A Novel, Solvent-Free Mechanochemistry Approach for Gold Extraction from Anode Slime

Gold extraction from anode slime often results in severe pollution as well as high consumption of reagents. Herein, a novel strategy, that in situ generates oxidative chlorine by a mechanochemistry approach, was developed for gold extraction from anode slime for the first time. By conducting dry ball milling of the mixed anode slime, KMnO4, and NH4Cl, elemental gold in anode slime was efficiently converted into water-soluble AuCl3 and then separated from solids by simple water leaching. A high gold yield of 97.71% was achieved under optimal conditions of 0.15 g of NH4Cl, water content of 9.09%, mass ratio of 20, rotation speed of 700 rpm, and reaction time of 60 min. Furthermore, this approach achieved a gold yield of 78.82%, while yields of other coexisting metals were nearly negligible. Compared with the hydrometallurgical process, this approach exhibited great advantages for its nearly solvent-free process, excellent selectivity for gold, and environmental friendliness.