Identification of intermediates and transformation pathways derived from photocatalytic degradation of five antibiotics on ZnIn2S4

A comprehensive study of degradation efficiency and transformation pathways derived from photocatalytic degradation of five antibiotics including tetracycline hydrochloride, chloramphenicol, rifampicin, lincomycin hydrochloride and erythromycin on ZnIn2S4 under visible light irradiation was investigated. All the five antibiotics cannot be detected after 90 min photocatalytic degradation by ZnIn2S4. The calculated pseudo-first-order constants (kr) were in the order of tetracycline hydrochloride (0.0858 min−1) > erythromycin (0.0846 min−1) > lincomycin hydrochloride (0.0285 min−1). However, degradation of rifampicin and chloramphenicol cannot be described by pseudo-first-order reaction kinetics. The electron paramagnetic resonance (EPR) results indicated that the main reactive oxygen species in this study was superoxide radical (O2-) and minor active species was hydroxyl radical (OH). Thirty-four, thirty, twenty, sixteen and eighteen kinds of intermediate species were identified by LCMS-IT-TOF during the 180 min photocatalytic degradation of rifampicin, erythromycin, chloramphenicol, lincomycin hydrochloride and tetracycline hydrochloride, respectively. The proposed photocatalytic degradation pathways provided detailed evolution process of five antibiotics, which would be meaningful for the researches on transformation behavior of antibiotics.