Photochemical Reaction Of Typical Phenolic Pollutants With Superoxide Anion Radicals In Atmospheric Aqueous Phase

In this paper,the photochemical reactions of superoxide anion radicals with1-naphthol（1-NP）,4-chloro-1-naphthol（4-CN）and ibuprofen（IBP）in atmospheric aqueous phase were studied by combining steady-state experiment with laser flash photolysis.Through steady-state experiment technology,the influence of different reaction conditions(O₂^·-concentration,reactant concentration and p H,etc.)on its steady-state transformation was explored,and the related reaction rate constants were determined.Used GC-MS to identify the reaction products,combine the steady-state and transient results to reasonably deduce the reaction mechanism.In the end,the main conclusions are as follows:（1）Through steady-state experiments,it was found that the conversion rate of1-naphthol was hindered by its initial concentration,and the increase of p H and riboflavin concentration promoted the photochemical reaction.The second order reaction rate constant of the photochemical reaction between 1-NP and superoxide anion radical was（3.64±0.17）×10⁸L mol^-1s^-1,and the main conversion products were 1,4-naphthoquinone and 2,3-epoxy-2,3-dihydro-1,4-naphthoquinone.The conversion rate of 1-naphthol at the air-water interface was higher than that in atmospheric aqueous solution.These results provide an important idea for the study of the photochemical transformation of 1-naphthol in atmospheric environment.（2）Using riboflavin（Rf）irradiated with 365 nm ultraviolet light to produce superoxide anions,the possibility of photochemical reaction in the atmospheric water phase of 4-chloro-1-naphthol reaction was studied.Using laser flash photolysis technology,the second-order reaction rate constant of the photochemical reaction between 4-CN and superoxide anion radical under 355 nm laser excitation was calculated,and the main conversion products were 1,4-Naphthoquinone（1,4-NQ）,5-hydroxy-1,4-naphthoquinone（5-HNQ）.The results of atmospheric model show that the reaction of 4-chloro-1-naphthol with superoxide anion radical was a potential route of pollutant transformation in atmospheric aqueous phase.（3）Steady-state studies had shown that the photochemical reaction of ibuprofen （IBP）with superoxide anion radical was strongly affected by p H value,riboflavin concentration,ibuprofen concentration,chloride ion and carbonate ion.The reaction of the superoxide anion radical with undissociated ibuprofen was dominant at p H below 6.1（k₁α₁﹤k₂α₂）,and when the p H was greater than 6.1,the reaction was dominated by IBP^-（k₁α₁>k₂α₂）.The calculated quantum yield of superoxide anion was 0.036 mol einstein^-1.The photochemical products of ibuprofen and superoxide anion radicals could be obtained by GC-MS as 1-（4-isobutylphenyl）ethanol and4-isobutylacetophenone（IBPE）.