Reaction rate constant of phosphate esters with hydroxyl radicals investigated using fluorescence probe method
The strong fluorescence of 7-hydroxycoumarin yielded by the reaction of coumarin with hydroxyl radicals(·OH)was used as a fluorescent probe to determine the yield of 7-hydroxycoumarin aqueous solutions with different concentrations of TBP and TiAP after gamma ray irradiation.The reaction rate constants of TBP and TiAP with·OH at room temperature were determined via pseudo-first order kinetic fitting(kTBP=(9.0±0.2)×109 L/(mol·s)and kTiAP=(5.3±0.2)×109 L/(mol·s)),respectively.Owing to the stronger hydrophobicity of TiAP compared with that of TBP,its reaction rate constant with·OH is lower than that of TBP,thus resulting in a higher yield of·OH in the TiAP solution compared to the TBP solution with the same concentration.This study provides a simple,convenient and efficient method for investigating the reactions between extractants and·OH.