An effective and selective stable metal-organic framework adsorbent (Al-MOF-5) for the removal of fluoride from water

A novel aluminum (Al)-containing Al-MOF-5 metal-organic framework (MOF) material for the removal of fluoride from the water was prepared using a hydrothermal method.The structure of the resulting product was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermogravimetry, Brunauer, Emmett, and Teller nitrogen adsorption, Fourier transform-infrared spectroscopy, and X-ray photoelectron spectroscopy methods.In batch tests, the effects of adsorbent dosage, pH, and temperature were studied.Result showed that the maximum adsorption capacity of adsorbent for fluoride was 46.08 mg/g.The Langmuir isotherm model and pseudo-second-order kinetics fitted the adsorption process well and the thermodynamics indicated that the adsorption of fluoride on the material was spontaneously endothermic.The Al-MOF-5 displayed a high removal rate of more than 70% at different pHs, and the only PO 4 3-could affect its adsorption efficiency for fluoride.Finally, Al-MOF-5 that had been regenerated six times in NaOH solution at a concentration of 0.3 mol/L still achieved a removal rate of nearly 50% for 10 mg/L fluoride solution.