Method for recovering zinc from solution

Abstract

A method for recovering zinc from an aqueous ammoniacal ammonium carbonate zinc solution, the method comprising the steps of: Contacting the aqueous ammoniacal ammonium carbonate zinc solution with an organic solution of a zinc extractant, such that a portion of the zinc is transferred from the aqueous ammoniacal ammonium carbonate zinc solution, producing a zinc-depleted aqueous ammoniacal ammonium carbonate solution and a zinc-enriched organic solution of a zinc extractant; Separating the zinc-enriched organic solution of a zinc extractant from the zinc-depleted aqueous ammoniacal ammonium carbonate solution; Contacting the zinc-enriched organic solution with an aqueous acidic solution, producing a zinc-enriched aqueous acidic solution and a zinc-depleted organic solution of a zinc extractant; and Recovering zinc from the zinc-enriched aqueous acid solution.

1 . A method for recovering zinc from an aqueous ammoniacal ammonium carbonate zinc solution, the method comprising the steps of:
 i. Contacting the aqueous ammoniacal ammonium carbonate zinc solution with an organic solution of a zinc extractant, such that a portion of the zinc is transferred from the aqueous ammoniacal ammonium carbonate zinc solution, producing a zinc-depleted aqueous ammoniacal ammonium carbonate solution and a zinc- enriched organic solution of a zinc extractant;   ii. Separating the zinc-enriched organic solution of a zinc extractant from the zinc-depleted aqueous ammoniacal ammonium carbonate solution;   iii. Contacting the zinc-enriched organic solution with an aqueous acidic solution, producing a zinc-enriched aqueous acidic solution and a zinc-depleted organic solution of a zinc extractant; and   iv. Recovering zinc from the zinc-enriched aqueous acid solution.   
     
     
         2 . The method according to  claim 1 , wherein the molar ratio of carbonate to zinc in the aqueous ammoniacal ammonium carbonate zinc solution is controlled to between 0.05 and 2.0. 
     
     
         3 . The method according to  claim 1 , wherein a portion of the carbonate is transferred from the aqueous ammoniacal ammonium carbonate zinc solution to organic solution of a zinc extractant, such that the method more specifically comprises the steps of:
 i. Contacting the aqueous ammoniacal ammonium carbonate zinc solution with an organic solution of a zinc extractant, such that a portion of the zinc and the carbonate is transferred from the aqueous ammoniacal ammonium carbonate zinc solution, producing a zinc-depleted carbonate-depleted aqueous ammoniacal ammonium carbonate solution and a zinc-and carbonate-enriched organic solution of a zinc extractant;   ii. Separating the zinc- and carbonate-enriched organic solution of a zinc extractant and zinc-depleted carbonate-depleted aqueous solution;   iii. Contacting the zinc-and carbonate-enriched organic solution with an acidic solution producing a zinc-enriched aqueous acid solution, a zinc- and carbonate-depleted organic solution of a zinc extractant and carbon dioxide; and   iv. Recovering zinc from the zinc-enriched aqueous acid solution.   
     
     
         4 . The method according to  claim 1 , wherein the method further comprises the step of:
 Leaching a zinc-containing carbonate-containing ore with an ammoniacal solution to produce the aqueous ammoniacal ammonium carbonate zinc solution.   
     
     
         5 . The method according to  claim 4 , wherein the zinc-containing ore is leached with an ammoniacal solution in the presence of ammonium carbonate to produce the aqueous ammoniacal ammonium carbonate zinc solution. 
     
     
         6 . The method according to  claim 3 , wherein the carbon dioxide produced in the step of:
 Contacting the zinc-and carbonate-enriched organic solution with an acidic solution producing a zinc-enriched aqueous acid solution, a zinc- and carbonate-depleted organic solution of a zinc extractant and carbon dioxide is absorbed into an aqueous solution to produce an aqueous solution of carbon dioxide.   
     
     
         7 . The method according to  claim 6 , wherein the carbon dioxide is absorbed into an aqueous solution containing ammonia. 
     
     
         8 . The method according to  claim 6  or  7 , wherein the carbon dioxide is absorbed into the zinc- and carbonate-depleted aqueous ammoniacal ammonium carbonate solution produced during step (i). 
     
     
         9 . The method according to  claim 6 , wherein the aqueous solution of carbon dioxide is used in the ammoniacal leaching of a zinc-containing ore to produce the aqueous ammoniacal ammonium carbonate zinc solution which is the feed to step (i). 
     
     
         10 . The method according to  claim 1 , wherein the aqueous ammoniacal ammonium carbonate zinc solution contains free ammonia, such that the method more specifically comprises a method for recovering zinc from an aqueous ammoniacal ammonium carbonate zinc solution containing free ammonia, the method comprising the steps of:
 i. Contacting the aqueous ammoniacal ammonium carbonate zinc solution containing free ammonia with an organic solution of a zinc extractant, such that a portion of the zinc and ammonia is transferred from the aqueous ammoniacal ammonium carbonate zinc solution containing free ammonia, producing a zinc- and ammonia-depleted aqueous ammoniacal ammonium carbonate solution and a zinc- and ammonia-enriched organic solution of a zinc extractant;   ii. Separating the zinc-enriched ammonia-enriched organic solution of a zinc extractant and zinc-depleted ammonia-depleted aqueous solution;   iii. Contacting the zinc-enriched ammonia-enriched organic solution with an ammonia scrub solution to reduce ammonia thereby producing a zinc-rich ammonia-depleted organic Contacting the zinc-enriched ammonia-depleted organic solution with an acidic solution producing a zinc-rich acid solution and a zinc-depleted ammonia-depleted organic solution of a zinc extractant; and   iv. Recovering zinc from the zinc-rich acid solution.   
     
