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Research on the Influenc E Factors of Photocattalytic Activity Nfluence of Micrarc Oxidation TiO2 Coatings

Author: WangLiJuan
Tutor: CaiQiZhou
School: Huazhong University of Science and Technology
Course: Materials Processing Engineering
Keywords: Microarc oxidation TiO2 photocatalysis solution pH value Inorganic anions Applied anodic bias
CLC: X703.1
Type: Master's thesis
Year: 2009
Downloads: 18
Quote: 0
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Abstract


As a new kind of wastewater treatment techno1ogy, semiconductor photocatalysisoxidation presents many virtues, such as high treatment efficiency, simple processequipment, easily controlled operation condition, non-selectivity and free secondarypollution, et al. Among many semiconductors, TiO2 is considered as perfect photocatalystdue to its strong oxidative ability, high photocatalytic activity, well biological, chemicaland optical stability. However, TiO2 is an amphoteric oxide, whose photocatalytic activityis influenced by the solution pH value, the applied anodic bias and the nature and contentsof inorganic anions. So, the effect of the solution pH value, the applied anodic bias and thenature and contents of inorganic anions on the photocatalytic activity of TiO2 and themechanism of the solution condition on photocatalytic degradation pattern of TiO2 areinvestigated, which has important theoretical significance for the preparation and structureadjustment of TiO2 films with high photocatalytic acitivity and play its full role indegradation of pollutants.In this study, TiO2 film is formed on pure titanium substrate in tungstate electrolytevia microarc oxidation technology and methyl orange is choosed as model pollutant toevaluate its photocatalytic activity. The effect of solution pH value, various inorganicanions and applied anodic bias on the photo-degradation rate of methyl orange isinvestigated on the basis of the analysis of morphologies and structures. The results showTiO2 film with rough and porous structure is bounded firmly to the titanium substrate. TiO2film consists mainly of rutile, also some anatase. Amorphous tungsten oxides, generatedby decomposition of WO42- under microarc discharge, distributes uniformly in the inner ofTiO2 film, which can promote the effective separation between electrons and holes.The solution pH influences degradation rate of methyl orange greatly. Thedegradation rate of methyl orange is lowest in neutral solution. Acidic or basic conditionpromote degradation of methyl orange, but the degradation rate of methyl orange in acidicsolution is higher than that in basic solution, the degradation efficiency of methyl orangereaches 98.89% when the solution pH is equal to 1.0. The effect of inorganic anions on thedegradation rate of methyl orange is divided into two types: (a) added NO3- increases the degradation rate of methyl orange strongly. The degradation efficiency of methyl orange isup to 98.78% when its concentration is 10mmol/L; (b) Cl-, SO42-, HCO3- and H2PO4- inhibitthe photo-degradation of methyl orange at different degrees. At last, applied anodic biaspromotes the separation between electrons and holes, and increases the degradationefficiency of methyl orange by 23.06%.

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CLC: > Environmental science, safety science > Processing and comprehensive utilization of waste > General issues > Wastewater treatment and utilization > Technology and methods
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