| Currently, the water pollution problem is a complicated engineering, it is important to note that the pesticide wastewater is one of the challenging topics for water treatment. Many researchers have been focus on the development of new materials and new technology for water treatment. As a new type of environment-friendly technology, photocatalytic oxidation has been promising in the treatment of pesticide wastewater. The key to the photocatalytic oxidation technology in degradation of pesticides is the catalyst, including its structure and properties. Owing to its excellent photocatalytic performance, good chemical and thermal stability, and will not cause secondary pollution, nano-TiO2 has been a popular catalyst in the photocatalysis area. In this paper, we have prepared TiO2 catalyst via a series of process using the cheap and abundant ilmenite as raw material, the optimized preparation conditions was investigated. In order to conquer the difficulty to separate for reuse of nano-TiO2, and further improve the materials’specific surface area, TiO2 was incorporated into SBA-15. In addition, the catalysts’photocatalytic performance for pesticide dimethoate have been investigated, their mutual relations and the important laws have also been discussed.1. TiOSO4 was prepared from Panzhihua ilmenite (Sichuan, China) using sulfuric acid-decomposition by liquid phase method, then nano-TiO2 with different polymorphs, morphologies and particle size were obtained by hydrolysis and calcination. We have discussed the effects of sulfuric acid molar volume, reaction time, initial pre-heating temperature, sulfuric acid concentration on the decomposition rate of ilmenite and the amount of reducing agent. The influences of different hydrolysis conditions on the crystallinity, morphology, and the yield of the TiO2 product were also discussed. In addition, the influences of different calcination temperature on the polymorphs and particle size of TiO2 have also been investigated. The results showed that when ilmenite reacted with 13.5 mol·L-1 H2SO4 solution at 160℃ for 120 min, it required 0.32 mol H2SO4, and the decomposition rate of ilmenite could be achieved 95.21%. It would be considered as the optimal conditions. The resulting titanium solution was qualified with 121 g·L-1 Ti4+ The as-prepared TiO2 with different morphologies were obtained under different hydrolysis conditions, the yield of the TiO2 product reached 92.18%. The resulting TiO2 with different polymorphs(anatase, rutile, anatase-rutile mixture), different particle size(40 nm-60 nm) and a purity above 99% were obtained under different calcination temperatures(600℃-950℃).2. A novel approach of different amount of TiO2 loaded over SBA-15 mesoporous materials were prepared according to the post-synthesis method by hydrolysis, using TiOSO4 solution as a precursor and SBA-15 as a support. Several factors including the catalyst calcination temperature, initial pH value of dimethoate solution, amount of catalyst, the different loading of TiO2 and different reaction temperature on dimethoate degradation have been investigated under simulated sunlight. In addition, the intermediates generated during photocatalysis have also been detected according to GC-MS analysis, stability of TiO2/SBA-15 catalyst and catalytic kinetics were also been discussed. The results showed that silica framework of highly ordered 2D hexagonal structure was still stable after titania incorporation and its specific area was larger than the commonly photocatalyst. The BET specific surface area of 26% TiO2/SBA-15 sample was up to 386 m2·g-1. It showed the highest photocatalytic ability for degradation of dimethoate. The dimethoate solution was completely degraded within 7 h, the photocatalytic performance of 26% TiO2/SBA-15 was 62% higher than pure TiO2. It was highly stable, and its photocatalytic activity was basically maintained after reused for 4 cycles. The photocatalytic reaction of dimethoate was fitted for the first order reaction. |
PDF Full Text Request