Synthesis Process Of BiOBr And Its Photocatalytic Properties For Benzene

In recent years, lots of volatile organic compounds (VOCs) that are formed during the industrial and agricultural developing processes are seriously harmful to air quality and human health. Among so many VOCs, Benzene series is very pernicious and difficult to degrade, and has a high concentration in the ambient air. The photocatalytic oxidation technology, that is an advanced green oxidation method, has the advantages of low energy consumption, high efficiency and complete degradation. It has been widely researched and used in the field of pollutant treatment and energy developing. BiOBr, as a new photocatalytic material, because of the special lamellar structure, inner-electric field, indirect transition model and good photocatalytic capability has been concerned by many researches. So, it is meaningful to find a simple and effective method to produce BiOBr that has excellent photocatalytic capability and analysis the impact factors of its photocatalytic capability during the processes of degrading Benzene. And this will provide theoretical and experimental basics for generalizing the use of photocatalytic technology and developing highly reactive catalytic materials.BiOBr powders were prepared by solvothermal method using Bismuth Nitrate as Bismuth resource, cetyltrimethylammonium bromide (CTAB) as Bromo source and absolute ethylalcohol as solvent. In the producing process, BiOBr powders with controlled morphologies and structures have been synthesized by changing the solvothermal temperature and the reactant Bi/Br molar ratio. Then the effects of the solvothermal temperature and the Bi/Br molar ratio that influence its morphologies, structures and light adsorption properties were researched and characterized by the means of XRD, SEM, TEM, BET, UV-Vis, etc. The results showed that the prepared BiOBr had nano-lamellar stacked structures when the Bi/Br molar ratio was 1:6. With the increase of solvothermal temperature, the crystallographic structure of BiOBr changed in some degree. The thickness of nano layers and the absorption intensity of ultraviolet light decreased with the increase of temperature. Under the comparison of other temperatures, BiOBr prepared at 120? in 90 minutes had the best photocatalytic active ability. Benzene photodegradation efficiency on this BiOBr was 65%, but only 15% on TiO2.BiOBr above prepared still had high Benzene removal efficiency and the photodegradation efficiency reduced less than 1% after recycling three times. At the preparing temperature of 120?, the morphologies and structures of BiOBr changed from lamellar to flower-like gradually. The particle size decreased, and specific surface area increased with the increase of preparing temperature. The photocatalytic active ability improved with the increase of the Bi/Br ratio. When the Bi/Br ratio was 2:1, the catalyst showed the highest photocatalytic capability, with Benzene photodegradation efficiency of 80%.The several important effects of photocatalytic degradation, including catalyst quantity, initial concentration of solution and water vapor content, were also discussed by using the prepared BiOBr under 120? and the Bi/Br ratio of 2:1. The results showed that photocatalytic efficiency increased with increase of catalyst quantity within a certain range. When the catalyst reached a certain amount, the removal efficiency would not increase obviously and the size of reaction area was not an important factor of influencing the photocatalytic efficiency. With the increase concentration of initial reactant, the photocatalytic efficiency improved. When the initial reactant concentration reached 2.3g/m3, the maximum removal efficiency was 90%. After that concentration, the photocatalytic efficiency would not improve with increasing concentration, because the catalyst had limit active ability and the competitions were formed between excessive Benzene molecules. In the system, some amounts of water vapor can help to improve the photocatalytic efficiency, but too much water vapor would restrict the photocatalytic capability of BiOBr. With the increase of UV light intensity, the number of photons in the system increased, and the degradation rate of benzene increased. Finally, kinetics analyses were studied during the processes of catalyzing Benzene, with one order reaction kinetics equation.