Adsorptive Elimination of Recalcitrant Metallic Contaminants from Aqueous Effluents Employing a CuO‐Encapsulated Hydrogel Nanocomposite Supported by <i>Cassia Nodosa‐</i> Derived Biochar

Abstract Heavy metal contamination in water poses severe environmental and health risks, including genotoxicity and cancer. This study presents novel adsorbents for chromium (Cr) and nickel (Ni) removal from synthetic wastewater, including Cassia nodosa L. biomass and biochar, CuO nanoparticles (CuO NPs), CuO/biochar‐based nanocomposites (NC), chitosan/PVA hydrogel (H), and biochar‐supported CuO‐encapsulated hydrogel nanocomposites (EHNC). Adsorption efficiency was optimized by varying pH (2 for Cr, 5 for Ni), contact time (0–480 min), adsorbent dose (0.1 g), and initial metal concentration (10–400 ppm). EHNC exhibited the highest removal efficiency, achieving 91.70% for Cr and 89.18% for Ni. Adsorption followed pseudo‐second‐order kinetics ( R 2 = 0.9969) and the Freundlich isotherm ( R 2 = 0.9991), confirming multilayer adsorption. SEM, XRD, and FTIR analyses were used to determine surface morphology and functional groups. Statistical analysis using simple linear regression (SLR) confirmed data reliability. This study highlights EHNC as a highly efficient, cost‐effective, and eco‐friendly adsorbent for sustainable industrial wastewater treatment.