Photodegradation of Chloramphenicol by UVA/Fe(III)/PMS for Antibiotic-Contaminated Wastewater: Degradation Kinetics and Mechanisms.

Abstract

The recalcitrance of chloramphenicol (CAP) in aquatic environments necessitates efficient advanced oxidation processes (AOPs). Herein, a UVA (350 nm)-driven Fe(III)/peroxymonosulfate (PMS) system was developed for CAP removal. The ternary UVA/Fe(III)/PMS system achieved complete CAP removal within 15 min at initial concentrations of 0.01 mM CAP, 0.06 mM Fe(III), and 0.08 mM PMS. For such ternary system, UVA irradiation (350 nm) exhibited a higher apparent degradation rate constant than UVC irradiation (254 nm), with kobs increasing from 0.219 to 0.317 min-1. CAP degradation was strongly influenced by solution pH and PMS dosage, with optimal performance at an initial pH of 3.4 and a Fe(III)/PMS molar ratio of 3:4. The presence of inorganic anions affected degradation, particularly HCO3- (10 mM), which reduced kobs by approximately 94%. Compared with conventional pseudo-first-order kinetics, an empirical hyperbolic model better described the initial rapid removal and subsequent deceleration (R2 ≥ 0.99), providing separate indicators of initial degradation rate and apparent oxidation capacity. Quenching experiments identified hydroxyl radical as the predominant reactive species, and LC-MS analysis detected 13 intermediates associated with side-chain oxidation and C-N bond cleavage. Multi-endpoint quantitative structure-activity relationship predictions revealed reduced developmental toxicity scores but variable aquatic toxicity among transformation products. Overall, this study demonstrates rapid CAP removal by UVA/Fe(III)/PMS and provides a kinetic framework for evaluating oxidant-limited AOP processes.

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