Degradation of Trichloromethane by the Combination of UV Irradiation and Peroxymonosulfate

Trichloromethane (TCM) is a harmful halogenated organic compound usually used in the industry and a typical disinfection by-product in the water treatment with the use of chorine as disinfectant. The degradation of TCM by peroxymonosulfate combined with UV irradiation at λ= 254 nm (UV/PMS) was investigated. Results showed that TCM was efficiently degraded by UV/PMS and about 80% of TCM was decomposed when the concentration of PMS was 0.5mM. Radical-scavenging experimental results indicated that both HO • and SO 4 •- might contribute to the degradation of TCM. However, HO • might first be captured by PMS to form SO 5 •- and then partly decomposed into SO 4 •- , which might react with TCM. The increased concentration of PMS led to the increased removal efficiency of TCM. Whilst, the efficiency was little affected by initial concentration of TCM, indicating that there might be competition reaction with TCM degradation for radicals.