Microfabrication of covalent organic framework-based magnetic bio-ceramic beads for defluoridation of water

Abstract

In this investigation, novel hybrid materials comprising covalent organic frameworks and hydroxyapatite, which possess appreciable defluoridation capacity, were synthesized. However, their powder form makes them difficult to use in column studies, particularly the separation after adsorption. Hence, these hybrid materials were modified with magnetic biopolymers and thus named iron oxide/alginate–gelatin/hydroxyapatite/covalent organic framework (MAGHCOF)-based bio-hybrid beads, and they revealed high fluoride adsorption performance in an aqueous system. The fabricated MAGHCOF beads were analyzed using FTIR, EDAX and SEM investigations. The response parameters for defluoridation were assessed, including reaction time, dosage, preliminary concentration, interfering anions, pH, and temperature. The results of analyses using MAGHCOF beads revealed that the high fluoride adsorption is mainly due to electrostatic interactions that robustly exist between fluoride and the metal nodes in the beads. Thermodynamic investigations showed that fluoride adsorption was spontaneous, endothermic and feasible in nature. The adsorption kinetic and isotherm data were more fitted with the pseudo-second-order and Langmuir models, correspondingly. The suitability for field application was explored using the fabricated MAGHCOF bio-hybrid beads, and results also exhibited that they are suitable at the field level. After six cycles, MAGHCOF bio-hybrid beads exhibited good regeneration performance, indicating that the MAGHCOF beads are promising materials for the defluoridation of water.