BiOX(Cl,Br,I)/Bi_(2)WO_(6)异质结型复合光催化剂用于高浓度氮氧化物的脱除

海中船舶排放的废气是大气污染的来源之一,其中的氮氧化物能使海洋酸化,不仅危害海洋生态系统,还会造成沿海城市空气污染,对人的身体健康也造成危害。光催化脱除大气中的氮氧化物被认为是可靠且有潜力的高级氧化脱除技术,但目前的研究大多针对低浓度(10^(-9)级)下氮氧化物脱除,针对船舶尾气中较高浓度(10^(-6)级)氮氧化物脱除的研究较少。本文采用超声辅助法制备了BiOX(Cl,Br,I)/Bi_(2)WO_(6)复合催化剂,紫外可见吸收光谱得到BiOX(Cl,Br,I)/Bi_(2)WO_(6)的带隙能分别为3.1eV、2.6eV和1.8eV,并且计算了其导带电位。光电流实验表明,BiOCl/Bi_(2)WO_(6)复合材料的光电流强度高于BiOBr/Bi_(2)WO_(6)和BiOI/Bi_(2)WO_(6)。模拟光催化脱硝实验表明,BiOCl/Bi_(2)WO_(6)在紫外线下NO的脱除率为37.5%,且BiOX/Bi_(2)WO_(6)复合光催化剂在5次循环后表现出良好的稳定性。通过原位红外吸收光谱分析,对BiOX/Bi_(2)WO_(6)催化剂上进行NO光催化氧化的中间产物进行了鉴定,提出了NO的氧化脱除途径。

Experimental studies on photocatalytic oxidation of nitric oxides using titanium dioxide

In order to remove nitric oxides （NO） from flue gas, experimental studies on the photocatalytic oxidation （PCO） of NO are carried out in an efficient laboratory-scale reactor. Nano-sized TiO2 particles loading on quartz sand are prepared and used as the photocatalyst. Effects of several key operating parameters on NO conversion are investigated, including operating temperature, NO inlet concentration, oxygen percentage, relative humidity and residence time. The results illustrate that the NO inlet concentration, the oxygen percentage and the relative humidity play an important role in the oxidation of NO. A lower NO inlet concentration and a higher oxygen percentage result in a higher NO conversion efficiency. When the relative humidity is 8%, the maximum value of NO conversion efficiency is achieved. In addition, the operating temperature and the residence time have a little effect on the conversion efficiency of NO.

In situ synthesis of Ti^(3+) self-doped mesoporous TiO_2 as a durable photocatalyst for environmental remediation

This study developed a facile approach for in situ synthesis of a Ti3＋ self-doped mesoporous TiO 2photocatalyst by an evaporation-induced self-assembly method using TiC l3,water,and F127 as the titanium precursor,solvent,and soft template agent,respectively. The as-prepared samples were investigated by X-ray diffraction,N2 adsorption-desorption measurements,ultraviolet-visible diffuse reflectance spectroscopy,electron paramagnetic resonance,and transmission electron microscopy. The influence of different reaction parameters such as the dosage of F127 and calcination temperature on the photocatalytic performance of the resulting products was evaluated. The optimized product exhibited high photocatalytic activity and stability in the oxidation of nitric oxide in air and photocatalytic degradation of methylene blue. The excellent photocatalytic performance of the Ti3＋ self-doped mesoporous TiO 2 photocatalyst is attributed to the cooperation between the mesoporous structure and self-doped Ti3＋ enhancing light absorption and effectively suppressing the recombination of photogenerated electrons and holes.

Efficient photocatalytic degradation of NO by ceramic foam air filters coated with mesoporous TiO_2 thin films

Ceramic foam air filters with three-dimensional（3D） porous structures and high surface areas were coated with mesoporous TiO 2 thin films by the reverse micellar method. The mesoporous TiO 2 thin films efficiently photocatalytically degraded nitrogen oxide（NO）. More than 92.5% of NO was degraded in a single pass for air filter samples containing different pore densities. The 3D porous structure of the ceramic air filters enhanced flow turbulence and mixing. This provided the catalytic system with excellent gas-dynamic properties,and sufficient contact between the reactant gas and catalyst surface. The higher pore density of the ceramic foam filters resulted in a higher photocatalytic rate. More adsorption sites for water vapor and the reactant and product gases improved the photocatalytic activity. The porous ceramic air filters coated with mesoporous TiO 2 had large surface areas,and thus high photocatalytic activity. This overcame the common disadvantages associated with using powdered TiO 2 photocatalysts on substrates. The 3D porous ceramic foam filters coated with mesoporous TiO 2 thin films exhibited a higher photocatalytic degradation rate of NO in air than the same thin film deposited on flat ceramic tiles. No deactivation was observed. A consistently high NO degradation rate was obtained between reaction cycles for the TiO 2-coated 3D porous ceramic filters.

Photocatalytic oxidation of nitric oxide from simulated flue gas by wet scrubbing using ultraviolet/TiO_2/H_2O_2 process

Nitric oxide(NO) from flue gas is hard to remove because of low solubility and reactivity. A new technology for photocatalytic oxidation of NO using ultraviolet(UV)/TiO2/H2O2 process is studied in an efficient laboratory-scale reactor. Effects of several key operational parameters on NO removal efficiency are studied, including TiO2 content, H2O2 initial concentration, UV lamp power, NO initial content, oxygen volume fraction and TiO2/H2O2 solution volume. The results illustrate that the NO removal efficiency increases with the increasing of H2O2 initial concentration or UV lamp power. Meanwhile, a lower NO initial content or a higher TiO2/H2O2 solution volume will result in higher NO removal efficiency. In addition, oxygen volume fraction has a little effect.The highest NO removal efficiency is achieved at the TiO2 content of 0.75 g/L, H2O2 initial concentration of 2.5 mol/L, UV lamp power of 36 W, NO initial content of 206×10-6 and TiO2/H2O2 solution volume of 600 m L. It is beneficial for the development and application of NO removal from coal-fired flue gas with UV/TiO2/H2O2 process.