Granular reduced graphene oxide/Fe₃O₄ hydrogel for efficient adsorption and catalytic oxidation of p-perfluorous nonenoxybenzene sulfonate

The catalytic performance of Fe₃O₄/reduced graphene oxide (Fe₃O₄/rGO) nanocomposite makes it attractive for the removal of emerging pollutants from water, but the combination of its efficient adsorption and degradation of per- and polyfluoroalkyl substances has not been studied. Here we report the optimal granular Fe₃O₄/rGO with high thermal and acid resistance stability through controlling its self-assembly for the adsorption and degradation of sodium p-perfluorous nonenoxybenzene sulfonate (OBS) from water. The maximum adsorption capacity for OBS was calculated to be 362.4 μmol/g according to Langmuir fitting. Electrostatic, π-π and hydrogen bonding interactions were involved in OBS adsorption, and the quaternary N in Fe₃O₄/rGO was a key adsorption site. The efficiency of the utilization of free radicals generated in Fenton-like and persulfate (PS) systems increased with the increase of OBS adsorbed onto the Fe₃O₄/rGO, while the increase of OBS amount adsorbed on Fe₃O₄/rGO would casue a slow OBS removal in the adsorption-degradation process due to the slow adsorption process. The Fenton-like oxidation was more efficient for OBS removal than PS oxidation. The spent Fe₃O₄/rGO was able to be reused in the Fenton-like system at least ten times, while the OBS removal in the PS reaction system was reduced to 47.8 % after six reuse cycles.