Adsorptive removal of fluoride from aqueous solutions using Al-humic acid-La aerogel composites

A novel and environmental friendly aerogel composite was synthesized by freeze-drying method using humic acid as low cost starting material. The as-prepared aluminum-humic acid-lanthanum (Al-HA-La) aerogel composites were fully characterized by nitrogen adsorption-desorption, SEM, EDX, XRD, FTIR and TGA Then, the adsorption behaviors of fluoride on Al-HA-La adsorbent were investigated systematically, including the influence of initial pH, adsorption kinetics, adsorption isotherms, desorption study, etc. Batch adsorption experimental results showed that the high fluoride removal of Al-HA-La was obtained in a wide initial pH range from 5 to 11. The adsorption equilibrium was achieved within 40 min (pH = 7.0), and the adsorption kinetics could be well fitted by the pseudo-second-order model. The adsorption isotherms could be well described by the Langmuir isotherm model and the maximum adsorption capacity calculated from Langmuir model was high up to 50 mg g−1 at 298 K (pH = 7.0). Moreover, the co-existing of other anions and cations showed limited influence on the adsorption of fluoride on Al-HA-La. Furthermore, the fluoride adsorbed on Al-HA-La could be effectively desorbed using 10−2 mol L−1 NaOH, and the desorption efficiency was as high as 90%.