Ball-Milled Biochar Supported and Sulfidated Nanoscale Zerovalent Iron for Cr(VI) Removal

Abstract Hexavalent chromium, Cr(VI), is a common heavy metal that, if not remediated, will do great harm to the environment. Recently, nanoscale zerovalent iron (nZVI), a widely used water remediation nanomaterial, can be applied for Cr(VI) removal. In this study, ball-milled biochars (BM-BC) prepared from ball milling peanut shells biochar were reacted with FeCl3 and Na2S2O3·5H2O to synthesize S-nZVI@BM-BC (sulfidated nZVI supported on BM-BC). The S-nZVI:BM-BC mass ratio, solution pH, Cr(VI) concentrations, and dosage of S-nZVI@BM-BC were assessed for effectiveness of S-nZVI@BM-BC in eliminating Cr(VI) from water. The results showed that ball milling increased the oxygen content on the biochars surface. Both ball milling of biochar and sulfidation of nZVI enhanced the Cr(VI) removal capacity of S-nZVI@BM-BC at an optimized condition of 200 mg/L S-nZVI@BM-BC, pH 3, and Cr(VI) starting concentration of 10 mg/L. Further analysis revealed that reaction by-products Cr(III)/Fe(III) (oxy)hydroxides sorb on BM-BC composites for easy removal. These findings suggest that S-nZVI@BM-BC can be used in the remediation of chromium-contaminated water.