Enhancement of Hexavalent Chromium [Cr(VI)] Remediation from Clayey Soils by Electrokinetics Coupled with a Nano-Sized Zero-Valent Iron Barrier

The effectiveness of coupling electrokinetics (EK) with a permeable reactive barrier (PRB) to remediate hexavalent chromium [Cr(VI)]-contaminated clayey soil (100mg/kg) was evaluated. Nano-sized zero-valent iron (nZVI) was used as reactive material in a PRB. The experimental setup consisted of an 8 cm-long soil chamber with a 4-cm diameter, which had two chambers on either side acting as the anode and cathode. A constant electrical gradient of 2V/cm was applied in all tests for 24 h. Cr(VI) removal for the base experiment (only applying EK) was found to be 14.78%. When the soil was treated by the coupled EK/PRB process, the Cr(VI) reduction and total Cr removal efficiencies were increased to 88 and 19%, respectively. In another attempt, the reservoir pH was maintained constant at 6.3 with PRB near the anode; this improved the total Cr removal efficiency to 42% by increasing the current intensity that passed through the soil specimen. Data suggest that redox and adsorption/desorption reactions were taking place during the EK/PRB process, resulting in significant reduction of Cr(VI) to the less toxic Cr(III). These findings indicate that this EK/PRB process is capable of removing Cr(VI) from clayey soils.