Characterization of B-TiO2 Synthesized under Different Conditions of Hydrolysis

TiO2 photocatalysts doped with boron (2% boron) with different water/alkoxide molar ratio were synthesized by the sol-gel method. The prepared samples were characterized by BET, RAMAN, FTIR, SEM and Photoluminiscence. A catalyst recycling study and a respirometry tests with activated sludge were realized. When the amount of water was modified during synthesis a noticeable change in the crystal structures, number of surface oxygens, the pore size and the length of the agglomerates were observed. A mesoporous anatase titania was present as the dominant phase, but rutile was present at high and low water concentration. The samples with the highest photocatalytic activity showed the presence of small agglomerates, high porosity, additional oxygen vacancies, the higher specific area and additional number of Ti-O-Ti bonds. The presence of boron is observed in the tricoordinated form that promotes the formation of oxygen vacancies and the photocatalytic properties. The formation of oxygen vacancies on the titania surface are related to the transition of the coordination of titanium (Ti4+ to Ti6+) and best degradation of Orange II is related to a closer coordination to Ti5+. B-TiO2 samples can be easily regenerated and no toxic by-products were produced during the photocatalytic reactions.