The photochemical degradation of bisphenol A(BPA)was studied in the presence of natural humic sub stances from different origins under simulated solar irradiation.BPA underwent insignificant direct photolysis in neutral water,but rapid photosensitized degradation in four humic substances solutions via pseudo-first-order reaction occurred.The photo-degradation rate of BPA was insensitive to the different initial BPA concentrations and was inhibited in aerated solution compared with the deoxygenated medium.The reactive oxy-gen species(ROS)such as·OH and 1O2 produced from excita-tion of humic substances under irradiation was determined from the quenching kinetic experiment using molecular probe.The five main intermediate photoproducts of BPA in Nordic lake fulvic acid(NOFA)were tentatively identified using gas chromatography/mass spectrometer(GC/MS).Based on the identification of ROS and the analysis of photoproduct formation,the possible phototransformation pathways of BPA were proposed,involving the direct pho-tolysis due to the energy transfer from the triplet state humic substance(3HS*)to BPA molecules and hydroxyl radical addition and oxidation as well.
The aqueous photodegradation of bisphenol A (BPA) in the presence of F e(Ⅲ)-oxalate complexes (Fe(Ⅲ)-Ox), which are common compositions of natural wa ter, was investigated in this study. BPA underwent rapid indirect photolysis in Fe(Ⅲ)-Ox solution under simulated solar irradiation, proceeding pseudo-first-or der kinetics. The photolysis rate increased with decreasing pH or initial BPA le vel and increasing Fe(Ⅲ)/oxalate concentration ratio. Hydroxyl radicals (·OH) , which were generated from the photochemical processes of Fe(Ⅲ)-Ox complexes and contributed to the photooxidation of BPA, were determined by molecular pro be and electron spin resonance (ESR) methods with the steady-state concentration of 2.56×10-14 mol/L. Superoxide anion radical(O2·-) was consi- dered as the p recursor of ·OH and qualitatively determined by adding nitro blue tetrazolium a s well as ESR experiments. Based on the structural analysis of the intermediat e photoproducts of BPA in Fe(Ⅲ)-Ox complexes solution, the possible degradation pathways of BPA were proposed, involving ·OH addition, alkyl scission and alky oxidation. The results indicate that the photochemical reactivity of Fe(Ⅲ) may affect the environmental fate of BPA in natural water significantly.
