Enhanced oxidation of antibiotic residuals (Levofloxacin) using a green composite of ZnO@polyaniline/bentonite (Zn@PA/BE) as multifunctional photocatalyst under visible light

Abstract

ABSTRACT Green nanocomposite of ZnO supported into polyaniline/bentonite hybrid structure (Zn@/PA/BE) was synthesised and characterised and assessed as a multifunctional photocatalyst of 1.86 eV as bandgap energy. The Zn@/PA/BE catalyst was applied in the oxidation of the levofloxacin (LV) residuals in water in the presence of visible light. The recognised oxidation results demonstrate significant enhancement in photocatalytic activity by using the polyaniline/bentonite composite as a carrier for ZnO catalyst. Using the Zn@/PA/BE at 0.5 g/L as dosage resulted in complete oxidation for 10, 20, 30, 40, and 50 mg/L after illumination intervals of 25, 40, 60, 70, and 85 min, respectively. This was confirmed by the significant declination in the TOC content of the treated sample (10 mg/L) until the complete removal after 45 min reflecting the complete degradation and mineralisation. The formed secondary organic compounds during the incomplete oxidation reactions were identified. The intermediate compounds suggested oxidation pathways of carboxylation/de-carboxylation, hydroxylation, de-methylation, de-piperazinylation, and defluorination mechanisms. The hydroxyl radicals were detected as the most effective oxidising species during the reactions based on the active trapping tests and probe molecule investigation. The recyclability experiments reflected the significant stability and reusability of Zn@/PA/BE as a photocatalyst during the oxidation of LV molecules.