Studies On Photodegradation Of Bromobenzene In Waters Under Simulative Sunlight Irradiation

It has been widely accepted that the active species in the hydrosphere are ubiquitously involved in the oxidation process of organic pollutants and can therefore exert significant impact on the transfer,conversion,fate and ecological effect of these compounds.Nevertheless,the microscopic researches on the kinetics,mechanisms and detailed reaction pathways of these processes are relatively few.Bromobenzene widely exists as one of the organic pollutant in waters.It is one of the organic intermediates in chemical synthetical processes and the representation of halogenated aromatics and organic solvent.Bromobenzene brings harmfulness to entironment and people's health.So how to degrade those contaminations is significative in entironment scientific research.The research progresses in degradation technologies of benzene or some of its derivatives in water are reviewed.The macroscopical reaction mechanism of HNO2(NO2-)and C6H5Br in aqueous solution has been studied.Different influence factors have been discussed,including different pH condition,initial concentration,irradiation time,different anions and the optimization of experimental conditions.By using liquid chromatography,the degradation rate of bromobenzene has been qualitatively analyzed.The concentration variations of Br~and NO2- have been analyzed by using ion chromatography.The reaction mechanism of HNO2 and C6H5Br in aquepus solution with the presence of O2 or absence of O2 is studied by laser flash photolysis transient absorption spectrum technique under irradiation at 355nm.The intermediate and final products have been analyzed after the irradiation of laser.The photolysis mechanism of C6H5Br…OH has been discussed.The main research results are listed as below; (1)The constant of action of C6H5Br with NO2- was negatively correlated with the.initial concentration of C6H5Br.The initial concentration of NaNO2 had influence on the degradation rate of C6H5Br.The degradation rate increased along with the initial concentration of NaNO2.The rate constant K was linear correlated with the concentration of NaNO2.The degradation rate of C6H5Br was faster under the acidic condition than the alkaline condition.Cl-,PO43-,SO42-,CO32-,NO3-restrained the degradation of C6H5Br.Br- was produced after irradiation.GC-MS analysis suggested the formation of bromophenol and nitrophenol.(2)The reaction mechanism of HNO2 and C6H5Br in aqueous solution was caused by the generation of OH radical through the photolysis of HNO2.The OH radical was added to bromobenzene by a second-order rate constant of 8.1×109 L·mor·s-1 to form an OH-adduct,C6H5Br…OH.The second-order rate constant of C6H5Br…OH with HNO2 was 3.0×107 L·mol-1·s-1.C6H5Br…OHO2 produced by the reaction of C6H5Br…OH with O2 decayed by a constant of 2.4×104 s-1.GC-MS analysis suggested the formation of multiple compounds containing nitryl or quinone through reaction of C6H5Br…OH with HNO2 or O2.