Preparation Of POM/TiO₂ And Its Photocatalytic Degradation Of Dye Wastewater

In recent years, TiO2 and heteropoly acid have drawn much attention as the green photocatalysts for environmental protection and remediation. Heteropoly acid is very soluble in water and most polarity solution, it is difficult to separate from the reaction system, and influenced the actual application. The studies show, heteropoly acid receives electrons which produced by light excite electronic of TiO2, then extends the time of electrons and holes combination, and then to improve the effect of photocatalysis. So, to prepare the composite photocatalysis by TiO2 and heteropoly acid is the best way to improve the photocatalysis property and to solve the proplem of separate.At present, the study of the ultrasonic degradation and ultrasonic preparation catalysts are very active both at home and abroad. The effect of ultrasonic cavitation makes high temperature locally, high pressure, strong shock waves and micro-jet. Those affects provide a new special physical and chemical environment for chemical reaction which is difficult to carry out under general conditions.This paper will research degradation methylene blue dye by composite catalysts of TiO2 and phosphotungstic acid (salt), and discusses the effect of ultrasonic in photocatalytic degradation and preparation of catalysts.On the one side, the study discusses the effects of ultrasonic and ultraviolet radiation the degradation of methylene blue by PW11O397-/TiO2 photocatalyst. The influences of power of ultrasonic, pH, catalyst dosage were evaluated. The degradation of methylene blue was favorable in alkaline solution especially at pH=7.5, in light of 17 cm height, and under 250 w of ultrasonic power. The optimum dosage of catalyst was between 0.2-0.4 g/L. Degradation process showed mineralization after decoloring effect. The effect of degradation methylene blue by the union of ultrasonic with photocatalysis and PW11O397-/TiO2 photocatalyst is better than by each of them.On the other side, we used the ultrasonic method to prepare a new complex photocatalyst with H3PW12O40 and TiO2. H3PW12O40/TiO2 compound has anatase phase which is directly synthesized without high-temperature calcination at a lower temperature (80℃), with high-intensity ultrasonic irradiation. The compound has the following characteristic:(a) the combination of the original H3PW12O40 and the anatase TiO2 basement produced a supported effect which increased photocatalytic activity; (b) it can initiate the photochemical reactions under solar irradiation. Solar photocatalytic activity of the H3PW12040/Ti02 was measured by the decomposition of organic dyes. H3PW12O40/TiO2 exhibited higher photocatalytic activity than TiO2 which prepared in the same method for decomposition of dyes under solar irradiation. Meanwhile, the composite catalyst is easy to separate for recycling after the reaction, and the efficiency of catalyst remains almost the same after five times of activities.