Photocatalytic Activity Of The Cerium Doped TiO₂-Outerloaded Activated Carbon Composites Prepared

In the paper, it is reviewed for the photocatalysis principle of TiO₂, the impactingfactors of photoactivity, the way of improving titania photocatalytic activity, theapplication in environmental protection of titania. Based on the shortcomings of TiO₂catalyst and practical application of photocatalytic technology, cerium dopedTiO₂-loaded activated carbon surface （TiO₂-Ce/Csurf） is prepared with highphotoactivity. Firstly the activated carbon, acted as hard template, is pretreated insupercritical CO2to synthesize double template. And then nanometer Ce-TiO₂particlesare loaded surface on the activated carbon by sol-gel method and heat treatment, whilethe carrier remains the original pore microstructure characteristics. The chemicalstructrue, surface morphology and phase of these samples are characterized by scanningelectron microscope （SEM）, X-ray diffraction （XRD）, thermogravimetric-differentialthermal analysis （TG-DTA）, and diffuse reflection spectrum （DRS）. The photocatalyticactivity of samples is evaluated by the degradation of methylene blue （MB） as standardanalog pollutant, while experimental conditions, affected photoactivity, is analyzed. Inaddition, TiO₂/activated carbon （TiO₂/AC） is prepared by supercritical fluid, and theadsorption kinetics of the supercritical fluid is explored.Ethanol and butanol is adsorped activated carbon at35oC,45oC and55oC insupercritical condition. The optimal adsorption time was300min and the optimaladsorption temperature was45oC for adsorption of ethanol and butanol on activatedcarbon,. Adsorption amount of ethanol and butanol saturated was1109.2mg·g-1and725mg·g^-1respectively. The equal mass concentration of ethanol and butanol was290.9mg·g^-1and381mg·g^-1, respectively. The adsorption effect of ethanol on activatedcarbon was better than butanol.TiO₂-Ce/Csurfcomposites are prepared by supercritical fluid deposition and sol-gelmethod. The average particle size of TiO₂on AC is25nm, which is smaller than pureTiO₂. The results show that Ce sustains crystalline growth and the doped Ce hinderedthe process of phase transition of TiO₂particles from anatase to rutile. With increasedtemperature, the photoactivity of TiO₂-Ce/Csurfincrease and then decrease.TiO₂-Ce/C_surf, prepared at600oC, shows the higher photoactivity than Ce-TiO₂/AC.The photoactivity of TiO₂-Ce/Csurfis higher than that of Ce-TiO₂+AC, TiO₂/AC andP25for MB degradation. It is attributed the fact that the synergy effect of Ce and AC onTiO₂. The used composites retained high activity for MB photocatalytic degradation.The photocatalytic degradation of MB by TiO₂-Ce/Csurfis followed the first-orderkinetics. Rate constant of MB degradation is the highest when doped-cerium content,calcined temperature and MB content are1.5%,600oC and5.5mg/L, respectively, withcatalyst content of1.5g/L, pH value of12and ventilation rate of30mL/s.