Removal of Cr(VI) from wastewater using acid-washed zero-valent iron catalyzed by polyoxometalate under acid conditions: Efficacy, reaction mechanism and influencing factors

Chromium is a contaminant commonly found in water and soil because of its widespread use in various industries. Hexavalent chromium (Cr(VI)) is known to be highly toxic and carcinogenic, and the removal of Cr(VI) has attracted much scientific attention. In this paper, with the aid of polyoxometalate (POM), Cr(VI) removal increased significantly by acid-washed zero-valent iron (ZVI) under acid conditions in air. POM can mediate the electron transfer from ZVI surface to O2 with enhancing the generation of H2O2, which is favorable for the removal of Cr(VI). The effects of iron loadings, POM concentrations, and initial pH values on the removal of Cr(VI) in ZVI/POM/air system were investigated and reaction mechanism was studied. Results indicated that POM is an efficient catalyst for Cr(VI) removal by acid-washed ZVI.