Reduction of Chromium(VI) in Saturated Zone Sediments by Calcium Polysulfide and Nanoscale Zerovalent Iron Derived From Green Tea Extract

摘要

Column studies were conducted to evaluate the effectiveness for in situ chemical reduction of Cr(VI) contaminated soil by two agents: calcium polysulfide (CPS) and nanoscale zerovalent iron (nZVI) synthesized using green tea extract. Column effluent was monitored for pH, Cr(VI), and total Cr. In addition, total S and Fe were tested to evaluate the implications for groundwater quality associated with the use of sulfur and iron based reagents, respectively. Aqueous Cr(VI) concentrations fell below the regulatory criteria (0.5 mg/L) immediately following injections of both treatment types. A total of three CPS injections at twice the stoichiometric requirement for treatment were needed to obtain non-detect effluent Cr(VI) concentrations. A single injection of 6.5 times the stoichiometric requirement of nZVI resulted in non-detect effluent Cr(VI) for the remainder of the experiment. Post-treatment soil analysis showed that CPS treated a higher percentage of Cr(VI) than nZVI.