Insight into the action of magnetite loaded with nano Ni/Fe bimetallic particles (Ni4/Fe@Fe3O4) toward carbon tetrachloride degradation in aqueous solution

Abstract

Nanometer zero-valent iron (nZVI), Fe2+ and H2 were potential electron donors for CT removal by nZVI. However, the action of these electron donors in CT reduction was often ambiguous. In this study, the actual catalytic activity of Ni4/Fe@Fe3O4 under common ions and humic acid (HA) was investigated. The results showed that Na+ and K+ had no effect on CT removal, Cl‐, SO42‐ and low concentration of Mg2+ was beneficial to CT removal, while NO3‐, HCO3‐, Ca2+ and HA exhibited the negative effects. According to the analysis results of gas chromatography (GC) and ion chromatography (IC), a possible dechlorination pathway of CT was proposed. Furthermore, the action mechanism of nZVI, Ni0 and magnetite (Fe3O4) on CT removal were explored. Among the three possible nZVI reducing mechanism, the use of H2 by Ni0 for the hydrodechlorination was dominant, while the direct reduction of nZVI was secondary. Fe2+, the product of nZVI corrosion, contributed little to CT degradation and required longer reaction time. Ni0 could not only utilize H2 but also form galvanic cells with nZVI to accelerate CT dechlorination. In addition, the support Fe3O4 significantly improved the dispersion of Ni/Fe nanoparticles and its corrosion product Fe2+ also promoted the CT removal. These findings were significant for comprehending the mechanisms of bimetallic nanocomposites in reducing CT, and might guide to the development of nZVI based technology for repairing polluted water or soil with organochlorine pollutants.