(562z) Simultaneous Transformation of Hexavalent Chromium and Carbon Tetrachloride Using Atomized Zerovalent Iron in Co-Contaminant Aqueous Medium

Shah, A. - Presenter, Howard University
Chawla, R., Howard University
Lee, B., Pacific Northwest National Laboratory
Hexavalent Chromium (Cr(VI)) and Carbon tetrachloride (CCl4) are two of the most toxic and prevalent contaminants in many of the hazardous waste sites, including DOE commissioned superfund sites such as Hanford site in Washington and Savannah River site in South Carolina, USA. Cr is a heavy metal used extensively for its anti-corrosive properties, whereas CCl4 is a chlorinated organic solvent historically used extensively as a metal degreasing agent in industries. This paper focuses on the simultaneous transformation of Cr(VI) and CCl4 in a co-contaminant aqueous medium by atomized Zerovalent Iron (ZVI). ZVI being a nontoxic, cheap, abundant and easy to produce reducing agent has proven to remediate hosts of several chlorinated organic compounds, heavy metals, nitrates and other contaminants. The experiments show that the both the contaminants undergo reduction at much higher rates at low pH values; hence, a pH of 2.5 was used to study the degradation. ZVI proved to be an effective reducing agent for both Cr(VI) and CCl when degraded separately as well as in a co-contaminant media, and the contaminants did not effects the degradation of each other in the co-contaminant media. Both the contaminants followed a pseudo-first order degradation kinetics, with the rate of Cr(VI) degradation being higher (Kobs =13.038 hr-1) than the degradation of CCl4 (Kobs =3.29 hr-1) for same reaction conditions. At a pH of 2.5, nearly 100 % degradation was achieved for both the contaminants using excess ZVI within a 2-hour period, in separate as well as in a co-contaminant media.