Sunlight-Driven AO7 Degradation with Perovskites (La,Ba)(Fe,Ti)O₃ as Heterogeneous Photocatalysts

Perovskites of the (La,Ba)(Fe,Ti)O₃ family were prepared, characterized, and utilized as heterogeneous photocatalysts, activated by natural sunlight, for environmental remediation of Acid Orange 7 (AO7) aqueous solutions. Catalysts were prepared by the ceramic (CM) and the complex polymerization (CP) methods and characterized by XRD, SEM, EDS, and band gap energy. It was found that catalytic properties depend on the synthesis method and annealing conditions. In the photocatalytic assays with sunlight, different AO7 initial concentrations and perovskite amounts were tested. During photocatalytic assays, AO7 and degradation products concentrations were followed by HPLC. Only photocatalysis with BaFeO₃-CM and BaTiO₃-CP presented AO7 removals higher than that observed for photolysis. However, photolysis leads to the formation of almost exclusively amino-naphthol and sulfanilic acid, whereas some of the perovskites utilized form less-toxic compounds as degradation products, such as carboxylic acids (CA). Partial substitution of Ba by La in BaTiO₃-CM does not produce any change in the photocatalytic properties, but the replacement of Ti by Fe in the La_0.1Ba_0.9TiO₃ leads to reduced AO7 removal rate, but with the formation of CAs. The best AO7 removal (92%) was obtained with BaFeO₃-CM (750 mg L^-1), after 4 h of photocatalytic degradation with solar radiation.