High performance and simultaneous sequestration of Cr(VI) and Sb(III) by sulfidated zerovalent iron

Chromium and antimony may coexist in industrial wastewater such as the textile and dyeing field. Sulfidated zero valent iron (S-ZVI) is attracting more attention due to its simple preparation and high reactivity with contaminants. The reaction with pollutants may be a complex mixture of redox, sorption, and coprecipitation. In this work S-ZVI was used to sequester Cr(VI) and Sb(III) simultaneously in open and well-mixed batch reactors. The correlation between Cr(VI) and Sb(III) sequestration by S-ZVI, the influence of different S/Fe molar ratios, the initial concentration of Cr(VI) and Sb(III), the initial pH and the addition of Fe(II) and other factors were investigated to evaluate the performance of S-ZVI and to demonstrate the reaction mechanism. Experimental results showed that S-ZVI could sequester Cr(VI) and Sb(III) efficiently and the S/Fe molar ratio had a dramatic effect on the removal rate, the highest kobs was obtained when the S/Fe molar ratio was 0.056. The X-ray photoelectron spectroscopy (XPS) showed that Cr(VI) could be reduced to Cr(III) and Sb(III) could be oxidized to Sb(V) simultaneously, adsorption and coprecipitation also coexisted in this system. A certain amount of Sb(III) could promote the sequestration of Cr(VI) but Sb(III) sequestration was hardly affected by Cr(VI). Furthermore, catalase was used as a masking agent of hydrogen peroxide, the results indicated that hydrogen peroxide may play an important role in the sequestration of Cr(VI) and Sb(III), which need to be further investigated.