Removal of Fluoride from Aqueous Solution Using Aluminum Alginate Beads

Fluoride is a contaminant in groundwater; hence numerous procedures for its removal are reported. Adsorption studies are specified as effective methods for removal of fluoride contamination from water sources. In the present study, aluminum cross-linked alginate beads are used as an adsorbent for fluoride removal from aqueous solutions. Adsorption experiments were carried out by batch contact method. The equilibrium was achieved in 4h. Optimal conditions were found to be pH 2 at 25°C, giving rise to 99.5% removal of fluoride. Various kinetic (pseudo-first and -second order, intraparticle diffusion, and Elovich) and isotherm [Langmuir, Freundlich, Dubinin-Radushkevich (D-R), and Temkin] models were applied to the adsorption data. The maximum adsorption capacity was determined as 75.2mg/g from the Langmuir isotherm. The value of mean sorption energy was calculated as 2.75kJ/mol (<8kJ/mol) from the D-R isotherm, which indicates a physical adsorption. Thermodynamic parameters were also calculated and negative ΔG values were related to a spontaneous nature of the adsorption. This study suggests that aluminum alginate beads can be used as efficient, cheap and eco-friendly adsorbents for the removal of fluoride from contaminated water.