The present study demonstrated the adsorption potential of goethite rich iron ore (GRI) of Daitari, Orissa, India under various pH, adsorbent dose, initial fluoride concentration and presence of major co-existing anions. Adsorption of fluoride on GRI was relatively fast in first 2 h followed by slow adsorption leading to equilibrium within 4-5 h. Maximum adsorption was achieved in the pH range of 4.5-5.5. The time course adsorption data was well fitted to both first-order and pseudo second-order rate expression while the experimental equilibrium sorption data were better to Freundlich isotherm indicating that the GRI surface was heterogeneous. The presence of co-existing anions also affected fluoride adsorption according to their affinity on the GRI surface in the following order: HCO3− > SO42− > Cl−> NO3−. Alkaline pH promotes the fluoride desorption, and more than 65 % of adsorbed fluoride was released to solution at pH ~ 10.
Keywords: Goethite; Iron Ore; Fluoride; Sorption;