Performance of Rod-Shaped Ce Metal–Organic Frameworks for Defluoridation

The performance of a Ce(III)-4,4′,4″-((1,3,5-triazine-2,4,6-triyl) tris (azanediyl)) tribenzoic acid–organic framework (Ce-H3TATAB-MOFs) for capturing excess fluoride in aqueous solutions and its subsequent defluoridation was investigated in depth. The optimal sorption capacity was obtained with a metal/organic ligand molar ratio of 1:1. The morphological characteristics, crystalline shape, functional groups, and pore structure of the material were analyzed via SEM, XRD, FTIR, XPS, and N(2) adsorption–desorption experiments, and the thermodynamics, kinetics, and adsorption mechanism were elucidated. The influence of pH and co-existing ions for defluoridation performance were also sought. The results show that Ce-H3TATAB-MOFs is a mesoporous material with good crystallinity, and that quasi-second kinetic and Langmuir models can describe the sorption kinetics and thermodynamics well, demonstrating that the entire sorption process is a monolayer-governed chemisorption. The Langmuir maximum sorption capacity was 129.7 mg g(−1) at 318 K (pH = 4). The adsorption mechanism involves ligand exchange, electrostatic interaction, and surface complexation. The best removal effect was reached at pH 4, and a removal effectiveness of 76.57% was obtained under strongly alkaline conditions (pH 10), indicating that the adsorbent has a wide range of applications. Ionic interference experiments showed that the presence of PO(4)(3−) and H(2)PO(4)(−) in water have an inhibitory effect on defluoridation, whereas SO(4)(2−), Cl(−), CO(3)(2−), and NO(3)(−) are conducive to the adsorption of fluoride due to the ionic effect.