Preparation Of A Novel Nanomaterial And Their Photocatalytic Degradation Of Dye Wastewater

Dye wastewater is difficult to deal due to its large quantity, high toxicity and difficulty totreat biologically. TiO2has been proved to be an excellent photocatalyst for degradation of dyewastewater due to its high photocatalytic activity, non-toxicity, good stability and availability.However, the utilization efficiency of solar light was limited severely by the wide band gap ofTiO2(3.2eV). Hence, much effort has been devoted to improve the utilization of solar light byextending the photoresponse of TiO2to the visible region, such as metal ion doping, non-metaldoping, noble metal deposition, narrow band-gap semiconductors coupling and dye sensitization.However, the above mentioned modification methods have kinds of shortages. Recently,conducting polymers and their derivatives have been reported as promising sensitizers to extendthe spectral response of TiO2to visible light effectively and prolong the lifetime of Electron-holepairs in TiO2photocatalysts. However, more work such as mechanism of heterojunction builtbetween TiO2and the conducting polymers, preparation of new kind of conducting polymersmodified TiO2, systematic study of photodegradation of dye wastewater and so on need to bedone.In this study, we use in-situ oxidative polymerization method to prepare PoPD/TiO2composite by selecting O-phenylenediamine which has a total π bond as monomer andammonium persulfate as oxidant. After then, we systematically study photodegradation ofmethylene blue(MB) wastewater. Details are as follows:(1) PoPD/TiO2composite photocatalyst are prepared successfully with in-situ oxidativepolymerization method by using O-phenylenediamine as monomer and ammonium persulfate asoxidant. After then, we study the effect of molar ratio of O-phenylenediamine to TiO2, HClconcentration, molar ratio of oxidant to monomer, reaction temperature and so on. Finally, weget the optimum preparation conditions by using MB as probe.(2) The prepared PoPD/TiO2composites are characterized by X-ray diffractometer(XRD),scanning electron microscopy(SEM), transmission electron microscopy(TEM), Fourier transformSpectrophotometer(FT-IR), UV-vis spectrophotometer(UV-Vis), Photocurrent Test. The resultsdemonstrate that a uniform and dense film with about2-5nm thickness coats on the surface ofTiO2. PoPD/TiO2composites have better absorption of visible light than neat TiO2. (3) Photocatalytic degradation of MB wastewater are studied under simulated visiblelight(xenon lamp with a light filter to remove UV part). The results show that PoPD/TiO2composites prepared under optimum conditions have much better degradation efficiency to MBthan neat TiO2. The degradation reaction follows pseudo-first order kinetics and the apparent rateconstant is proportional to the initial MB concentration. PoPD/TiO2composites have longerservice life and high activity when recycled.