Tio <sub> 2 </ Sub> / Preparation And Properties Of Expanded Graphite Photocatalyst

1. Preparation and characterization of catalystsThe supported TiO₂ catalysts on exfoliated graphite were successfully prepared by impregnation method using exfoliated graphite as support and tetrabutyl titanate as titanium source. The catalysts doping Fe were prepared by adding certain mass of Fe(NO3)3·9H2O into the mixed solution of tetrabutyl titanate and ethanol. The samples were obtained finally through the steps of impregnation, drying and calcination. The calcination technology of calcination method, time, and temperature, and the optimum loading amount of TiO₂ on exfoliated graphite were investigated. The photocatalysts were characterized by XRD, Raman, BET, and SEM analyses. The catalysts with 8wt% TiO₂ were inserted into furnace at 850℃, cooled and taken out from furnace at different intervals. The XRD results showed that the concentration of anatase increased and reached the largest for retention period 6h, and then mainly high activity anatase phase of TiO₂ had transformed to rutile structure after 6 h of catalysts detention time. Raman spectroscopy results revealed that amorphous phase of TiO₂ transformed to anatase structure gradually and the proportion of anatase reached the largest after 6 hours of catalysts residence time to agree with that results of XRD spectrum, and then the structure of exfoliated graphite was destroyed after 7 h of catalysts detention time. With the patterns of BET, the exfoliated graphite and the catalysts all had big pore structure, and the adsorption of catalysts could be greatly improved by loading TiO₂ on the surface of exfoliated graphite. XRD results showed that the proportion of anatase was high while catalysts were calcined at 600℃for 2h. SEM research revealed that catalysts which temperature decreased from 850℃for 6h had more perfect reticular multi-layered structure than that calcined at 600℃for 2h, because high temperature was favorable to expansion of Expansible graphite. The catalytic activities were studied with the reaction of photocatalytic degradation of benzene and dyestuff.2.The studies of the catalytic activity for the photodegradation of benzeneThe catalytic activities were studied with the reaction of photocatalytic degradation of benzene. The method of catalyst preparation was investigated such as calcination time, calcination temperature, and doping catalysts. The catalysts with 8wt% TiO₂ were prepared by being inserted into furnace at 850℃, cooled and taken out from furnace at different intervals. The results indicated that the catalysts prepared for 6 h had high activity, the photocatalytic degradation rate of benzene could reach over 60 %, and the photoactivity of the catalysts was still well kept after 110 h. The research investigated the optimum loading amount of TiO₂ on exfoliated graphite in enhancing the photocatalytic activity of TiO₂. Based upon these observations, as the mass concentration of TiO₂ was 8%, the sample had better activities. The catalyst doping Fe had superior activities, the photocatalytic degradation rate of benzene could reach 75 % and also had better stability, the photoactivity of the catalysts were still well kept after 110 hours.3. The studies of the catalytic activity for the photodegradation of dyestuffThe catalytic activities were investigated with the reaction of photocatalytic degradation of methyl violet, Basic Violet 4 and methyl orange in stainless steel box, and the calcinations temperature were investigated. Based upon these researches, while the mass concentration of TiO₂ was 8%, the catalyst heated for 2 h at 600℃had high activity and the photocatalytic degradation rate of methyl violet, Basic Violet 4 and methyl orange could reach over 98%,98% and 96% respectively. According to the studies, catalysts had better ability of adsorption and the adsorption ratio of methyl violet, Basic Violet 4 and methyl orange could reach 88%,89%,86%, because of perfect reticular multi-layered structure of exfoliated graphite which was propitious to adsorption. According to the data of research, the catalysts had better activities and adsorption capacity of dye.