Hydraulic Properties of Selected Materials and Their Effects on Remediation Cr(VI) Contaminated Groundwater

Abstract

To find an economically feasible and directly usable natural permeable reactive barrier (PRB) filler, sponge iron was selected from seven natural materials with excellent removal efficiencies of Cr(VI). The synergism of sponge iron and maifanite increased by 20.90% and showed the best removal effect of 40.187%. In the dynamic column experiment, sponge iron played a major role in the removal of Cr(VI), so increasing its proportion could improve the removal efficiencies, but the permeability of the reaction system would decline. Maifanite can effectively promote the fixation of Cr(III) and inhibit the reduction of permeability. Reducing Cr(VI) concentration and prolonging the hydraulic retention time were favorable for chromium removal. Thomas, Yoon-Nelson, and Adams-Bohart models can all well simulate the penetration curve under the high proportion of sponge iron. After adsorption, chromium in the reaction medium mainly existed as residue and oxidation rather than a water-soluble state, indicating that Cr(VI) in water was reduced to Cr(III) and fixed permanently. Comprehensively considering the saturated adsorption capacity and hydraulic properties, a ratio of sponge iron to maifanite of 5∶1 is reasonable to apply in restoration Cr(VI) contaminated groundwater.