Evaluation and DFT analysis of 3D porous rhombohedral Fe-modified MgO for removing fluoride efficiently

Abstract

Three-dimensional porous rhombohedral Fe-modified MgO mixed metal oxide (CMF) adsorbent was successfully prepared via a one-step hydrothermal method without the use of a template and surfactant. This material can be used to remove excess fluoride from water. Because of the integration of Fe, it efficiently responds to low concentrations of fluoride in water, and the resulting adsorbent exhibits lamellar peeling and reorganization; it also captures a large amount of fluoride. The adsorption behavior of fluoride on the surface of CMF conforms to the Freundlich isothermal model and to the pseudo-second-order kinetics model. The maximum adsorption capacity of CMF for fluoride was as high as 126.79 mg/g. Electrostatic attraction, ion exchange, and bonding of fluoride and metal were the adsorption mechanism of CMF. DFT analysis showed that Fe-modified MgO with a low doping rate is more beneficial for the adsorption of fluoride, and the adsorption energy is −1.139 eV. F bonds to metal via orbital hybridization. Moreover, cycling experiments indicated that the material has good reusability and can be used for long-term absorption of fluoride. This task may contribute to the task of developing sustainable water resources, which is beneficial to human life and natural environment.