Reduced graphene oxide supported nanoscale zero-valent iron (nZVI/rGO) for in-situ remediation of Cr(VI)/nitrate-polluted aquifer

Abstract

The compound pollution of nitrate and hexavalent chromium (Cr(VI)) in groundwater poses a serious risk to human health. Graphene oxide supported nanoscale zero-valent iron (rGO/nZVI) can effectively remediate Cr(VI) in groundwater. Xanthan gum is used as a good stabiliser and carrier to improve the stability of rGO/nZVI in aquifers. But the process and mechanism of in-situ simultaneous remediations of nitrate and Cr(VI) compound contamination by rGO/nZVI are still unclear. In this study, we investigated the process and mechanism of nitrate and Cr(VI) remediation using rGO/nZVI in simulated aquifers. The results show that rGO/nZVI has a good affinity for NO3−-N and Cr(VI), and the fitted maximum adsorption amounts of NO3−-N and Cr(VI) are 18.03 mg/g and 94.70 mg/g, respectively. There is a negative synergistic phenomenon between NO3−-N and Cr(VI), and Cr(VI) will preferentially occupy the active site of rGO/nZVI and inhibit NO3−-N removal. Xanthan gum-rGO/nZVI slurry injected into the aquifer can successfully form a stable reaction zone, which can continuously remove NO3−-N and Cr(VI) with high adsorption capacity of 8.88 mg/g and 61.06 mg/g at 96 h.