Degradation of trimethoprim by sulfate radical-based advanced oxidation processes: kinetics, mechanisms, and effects of natural water matrices

In this study, we investigated the removal efficiency of a broad-spectrum antimicrobial agent trimethoprim (TMP) in a UV-activated persulfate system(UV/PS). The pseudo-first-order reaction kineticmodel based on the steady-state hypothesis was used to explain TMP degradation behavior in UV-activated persulfate system. Due to the low quantum yield and molar absorptivity of TMP at 254 nm, the direct photolysis of TMP was slower. Since the free radicals generated by adding H2O2 or PS to the system can react with TMP, the degradation rate was significantly accelerated, and SO4 center dot- played a dominant role in the UV/PS system. k(HO center dot,TMP) and k(SO4 center dot-,TMP) were determined by the pseudo-first-order reaction kinetic model to be 6.02x10(9) and 3.88x10(9) M(-1)s(-1), respectively. The values were consistent with competitive kinetic measurements. The pseudo-first-order reaction kinetics model can predict and explain the effect of PS concentration, natural organicmatter, and chloride ion on the TMPdegradation in the UV/ PS system. The observed pseudo first-order rate constants for TMP degradation (k(obs)) increased with the persulfate concentration, but it significantly decreased in the presence of NOMand chloride. SO42- has no effect on the degradation of TMP, while HCO3- promotes the degradation and NO3- inhibits the degradation. The common transition metal ion (such as Cu2+, Zn2+, and Co2+) in industrial wastewater has a synergistic effect on theTMP degradation in theUV/PS system, but excessivemetal ions will lead to a decrease of the degradation rate.

Automated summary

The study found that free radical reactions in UV-activated persulfate systems significantly promoted the degradation of trimethoprim (TMP). Factors such as persulfate concentration, natural organic matter, and chloride ions all influence the degradation rate of TMP. Transition metal ions in industrial wastewater have a synergistic effect on TMP degradation in UV/PS systems.