Experimental Study on Enriching Precious Metals from Hot Residue

A process for concentrating precious metals through oxidizing roasting desulphurization and sulfuric acid selective leaching of base metal copper and nickel was proposed according to the phase and element composition of hot residue materials containing precious metals. A discussion was made on the effects of particle size,roasting time,roasting temperature,sulfuric acid concentration,leaching time and leaching temperature on the enrichment ratio of the precious metals. The optimal process parameters were obtained as follows: grain size of 0. 080 ~ 0. 106 mm,roasting time of 6 h,roasting temperature of 700 ℃,sulfuric acid concentration of 45%,leaching time of 5 h and leaching temperature of 95 ℃. Under this condition,the desulfurization rate was 98. 89%,leaching rate of copper and nickel at98. 33% and 98. 12% respectively,Au,Ag,Pt and Pd contents in the leaching residues of 1 198. 60 g / t,1 807. 79 g /t,1 801. 27 g / t and 1 937. 66 g / t respectively,leading to an enrichment ratio of 14. 19 for the precious metals from the raw material to the sulfuric acid leaching residue. This process is characterized by simple operation,high enrichment ratio,high recovery and low cost,which can provide a reference for enriching precious metals from hot residues.