Degradation of 4-chlorophenol in a Fenton-like system using Au–Fe3O4 magnetic nanocomposites as the heterogeneous catalyst at near neutral conditions

Abstract

Magnetic Au–Fe₃O₄ nanocomposites with various Au weight loading were synthesized through a one step strategy. The morphology and physicochemical properties of the as-synthesized solids were characterized through various methods. After that, the catalysts were applied to activate H₂O₂ for the degradation of 4-chlorophenol (4-CP). The results showed that Au–Fe₃O₄ can catalyze oxidation of 4-CP efficiently in the presence of H₂O₂ at pH 5, which may be attributed to the synergistic catalysis in the nanocomposites for hydroxyl radical generation. And then, the influence of reaction parameters on the oxidation of 4-CP, including the Au weight loading of the nanocomposites, pH, catalyst dosage, H₂O₂ dosage and temperature, were assessed. The stabilization and reusability of the Au–Fe₃O₄ nanocomposites was shown to be excellent, with no leakage of Au. The hydroxyl radicals (˙OH) were the main reactive radicals released in the Au–Fe₃O₄/H₂O₂ system according to the addition of tert-butanol and the spin-trapping electron paramagnetic resonance (EPR) by means of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), while the ˙OH in the bulk solution acted in the main role for 4-CP degradation. Finally, the mechanism of H₂O₂ activated with Au–Fe₃O₄ for 4-CP degradation was proposed.