Kinetics Study on the Degradation of Tri-ethyl Phosphate in O3, UV, and UV/O3 Treatments

Tri-ethyl phosphate (TEP) degradation is an important water treatment process, and here, we report on the study of O3, UV, and UV/O3 effects. Aqueous TEP solutions containing an initial concentration of 50 ppm phosphorus were treated, respectively, at ambient temperature for different amount of time, and the resulted phosphate ions was quantitatively determined by ion chromatography. Corresponding TEP concentration change was calculated based on the measured phosphate content. Using the integration method, we were able to estimate the reaction order of TEP degradation together with the reaction rate constant. It was found that O3 or UV alone hardly reacts with TEP, even with a prolonged digestion time of 50 min. In contrast, a TEP digestion ratio as high as 98.3 % has been recorded with the UV/O3 treatment. The hydroxyl radicals produced by UV/O3 are believed to play the critical role in TEP degradation. Reaction between hydroxyl radicals and TEP follows first-order kinetics with the reaction rate constant of 0.082. Thus, a mathematical model for predicting evolution of TEP concentration during the degradation process has been established.