Increasing silver leaching rate from leaching-resistant zinc residues by thiourea leaching method with pressurized preoxidation process

摘要

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 silver leaching rate is greatly improved. The optimum preoxidation conditions are: particle size range 4060 μm, oxygen partial pressure 10 6 Pa, temperature 8090 ℃, 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.