorganic ligand. 15. A process in accordance with claim 1 wherein the substituent agent is more electronegative relative to the complex anion intercalated in the LDH material. 16. A process in accordance with claim 1, further comprising, after (II), separating the LDH material to obtain a separated LDH material comprising the one or more other elements incorporated into the crystal structure or matrix of the separated LDH material; andsubjecting the separated LDH material to heat treatment or thermal decomposition to recover the one or more other elements. 17. A process in accordance with claim 16, further comprising, prior to or during the heat treatment or thermal decomposition of the separated LDH material, adding a further additive to the separated LDH material. 18. A process in accordance with claim 17, further comprising controlling a ratio of the further additive to the separated LDH material. 19. A process in accordance with claim 17, wherein the further additive comprises crystalline silica, amorphous or chemically-precipitated silica, silicic acid, tetra-ethylsilica(te), or silica added to the LDH interlayers. 20. A process for selectively separating a metallic constituent from one or more other elements and other materials accompanying metallic constituent in a mixture, the process comprising:(a) providing the mixture in an aqueous solution such that the metallic constituent forms a complex anion selected from the group consisting of a uranyl complex anion, a vanadyl complex anion, a chromium complex anion, a transuranic complex anion, and a radionuclide complex anion in the aqueous solution and wherein the one or more other elements forms a cation or a complex cation in the aqueous solution;(b) contacting the aqueous solution with a layered double hydroxide (LDH) material such that the complex anion is intercalated within interlayers of the LDH material, and introducing additives comprising bicarbonates or carbonates into the aqueous solution to optimize a crystal structure or matrix of the LDH material, wherein the one or more other elements are selectively incorporated into the crystal structure or matrix;(c) after (b), separating the LDH material from the aqueous solution; and(d) after (c), selectively recovering the metallic constituent from the interlayer of the LDH material by subjecting the LDH material from step (b) to a recovery treatment step; wherein the selectively recovering step comprises:(I) subjecting the LDH material to heat treatment or thermal decomposition in an anoxic, reducing, inert or oxidizing gas, thereby forming a collapsed or metastable LDH material and resulting in formation of a first oxide material comprising the metallic constituent, a second oxide material comprising the one or more other elements, and a third material, or further mineral phases, comprising the metallic constituent and the one or more other elements; or(II) subjecting the LDH material to ion exchange by adding the LDH material and one or more substituent agents to an ion-exchanging solution such that the one or more substituent agents displaces at least some of the intercalated complex anion by an ion exchange mechanism, thereby resulting in the intercalated complex anion being released from the interlayers into the ion-exchanging solution, wherein the ion-exchange comprises controlling pH conditions of the ion-exchanging solution. 21. A process in accordance with claim 20 wherein the step of contacting the LDH material with the aqueous solution comprises dissolving at least a part of the LDH material into the solution thereby obtaining dissolved LDH material in the solution followed by controlling the reaction conditions in the aqueous solution for in situ precipitation of LDH material formed in situ from the dissolved LDH material such that the complex anion is intercalated within interlayers of the LDH material formed in situ and wherein one or more of the other elements are incorporated into a crystal structure or matrix of the LDH material formed in situ.