Adsorption capacity of bone char for removing fluoride from water solution. Role of hydroxyapatite content, adsorption mechanism and competing anions

The adsorption of fluoride from water on bone char (BC) was investigated in this work, and the fluoride adsorption capacity of BC was compared to that of hydroxyapatite (HAP). The adsorption capacity of BC and HAP drastically increased while decreasing the pH from 7.0 to 5.0. Furthermore, the fluoride adsorption on BC was due to its HAP content and was not considerably affected by the presence of the anions Cl−, HCO3−, CO32−, SO42−, NO3− and NO2−. The mechanism of fluoride adsorption on BC was attributed to electrostatic interactions between surface charge of BC and fluoride ions in solution.