Method for Recovering Gold

Abstract

The invention relates to a method for recovering gold from an intermediate product or residue containing sulphur and iron generated in the leaching of a sulphidic raw material. The recovery of gold and the other valuable metals in the raw material takes place in a chloride environment. The gold contained in the intermediate product or residue is leached with divalent copper and chlorine in a copper (II) chloride—sodium chloride solution in conditions where the oxidation-reduction potential is in the range of 650-750 mV and the pH between 1 and 1.6. The acid generated during the feed of chlorine is neutralized with a suitable alkali. Neutralization avoids the costs of dissolving the iron.

1 . A method for recovering gold from an intermediate product or leach residue containing sulphur and iron generated in the leaching of a sulphidic raw material in atmospheric chloride leaching, characterised in that the gold is leached from the intermediate product or residue in an aqueous copper (II) chloride—sodium chloride solution in atmospheric conditions with chlorine and the divalent copper contained in the solution, where the oxidation-reduction potential of the suspension that is formed is kept in the range of 650-750 mV; the acid generated during the dissolution of sulphur is neutralized with alkali and thus the pH is kept at a value between 1-1.6, so that the iron remains mainly undissolved; the dissolved gold is recovered by some method known as such.  
     
     
         2 . A method according to  claim 1 , characterised in that the amount of divalent copper in solution is 20-80 g/l.  
     
     
         3 . A method according to  claim 2 , characterised in that the amount of sodium chloride in solution is 200-330 g/l.  
     
     
         4 . A method according to  claim 3 , characterised in that the temperature is maintained in the range between 80° C. and the boiling point of the suspension.  
     
     
         5 . A method according to  claim 4 , characterised in that the acid generated during the dissolution of sulphur is neutralized with basic copper (II) chloride.  
     
     
         6 . A method according to  claim 4 , characterised in that the acid generated during the dissolution of sulphur is neutralized with an alkali, which is one of the group NaOH, KOH, CaO, CaCO 3  or MgO.  
     
     
         7 . A method according to  claim 6 , characterised in that the dissolved gold is recovered using active carbon.  
     
     
         8 . A method according to  claim 6 , characterised in that the dissolved gold is recovered by electrolysis.  
     
     
         9 . A method according to  claim 6 , characterised in that the dissolved gold is recovered by chemical precipitation.  
     
     
         10 . A method according to  claim 1 , characterised in that the amount of sodium chloride in solution is 200-330 g/l.  
     
     
         11 . A method according to  claim 1 , characterised in that the temperature is maintained in the range between 80° C. and the boiling point of the suspension.  
     
     
         12 . A method according to  claim 1 , characterised in that the acid generated during the dissolution of sulphur is neutralized with basic copper (II) chloride.  
     
     
         13 . A method according to  claim 1 , characterised in that the acid generated during the dissolution of sulphur is neutralized with an alkali, which is one of the group NaOH, KOH, CaO, CaCO 3  or MgO.  
     
     
         14 . A method according to  claim 1 , characterised in that the dissolved gold is recovered using active carbon.  
     
     
         15 . A method according to  claim 1 , characterised in that the dissolved gold is recovered by electrolysis.  
     
     
         16 . A method according to  claim 1 , characterised in that the dissolved gold is recovered by chemical precipitation.