Removal of fluoride ion from groundwater by adsorption on lanthanum and aluminum loaded clay adsorbent

A novel fluoride ion adsorbent, which uses natural clay modified by lanthanum and aluminum, was successfully prepared. The adsorbent was characterized by scanning electron microscope, BET surface area measurement, and X-ray photoelectron spectroscopy. Batch experiments were carried out to investigate the adsorbent performance for fluoride ion. Fluoride ion adsorbent onto modified clay followed the pseudo-second order kinetic model with the correlation coefficient value of 0.9846. The isotherm data was well fitted to the Langmuir model. The adsorption capacity of the modified clay was 1.3033 mg/g. The optimum pH value for fluoride ion removal was 6. The modified clay adsorbent can be regenerated by KAl(SO₄)₂·12H₂O. Six times’ regeneration experiments showed that the regeneration rate of the modified clay still higher than 80 %, and the mass loss rate lower than 10 %. The modified clay performed strong adsorption capacity for fluoride ion and high regeneration rate. It could be a cost-effective adsorbent to remove fluoride from groundwater in undeveloped regions.