Solar light induced photocatalytic efficiency of double perovskites towards dyes mixture degradation: a response surface methodology-based optimization approach

The higher band gaps of traditional semiconductor oxides hinders their widespread applications due to its limited solar light utilization. Perovskites are emerging photocatalysts to utilize the ultraviolet and visible part of the solar spectrum to reveal their efficiency in advanced oxidation processes. In the current study, visible light responsive double perovskites oxides of A₂BB^/O₆ stoichiometry was tailored and applied to eliminate toxic synthetic dyes added into freshwater streams as industrial effluents. The SEM and EDX confirmed the smooth and regular surfaces and stoichiometric ratio and elemental composition. The interpretation of the XRD spectrum confirmed a monoclinic crystal unit with a 29.23 nm average crystallite size. The optical band gap of materials lies in the visible region. The fabricated materials were applied to diminish methylene blue (MB) and Eosin Y (EY) dye individually. The degradation efficiencies of MB and EY dyes were 97.44 and 99.41% at optimum conditions of 60 min irradiation time, 0.05 g catalyst dosage, 60 mg/L dye concentration, and pH 11, and 5 respectively, followed by their mixture under solar light irradiations. The optimized parameters describe the efficiency of A₂BB′O₆ perovskites under solar light irradiations. The MB and EY removal followed the first-order kinetics model with R2 values of 0.981 and 0.8832; the rate constant values were 0.0555 s⁻¹ and 0.0692 s⁻¹, respectively. Response surface methodology modeling reveals that the removal of MB follows the quadratic model while EY degradation fit well with the reduced quadratic model, having maximum desirability factors value and maximum significant terms, with R² 0.9951, 0.9986 and adjR² values 0.9889, 0.9976 for MB and EY respectively.