Photochemical Behaviour Of Hexachlorobenzene In Aqueous Phase And Organic Phase

Persistent organic pollutants（POPs）， because of their low photo-degradation,biodegradation,chemical degradation and high toxicity in theenvironment,POPs can abiding existence in the environment.Due to its low watersoluble and high fat soluble,and through the biological web in the environment,POPshave great harm to human health. Hexachlorobenzene（HCB） is one of the POPs,it isstill used to product the Pentachlorophenol（PCP） and Sodium pentachlorophenate（PCP-Na） despite their ban now. The waste water and waste gas containing HCBemissioned by the industrial production can influence the environment,and the HCBadsorbed in atmospheric particulates can make long distance migration and return tothe land with rain and snow,it can have great harm to human and environment withthis cycle.So,study the environmental behavior of HCB has the vital significance.Thesun radiation play an important role to the life on earth,so studying the photochemicalbehavior of HCB have great value to analysis the changes of HCB in theenvironment.For now,the research on nvironmental behavior of HCB are mainly focuson sediments and the soil,and seldom studies on nature water.The paper took the HCB as the research object,and carried out the research onthe photochemical behaviour of HCB in aqueous,and discussed the influence of somefactors on photoconversion of HCB,such as H₂O₂、K⁺、Na⁺、Fe²⁺、Fe³⁺、HCO₃^-、NO₃^-、NO₂^-、SO₄^2-and simulated sunlight/Fenton,and the reaction mechanism was alsodeduced.Because of it is high fat soluble,HCB can exist easily in the organic matter,sowe choose the organic solvent as simulation of the composition of plant skin to studythe photochemical behaviour of HCB.The photoconversion of HCB in aqueous phase by UV follows the first-orderkinetic reaction mode,the main production of the photoconversion of HCB in aqueousphase were Pentachlorobenzene,1,2,3,5-tetrachlorobenzene,1,2,3,4-tetrachlorobenze-ne and1,2,4,5-tetrachlorobenzene.The conversion rate of HCB increased with the increase of the initial concentration of H₂O₂, the main production of thephotoconversion of HCB in aqueous phase were Pentachlorobenzene,1,2,3,5-terachlorobenzene,1,2,3,4-tetrachlorobenzene and1,2,4,5-tetrachlorobenzene.The photoconversion of HCB was accelerated under the condition of pH=7.48; NO₂^-suppressed the photoconversion of HCB; HCO₃^-and SO₄^2-had little effect on thephotoconversion of HCB;the effects of NO₃^-on the photoconversion of HCB weredifferent with different concentration.The conversion rate of HCB in organic phase was n-hexane> Methanol>Acetonitrile> Actone.The photoconversion mechanism of HCB in organic phase wasreductive dechlorination. The main production of the photoconversion of HCB werePentachlorobenzene,1,2,3,5-terachlorobenzene,1,3,5-trichlorobenzene1,3,4-trichlor-obenzene and1,3-dichlorobenzene in n-hexane,and in Methanol werePentachlorobenzene,1,2,3,5-terachlorobenzene,1,2,4,5-terachlorobenzene,and inAcetonitrile were Pentachlorobenzene,1,2,3,5-terachlorobenzene,1,2,4,5-terachlorobenzene,1,3,4-trichlorobenzene. The main production of thephotoconversion of HCB in Actone were Pentachlorobenzene,1,2,3,5-terachloroben-Zene and Benzene.The conversion rate of HCB was high under the condition oforganic solvent content was20%while it was low under the condition of organicsolvent content was0.2%in Methanol and Acetonitrile; the effects of Actone on thephotoconversion of HCB were different with different concentration.The oxidability of simulation sun light/Fenton was stronger than Fenton, Fe²⁺andH₂O₂for HCB. NO₂^-, HCO₃^-, strong acid and alkaline conditions suppressed thephotoconversion of HCB; NO₃^-had little effect on the photoconversion of HCB underthe condition of simulation sun light/Fenton.