Synthesis, Characterization, and Adsorptive Performance of Zinc Oxide and Zinc Oxide–Cellulose Acetate Nanoparticles for the Removal of Zn²⁺, Pb²⁺, and Cd²⁺ from Aqueous Solutions

Heavy metal pollution, particularly by Zn²⁺, Pb²⁺, and Cd²⁺, presents a significant threat to aquatic ecosystems and public health. This study explores the preparation, characterization, and adsorption efficiency of zinc oxide (ZnO) nanoparticles and their cellulose acetate-based nanocomposite (ZnO–CA) to remove these toxic metal ions from aqueous solutions. Cellulose acetate was synthesized from sugarcane bagasse, an agricultural waste, while ZnO was produced via a modified co-precipitation method using various standard methods. The materials were characterized using FTIR, SEM, TEM, EDX, and BET surface area analysis. Batch adsorption experiments were conducted to evaluate the effects of pH, contact time, initial metal concentration, and adsorbent dosage. The ZnO–CA composite displayed a significantly enhanced BET surface area (197.43 m²/g) compared to pristine ZnO (109.64 m²/g), with improved porosity and surface chemistry. Maximum removal efficiencies were recorded at 99.81% for Pb²⁺, 97.32% for Cd²⁺, and 94.18% for Zn²⁺, with equilibrium achieved at 120 minutes. The adsorption process was pH-dependent and favored at values above the point of zero charge, while thermodynamic studies confirmed spontaneity and endothermicity. This research confirms that ZnO–CA nanocomposites are promising, low-cost, and environmentally friendly adsorbents. It is recommended that future work investigates regeneration and scale-up potential. This study contributes to sustainable water treatment strategies by valorizing biowaste into functional nanomaterials for effective heavy metal remediation.