Abstract
As for the leaching-resistant zinc residues, the silver leaching rate can be over 98% through the process of pressurized preoxidation and thiourea leaching. Compared with the method of extracting the silver directly from the leaching-resistant zinc residues, the silyer leaching rate is greatly improved. The optimum preoxidation conditions are: particle size range 40 - 60 mum, oxygen partial pressure 10(6) Pa, temperature 80 - 90 degreesC, pH = 1. 0, and leaching time 5 h. After pretreatment, the time of thiourea leaching silver is shortened to 1. 5 h, and the thiourea consumption is reduced greatly. The oxidation mechanism and the thiourea leaching kinetics were also explored.