Photocatalytic Degradation Of Two Dyes By The H₃PW₁₂O₄₀/TiO₂ Nano-composite Catalyst

Dye wastewater mainly comes from the production of dyes and dye intermediates industry. Dyes and their intermediates have a wide range variety, with a high concentration, color depth, organic matter complex composition, toxic, and poor characteristics of bio-degradable. At present, the treatments of dye wastewater are: flocculation precipitation, electrolysis, oxidation, adsorption, photocatalysis, bio-degradation and other methods. Because photocatalysis has the advantages of simple process, no secondary pollution, and absolutely mineralization, it becomes an effective way to degradation dye wastewater.In this paper, sol-gel method and hydrothermal method with temperature-programmed were used to prepare H3PW12O40/TiO2 nano-powder catalyst which was doped with different amount of H3PW12O40. The inductively coupled plasma-atomic emission spectroscopy (ICP-AES) test, X-ray diffraction (XRD) test, UV-Vis diffuse reflectance spectrum (UV-VIS DRS) test, and Nitrogen adsorption-desorption test were used to characterize the physical and chemical properties of catalysts above-mentioned.Using the xenon lamp (300W) as simulated sunlight, photocatalytic degradation of acid fuchsin and malachite green were carried out in order to research the photocatalytic activity of the catalysts and discuss the influence of irradiation time, the amount of H3PW12O40 doping, the amount of catalyst, the initial concentration of pollutants and the different conditions of photocatalytic reaction. Experimental results show that the H3PW12O40/TiO2 powder catalyst illustrate more efficient than pure TiO2, and catalytic efficiency increase above 20%. For acid fuchsin solution, the most efficient degradation conditions were: TiO2 doped with 25% H3PW12O40, catalyst dosage of 0.75g/L and acid fuchsin solution of 20mg/L initial concentration, conversion reached 97.44% after irradiating the catalyst for 120min. The optimum conditions of the photocatalytic degradation of malachite green were: TiO2 doped with 10% H3PW12O40, catalyst dosage of 0.75g/L and malachite green solution of 10mg/L initial concentration, conversion reached 96.74% after irradiating the catalyst for 120min.Under optimum conditions, the photocatalytic degradations of two kinds of dyes were carried out respectively. TOC test results show that the TOC value of acid fuchsin solution reduces by 76.49% after irradiating 12h, while the malachite green solution reduces by 66.58%. These results indicate that the self-made catalysts have good mineralization effect for two dyes.