Green biosynthesized zinc-based nanocomposite for efficient removal of emerging contaminants

Heterogeneous ZnO@Bi2O3 nanoparticles have been developed via green methodology using Azadirachta indica plant extract and further used for photodegradation of hazardous and bioaccumulating drugs (paracetamol and diclofenac). The spectroscopic and microscopic analysis confirmed the visible light active nature of highly crystalline nanocomposite having particle size (50–75 nm) with the deposition of ZnO nanoflakes over Bi2O3 nanoplates. The results show that ZnO@Bi2O3 displays an excellent photocatalytic performance among other parent products under visible light. In addition, the efficiency of degradation of targeted drug is >93% at optimized conditions (concentration of drugs, pH, and catalytic dose) for selected pollutants (20 mg L−1, 25 mg, and 7pH). Moreover, Ist-order kinetics followed and signaled its high effectiveness (Adsorption capacity: 13.51 mg g−1) due to enlarged surface area (40 m2 g−1), small band-energy value (1.9 eV), and semiconducting- behavior observed by synergism of Bi2O3 (23.5 m2g−1; 2.8 eV) and ZnO (19.4 m2g−1; 3.0 eV). The decreased recombination rate of charge carriers, effectual generation of photoinduced charge carriers, formation of hetero-junction system and unique morphology are the responsible factors for improved photodegradation characteristics of prepared ZnO@Bi2O3 nano-composites. Role of active species and pH of drugs solution in degradation process was also studied. ZnO@ Bi2O3 significantly reduced the natural half-life of selected pollutants and converted them into safer-small metabolites, as confirmed by Liquid chromatography-mass-spectrometry analysis. Green-nano photo catalyst's reusability has been repeatedly demonstrated its sustainability and noteworthy effectiveness for industrial applications. Because of its exceptional properties (high surface area and photo-induced nature), this may be used as an alternative, efficient, green material to clean up several environmental pollutants.