Mechanism of dual reduction centers containing nano zero-valent iron and single-atom iron carbon spheres for removing hexavalent chromium from water

Abstract

The passivation and agglomeration issues of ZVI were effectively addressed through the preparation of a carbon-coated material (ZVI/BC-0.8–800) containing embedded iron atoms and nZVI，which exhibits excellent reducing properties towards Cr(Ⅵ). Our results demonstrate that ZVI/BC-0.8–800 possesses iron atoms and nZVI, achieving a remarkable removal rate of 99.8 % for Cr(Ⅵ) within 20 minutes, surpassing that achieved by commercial nZVI. Moreover, nearly all Cr(Ⅵ) is reduced to Cr(III). After ageing different water bodies or in the air for 15 days, the removal rate of ZVI/BC-0.8–800 remains at approximately 70 % when placed in water reaches up to 95 % in air. This efficient and stable removal is due to the protective effect of carbon materials, and the presence of iron atoms and nZVI as the double reduction center in the Cr(Ⅵ) removal process, which enhances the reduction effect. The respective contribution rates from iron atoms and nZVI are 29.13 % and 50.32 % respectively. Overall, this multi-form composite with double reduction centers consisting primarily of nZVI embedded within a carbon material holds great promise for in-situ groundwater remediation applications.