Synthesis, Characterization and Application of Azadirachta Indica Leaf-Derived Zinc Oxide Nanoparticle for Remediation of Heavy Metals in Dumpsite-Contaminated Soil

Azadirachta indica (neem) leaf extract-mediated synthesis of zinc oxide nanoparticles (ZnO NPs) provides an eco-friendly, cost-effective, and sustainable approach for heavy metal remediation in contaminated environments. This study evaluated the potential of A. indica-derived green nanoparticles for remediating dumpsite-contaminated soil. Soil samples were collected at a depth of 0–10 cm using a soil auger along the Gujba Road dumpsite in Damaturu, Yobe State, Nigeria. Physicochemical parameters were determined using standard procedures, and heavy metal concentrations were analysed via Atomic Absorption Spectroscopy (AAS). Aqueous extract from 200 g of A. indica leaf powder in 1,000 mL of distilled water was mixed with zinc salt under heated conditions to synthesize ZnO NPs. Characterization by UV-Visible spectroscopy and Fourier-Transform Infrared (FTIR) spectroscopy confirmed the successful green synthesis of ZnO NPs. Phytoremediation efficacy on the contaminated soil was evaluated at 0, 7, 14, 21, and 28-days post-application. Data were analysed using Analysis of Variance (ANOVA) at $p < 0.05$. Results indicated that the dumpsite soil exhibited alkaline pH, elevated electrical conductivity, and high organic carbon and nutrient contents. Prior to treatment, arsenic (As) and cadmium (Cd) concentrations exceeded World Health Organization permissible limits. Application of synthesized ZnO NPs led to a progressive reduction in arsenic, cadmium, and lead (Pb) concentrations across the sampling intervals.