Recovery of gold and silver in secondary

This thesis investigates the recovery of gold and silver from secondary slag resulting from the gold refining process using co-precipitation with metal hydroxides. The objective was to identify effective methods for recovering these precious metals from secondary waste materials. A combination of physical processes, including comminution and shaking table techniques, along with chemical separation methods employing nitric acid and aqua regia, were utilized. The results demonstrated that the physical separation process successfully liberated an alloy of Au-Ag-Cu from slag materials of a particle size under 70 mesh, leading to an increase in concentration of gold from 0.015% to 0.126% and silver from 0.174% to 1.56%. Two-stage leaching processes further enhanced the recovery of silver as AgCl precipitate and gold as [AuCl4], which contained AgNO3 impurities. Subsequent concentration of the leachate was accomplished through co-precipitation with metal hydroxides, achieving notably high purity of gold and silver. The findings indicate that gold and silver purification was most effectively conducted using 1M nitric acid compared to 1M hydrochloric acid, providing a significant advancement in sustainable mining engineering practices.