Removal of hexavalent chromium in natural groundwater using activated carbon and cast iron combined system

Abstract A permeable reactive barrier (PRB) using activated carbon and cast iron combined system was to be built at a field site in Northern China to remove Cr(VI) in the groundwater. In this study, laboratory column experiments were conducted to evaluate the efficiency of the combined system at mass ratios of 1:1 and 3:1. The results showed that the combined system has a higher removal rate than that of the single material and leads no secondary pollution. Different mass ratio was proved to have much effect on the Cr(VI) removal capacity (mg Cr/g materials), the removal capacity was 3.806 mg/g at 1:1, while it was only around 0.776 mg/g in the single cast iron column. Larger carbon particles and higher flow rate can lead to a significant decrease in Cr(VI) removal due to lower specific surface area and lower hydraulic residence time (HRT), respectively. The breakthrough curves could be adequately reproduced by the Dose-Response model, for security, the half-life time used in the PRB thickness calculation was 0.4d chosen at the break through time. The results could be useful to groundwater remediation at chromium-polluted sites.