Removal of hexavalent chromium in soil and groundwater by supported nano zero-valent iron on silica fume

Abstract

Silica fume supported-Fe0 nanoparticles (SF-Fe0) were prepared using commercial silica fume as a support. The feasibility of using this SF-Fe0 for reductive immobilization of Cr(VI) was investigated through batch tests. Compared with unsupported Fe0, SF-Fe0 was significantly more active in Cr(VI) removal especially in 84 wt% silica fume loading. Silica fume had also been found to inhibit the formation of Fe(III)/Cr(III) precipitation on Fe nanoparticles' surface, which was increasing the deactivation resistance of iron. Cr(VI) was removed through physical adsorption of Cr(VI) onto the SF-Fe0 surface and subsequent reduction of Cr(VI) to Cr(III). The rate of reduction of Cr(VI) could be expressed by pseudo first-order reaction kinetics. The rate constant increased with the increase in iron loading but decreased with the increase in initial Cr(VI) concentration. Furthermore, column tests showed that the SF-Fe0 could be readily transported in model soil.