| Effects of surfactants on photodegradation of oxytetracycline（OTC） in aqueous solution was investigated with Xe lamp（>290 nm）as simulated sunlight. The photodegradation of OTC at pH=7.5 followed pseudo-first-order kinetics and can be promoted by CTAB, SDS, SDBS and Tween80, in which CTAB exerted the most significant enhancement. The effects of CTAB on the photodegradation of OTC demonstrated pH and concentration-dependent. Photolysis of OTC was inhibited at pH=5.5, whereas it was promoted at pH=7.5 and pH=9.0 by CTAB. A positive correlation between the photolysis rate constants of OTC and the CTAB concentration was observed at pH=7.5. CTAB can decrease the pKa of OTC and thus increase the proportion of anion forms of OTC, which is proposed as an important reason for the promotion effect of CTAB on the photolysis of OTC. In addition, photolysis rate constants of OTC coexisted with CTAB in pure water and surface water were 1.62 and 4.96 times higher than those of OTC alone respectively under natural sunlight. |
