Study On Photocatalytic Degradation Of Dye

In this paper, the TiO2 powder and SO^2-₄ /Fe₂O₃-TiO₂ composite wereprepared by the sol-gel method using ethanol as the solvent. Thestructures of TiO₂ powder and SO^2-₄ /Fe₂O₃-TiO₂ composite were analyzedby thermograrimetric analysis, transmission electron microscopy, X-raydiffraction. The results show that the diameter of the powder is nanometer;the temperature and time of annealing affected the proportion of theanatase and the rutile; the weight of the pioneer of TiO2 is invariableexceed 510℃, the loss of the weight is 24.98%; the weight of the pioneerof SO^2-₄ /Fe₂O₃-TiO₂ is invariable exceed 500℃,the loss of the weigh ofthe pioneer is 20.7%. It was found that the photocatalytic activity of TiO₂is the highest calcined at 550℃ for 2h。While the SO^2-₄ /Fe₂O₃-TiO₂ hashighest photocatalytic activity calcined at 500℃ for 2h.Thephotocatalytic reactivity of SO₄ /Fe₂O₃-TiO₂ is higher than that of TiO2,and the best amount of n(Ti):n(Fe) is 6:1. TiO₂/UV and SO^2-₄ /Fe₂O₃-TiO₂/UV photocatalytic degradation ofcongo red, alizarine green, crystal violet, had been investigated. Theinfluence of initial pH, the reaction temperature, the amount of catalystand the reaction time had been investigated. Using TiO₂ as thepotocatalyst, the conditions as follow: the initial dye solution wasalkalescent, the catalyst 1.5-2.0g/L, the concentration of H₂O₂ 4-6mmol/L;the results indicated that the decolorizing rates of these three dyes wereall over 90% ,degraded for 2.0h. Using SO^2-₄ /Fe₂O₃-TiO₂ as thepotocatalyst, the conditions as follow: the initial dye solution was acidic,the catalyst 2.0g/L, the concentration of H₂O₂ 3-4mmol/L; the resultsindicated that the decolorizing rates of these three dyes were all over95% ,degraded for 1.5h. The pH and the NO^-₃ as well as NH⁺₄ were detected in the reaction.During the degradation process, the pH fell and then rose gain. From theaspect of transformation of nitrogen atoms, It was found that thosenitrogen atoms in azo bone were more stable and hardly transformed toNO^-₃ and NH4 ionic, the nitrogen of the azo transformed into molecule ofthe nitrogen; While those nitrogen atoms in other forms could generatedthese ionic species. The relation ship among the NO^-₃ and NH⁺₄ was alsoclarified.