Assessing the outlook for perchlorate remediation.

Perchlorate (ClO4) may appear to be just another addition to a growing list of halogenated chemicals that persist in the environment, but the chemical characteristics of this inorganic anion make it quite unusual. Typical chlorinated aliphatic compounds, such as trichloroethylene (TCE), are relatively insoluble carbonaceous compounds, strictly used for industrial purposes. They are volatile, adsorb, and are reduced by metals such as zerovalent iron. In contrast, perchlorate is a highly soluble inorganic anion (2.09 kg/L for NaClO4) (1) that adsorbs poorly to mineral surfaces and activated carbon and is not retarded during groundwater transport.