Comparative study in single- and binary-contaminant systems: Photodegradation of tetracycline and imidacloprid on flower-shaped Ag/AgBr/BiOBr under visible-light irradiation

To compare the photodegradation in single- and binary-contaminant systems, the representative antibiotic (tetracycline) and insecticide (imidacloprid) were employed as two contaminants of emerging concern. And Ag/AgBr modified BiOBr was synthesized hydrothermally in an ionic liquid-water medium and characterized by various techniques to support the mechanism study. The as-prepared flower-shaped Ag/AgBr/BiOBr exhibits superior photocatalytic activity to Ag/AgBr and BiOBr. The paralleled experiments were conducted in single-contaminant systems to optimize the solution chemistry for the comparison study, which suggested the photodegradation rate (DR) peaks at 1.0 g/L over the catalyst dosage ranged from 0.6 to 1.4 g/L, and the raised initial concentration reduces the DR. Additionally, the electrostatic interaction between reactant and photocatalyst causes the DR fluctuation over initial pH. In the mechanism study, the contributions of the dominant active species (•O2- and h+) were analysed quantitatively through the quenching tests with scavengers. Furthermore, the electrostatic interactions between the reactants and the active species causes the disequilibrated contributions of •O2- and h+ in single-contaminant systems. The comparison study demonstrated the synergistic effect in binary-contaminant systems distinctly, which is caused by the mutually complementary utilization of the h+ and •O2- during the photodegradation of tetracycline and imidacloprid.