Green synthesis of Nb-doped ZnO nanocomposite for photocatalytic degradation of tetracycline antibiotic under visible light

• Nb-doped ZnO composites were synthesized using Vernonia amygdalina leaves extract. • The band gap value of ZnO decreased with Nb doping. • Nb-ZnO exhibited an enhanced photocatalytic activity toward tetracycline. • Nb-ZnO maintained good stability after five degradation recycles. This study describes a novel green synthesis of Nb-ZnO based on Vernonia amygdalina leaves extract as a reactant without using any commercial chemicals. The fabricated composites were characterized and applied for degradation of tetracycline under visible light. Nb-ZnO samples showed markedly improved photocatalytic activity compared to ZnO. The photocatalyst with an Nb:Zn molar ratio of 1:1 had the highest tetracycline degradation efficiency, reached 93.2% in 180 min. The Nb-ZnO composite also possessed superior recyclability and stability. The photocatalytic mechanism was established with the main participation of • O 2 − and • OH reactive radicals. Nb-ZnO can be used as a promising photocatalyst for antibiotic removal.