Preparation Of Poly-o-phenylenediamine Sensitized Titania PoPD/TiO₂Composite Photocatalysts And Study On Their Photocatalytic Activity For Dye Wastewater

Dyes are generally recognized as a kind of important organic pollutants with the characteristics of strong toxicity, poor biodegradability and difficulty to biochemical degradation. According to statistics, in China6-7tons dye wastewater flows into water bodies, which can bring a series of environmental problems and also causes different degrees of harm. Therefore, the prevention and xomprehensive treatment of dye wastewater should be paid much attention. The photocatalysis oxidation of TiO2, a kind of advanced oxidation process, is a new technique of wastewater treatment developing rapidly in recent years due to its chemical stability, non-toxic, low selectivity and cost-effectiveness. However, the photocatalytic activity of TiO2is powerfully influenced by surface property, particles size, light response range and other factors, and then the photocatalytic degradation efficiency of organic pollutants is not high. So various means are used to modify it. In this paper, base on conjugated large (?) bond and high adsorption of poly-o-phenylenediamine, we prepared PoPD/TiO2composite photocatalyst, making a special study on treating dye wastewater. This thesis includes the following three parts:(1) PoPly-o-phenylenediamine (PoPD) sensitized nanoparticles TiO2were successfully prepared by’in situ’ polymerization of oPD in the presence of TiO2nanocrystalline with ultraviolet light photoinitiating method. In the method, hydroxyl radicals created by TiO2under the ultraviolet light irradiation substituted traditional oxidant such as ammonium persulfate to induce polymerization of o-phenylenediamine monomer onto the surface of TiO2. The factors, such as photoinitiating time, reactants oPD/TiO2molar ratio, reaction temperature and pH, which influence the synthesis of PoPD/TiO2composite photocatalyst were studied thoroughly and the optimum was selected.(2) The prepared PoPD/TiO2composite photocatalyst was characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and UV-vis diffuse reflection spectra (UV-vis/DRS). The results demonstrated that a dense conductive PoPD layer with reasonable thickness was formed on the surface of TiO2, which can enhance adsorption of organic pollutants and make more use of visible light. (3) The photocatalytic decolorizadation of methylene blue (MB) and acid fuchsine (AF) were studied with PoPD/TiO2composite under lamp illumination. The experimental parameters such as initial concentration, pH values, and reaction temperature and catalyst dosage were systematically studied in the work. The results indicated that the composite photocatalyst showed much higher adsoiption capacity of dye and photocatalytic decolorization efficiency than the pure TiO2catalyst. In terms of Langmuir-Hinshelwood model the photocatalytic decolorization reaction followed pseudo-first order kinetics in low concentration. Moreover, the composite photocatalyst owned high reusable ability.