Photoelectrocatalytic degradation of p-chloronitrobenzene by g-C3N4/TiO2 nanotube arrays photoelectrodes under visible light irradiation

Abstract

As a typical refractory pollutant, p-chloronitrobenzene (p-CNB) from industrial wastewater poses a serious threat to the aquatic environment safety and human health. The photoelectrocatalytic (PEC) technology is regarded as a promising and cleaner approach for p-CNB removal. Therefore, the graphitic carbon nitride (g-C₃N₄) modified TiO₂ nanotube arrays (g-C₃N₄/TNAs) were prepared as the photoelectrodes for p-CNB degradation. The PEC degradation efficiency for p-CNB by g-C₃N₄/TNAs (0.00484 min^-1) was much higher than that by bare TNAs (0.00135 min^-1) under visible light. The g-C₃N₄/TNAs photoelectrodes exhibited excellent visible-light response, efficient charges separation and high redox potentials of electron/hole, which was favorable for p-CNB degradation. The radical scavenging experiments indicated that both reductive electrons and oxidized species (holes and ·OH) played crucial roles simultaneously during the dechlorination process, whereas the mineralization of p-CNB mainly depended on the photo-generated holes and ·OH. The degradation pathways of p-CNB were proposed through GC/MS spectra. The acute toxicity, bioaccumulation factor and mutagenicity of identified intermediates were reduced after PEC degradation by g-C₃N₄/TNAs photoelectrodes. The Z-scheme g-C₃N₄/TNAs provided an efficient approach for simultaneous dechlorination and mineralization of refractory pollutants.

Keywords: Dechlorination; Graphitic carbon nitride; Photoelectrocatalytic degradation; TiO(2) nanotube arrays; p-Chloronitrobenzene.