Degradation of trichloroethylene and perchloroethylene by a zero-valent iron permeable reactive barrier: preliminary tests

Zero-valent iron materials may be employed with high contaminant removal efficiency in permeable reactive Barriers (PRBs) for the remediation of chlorinated solvents in groundwater. The basis of this in situ cleanup technology is simple: the groundwater flow passes through the reactive substrate and the chlorinated solvents are converted by means of oxidation–reduction processes to nontoxic hydrocarbons, such as alkanes and alkenes, and chloride ions. Two cast iron aggregates (WSR size 8/50 and Brown size 8/50, from Peerless Powders and Abrasive Inc.) are evaluated in this work as a substrate for a PRB, proposed as remediation technology for a polluted site in which the main contaminants are perchloroethylene (PCE) and trichloroethylene (TCE). The zero-valent materials were characterized by means of particle-size analysis, and some batch tests, considering different equilibrating periods, were performed. The used aqueous phase had a chemical composition very similar to the polluted groundwater and it contained PCE and TCE concentrations equal to the maximum values detected in the site (7.52 mg/l of PCE and 6.65 mg/l of TCE). The leaching of metals from the reactive substrates and the effect of dissolved salts on the life of the PRB were also evaluated. The Brown material appeared to be more efficient than the WSR material in TCE degradation and more efficient with TCE compared to PCE, probably because of a competitive effect between the pollutants. No toxic metals were released in the aqueous phase. This study confirmed the efficiency of zero-valent iron materials in the remediation of chlorinated solvents.