Eco-Friendly Fabrication of Porous ZnO Nanostructures Using Araucaria heterophylla Leaf Extract for Catalytic Wastewater Treatment: A Sustainable Approach to Toxic Pollutant Removal

The current investigation documented the construction of eco-friendly zinc oxide nanoparticles (ZnO NPs) using Araucaria heterophylla leaf extract. The synthesized material is characterized through various techniques. The x-ray diffraction (XRD) spectrum depicted prominent diffraction peaks. 31.9 nm was determined to be the average particle size. The spherical and aggregated ZnO NPs were visible in the scanning electron microscope (SEM) results. Energy dispersive x-ray (EDX) spectra results confirmed the existence of Zinc and oxygen elemental peaks. FTIR results of synthesized ZnO NPs and leaf extract elaborated on the participation of phytochemical constituents. Catalytic activity is investigated for Methylene blue (MB) and Congo red dye (CR). For both dyes, the best outcomes are achieved when the dye concentration is 5 mg/L and the adsorbent dose is 10 mg, with a contact duration of 20 min. Adsorption isotherms (Langmuir and Freundlich) and kinetic models including pseudo first order, Elovich, intraparticle diffusion, and Boyd were also applied for dye degradation studies. Antioxidant potential is assessed with three different approaches: total antioxidant, 2,2-diphenyl-1-picrylhydrazyl (DPPH) activity, and total phenolic contents. The scavenging free radical activity percentage was calculated to be 82 ± 0.07 with 1500 μg/mL concentration. In comparison to the standard, total antioxidant activity is 0.569 ± 0.07 (% w/w). While total phenolic contents were 244 ± 1.4 mg GAE/g. Hence, this study demonstrated that biosynthesized ZnO NPs exhibit adequate potential for environmental remediation studies.