Catalytic oxidative removal of 2,4-dichlorophenol by simultaneous use of horseradish peroxidase and graphene oxide/Fe3O4 as catalyst

• 2,4-DCP could be efficiently removed by the combination of HRP and GO/Fe3O4 with H2O2 as oxidant.
• A synergistic effect was observed between HRP and GO/Fe3O4 for the oxidation of 2,4-DCP.
• Reaction conditions such as pH, temperature, loads of HRP, H2O2 and GO/Fe3O4 were optimized.
• A possible pathway was proposed for the oxidative removal of 2,4-DCP in the system of GO/Fe3O4–HRP.

A composite of graphene oxide and nano-Fe3O4 (GO/Fe3O4) was prepared and characterized as an artificial enzyme-like catalyst. By combining the artificial enzyme-like catalyst and a natural enzyme horseradish peroxidase (HRP) as a binary enzymatic catalyst, the catalytic oxidative removal of 2,4-dichlorophenol (2,4-DCP, 50 mg L−1) was achieved in the presence of H2O2 (0.7 mmol L−1) in aqueous media at near neutral pH value (pH 6.4) and room temperature. It was observed that the single use of HRP and GO/Fe3O4 produced a 2,4-DCP removal of 35% and 9%, respectively, whereas their simultaneous use yielded a removal as high as 93%. This indicates that there is a synergistic effect between GO/Fe3O4 and HRP. The effects of initial pH value, temperature, initial concentrations of HRP, GO/Fe3O4 and H2O2 were optimized. The intermediate products during the catalytic oxidation of 2,4-DCP in the system of GO/Fe3O4–HRP were identified by gas chromatography/mass spectrometry, and the possible degradation pathway of 2,4-DCP was proposed. In addition, the GO/Fe3O4 composite could be easily separated from the reaction solution with a magnetic field, and the recycled GO/Fe3O4 showed a good catalytic stability.

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