Biosynthesis and Analytical Characterization of Iron Oxide Nanobiocomposite for In-Depth Adsorption Strategy for the Removal of Toxic Metals from Drinking Water

The biosynthesis of the iron oxide nanoparticles was done using Ixoro coccinea leaf extract, followed by the fabrication of iron oxide nanobiocomposites (I-Fe₃O₄-NBC) using chitosan biopolymer. Furthermore, the synthesized I-Fe₃O₄-NPs and I-Fe₃O₄-NBC were characterized, and I-Fe₃O₄-NBC was applied to remove toxic metals (TMs: Cd, Ni, and Pb) from water. The characterization study confirmed that the nanostructure, porous, rough, crystalline structure, and different functional groups of chitosan and I-Fe₃O₄-NPs in I-Fe₃O₄-NBCs showed their feasibility for the application as excellent adsorbents for quantitative removal of TMs. The batch mode strategy as feasibility testing was done to optimize different adsorption parameters (pH, concentrations of TMs, dose of I-Fe₃O₄-NBC, contact time, and temperature) for maximum removal of TMs from water by Fe₃O₄-NBC. The maximum adsorption capacities using nanocomposites for Cd, Ni, and Pb were 66.0, 60.0, and 66.4 mg g⁻¹, respectively. The adsorption process follows the Freundlich isotherm model by I-Fe₃O₄-NBC to remove Cd and Ni, while the Pb may be adsorption followed by multilayer surface coverage. The proposed adsorption process was best fitted to follow pseudo-second-order kinetics and showed an exothermic, favorable, and spontaneous nature. In addition, the I-Fe₃O₄-NBC was applied to adsorption TMs from surface water (%recovery > 95%). Thus, it can be concluded that the proposed nanocomposite is most efficient in removing TMs from drinking water up to recommended permissible limit.