Development and evaluation of hydrogen peroxide mediated zinc oxide photocatalytic nanoparticles from Peepal (Ficus Religiosa) leaf extract for the treatment of actual tannery wastewater

Abstract

Advanced oxidation processes, such as heterogeneous photocatalysis, can break down recalcitrant compounds. The overall effectiveness of the majority of semiconductor-based photocatalysts during continuous operation and in actual wastewater matrices is still insufficient. This research examines the concurrent removal of chemical oxygen demand and chromium(VI) from real tannery wastewater. This is achieved through the application of a photocatalyst namely zinc oxide nanoparticles prepared using Ficus Religiosa leaf extract. The Tauc plot revealed the bandgap energy of zinc oxide to be 3.40 eV and the XPS survey picture confirmed that the binding energy between two peaks of Zn_3/2 and Zn_1/2 is 23.15 eV, confirming the formation of zinc oxide. 97.25% chromium(VI) and 89.3% chemical oxygen demand removal was achieved under optimal conditions of pH, H₂O₂ and the catalyst dosage level of 7, 19.5 mM, and 4 mg L⁻¹, respectively. Also, the degradation studies followed pseudo first order kinetics with a rate constant value of 0.0827 min⁻¹ and an R² value of 0.98. Furthermore, the catalyst's reusability was confirmed under optimal conditions. This article shows an eco-friendly method for synthesizing zinc oxide nanoparticles.