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

A bimetallic nanocomposite, named as Ni 4 /Fe@Fe 3 O 4 , which was prepared via loading Fe/Ni bimetallic onto magnetite (Fe 3 O 4 ), 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 Ni 4 /Fe@Fe 3 O 4 dosage on the reaction system were studied. The experimental results showed that the nanoscale Ni/Fe@Fe 3 O 4 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 Ni 4 /Fe@Fe 3 O 4 . The degradation kinetics of CT by Ni 4 /Fe@Fe 3 O 4 nanocomposites was conformed to the pseudo first-order kinetics and the activation energies (Ea) was 25.87 kJ/mol. Moreover, Ni 4 /Fe@Fe 3 O 4 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 Fe 2+ released by Ni 4 /Fe@Fe 3 O 4 . (4) Ni 0 might induce the conversion of H 2 to active atomic hydrogen (·H) to degrade chloromethane. These results exhibited that Ni 4 /Fe@Fe 3 O 4 will be a nanocomposite with great application potential for CT degradation from aqueous solutions. • Bimetallic nanocomposite Ni 4 /Fe@Fe 3 O 4 exhibited obvious superiority in CT degradation. • Ni 4 /Fe@Fe 3 O 4 had good reusability and stability. • The degradation by-products of CT were monitored in real time. • The possible removal mechanism of CT by Ni 4 /Fe@Fe 3 O 4 were proposed.