Oxidative Pressure Leaching Gold From Refractory Sulfide Gold Ores With Ammoniacal Ammonium Thiocyanate Solution

As the increasing demand for gold and decreasing amounts of gold ore that are easy for floating and smelting in the world. How to extract gold economically, efficiently and environment friendly from refractory gold ore has become a hard issue for gold industry。In this paper, Oxidative pressure leaching gold from refractory sulfide gold ores with ammoniacal ammonium thiocyanate solution was studied supported by the National Natural Science Foundation, We get to know that the Au element mostly presented in the form of microscopic gold and wrapped gold。The content of arsenic and sulfur is very high。It’s a kind of typical refractory gold ore。In this article, The possibility of decomposing pyrite and arsenop-yrite under basic condition was analyzed by thermodynamic calculation。 The thermodynamic model of Au(Ⅰ)-NH4SCN-NH3-H2O and Au(Ⅲ)-NH4SCN-NH3-H2O were researched and established。The analysis shows that gold from refractory gold ores can be completely dwqissolved into solution theoretically。E-pH diagram for Au-SCN--H2O system at room temperature is drawed out。It suggests that Au+and Au3+can be bonded with SCN-to form stable comples of Au(SCN)2-and Au(SCN)43-, Thus the gold redox potential can be reduced to blelow the potential of oxygen produced by water。E-pH diagram for SCN--H2O system shows that SCN-ions can be decomposed into several products according to different conditions。Sulfide gold leaching effect is not good either in alkaline or acidic conditions at ambient temperature and pressure。Oxidative pressure leaching gold from sulfide gold concentrate in ammonium thiocyanate a-mmonia system were tested, the effects of leaching temperature, concentration of copper, leaching time, the ratio of liquid to solid, the concentration of ammonia, oxygen pressure, the concentration of ammonium thiocyanate etc to gold leaching were studied。The results shows that in the comprehensive condition NH4SCN concentration3mol/L, the stirring speed750r/min, ammonia concentrate ion 4.64mol/L, the concentration of copper1.5g/L, leaching temperatrue150℃, leaching time6hours, the gold leaching ratio is61.7%。After leached repeatedly three times, the extraction percentages of gold can leach90%。SCN-ions can decompose both under acidic and alkaline condition-s。the SCN-ions does not decompose to generate the solid phase sulfur nder acidic conditions. Decomposition products need to be further demonstrated。...