Optimization of molar concentration of AlCl3 salt in the sol–gel synthesis of nanoparticles of gamma alumina and their application in the removal of fluoride of water

Nanoparticles of gamma alumina prepared by sol–gel method, using alcoholic aluminum chloride (AlCl3) precursor has been demonstrated as an effective adsorbent for fluoride removal of water. Increasing the molar concentration of AlCl3 from 0.1 to 0.25 M was found to increase the nanoalumina content in the same ratio with good yield. Different analytical techniques like thermogravimetry and differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy and Brunauer, Emmett and Teller surface area analysis were employed for the characterization of the synthesized nanoparticles whereas batch adsorption studies were performed for the understanding of adsorption kinetics of fluoride in water of neutral pH. Adsorption kinetics has exhibited excellent fluoride removal capability of ~23 mg/g from the nanoparticles derived using up to 0.2 M AlCl3 precursor. Nanoparticles derived from 0.25 M AlCl3 have shown comparatively less fluoride removal (~18 mg/g). Langmuir equilibrium model was found more suitable for describing the fluoride adsorption mechanism. Presence of sulphate, carbonate, nitrate, and chloride anions in water influenced the fluoride removal efficiency noticeably.