Insights into the solar-light activated adsorption-photocatalysis of ZnLaxBi2−xO4 heterojunctions for tetracycline hydrochloride removal

Metal oxides-based heterojunction fabrication is a promising strategy to eliminate antibiotics from wastewater via adsorption-photocatalysis. ZnLaxBi2−xO4 hybrids with various La/Bi molar ratios were fabricated for enhancing the adsorption-photocatalytic elimination of tetracycline hydrochloride (TCH). Oxygen-defected ZnLaxBi2−xO4 composites provided the sufficient sites for photon capture and pollutants adsorption. In addition, the tight p-n-p type interface among oxygen-defected La2O3, ZnO, and spinel ZnBi2O4 favored the rapid transfer and migration of photo-excited e-/h+ pairs, enlarging the visible light utilization. Hence, ZnLaxBi2−xO4 samples had the better adsorption-photocatalytic activity than ZnLa2O4 and ZnBi2O4 for TCH removal. Langmuir and second-order models well described the adsorption isotherms and kinetics of ZnLaxBi2−xO4 samples, respectively. The adsorption capacity of optimal ZnLa1.75Bi0.25O4 with a La/Bi molar ratio of 7:1 was 406.85 mg g−1, and its removal efficiency of 210 mg L−1 TCH solution was 98.04 % within 150 min. The change in valence states of surface compositions induced to the declined removal efficiency of ZnLa1.75Bi0.25O4 to 91.95 % after five cycle times.