Photocatalytic degradation of nitrobenzene in wastewater by persulfate integrated with Ag/Pb3O4 semiconductor under visible light irradiation

Abstract

Nitrobenzene oxidation was executed utilizing an innovative method, in which Ag/Pb3O4 semiconductors irradiated by visible light were used for activation of persulfate into sulfate radicals. Batch mode experiments were accomplished to elucidate the effect of persulfate concentrations and Ag/Pb3O4 dosages on the nitrobenzene oxidation behaviors. The physicochemical properties of original and reacted Ag/Pb3O4 were illustrated by X-ray diffraction analyses, UV-Vis diffuse reflectance spectra, FE-SEM images, EDS analyses, photoluminescence spectra and X-ray photoelectron spectra, respectively. The main oxidant was hypothesized to be sulfate radicals, induced from persulfate caused by photocatalysis of Ag/Pb3O4. It was clearly reflected on the scavenging experiments with addition of benzene, ethanol and methanol individually. As far as degradation pathways concerned, nitrobenzene was essentially transformed into hydroxycyclohexadienyl radicals, and sequentially converted to 2-nitrophenol, 3-nitrophenol or 4-nitrophenol simultaneously. Denitration of nitrophenols gave rise to synthesis of phenol, followed with generation of hydroquinone and p-benzoquinone.