Common Anions Affected Removal of Carbon Tetrachloride in Groundwater Using Granular Sponge Zerovalent Iron

Significant attention has been devoted over the past two decades to research and field applications of zerovalent iron (ZVI) technologies for groundwater remediation. The uncertainty of ZVI effectiveness under complex subsurface environment will affect the application of ZVI remedial techniques. The effects of groundwater common anions Cl−, SO42−, and HCO3− on CCl4 degradation by sponge ZVI were investigated through batch experiments. The surface structure and composition of ZVI before and after reaction were determined by SEM-EDS, X-ray diffraction, and X-ray photoelectron spectroscopy. Cl−, SO42−, and HCO3− promoted the degradation of CCl4 with the order of HCO3− > SO42− > Cl−. HCO3− enhanced the effect of ZVI on CCl4 degradation as a buffer and an oxidant providing cathodic reaction; SO42− dissolved the hydroxide on the ZVI surface to promote the degradation; and Cl− accelerated the degradation rate by pitting corrosion on the ZVI surface. After reaction, the iron oxides on ZVI surface were FeOOH and Fe2O3 in Cl−, SO42− system and the FeOOH was the only iron oxide in HCO3− system. The results suggest that the performance of ZVI will be affected by the composition of field groundwater.