[Photolysis Mechanism of p-Nitrophenol by Nitrocellulose Membrane in Aqueous Solution]

To investigate the potential application of nitrocellulose membrane (NCM) in water treatment, this study examined the photolysis of p-nitrophenol, with NCM as the source of reactive oxygen species. Effects of solution pH, light conditions, and water dissolved substances on p-nitrophenol photolysis were investigated, and possible mechanisms were discussed. The results demonstrated that the quantum yield for hydroxyl radicals from the NCM was 1.30×10^-4, which is approximately 1.86 times higher than that from TiO₂. The photolysis rate of p-nitrophenol in the presence of NCM was 0.0055 min^-1, which is much higher than that in pure water (9.52×10^-4 min^-1). This promotion was mainly caused by photo-induced generation of ·OH on NCM surface under light, in which UVA plays an important role in photolysis. The photolysis rate of p-nitrophenol increased with the increase of light intensity and membrane area. Acidic solution (pH=2.0) was preferred for the degradation of p-nitrophenol, with a photolysis rate of 0.0165 min^-1; the corresponding degradation of p-nitrophenol exceeded 90% in 120 min. The effects of dissolved substances on photolysis were significantly different. NO₃^- promoted photolysis by generation of ·OH, and dissolved organic matter decreased photolysis through light attenuation. The intermediate products of gas chromatography-mass spectrometry analysis mainly included phenol, hydroquinone, malonic acid, and oxalic acid, and the possible photolysis pathway was given accordingly.