Processes for the recovery of uranium
The present disclosure describes a method of recovering uranium including a continuous ion exchange (CIX) process including a single cycle or a dual cycle CIX process and at least a gradient elution or resin crowding process. The present disclosure also describes an apparatus including a single cycle or dual cycle CIX system and a gradient elution and/or resin crowding system.
1 . A method of recovering uranium, wherein the method comprises:
a) providing a source of uranium;
b) providing one or more CIX systems including a solid media that binds uranium;
c) applying the source of uranium to the solid media under conditions that cause the uranium to bind to the solid media; and
d) recovering the uranium by a single cycle or dual cycle CIX process;
wherein the single cycle CIX process comprises a single CIX system which is a primary CIX system comprising a primary chelating or complexing cationic exchange (CE) media that binds uranium and the single cycle CIX system further comprises a gradient elution (GE) system or a resin crowding (RC) system; or
wherein the dual cycle CIX process comprises two CIX systems which include the primary CIX system comprising a CE media that binds uranium and a secondary CIX system comprising an anionic exchange (AE) media that binds uranium and wherein the dual cycle CIX system further comprises a GE system and/or an RC system; and
wherein the GE process performed in the primary CIX system of the single cycle or dual cycle CIX process comprises applying a dilute basic solution to the CE media during a regeneration pretreatment step of the primary CIX system; or
wherein the RC process performed in the primary CIX system of the single cycle or dual cycle CIX process comprises adjusting the pH of a portion of a uranium loaded primary regeneration solution with a dilute acid to obtain a crowd solution;
optionally, the method further comprises pretreating the source of uranium before step c), and optionally wherein pretreating comprises filtering or clarifying the source of uranium using an activated clay, an activated carbon, an activated silica, a flocculent, or a combination thereof.
2 . The method of claim 1 , wherein the CE media comprises a weakly acidic CE media with chelating aminomethyl phosphonic acid groups, an aminophosphonic chelating media, a macroporous polystyrene based chelating media with iminodiacetic groups, or a composition or material including an agent having chelating groups, functionalities, or moieties that bind uranium or comprises iminodiacetic groups, chelating aminomethyl phosphonic acid groups, or aminophosphonic groups, and optionally wherein the composition or material comprises beads, wires, meshes, nanobeads, nanotubes, or hydrogels; and
wherein the AE media comprises a functional group including a Type 1 quaternary ammonium, a functional group including a type II quaternary ammonium, or a composition or material comprising an agent having one or more chelating groups, functionalities, or moieties, and optionally, the composition or material comprises beads, wires, meshes, nanobeads, nanotubes, nanowires or other nano-structures, or hydrogels.
3 . The method of claim 1 , wherein the source of uranium is a source of phosphoric acid comprising uranium in any oxidation state.
4 . The method of claim 1 , wherein recovering the uranium by a single cycle CIX process or by a dual cycle CIX process comprises pretreating the CE media with an alkali solution to neutralize free acid in the CE media and followed by regenerating the CE media with an alkali carbonate solution at a pH that is greater than about 9.0, to produce a uranium loaded primary regeneration solution and a regenerated CE media, and optionally wherein the alkali solution for pretreating the CE media comprises ammonium hydroxide or sodium hydroxide.
5 . The method of claim 4 , wherein regenerating the CE media with an alkali carbonate solution comprises converting the uranium to an anionic uranyl carbonate complex and producing the uranium loaded primary regeneration solution comprising the anionic uranyl carbonate complex, wherein the alkali carbonate solution comprises ammonium carbonate, sodium carbonate, or potassium carbonate, and optionally wherein regenerating the CE media further comprises washing the regenerated CE media with water or a slightly acidic solution before reentry of the CE media into the CIX process.
6 . The method of claim 4 , wherein the single cycle CIX process further comprises concentrating the uranium loaded primary regeneration solution in an evaporation unit to reduce the water content, decomposing excess alkali carbonate, and followed by reducing the pH of the solution to form a uranyl precipitate, and optionally wherein the method further comprises filtering the uranyl precipitate followed by washing the precipitate with water to remove excess alkali carbonate or entrained carbonate/bicarbonate from the uranyl precipitate.
7 . The method of claim 6 , wherein the method further comprises digesting the uranyl precipitate with an acid solution to produce a uranyl salt solution, and optionally wherein the acid solution comprises sulfuric acid, nitric acid, or hydrochloric acid.
8 . The method of claim 7 , wherein the method further comprises treating the uranyl salt solution with an alkali solution to raise the pH of the solution from about pH 2.5 to about pH 7, or from about pH 3.5 to about pH 6, to obtain a pH adjusted solution, optionally wherein the alkali solution comprises an alkali hydroxide, and optionally wherein the alkali solution has a pH greater than about pH 10.
