Processes that involve aqueous solutions used in the extraction and recovery of metals from ores. Leaching is used to treat metallic ores to form a solution of a salt and a metal. Dilute sulphuric acid is the most commonly used agent. The metal is then recovered from the salt solution by precipitation and/or concentration, and uses processes such as carbon adsorption, ion exchange, solvent extraction, and electrolysis. Almost all non-ferrous metals are produced using hydrometallurgy, such as gold, silver, copper, aluminium, nickel, zinc, cobalt, uranium, molybdenum, tungsten, and beryllium. See lixiviation.