Modeling the Kinetics of UV/Peracetic Acid Advanced Oxidation Process

Peracetic acid combined with UV (i.e., UV/PAA) has emerged as a novel advanced oxidation process (AOP) for water disinfection and micropollutant degradation, but kinetic modeling for this AOP was lacking. In this study, a comprehensive model was developed to elucidate the reaction mechanisms and simulate reaction kinetics of UV/PAA process. By combining radical scavenging experiments and kinetic modeling, accurate quantum yield of PAA under UV254 (Phi = 0.88 +/- 0.04 mol-Einstein(-1)) was determined via simultaneously quenching (OH)-O-center dot and CH3C(O)O-center dot with 2,4-hexadiene. The comparison between experimental observations and model predictions over a wide range of conditions allowed estimation of the rate constants of PAA with (OH)-O-center dot (k center dot(OH/PAA) = 1.3 +/- 0.2 x 10(9) M-1 s(-1)) and HO2 center dot (k(HO2 center dot/PAA) <= 5 x 10(2) M-1 s(-1)) with good accuracy. With derived Phi, k center dot(OH/PAA )and k(HO2 center dot)/PAA the kinetic model accurately predicts PAA decay under UV254 photolysis across varying PAA and H2O2 concentrations and water pH (5.8-7.2). Meanwhile, the model reveals that UV/PAA generates a lower (OH)-O-center dot concentration than UV/H2O2 at equivalent oxidant concentrations, with CH3C(O)OO center dot as the most abundant carbon-centered radical. This study significantly improves the knowledge of reactive species generation and reaction kinetics and mechanisms under UV/PAA, and provides a useful kinetic model for this AOP in water treatment.