A low-cost and high efficient zirconium-modified-Na-attapulgite adsorbent for fluoride removal from aqueous solutions

In this work, the sorption of fluoride on a novel zirconium-modified-Na-attapulgite (Zr-A) adsorbent was studied. The adsorbent was characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM) with EDAX analysis, X-ray photoelectron spectroscopy (XPS) and pH(ZPC) measurement. Physico-chemical parameters such as adsorbent dose, pH. initial fluoride concentration, temperature, equilibrium contact time and co-existing anions were studied in a series of batch adsorption experiments. The fluoride adsorption by the Zr-A adsorbent agreed well with the Langmuir model. The maximum adsorption capacity of the adsorbent is about 24.55 mg/g. The fluoride adsorption kinetics over the adsorbents was well described by the pseudo-second-order kinetic model. After six regeneration cycles, the Zr-A adsorbent still showed high adsorption capacity. Finally, possible defluoridation and regeneration mechanisms were proposed. (C) 2011 Elsevier B.V. All rights reserved.