Zero-valent iron and organo-clay for chromate removal in the presence of trichloroethylene

Abstract

Hybrid barriers of zero-valent iron (Fe0) filings and hexadecyltrimethylammonium (HDTMA)-bentonite were simulated in columns to remove chromate and trichloroethylene (TCE) via reduction and sorption. The normalized reduction rate constant (and SA) of chromate with the mixture of Fe0 filings and HDTMA-bentonite was about twice higher than that with Fe0 filings only, suggesting that chromate reduction was enhanced when HDTMA-bentonite was mixed with Fe0 filings. For the column of two separate layers of Fe0 and HDTMAbentonite, the reduction rate of chromate slightly increased, but not as much as in the column with mixtures of Fe0 filings and HDTMA-bentonite. In addition, the sorption rates of both TCE and chromate in the column with mixtures of Fe0 filings and HDTMA-bentonite were lower than in the columns of both HDTMA-bentonite only and two separate layers of Fe0 and HDTMA-bentonite. Based on the observation from this study, hybrid barriers can be more effective for mixed contaminants.