Removal of Heavy Metals from Industrial Effluents

Increasingly stringent effluent discharge requirements have spurred an interest in more effective and economical methods of removing heavy metals from industrial wastes. Increasing scarcity and prices of metals also hasten efforts to achieve metal removal and recovery. Neutralization and chemical precipitation have been utilized for years. Operating data indicate metal removals are possible beyond those indicated by metal hydroxide solubilities, apparently as a result of coprecipitation. Reported costs of neutralization are given as a function of waste character. Metal sulfides exhibit lower solubilities than do metal hydroxides. This fact is used to advantage in sulfide-precipitation systems, utilizing a variety of sources of sulfide ion. Other treatment systems, such as cementation, ion exchange, sorption, or reverse osmosis are utilized in special cases, and are examined.