Effects of environmental factors on sulfamethoxazole photodegradation under simulated sunlight irradiation: Kinetics and mechanism

摘要

To advance the knowledge of the environmental fate of sulfamethoxazole(SMX),we systematically investigated the effects of natural water constituents and synthetic substances(i.e.,TiO2 nanoparticles(nTiO2) and Ti-doped β-Bi2O3(NTB)) on the photodegradation kinetics of SMX under xenon lamp irradiation.The photolysis of SMX in aqueous solution followed first-order kinetics.Our results showed that higher concentrations of SMX,fulvic acid,suspended sediments,NTB and higher pH value decreased the photodegradation rates of SMX,whereas H2O2 improved the SMX photodegradation.TiO2 nanoparticles had a dual effect on photodegradation due to their photocatalytic activity and photoabsorption of photons.No intermediates more toxic toward Vibrio fischeri than SMX were produced after direct photolysis and photocatalytic degradation for 3 hr.The photolysis of SMX involved three pathways:hydroxylation,cleavage of the sulfonamide bond,and fragmentation of the isoxazole ring.This study lays the groundwork for a better understanding of the environmental fate of SMX.