9 . The method of claim 8 , wherein the method further comprises adding hydrogen peroxide to the pH adjusted solution in an amount sufficient to form a uranyl peroxide precipitate, optionally wherein the method further comprises separating uranyl peroxide precipitate from the pH adjusted solution, by (i) settling, filtering, or centrifuging the precipitate, followed by washing the precipitate with water, or (ii) washing the precipitate on a filter or repulping the precipitate with water, followed by settling, filtering, or centrifuging the precipitate; and optionally wherein the method further comprises additional washing of the uranyl peroxide precipitate with water.
10 . The method of claim 9 , wherein the method further comprises drying the uranyl peroxide precipitate to form a dry solid.
11 . The method of claim 10 , wherein the method further comprises heating the dry solid to a temperature sufficient to decompose or calcine the dry solid to form uranium oxide.
12 . The method of claim 5 , wherein the dual cycle CIX process further comprises treating the uranium loaded primary regeneration solution in the secondary CIX system including the AE media, and wherein the anionic uranyl carbonate complex is transferred to the AE media.
13 . The method of claim 12 , wherein the method further comprises treating the AE media with a water solution to produce a washed AE media.
14 . The method of claim 13 , wherein the method further comprises treating the washed AE media with an acidic solution to remove uranium from the AE media to produce a uranium loaded secondary regeneration solution containing the uranium in a cationic form and a regenerated AE media, and optionally wherein the acidic solution comprises a dilute sulfuric acid, nitric acid, or hydrochloric acid.
15 . The method of claim 14 , wherein the method further comprises treating the uranium loaded secondary regeneration solution with an alkali solution to raise the pH of the solution from about pH 2.5 to about pH 7, or from about pH 3.5 to about pH 6, to obtain a pH adjusted solution, optionally wherein the alkali solution comprises an alkali hydroxide, an ammonium hydroxide, or a sodium hydroxide, at a concentration ranging from 10% to about 30%; and optionally wherein the alkali solution has a pH greater than pH 10.
16 . The method of claim 15 , wherein the method further comprises adding hydrogen peroxide to the pH adjusted solution in an amount sufficient to form a uranyl peroxide precipitate, optionally wherein the method further comprises separating uranyl peroxide precipitate from the pH adjusted solution, by (i) settling, filtering, or centrifuging the precipitate, followed by washing the precipitate with water, or (ii) washing the precipitate on a filter or repulping the precipitate with water, followed by settling, filtering, or centrifuging the precipitate; and optionally wherein the method further comprises additional washing of the uranyl peroxide precipitate with water.
17 . The method of claim 16 , wherein the method further comprises drying the uranyl peroxide precipitate to form a dry solid.
18 . The method of claim 17 , wherein the method further comprises heating the dry solid to a temperature sufficient to decompose or calcine the dry solid to form uranium oxide.
19 . The method of claim 1 , wherein the primary CIX system comprises a GE system or an RC system, wherein the secondary CIX system comprises a GE system or an RC system, or wherein the primary and secondary CIX systems comprise a GE and/or RC system.
20 . The method of claim 1 , wherein the GE process comprises applying increasing strength of the dilute basic solution to remove non-uranium cations from the primary CE media, and optionally wherein the dilute basic solution comprises ammonium carbonate solution, dilute sodium carbonate solution, or dilute potassium carbonate solution.
21 . The method of claim 1 , wherein in the RC process the portion of the uranium loaded primary regeneration solution is obtained from an initial application of the primary regeneration solution to the primary CE media or from recycled/stored uranium loaded regeneration solution of low purity.
22 . The method of claim 21 , wherein the RC process further comprises applying the crowd solution onto CE media during a regeneration pretreatment step of the primary CIX process.
23 . The method of claim 1 , wherein the GE process performed in the secondary CIX system of the dual cycle CIX process comprises applying a weak acidic solution to the secondary AE media in the secondary CIX system during a regeneration pretreatment step.
24 . The method of claim 23 , wherein the GE process comprises applying increasing strength of the weak acidic solution to remove non-uranium anions from the secondary AE media, and optionally wherein the weak acidic solution comprises weak sulfuric acid solution, weak hydrochloric acid solution, or weak nitric acid solution.
25 . The method of claim 1 , wherein the RC process performed in the secondary CIX system of the dual cycle CIX process comprises adjusting the pH of a portion of a uranium loaded secondary regeneration solution with a weak base to obtain a crowd solution, and optionally wherein the portion of the uranium loaded secondary regeneration solution is obtained from an initial application of the uranium loaded secondary regeneration solution to a secondary AE media in the secondary CIX system or from recycled/stored uranium loaded regeneration solution of low purity.
26 . The method of claim 25 , wherein the RC process further comprises applying the crowd solution onto the secondary AE media during a regeneration pretreatment step which takes place after the secondary AE media is loaded with uranium and before regeneration of the secondary AE media.