Recovery of lead and silver from lead-bearing wastes using reducing-matting smelting process

In view of the difficulty in environmental and economic treatments of lead-bearing wastes generated in lead and zinc smelter,a new reducing-matting smelting process was proposed to recycle secondary lead from multiple lead-bearing wastes in this paper. In the process,the designed mixture of lead sludge,lead slag,lead ashes and pyrite cinder was used as a smelting object,and ferric oxide,soda and mirabilite and coal powders were a sulfur-fixing agent,additive and reductant,respectively. The effects of factors on the direct recovery rates of lead and silver during the smelting process were studied in detail based on thermodynamic calculations. The optimum conditions are obtained as the following:the mass ratio of FeO to SiO₂ is 1.10,the mass ratio of CaO to SiO₂ is 0.30,the mass ratio of Na₂CO₃ to Na₂SO₄ is 0.7:0.3,the dosage of coal powders is 15% of lead-bearing wastes,the smelting temperature is 1200℃,and the smelting time is 2 h. Comprehensive experiments show that under the optimum conditions,the direct recovery rates of lead and silver are 85.95% and 83.15%,respectively. The process has significant advantages of sulfur fixation,comprehensive utilization and one-step lead smelting.