Photodegradation of Toluene by Composite Photocatalysts of Organobentonites and TiO<sub>2</sub>: Influences of Carbon Chain Length

Abstract

Composite photocatalysts, prepared by mechanical grinding TiO2 with bentonite/ organobentonite, were applied in the dynamic photodegradation of gaseous toluene. A substrate enriched environment surround the loaded TiO2 was formed by the adsorption of the added sorbents, leading to an increase in the degradation rate. The performance of composite catalysts was quite different in the initial and the long-term period of photocatalysis. The differences could be attributed to the adsorption properties of added sorbents related to adsorbility, hydrophilicity and diffusion feasibility, etc. The longer alkyl-chain of organobentonite formed a better partition phase resulting in an ideal adsorption capacity. However, as the alkyl-chain length increased, the diffusion path was segmentally clogged which seriously hindered the photocatalysis in the initial period. Although the adsorption capacity of original bentonite was quite small, the facility of diffusion changed it into the best performer in the initial period. Organobentonite with relatively short alkyl-chain conceived a little smaller adsorption capacity than the longer one. Moreover, the former one showed much more trending to diffuse the adsorbed toluene to catalyst. The long-term period of photocatalysis was also affected by the hydrophilicity of catalyst. Hence, the performance of organobentonites added composite catalyst mended a lot in the final degradation rate. Thus, organobentonite as 20DTAB with the advantage of large adsorption capacity and good diffusion feasibility is believed to be a promising carrier of photocatalys.