Evaluation of Calcium Polysulfide as a Reducing Agent for the Restoration of a Cr(VI)-Contaminated Aquifer.

This study aims at investigating the efficiency of calcium polysulfide (CPS) as a reducing agent for decontamination of a heavily Cr(VI)-contaminated aquifer. Batch experiments were carried out in order to evaluate the effect of time, CPS concentration and the presence of soil on the reductive behavior of CPS. CPS was used at several stoichiometric excesses with respect to Cr(VI) concentration detected in the contaminated groundwater. In addition, the effect of CPS on other groundwater constituents like nitrates, and potential mobilization of soil elements were also evaluated. Finally, column tests were carried out in order to evaluate the efficiency of CPS for the Cr(VI) reduction in flow conditions. The results showed that CPS can be an effective reducing agent for the remediation of the Cr(VI) contaminated aquifer especially at pump and treat methods. The required minimum dose of CPS for reducing Cr(VI) from the initial level of 1000 μg/L below the environmental limit of 50 μg/L was found equivalent to approximately 2.8 mg/L of sulfide anions. Moreover CPS use did not significantly affect soil properties and mobilization of soil elements.