Effect of nano-scale, reduced graphene oxide on the degradation of bisphenol A in real tertiary treated wastewater with the persulfate/UV-C process

Abstract

In this study, the effect of home-made, reduced graphene oxide (rGO) nanoparticles on persulfate (PS)/UV-C oxidation of bisphenol A (BPA; 8.8 μM), an endocrine disruptor and model micropollutant, in real tertiary treated urban wastewater (TWW) was examined. Experimental results revealed that the presence of rGO induced a significant improvement in the degradation of BPA by the PS/UV-C treatment system. Fast and complete BPA removal accompanied with 44% dissolved organic carbon (DOC) abatement was achieved within 30 min at reaction conditions of 0.01 g/L rGO, 0.125 mM PS, at the natural pH of the TWW (pH = 7.5). This high performance on BPA degradation at the natural pH TWW could be attributable to the synergistic effect between the rGO nanoparticles and the PS/UV-C photochemical oxidation causing additional activation of PS and adsorption of BPA, DOC and degradation products onto the rGO surface. Radical quenching studies revealed that sulfate radicals prevailed over hydroxyl radicals. The Vibrio fischeri bioluminescence inhibition assay indicated that no toxic degradation products were formed during rGO/PS/UV-C treatment. By liquid chromatography time of flight mass spectrometry (LC-TOF-MS) analysis the formation of thirteen degradation products during PS/UV-C and rGO/PS/UV-C treatment of BPA was confirmed. This study underlined that the combined rGO/PS/UV-C treatment process could offer a sustainable, ecotoxicologically safe and kinetically attractive solution for the effective elimination of micropollutants from waters and wastewaters.