Research Of Photoelectric Catalystic Degradation Of Organic Dyes

The treatment of toxic and dye wastewater is one of the biggest technical difficulties due to the lack of highly effective solution, which has cause severe hazard both to the humankind and our environment. In this paper, a novel TiO₂ thin films modified by non-uniform doping was adopted for the photocatalytic degradation. Various characterization techniques were used to research the mechanism of photocatalytic degradation. At the same time, PbO₂ electrode was prepared, which had the higher oxygen potential and good photocatalytic activity. And the structure was characteristic, and studied degraddtion of RhB under visible light. The mechanism of RhB by photoelectrocatalytic degradation was discussed.Sol-Gel method was used to prepare the novel TiO₂ thin films modified by vanadium ion doped (VD_x VT_x, VB_x) and lead ion doped (PbD_x PbT_x) on the glasses. The crystal of the films was anatase by XRD analysis. The transmittances of each film were different on the same concentration of different doped method. It was observed that the non-uniform doped TiO₂ films modified by VD_x/PbD_x method had higher photocatalytic activity and best rate of molar. The photocatalytic degradation of methyl orange is used as the probed reaction. The result is that the apparent rate constant k of non-uniform doped vanadium ion TiO₂ films was 2.3 times that of pure TiO₂ films whose the rate molar of V/Ti is 1.0%. And the apparent rate constant k of non-uniform doped lead ion TiO₂ films was 2.52 times that of pure TiO₂ films whose the rate molar of Pb/Ti is 0.5%.The result showed that when the doped metal ion clustered in the inner of thin film, the effective capture or recombination chance of electron-hole pair was decreased, but the separation of electron-hole pair was enhanced. The electron life was prolonged and the recombination chance of electron-hole pair was restrained, so the resistance of charge movement turned small and the electron was easy to transfer. The ideal doping effect was that the ion doptant captured the electron/hole near the surface of TiO₂ thin film, then the captured electron/hole transferred to the surface to had photocatalytic reaction.Constant potential technique was used to electrodeposit PbO₂ films with higher oxygen potential and good photocatalytic activity. The crystals included both β and α . The surface was flat and the thickness was about 0.6 μ m. The electrode hadabsorption in visible light region, so it can have photoelectrocatalytic degradation under the visible light. XPS analysis showed that the Lead of the film surface of PbO2 is only +4 valency. The EIS showed that the charge transfer resistance of PbO2 turned to small under the visible light.The photoelectrocatalytic degradation of RhB is influenced by the adsorption of RhB on the PbO2 surface. The Langmuir adsorption isotherm equation of RhB on the PbO2 surface Ce/qe=1.30992X+30.8591 is put forward on the basis of the experimental results.The synergetic effect of the combination of photo catalytic and electric technology was discussed with RhB. It was observed that the synergetic effect performed well and the promoting factor f was 741%.The influence factors on the photoelectrocatalytic degradation of RhB were investigated. The degradation of RhB is more efficient in acidic medium. And it performed the best in the electrolyte of NaCl. The degradation efficiency of RhB increased with a increase of the potential. The degradation efficiency of RhB increased greatly when H2O2 was added.The mechanism of photoelectrocatalytic degradation of RhB was proposed. The reaction leads mainly to N-de-alkylation of the RhB chromophore skeleton. The removal of COD with reaction times followed the first reaction kinetics. The reaction kinetics constant of COD removal was 0.00359mm'1. The new products were DER^ EER^ DR> ER and R. The products were all experience a process of up then down except the original dye. It was showed that the process of producing and degradation.With PbO2 as the photoelectric catalyst, the photoreaction leads mainly to N-dea lkylation of the dye. By contrast, cleavage of the whole conjugated chromophore stru cture predominates in the electric chemistry oxidation.