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

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)-O-center dot) 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)-O-center dot 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.