Biosynthesis of aluminium oxide nanobiocomposite and its application for the removal of toxic metals from drinking water

This work aimed to synthesize the aluminium oxide nanoparticles using Ixoro coccinea leaf extract. Furthermore, the synthesized Ixoro coccinea aluminium oxide nanoparticles (I–Al₂O₃-NPs) and nanocomposites (I–Al₂O₃-NC), including them as the fillers in a chitosan matrix were characterized, and I–Al₂O₃-NC was applied to remove the toxic metals (TMs) including Cd, Ni, and Pb from water. Optimization of different batch experimental adsorption parameters (pH, concentration of TMs, dose of I–Al₂O₃-NC, temperature, and time of contact) was done to check the feasibility of I–Al₂O₃-NC for maximum removal of TMs from water. The extreme adsorption capacities using nanocomposites for Cd, Ni, and Pb were 66.0, 60.0, and 66.4 mg g⁻¹, respectively. The I–Al₂O₃-NC followed the Freundlich isotherm model for removing Cd and Ni while showing the monolayer surface coverage for the removal of Pb. For this process, the best-fitted kinetic model was the pseudo-second-order equation. The enthalpy, entropy, and free energy of metal ion adsorption, among other parameters of thermodynamics, were estimated. The process was found to be exothermic, advantageous, and spontaneous. Kinetic studies show that intra-particle diffusion is essential for eliminating TMs. In addition, I–Al₂O₃-NC was applied for the adsorption of TMs from surface water and determined to be effective in removing these contaminants up to an acceptable drinking water standard. Regeneration of adsorbent suggested that green synthesized I–Al₂O₃-NC may be an active tool for removing Cd, Ni, and Pb ions from contaminated water.