Efficient degradation of bisphenol A over facilely optimized ternary Ag/ZnO/ZnAl‒LDH composite with enhanced photocatalytic performance under visible light irradiation

For the advanced treatment of micropollutants from wastewater, this study synthesized a ternary Ag/ZnO/ZnAl‒LDH composite photocatalyst with performance optimization based on the Taguchi approach. The optimal synthesis parameters were statistically determined as the Ag doping amount of 5 wt%, Zn 2+ and Al 3+ with a molar ratio of 3:1, Ag/ZnO and ZnAl‒LDH with composite ratio of 3:2, and PEG-200 dosage of 25 mL. The optimally synthesized Ag/ZnO/ZnAl‒LDH achieved the efficient degradation of bisphenol A (BPA) under visible light irradiation, and the reaction rate constant was about 4.8-, 2.2- and 12.0-fold higher than that of ZnO, Ag/ZnO and ZnAl‒LDH, respectively. As proved by various characterizations, the enhanced photocatalytic performance of Ag/ZnO/ZnAl‒LDH can be attributed to the improvements of optoelectronic properties, such as the widened visible light responsivity and facilitated charge transfer, thus resulting in a significant increase of hydroxyl radicals (·OH) formation. Fluorescence measurements and radical quenching experiments indicated that ·OH mainly contribute to the degradation of BPA, and the oxidation of H 2 O by holes was the dominant formation pathway. According to the above results, this study summarized and proposed the enhanced photocatalytic mechanism of Ag/ZnO/ZnAl‒LDH for ·OH production and BPA removal.