Photochemical degradation of carbofuran and elucidation of removal mechanism

Carbofuran removal by the photo-Fenton reaction was investigated under various H2O2 dosage rate (0–6 mg L−1 min−1) and Fe3+ dosage (5–50 mg L−1). The outcomes demonstrate that the photo-Fenton reaction was influenced by both the factors. An initial carbofuran concentration of 50 mg L−1 was completely degraded within 30 min, and 93% dissolved organic carbon (DOC) removal was observed after 120 min of treatment at initial pH 3, H2O2 dosage rate of 4 mg L−1 min−1 and Fe3+ dosage of 35 and 50 mg L−1. However, no significant improvement in the carbofuran removal was observed when the H2O2 dosage rate and Fe3+ dosage were increased beyond 4 mg L−1 min−1 and 35 mg L−1, respectively. The carbofuran removal was fitted using the pseudo-first order reaction model and the highest apparent rate constant of 10.5 × 10−2 min−1 was obtained. Five major carbofuran intermediates were identified, which indicate that C–O bond of the carbamate group and 3-C position of the furan ring were oxidized as a result of the photo-Fenton reaction.