Thiosulphate Leach Process

Abstract

An improved thiosulphate leach process for the recovery of gold from ores and other gold-bearing materials, characterised in that the leach solution comprises thiosulphate, thiourea or a reagent chemically related thereto, and an oxidant that does not oxidise thiosulphate, the process producing a pregnant leach solution from which gold may be recovered.

1 . An improved thiosulphate leach process, the process characterised by the method steps of submitting a gold-bearing material to a leach in a thiosulphate solution, wherein thiourea or a reagent chemically related thereto, and at least one oxidant, are present in the thiosulphate leach solution, and subsequently recovering gold from the resulting pregnant leach solution.  
   
   
       2 . A process according to  claim 1 , wherein thiourea is provided in a concentration of about 0.01 mole/L.  
   
   
       3 . A process according to  claim 1 , wherein the oxidant present is a complex of ethylenediamenetetraacetate (EDTA) with a multivalent metal.  
   
   
       4 . A process according to  claim 3 , wherein the multivalent metal is iron and the complex FeEDTA.  
   
   
       5 . A process according to  claim 1 , wherein thiosulphate is added in the form of a soluble salt.  
   
   
       6 . A process according to  claim 5 , wherein the soluble salt is the sodium salt of thiosulphate.  
   
   
       7 . A process according to  claim 1 , wherein thiosulphate is provided in a concentration of about 0.1 to 0.3 mo/e/L.  
   
   
       8 . A process according to  claim 4 , wherein the oxidant FeEDT A is prepared prior to addition to the leach solution.  
   
   
       9 . A process according to  claim 4 , wherein the oxidant FeEDT A is prepared by adding suitable amounts of iron salts and EDT A directly to the leach solution.  
   
   
       10 . A process according to  claim 4 , wherein the concentration of FeEDTA in the leach solution is about 0.002 mole/L  
   
   
       11 . A process according to  claim 1  wherein the pH of the leach is preferably maintained between about 6 to 7.  
   
   
       12 . A process according to  claim 1 , wherein the reagent chemically related to thiourea is a thio-substituted organic compound.  
   
   
       13 . A process according to  claim 12 , wherein the reagent chemically related to thiourea is one of formamidine disulphide or thlosemicarbazide.  
   
   
       14 . An improved thiosulphate leach process for the recovery of gold from ores and other gold-bearing materials, characterised in that the leach solution comprises thiosulphate, thiourea or a reagent chemically related thereto, and an oxidant that does not oxidise thiosulphate, the process producing a pregnant leach solution from which gold may be recovered.  
   
   
       15 . A process according to  claim 14 , wherein the oxidant present is a complex of ethylenediamenetetraacetate (EDTA) with a multivalent metal.  
   
   
       16 . A process according to  claim 15 , wherein the multivalent metal is iron and the complex FeEDTA.  
   
   
       17 . A process according to  claim 14 , wherein the FeEDTA is provided at a concentration of about 0.002 mole/L.  
   
   
       18 . A process according to claim  14 , wherein the thiosulphate is provided at a concentration of between about 0.1 to 0.3 mole/L  
   
   
       19 . A process according to  claim 14 , wherein thiourea is provided at a concentration of about 0.01 mole/L  
   
   
       20 . A process according to  claim 14 , wherein gold is recovered from the pregnant leach solution by way of either cementation or ion exchange.  
   
   
       21 . A process according to  claim 14 , wherein the pH of the leach is preferably maintained between about 6 to 7.  
   
   
       22 . A process according to  claim 12 , wherein the reagent chemically related to thiourea is a thio-substituted organic compound.  
   
   
       23 . A process according to  claim 22 , wherein the reagent chemically related to thiourea is one of formamidine disulphide or thiosemicarbazide.  
   
   
       24 . An improved thiosulphate leach process substantially as hereinbefore described with reference to Examples 2 to 6.