Kinetics, degradation mechanisms and antibiotic activity reduction of chloramphenicol in aqueous solution by UV/H2O2 process

Abstract

In this study, the aim was to explore the effectiveness of the UV/H2O2 photolysis (UVP) process in terms of antimicrobial activity reduction and increasing the mean oxidation number of carbon (MONC) under the degradation of chloramphenicol (CHPL) drug. CHPL degradation kinetics and the effects of foreign anions on CHPL degradation were explored in this study. The order of the inhibition effect was found as Cl− > NO3− > HCO3− due to their different in HO• radical scavenging capacity. A pseudo-first-order model for CHPL degradation was well established, and the rate constant (kobs) was 2.93 × 10−2 min−1 (R2 = 0.98) in UVP. Thirteen intermediate products were detected in MS-chromatogram and were identified through different proposed degradation pathways. The cleavage of the amide side chain in CHPL was more effective in CHPL degradation due to an electrophilic attacks by HO. radicals on it. The inactivation rates of E. coli were decreased due to the reduction of -NO2 group into -NH2 functional group in CHPL that leads to the production of low toxic compounds on CHPL degradation. HIGHLIGHTS Degradation of chloramphenicol drug occurred by UV-irradiation and hydrogen peroxide together.; HO• radical formed in the presence of H2O2 could effectively contribute to the degradation of CHPL.; MONC was increased with increasing the formation of daughter fragments.; Reduction of CHPL decreases the antimicrobial activity.; Dynamics of drug cleavage follows pseudo-first-order kinetics.;

Keywords

• electrophilic effect
• hydroxyl radical
• mean oxidation number
• photocatalysis
• toxicity