     
         11 . The method according to  claim 10 , wherein the ammonia scrub solution preferably has a pH in the range 2 to 7. 
     
     
         12 . The method according to  claim 10 , wherein the molar ratio of carbonate to zinc in the aqueous ammoniacal ammonium carbonate zinc solution containing free ammonia is controlled to between 0.05 and 2.0. 
     
     
         13 . The method according to  claim 1 , wherein the aqueous ammoniacal ammonium carbonate zinc solution contains impurities, such that the method more specifically comprises a method for recovering zinc from an aqueous impurity-containing ammoniacal ammonium carbonate zinc solution, the method comprising the steps of:
 i. Contacting the aqueous impurity-containing zinc ammoniacal ammonium carbonate solution with an organic solution of a zinc extractant, such that a portion of the zinc and the impurities from the aqueous impurity-containing ammoniacal ammonium carbonate zinc solution producing an impurity-depleted zinc-depleted aqueous ammoniacal ammonium carbonate solution and an impurity-enriched zinc-enriched organic solution of a zinc extractant;   ii. Separating the impurity-enriched zinc-enriched organic solution of a zinc extractant and impurity-depleted zinc-depleted aqueous solution;   iii. Contacting the impurity-enriched zinc-enriched organic solution with an impurity scrub solution to reduce the impurities thereby producing an impurity-depleted zinc-enriched organic solution of a zinc extractant and an impurity-enriched solution;   iv. Contacting the impurity-depleted zinc-enriched organic solution with an acidic solution producing a zinc-enriched aqueous acid solution and an impurity-depleted zinc-depleted organic solution of a zinc extractant; and   v. Recovering zinc from the zinc-enriched aqueous acid solution   
     
     
         14 . The method according to  claim 11 , wherein the impurity scrub solution preferably has a pH in the range 0 to 5. 
     
     
         15 . The method according to  claim 11 , wherein the molar ratio of carbonate to zinc in the aqueous ammoniacal ammonium carbonate zinc solution containing free ammonia is controlled to between 0.05 and 2.0 
     
     
         16 . The method according to  claim 10 , wherein the aqueous ammoniacal ammonium carbonate zinc solution contains both free ammonia and impurities, where the method more specifically comprises both the steps of:
 Contacting the zinc-enriched ammonia-enriched organic solution with a ammonia scrub solution to remove ammonia thereby producing a zinc-enriched ammonia-depleted organic solution of a zinc extractant and an ammonia-enriched solution;   
       and
 contacting the impurity-enriched zinc-enriched organic solution with an impurity scrub solution to remove the impurities thereby producing an impurity-depleted zinc-enriched organic solution of a zinc extractant and an impurity-enriched solution. 
 
     
     
         17 . The method according to  claim 1 , wherein the molar ratio of ammonia to zinc in the aqueous solution is between 3 and 20. 
     
     
         18 . The method according to  claim 1 , wherein the zinc extractant is selected from the group: liquid organophosphorus extractant, liquid oxime extractant, carboxylic acid extractant and combinations thereof. 
     
     
         19 . The method according to  claim 1 , wherein the zinc extractant is Bis(2-ethylhexyl) hydrogen phosphate. 
     
     
         20 . The method according to  claim 1 , wherein the method further comprises the step of:
 adding a phase modifier to the organic solution of a zinc extractant prior to the step of:   contacting the aqueous ammoniacal ammonium carbonate zinc solution with an organic solution of a zinc extractant, such that a portion of the zinc is transferred from the aqueous ammoniacal ammonium carbonate zinc solution, producing a zinc-depleted aqueous ammoniacal ammonium carbonate solution and a zinc-enriched organic solution of a zinc extractant   
     
     
         21 . The method according to  claim 1 , wherein the organic solution of a zinc extractant, comprises a zinc extractant and a diluent. 
     
     
         22 . The method according to  claim 1 , wherein the molar ratio of carbonate to zinc in the organic solution is between 0.05 and 2.0. 
     
     
         23 . The method according to  claim 1 , wherein the molar ratio of ammonia to zinc to carbonate in the aqueous ammoniacal ammonium carbonate zinc solution is about 4:1:1. 
     
     
         24 . The method according to  claim 1 ; wherein at least 10% of the zinc species present in the organic solution following the step of:
 Contacting the aqueous ammoniacal ammonium carbonate zinc solution with an organic solution of a zinc extractant, such that a portion of the zinc is transferred from the aqueous ammoniacal ammonium carbonate zinc solution, producing a zinc-depleted aqueous ammoniacal ammonium carbonate solution and a zinc-enriched organic solution of a zinc extractant,   
       is in the form of ZnRHCC>3, where R is the extractant.