Kinetics, degradation pathway and reaction mechanism of advanced oxidation of 4-nitrophenol in water by a UV/H2O2 process

Photooxidation of 4-nitrophenol (4-NP) in water by the UV/H2O2 advanced oxidation process was carried out in order to investigate the kinetics and pathway of 4-NP degradation. The experimental results showed that the photodegradation of 4-NP accorded well with pseudo-first order kinetics. The effects of different parameters, such as H2O2 dosage, pH value and various anion scavengers on the degradation of 4-NP have been investigated in detail. It was found that acidic conditions are more favorable to the degradation of 4-NP but many anions, such as HCO3-, NO3- and Cl-, slow down the photooxidation rate of 4-NP. Hydroquinone, 1,2,4-trihdroxybenzene, 4-nitropyrogallol, and 4-nitrocatechol were tentatively identified as the intermediates of 4-NP degradation by GC/MS after samples were derivatized by N,O,bis(trimethylsilyl)-trifluoroacetamide (BSTFA). A degradation pathway was proposed to account for the observed intermediates produced during 4-NP degradation by the UV/H2O2 process. (C) 2003 Society of Chemical Industry.