Recovery of precious metals and copper from copper/gold ores using resin technology

Abstract

A process for the selective recovery of precious metals from a medium loaded with precious metals and base metals. The selective recovery of precious metals is achieved by exposing the medium to an aqueous solution containing a complex of formula MX 2 —, wherein M is a metal of group IB or IIB of the Periodic Table of Elements, and X is a monovalent radical. A second invention relates to the removal of copper from the medium whereby elution of copper is achieved by exposing the medium to an aqueous solution capable of oxidising Cu(I) to Cu(II) whilst not eluting precious metals from the medium.

1 . A process for the selective recovery of precious metals from a medium loaded with precious metals and base metals, wherein said selective recovery is achieved by exposing said medium to an aqueous solution containing a complex of formula MX 2 —, wherein M is a metal of group IB or IIB of the Periodic Table of Elements, and X is a monovalent radical.  
     
     
         2 . The process of  claim 1 , wherein said precious metal is selected from the group consisting of: gold, silver and platinum metals group.  
     
     
         3 . The process of  claim 1  or  2 , wherein said medium is an ion exchange medium or activated carbon.  
     
     
         4 . The process of  claim 3 , wherein said ion exchange medium is an anion exchange medium.  
     
     
         5 . The process of  claim 4 , wherein said anion exchange medium is in the form of an anion exchange resin.  
     
     
         6 . The process of any one of claims  3 - 5 , wherein said ion exchange medium has an anion exchange functional group which is benzyltrimethylammonium chloride.  
     
     
         7 . The process of any one of claims  1 - 6 , wherein said metal M of formula MX 2 — is selected from the group consisting of: copper(I), gold(I), silver(I), cadmium(I) and mercury(I).  
     
     
         8 . The process of any one of claims  1 - 7 , wherein said X of formula MX 2 — corresponds to a monovalent anion selected from the group consisting of: halides, cyanide, thiocyanate and isothiocyanate.  
     
     
         9 . The process of  claim 8 , wherein said halide is selected from the group consisting of: chloride, bromide, iodide, fluoride, cyanide and thiocyanate.  
     
     
         10 . The process of any one of claims  1 - 9 , wherein said complex anion of formula MX 2 — is either Cu(CNS) 2 — or Cu(CN) 2 —.  
     
     
         11  The process of  claim 10 , wherein said complex anion of formula MX 2 — is Cu(CN) 2 —.  
     
     
         12 . The process of any one of claims  1 - 11 , wherein said complex anion of formula MX 2 — is linear.  
     
     
         13 . The process of any one of claims  1 - 12 , wherein said aqueous solution of said complex anion of formula MX 2 — also includes a salt of formula M′X, wherein said M′ is the counter cation in relation to the complex anion of formula MX 2 —.  
     
     
         14 . The process of any one of claims  1 - 13 , wherein the concentration of said complex anion of formula MX 2 — in said aqueous solution is that sufficient to elute said precious metals from said medium.  
     
     
         15 . The process of any one of claims  1 - 14 , wherein the concentration of said complex anion of formula MX 2 — in said aqueous solution is not more than that wherein said complex anion of formula MX 2 — remains soluble.  
     
     
         16 . The process of  claim 14  or  15 , wherein said concentration of the complex anion of formula MX 2 — in the aqueous solution is at least about 0.01M.  
     
     
         17 . The process of any one of claims  14 - 16 , wherein said concentration of the complex anion of formula MX 2 — in the aqueous solution is in the range of between about 0.1M to about 0.5M.  
     
     
         18 . A process for the elution of copper from a medium loaded with precious metals, copper and optionally other base metals, wherein said elution is achieved by exposing said medium to an aqueous solution capable of oxidising Cu(I) to Cu(II), whilst not eluting said precious metals from said medium.  
     
     
         19 . A process for the elution of copper from a medium loaded with precious metals, copper and optionally other base metals, wherein said process comprises: 
 (a) selectively recovering said precious metals from said medium in accordance with the process of any one of claims  1 - 17 , and    (b) eluting said copper from said medium by exposing said medium to an aqueous solution capable of oxidising Cu(I) to Cu(II).    
     
     
         20 . The process of  claim 18  or  19 , wherein said aqueous solution capable of oxidising Cu(I) to Cu(II) comprises an oxidising agent, together with an acid.  
     
     
         21 . The process of  claim 20 , wherein said oxidising agent is selected from the group consisting of: hydrogen peroxide, Caro's acid (H 2 SO 5 ) and acid ferric sulfate.  
     
     
         22 . The process of  claim 20  or  21 , wherein said aqueous solution capable of oxidising Cu(I) to Cu(II) comprises an amount of hydrogen peroxide between about 0.25-2% by weight hydrogen peroxide and about 1-10% by weight acid.  
     
     
         23 . The process of  claim 20  or  21 , wherein said aqueous solution capable of oxidising Cu(I) to Cu(II) comprises about 0.5% by weight hydrogen peroxide and about 5% by weight acid.  
     
     
         24 . The process of any one of claims  20 - 23 , wherein said acid is a mineral acid.  
     
     
         25 . The process of  claim 24 , wherein said acid is sulfuric acid.  
     
     
         26 . The process of any one of  claims 19  to  25 , wherein prior to exposing said medium to said aqueous solution capable of oxidising Cu(I) to Cu(II), said medium is contacted with a mineral acid.  
     
     
         27 . A process for the selective recovery of precious metals from a medium loaded with precious metals and base metals comprising: 
 (b) eluting copper from said medium in accordance with the process of  claim 18 , wherein said elution of copper occurs prior to said selective recovery of precious metals, and subsequently    (b) selectively recovering precious metals by exposing said medium to an aqueous solution containing a complex of formula MX 2 —, wherein M is a metal of group IB or IIB of the Periodic Table of Elements, and X is a monovalent radical, in accordance with the process of any one of  claims 1  to  17 .