Intrinsic and photocatalytic disinfection properties of CaTiO3, SrTiO3, and BaTiO3 alkaline earth metal titanate perovskites

ABSTRACT The use of alkaline earth metal titanate perovskites across various industries is increasing due to their wide application possibilities. However, this raises concerns regarding their potential environmental impact, including microorganisms living in or entering surface water bodies. Accordingly, calcium, strontium, and barium titanates were hydrothermally prepared to investigate their photocatalytic disinfection efficiency against Gram-negative Escherichia coli and Gram-positive Bacillus licheniformis bacteria under UV-A light irradiation. The photocatalysts were characterized by X-ray diffraction, scanning electron microscopy, diffuse reflectance spectroscopy, and infrared spectroscopy measurements. Their photocatalytic activity was also evaluated by the photocatalytic oxidation of phenol. Commercially available alkaline earth metal titanates were used as references. For phenol degradation, our strontium titanates had significantly better photoactivity than calcium and barium titanates (r 0 = 41.60 compared to 4.28 and 10.03×10 −10 M s −1 , respectively), while being considerably more efficient than the commercial references. This result was attributed to the presence of SrCO 3 acting as a co-catalyst, higher specific surface area, and more favorable band positions, enabling the generation of hydroxyl radicals. Disinfection results show that unmodified alkaline earth metal titanates have no or negligible disinfectant effect. Hydrothermally synthesized calcium and strontium titanates generated more hydroxyl radicals than the hydrothermally synthesized barium titanate and the references. For E. coli , the former samples had nearly identical disinfectant effect to UV-A light (∼80% bacterial inactivation over 2 h), while the other catalysts, which generated significantly fewer hydroxyl radicals, decreased the disinfection efficiency of UV-A light by ∼40–70% due to the catalyst particles screening the photons from bacteria. A similar trend was observed for B. licheniformis with higher disinfection efficiencies (100% for UV-A light and the most efficient samples under 1 h) and higher activity reductions of ∼30–100%. These results contribute to the decision-making process regarding the risks associated with alkaline earth metal titanate perovskites in various industries.