ABSTRACT
Several alternatives are available for solubilizing the potentially wide range of waste solids ranging from scrap metal, appliance and hardware components, electrical and electronic scrap, mineral wastes, water purification sludges, flue dusts, fuel, and combustion ashes and residues. These solubilizing alternatives consist of reaction with acids, alkalies, chlorination, sulfidization, alloying, and formation of volatile compounds with carbon monoxide, and volatilization by heating for some metals and their compounds. Additional examination is appropriate here concerning experience with metal recovery by acid leaching for a variety of solids with low metal contents, ranging from mining wastes and coal ash to municipal waste residues. Acid solubilization is one of the most obvious initial preparation stages for conditioning metal waste sludges for application of the recovery processes discussed above for metals in solution. The Environmental Protection Agency contract studies have been conducted of the removal of metals from municipal sludges by hot acid treatments.
