Evaluation of calcium polysulfide as a reducing agent for the restoration of a Cr(VI)-contaminated aquifer

This work aims at investigating the efficiency of applying calcium polysulfide (CPS) as a reducing agent for the decontamination of a heavily Cr(VI)-contaminated aquifer. Series of batch experiments were carried out in order to evaluate the reductive behavior of CPS towards the aqueous and solid phase. CPS was added in several stoichiometric excesses (2.0X, 2.6X, 4.6X and 6.5X) with respect to the Cr(VI) concentration measured in the contaminated groundwater. The effect of time on Cr(VI) reduction by CPS was tested performing short term batch experiments. In addition, the effect of CPS on other groundwater constituents, e.g. nitrates, and potential mobilization of soil elements, sensitive to redox changes (Mn, As, Co, etc.), were also evaluated. The experimental results showed that CPS can be effectively used for the remediation of the Cr(VI) contaminated aquifer without affecting significantly the soil properties.