Using Low-Cost Iron Byproducts from Automotive Manufacturing to Remediate DDT

Abstract

Water, soil and sediment contaminated with DDT poses a threat to the environment and human health. Previous studies have shown that zerovalent iron (ZVI) can effectively remediate water contaminated with pesticides like DDT, metolachlor, alachlor. Because the type of iron can significantly influence the efficiency and expense of ZVI technology, finding a cheaper and easily available iron source is one way of making this technology more affordable for field application. This study determined the effects of iron source, solution pH, and presence of Fe or Al salts on the destruction of DDT. Batch experiments demonstrated successful removal of DDT (>95% in 30 d) in aqueous solutions by three different iron sources with the following order of removal rates: untreated iron byproduct (1.524 d−1) > commercial ZVI (0.277 d−1) > surface-cleaned iron byproduct (0.157 d−1). DDT removal rate was greatest with the untreated iron byproduct because of its high carbon content resulted in high DDT adsorption. DDT destruction rate by surface-cleaned iron byproduct increased as the pH decreased from 9 to 3. Lowering solution pH removes Fe (III) passivating layers from the ZVI and makes it free for reductive transformations. By treating DDT aqueous solutions with surface-cleaned iron byproduct, the destruction kinetics of DDT were enhanced when Fe(II), Fe(III) or Al(III) salts were added, with the following order of destruction kinetics: Al(III) sulfate > Fe(III) sulfate > Fe(II) sulfate. Cost analysis showed that the cost for one kg of surface-cleaned iron byproduct was $12.33, which is less expensive than the commercial ZVI. Therefore, using surface-cleaned iron byproduct may be a viable alternative for remediating DDT-contaminated environments.