Exploring the potential of magnetic persimmon tannins-based bio-adsorbent for Cd (II) ions removal from water: Experiment and DFT study

Cadmium (Cd (II)) pollution in water and soil is a global problem that poses a serious threat to both human health and the ecological balance of the environment. Therefore, the development of efficient and environmentally friendly bio-adsorbent materials is the key to remediating Cd (II) pollution. Herein, a magnetic persimmon tannins composites bio-adsorbent (Fe 3 O 4 /PT, MPT) which is decorated with iron oxide has been successfully prepared by the crosslinking method for investigating its adsorption potential and mechanisms of Cd (II) in aqueous solution. The maximum Cd (II) adsorption capacity of MPT adsorbent is 73.33 mg/g. Further, the adsorption kinetic and isotherm are in line with the pseudo-second-order model and Freundlich equilibrium isotherm model. The thermodynamic study showed that the adsorption process is exothermic and spontaneous. Especially, the density functional theory calculations of geometric configuration and isosurface diagram both confirm the interaction mechanisms between MPT and Cd (II) including chelation reactions and electrostatic interactions, which are consistent with experiment results. All these results indicate that MPT bio-adsorbent can be used as an efficient, environmentally friendly and low-cost bio-adsorbent for the removal of Cd (II) contaminants from aqueous solution.