Performance And Mechanism Of Cr(Vi) Removal By Resin-Supported Nanoscale Zero-Valent Iron (Nzvi): Role Of Nzvi Distribution

Four composite resins with different nanoscale zero-valent iron (nZVI) distributions were used to remove hexavalent chromium (Cr(VI)) from water. The effects of nZVI distributions on the performances and mechanisms of the composite resins were investigated during the Cr(VI) removal process. The stability experiments showed that the hybrids with a more uniform nZVI distribution than others were more favorable for inhibiting nZVI dissolution into iron ions under acidic pH (1.5-3.5), and that hybrids with different nZVI distributions exhibited no significant differences in Cr(VI) removal under the influences of aging and solution pH. Results of the reactivity experiments showed that the Cr(VI) removal efficiency decreased with increasing initial Cr(VI) concentration, and that 72.09%-97.18% of 100 mg/L Cr(VI) could be removed from aqueous solutions by four composite resins with different nZVI distributions. The presence of phosphate, silicate, and nitrate inhibited Cr(VI) removal; further, the hybrids with a more uniform nZVI distribution than others exhibited a better removal selectivity. The adsorption kinetics data agreed well with those from the pseudo-second-order model (R-2 >= 0.9710). The reactivity experiments combined with X-ray photoelectron spectroscopy showed that the composite resin with a peripheral nZVI distribution has a strong reduction ability and high removal performance. With increasing uniformity in the nZVI distribution, the reduction performance weakened and the adsorption performance enhanced during Cr(VI) removal. The findings of this study demonstrate the importance of nZVI distribution on Cr(VI) reduction and immobilization when the nZVI nanocomposite is applied to treat Cr(VI) contaminants. The results will help to optimize the design and fabrication of nZVI nanocomposites of improved reactivity for environmental decontamination.