Biosynthesis of ZnO/SiO2 nanocatalyst with palash leaves’ powder for treatment of petroleum refinery effluent

This work aims the synthesis and characterization of ZnO/SiO₂ nanocatalyst from plant waste material by green route and application of this ZnO/SiO₂ nanocatalyst for the treatment of petroleum refinery effluent. Butea monosperma (Palash) leaves’ powder was used as reducing and stabilizing agent for synthesis of ZnO/SiO₂ nanocatalyst. Palash leaves contain broad variability of biomolecules which work as reducing and capping agent. In this research work, COD and acenaphthylene which is Polycyclic Aromatic Hydrocarbons (PAH) were degraded by synthesizing ZnO/SiO₂ nanocatalyst under UV-light in an annular photocatalytic reactor. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), FIELD emission gun-Scanning electron microscopy (FEG-SEM), Energy dispersive X-ray (EDX) and Transmission electron microscopy (TEM) analysis confirmed the formation of ZnO/SiO₂ nanocatalyst. Characterization studies revealed that spherical and hexagonal nanoparticles with particle size ranging from 8 ± 5 nm to 40 ± 5 nm and mean particle with diameter of 20 ± 5 nm were synthesized using this method which is stable in the environment. Brunauer, Emmett and Teller (BET) surface area of ZnO/SiO₂ nanocatalyst is found to be 150.25 m²/g. Fractional Factorial design was applied to find optimum condition of process parameters and found that optimum percent. Removal of COD (mg/l), and acenaphthylene were achieved at reaction condition of 1 g/L of ZnO/SiO₂ nanocatalyst loading, 30°C temperature and 4 h reaction time and found that optimum percent removal of COD (mg/l), and acenaphthylene is 75%, and 73% respectively. Various metals, naturally present in palash leaves’ powder, decrease band gap of energy and improve photocatalytic activity of nanocatalyst.