Reduction of Nitro Aromatic Compounds in Fe(0)-CO2-H2O Systems: Implications for Groundwater Remediation with Iron Metal

摘要

The properties of iron metal that make it useful in remediation of chlorinated solvents may also lead to reduction of other groundwater contaminants such as nitro aromatic compounds (NACs). This possibility has been investigated in batch experiments using aqueous carbonate media to determine the kinetics and mechanism of nitro reduction by iron metal, and to learn more abut he effect of precipitation on the reactivity of the metal surfaces under geochemical conditions. Nitrobenzene is reduced by iron under anaerobic conditions to aniline with nitrosobenzene as an intermediate product. Detectable amounts of coupling products such as azobenzene and azoxybenzene were not found. First-order reduction rates are similar for nitrobenzene and nitrosobenzene, but aniline appearance occurs more slowly. The nitro reduction rate increased linearly with concentration of iron surface area, giving a specific reaction rate constant which is roughly 16-fold greater than has been reported for dehalogenation of carbon tetrachloride.