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

Nanometer zero-valent iron (nZVI), Fe 2+ and H 2 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 Ni 4 /Fe@Fe 3 O 4 under common ions and humic acid (HA) was investigated. The results showed that Na + and K + had no effect on CT removal, Cl ‐ , SO 4 2 ‐ and low concentration of Mg 2+ was beneficial to CT removal, while NO 3 ‐ , HCO 3 ‐ , Ca 2+ 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, Ni 0 and magnetite (Fe 3 O 4 ) on CT removal were explored. Among the three possible nZVI reducing mechanism, the use of H 2 by Ni 0 for the hydrodechlorination was dominant, while the direct reduction of nZVI was secondary. Fe 2+ , the product of nZVI corrosion, contributed little to CT degradation and required longer reaction time. Ni 0 could not only utilize H 2 but also form galvanic cells with nZVI to accelerate CT dechlorination. In addition, the support Fe 3 O 4 significantly improved the dispersion of Ni/Fe nanoparticles and its corrosion product Fe 2+ 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. • Common ions and humic acids affected the actual activity of Ni 4 /Fe@Fe 3 O 4 . • The use of H 2 by Ni 0 for the dechlorination was the main mechanism of CT removal. • Ni 0 accelerated n-ZVI corrosion and the electron transfer between nZVI and CT. • Ni 4 /Fe@Fe 3 O 4 nanocomposite was a promising technology for CT removal.