Enhanced dechlorination of carbon tetrachloride by Ni-doped zero-valent iron nanoparticles @ magnetic Fe3O4 (Ni4/Fe@Fe3O4) nanocomposites

A bimetallic nanocomposite, named as Ni4/Fe@Fe3O4, which was prepared via loading Fe/Ni bimetallic onto magnetite (Fe3O4), was applied to the reductive dechlorination of carbon tetrachloride (CT) for the first time and was identified by scanning electron microscopy (SEM), X‐ray energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) to explore its structure and properties. The effects of the Ni loading (weight ratio of Fe/Ni), CT concentration, initial solution pH, temperature and Ni4/Fe@Fe3O4 dosage on the reaction system were studied. The experimental results showed that the nanoscale Ni/Fe@Fe3O4 bimetallic particles with a mass ratio of 4% of Ni/Fe exhibited excellent performance for CT degradation. The removal efficiency of CT can reach 96.3% within 35 min with only 0.2 g/L of Ni4/Fe@Fe3O4. The degradation kinetics of CT by Ni4/Fe@Fe3O4 nanocomposites was conformed to the pseudo first-order kinetics and the activation energies (Ea) was 25.87 kJ/mol. Moreover, Ni4/Fe@Fe3O4 presented good reusability and stability after four cycles. Based on the detection results of CT degradation products by gas chromatography (GC), a possible degradation mechanism was discussed, which can be divided into the following ways: (1) Migration and adsorption of CT molecules. (2) Direct reductive dechlorination of CT molecules by nano zero-valent iron (nZVI). (3) Reduction dechlorination of CT by Fe2+ released by Ni4/Fe@Fe3O4. (4) Ni0 might induce the conversion of H2 to active atomic hydrogen (·H) to degrade chloromethane. These results exhibited that Ni4/Fe@Fe3O4 will be a nanocomposite with great application potential for CT degradation from aqueous solutions. [Display omitted] •Bimetallic nanocomposite Ni4/Fe@Fe3O4 exhibited obvious superiority in CT degradation.•Ni4/Fe@Fe3O4 had good reusability and stability.•The degradation by-products of CT were monitored in real time.•The possible removal mechanism of CT by Ni4/Fe@Fe3O4 were proposed.