The effect of calcination temperature on the structure and activity of TiO2/SiO2 composite catalysts derived from titanium sulfate and fly ash acid sludge

The composite catalysts of TiO2/SiO2 were prepared though a sol-gel process followed by the calcination crystallization process. The inexpensive precursors, titanium sulfate and fly ash acid sludge, were used as providing titania and silica sources, respectively. The decomposition of fly ash acid sludge was digested with NaOH to extract silica, and the obtained sodium silicate was used to prepare TiO2/SiO2 composite. The effect of calcination temperature on the structure of TiO2/SiO2 composites was studied by means of XRD, BET, FTIR, SEM, photocatalysis and adsorption test. It was found that the anatase-to-rutile phase transition temperature of TiO2/ SiO2 composite powders was significantly higher than that of pure TiO2. The presence of the Ti-O-Si bond was confirmed in the final products when the incorporation of titania into silica were performed. The photocatalytic performance of TiO2/SiO2 composite annealed at different temperatures was evaluated by Rhodamine B (RhB) as the target pollutant under visible-light irradiation. Results indicated that the sample exhibited the highest photocatalytic activity when the calcination temperature is up to 600 degrees C. After 4 h visible-light irradiation, about 90% of RhB was removed by this type of photocatalysts.