Study On Dechlorination Of 2,4,6-Trichlorophenol By Ultraviolet Advanced Reduction Processes

Chlorinated organic compounds are common organic matter, which are widely used in production and life. While bringing convenience to the human life, it also caused a lot of pollution. The UV advanced reduction method was proved to be an effective method for the degradation of chlorinated organic compounds.At this stage, the species of ultraviolet lamp and reducing agent is less in the UV advanced reduction method. Low pressure mercury lamp which has the main wavelength of 254 nm is the most widely used. Reducing agent such as sodium sulfite, potassium iodide, ferrous ion, sodium dithionite is the commonly used. There is some other selection on ultraviolet lamp and reducing agents.In this paper, 2,4,6-trichlorophenol was used as the target pollutant, and the removal of chlorine was used as the detection index. Select five kinds of reducing agent(Na2SO3, Na BH4, Na2S2O4, Na H2PO2, Na2S), Na BH4 and Na H2PO2 are studied less as reducing agent in UV advanced reduction metuod. We studied the abliity of dechlorination of reductant on the same wavelength ultraviolet irradiation. At the same time, select three wavelength ultraviolet light(UVC with main wavelength of 254 nm, VUV with wavelength of 254 nm and a small amount of 185 nm, 380-385 nm LED ultraviolet), the excitation function of UV wavelength on reducing agent was discussed. PH is the important factors for the effect of dechlorination.In the research of the UVC advanced reduction method and VUV advanced reduction method, Na BH4 is the best as reducing agent for the chlorine removal of 2,4,6-trichlorophenol. When the concentration of 2,4,6-TCP and Na BH4 was 0.177 mmol/L and 0.885 mmol/L, the solution p H was 11, the removal rate of 60 min was 92% and 82.1% respectively.Na H2PO2 can be activated by UVC to degrate 2,4,6-TCP, making it dechloronation. UVC/Na H2PO2 is a new UVC advanced reduction method.VUV can directly photolysis 2,4,6-trichlorophenol and has a better effect than UVC, because VUV has the higher energy to break the chemical bond. Under the condition of high p H, the effect of UVC advanced reduction method is better than that of VUV advanced reduction method for a reductant. Photolysis of H2 O by VUV can product hydroxyl radical, which react with reducting free racical lead to the decrease of effect of dechlorination.At the same time, through the study of UVA advanced reduction method, we found long wavelength, low photon energy, is not enough to stimulate the activation of the reducing agent, cannot remove chlorine from 2,4,6-trichlorophenol.