Remove of fluoride using covalent organic framework supported aluminium oxide: An experimental and computational mechanism

Fluoride pollution is a problem of increasing concern to global public health, and it is important to reduce the concentration of fluoride ions in water. In this paper, the composite adsorbent (Al2O3-COF) of Al2O3 and melamine polymer network (MPN) was prepared by the solvothermal method, and the physicochemical properties of the material were characterized. The characterizations showed that Al2O3-COF had a porous and loosely packed morphology, and the adsorption behavior conformed to the pseudo-first-order kinetic and the Langmuir isotherm model. This study showed that Al2O3-COF exerted the synergistic effect of Al2O3 and COFs to adsorb fluoride, with an adsorption capacity superior to that of a single alumina at 66.2 mg/g. The adsorption performance test showed that the interfering anions (PO43-, Cl-, Br-, NO3-, SO42-) had little effect on the adsorption performance of Al2O3-COF while maintaining a fluoride removal rate of over 83 %. After 5 cycles of recycling, more than 75 % of fluoride ions could also be removed. In addition, insights into the adsorption mechanism of Al2O3-COF, mainly through ion exchange and chemisorption, were calculated by density functional theory. This experiment is to apply COFs in the field of F- adsorption, which can provide ideas and guidance for future research.