Research On Low Concentration Xylene Degradation By H₂O₂ Enhanced Uv Photocatalysis

As a kind of typical VOCs,xylene is widely used in various industrial fields.If xylene directly discharges into the atmosphere without governance,it would be a potential threat to human health.In this paper,the effects of reinforced UV-photo--catalytic oxidation by H₂O₂ on the degradation of low concentration of xylene,the reaction parameters of strengthening UV and photo catalysis by H₂O₂were studied.At the same time,xylene’s degradation mechanism was analyzed.The results shows that using ultraviolet alone,the degradating effect under the wavelength of 185 nm UV light was better than 254 nm UV light obviously.Relative humidity is the key factor to the degradation efficiency.Photolysis could barely oxidize xylene.However,under high humidity conditions,photolysis could produce hydroxyl radical which can degradate the xylene efficiently.When the initial concentration of xylene was 100mg/m³,the residence time was 60 s and relative humidity was 60-65%,the degradation rate of xylene could reach 38.6%.Hydrogen peroxide could improve ultraviolet degradation efficiency of xylene effectively.When wavelength was 185 nm,pH=3,hydrogen peroxide concentration was 30%,initial concentration of xylene was 100 mg/m³ and the relative humidity was 65%,the degradation efficiency of xylene could reach 60.3%.As a kind of catalyst,TiO₂ can cooperate with ultraviolet to degradate xylene.Under this condition,the degradation rate of xylene was 82.7%and the reaction rate constant was 0.031s^-1.The rate constant of UV185nm+H₂O₂+TiO₂ was 7.8 times higher than technology of UV254nm+H₂O₂.It was also 2.21 times higher than UV185nm+H₂O₂,and 1.3 times higher than UV254nm+H₂O₂+TiO₂.But mineralization rate of xylene was just 11%.Therefore,most of xylene was converted to intermediate based on material balance.The hydrogen peroxide can significantly enhance photocatalytic to degradate xylene.The synergy of UV185 nm and hydrogen peroxide was the best,but the project application is limited because of higher residence time and demanding operating conditions.