Preparation Of ZnO Photocatalytic Materials Basing On The Microemulsion System

In the industrial wastewater treatment process, much attention has been focused on the treating dye wastewater due to its big emissions, multiple species, high toxicity, low biodegradability, toxic and carcinogenic properties, which has resulted in serious environmental pollution. Based on the improvement of the photochemical oxidation technology, photochemical catalytic oxidation technology, a kind of deep oxidation technology, has been developed. photochemical catalytic oxidation technology can degrade the most difficultyly degradable organic pollutants existed in the dye wastewater to nontoxic or low toxic small molecules, showing great potential application in organic dyes wastewater treatment.Based on the microemulsion system, the mesoporous ZnO material has been prepared by using homemade polystyrene microemulsion as templates in this paper. At the same time, the hexagonal cylinder-like ZnO with a regular twinning microstructure were successfully synthesized via a cationic surfactant-assisted hydrothermal microemulsion route. The effects of preparation conditions on the structure, morphology and properties of ZnO were investigated and the suitable preparation conditions were obtained. Moreover, the possible formation mechanism was also proposed.The photocatalytic performance of ZnO/UV system was investigated by using the mesoporous ZnO and hexagonal cylinder-like ZnO with a regular twinning microstructure as photocatalyst and the Reactive Brilliant Red KE-3B and Reactive Brilliant Red K-2BP as simulated dye wastewater, respectively. The effects of operating parameters on the decolorization ratio were studied and the the suitable operating conditions were obtained. Based on the experimental results, the probable pathways for the formation of intermediates were also proposed.Experimental results showed that the polystyrene microemulsion was a good pore forming intermediary. The specific surface area, pore volume and pore size distribution of the synthesized mesoporous ZnO calcined at 500 oC for 6 h were 11.013 m²Â·g^-1, 0.135 cm³Â·g^-1 and 40.2 nm, respectively. The porous ZnO exhibited higher photocatalytic activity than that of nonporous ZnO when the two samples are calcined at the same temperature. In this study, a cationic surfactant-assisted microemulsion process combined with hydrothermal techniques had been developed for synthesizing hexagonal cylinder-like ZnO with a regular twinning microstructure. The results showed that the reaction temperature, the reaction time, the molar ratio (w) between water and CTAB, cosurfactant, the concentration of surfactant, the concentration of reactant exhibited obvious influence on the morphologies and structures of the products. The absorbance of products, which prepared at 140 oC for 14 h when w = 10, [CTAB] = 0.21 mol/L, with 1μm in diameter and 3μm in length, exhibited the strongest absorbance peak in UV-vis absorption spectra.The photocatalytic degradation rate of Reactive Brilliant Red KE-3B and Reactive Brilliant Red K-2BP were both followed the pseudo-first-order kinetic when ZnO/UV system was used. Moreover, the key operation parameters such as catalyst loading, initial dye concentration, solution pH, hydrogen peroxide dosage and anions (SO42?, NO3?, Cl? and CO32?) can affect the decolorization.