[Degradation of diuron by persulfate oxidation activated by EDTA-ferrous ion in aqueous system].

The method of diuron [3-(3,4-dichlorophenyl)-1, 1-dimethylurea] degradation by persulfate oxidation activated by EDTA-ferrous ion in aqueous system was conducted. Based on both of the degradation performance and the operating costs, optimal reaction condition was proposed. Operating at K2S2O8 initial concentration 2.0 mmol x L(-1), Fe(II) initial concentration 1.0 mmol x L(-1), EDTA initial concentration 0.5 mmol x L(-1), reaction time 300 min and pH = 7.0, about 67.6% of 0.1 mmol x L(1) diuron was degradation. Hydroxyl radicals and sulfate radicals produced in the system were determined by molecular probes (ethanol and tert-butanol) methods. The degradation products of diuron were identified with LC/MS methods and the degradation pathways of diuron were discussed.

Photodegradation of bisphenol A in Fe(III)-oxalate complexes solution.

The aqueous photodegradation of bisphenol A (BPA) in the presence of Fe(III)-oxalate complexes (Fe(III)-Ox), which are common compositions of natural water, was investigated in this study. BPA underwent rapid indirect photolysis in Fe(III)-Ox solution under simulated solar irradiation, proceeding pseudo-first-order kinetics. The photolysis rate increased with decreasing pH or initial BPA level 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 probe and electron spin resonance (ESR) methods with the steady-state concentration of 2.56 x 10(-14) mol/L. Superoxide anion radical (O2*-) was considered as the precursor of *OH and qualitatively determined by adding nitro blue tetrazolium as well as ESR experiments. Based on the structural analysis of the intermediate 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.

Determination of hydroxyl radicals with salicylic acid in aqueous nitrate and nitrite solutions.

The qualitative and quantitative analyses of reactive oxygen species are essential to determine their steady-state concentration and related reaction mechanisms in environmental aquatic systems. In this study, salicylic acid was employed as an innovative molecular probe of hydroxyl radical(OH) generated in aqueous nitrate and nitrite solutions through photochemical reactions. Kinetic studies showed that the steady-state concentrations of OH in aqueous NO3- (10 mmol/L, pH = 5) and NO2- (10 mmol/L, pH = 5) solutions under ultraviolet irradiation were at a same magnitude, 10(-15) mol/L. Apparent quantum yields of OH at 313 nm were measured as 0.011 and 0.07 for NO3- and NO2- respectively, all comparable to the results of previous studies.