The Principles and Applications of Ammonia Leaching of Metals—A Review

Abstract An extensive literature survey on the principles and applications of ammonia leaching processes in hydrometallurgy is presented in this paper. The combination of ammonia anal ammonium salts is known to be a powerful lixiviant used in hydrometallurgical processes. Many metals can be extracted using the mixture of ammonia/ammonium. The thermodynamics and kinetics of the dissolution of various metals in ammonia/ammonium salts have been reviewed. The solubility, volatility, and complexation ability of various metals with ammonia have been reviewed and discussed. Eh-pH diagrams of various metal-ammonia-water systems are presented. Also presented is a comprehensive literature survey on the leaching behavior of metals in ammoniacal solutions. The metals considered in this paper are copper, cobalt, nickel, zinc, cadmium, silver, gold and palladium.