Barium removal by photocatalytic process: An alternative for water treatment

This study describes the application of TiO2 in different forms (anatase, P25, TiO2 commercial), ZnO and Nb2O5 for barium ions (Ba(II)) reduction by photocatalysis process. Specific surface area (B.E.T method), X-ray diffraction and photo-acoustic spectroscopy techniques were applied for the catalysts characterization. The parameters studied in the reaction were: presence of additives, pH, amount of catalyst, effect of inorganic compounds, adsorption, photolysis, type of catalyst, additives and the time of contact of the additive/catalyst. No significant reduction in the Ba(II) concentration was observed in absence of additive, however a reduction higher than 50% was observed in the presence of addictive after 120 min of reaction time. Moreover, the effect of Cl− ions, generally present in natural waters, indicated an increase in the Ba(II) reduction time. The adsorption and photolysis tests were not efficient in the Ba(II) removal. However, the contact time between the additive (formic acid) and the catalyst, before the photocatalytic process, showed an improvement in the catalytic activity for all catalysts studied. Therefore, the photocatalysis tests indicated that the catalysts that showed the highest efficiency in the Ba(II) removal were anatase, P25 and ZnO, respectively. The maximum percentage of Ba(II) removal was obtained using anatase as catalyst and at optimized conditions Ba(II) removal was higher than 99% were obtained a reaction time of 90 min.