Separation of Low Concentration of Fluoride from Water by Electrodialysis (ED) in the Presence of Chloride and Sulfate Ions

Abstract

Abstract Removal of low concentration of fluoride (2 mg F−/L) in the presence of chloride and sulfate ions from aqueous solution by electrodialysis was studied. The equivalent ratios of sulfate and/or chloride were investigated as co-existing ions on fluoride removal from aqueous solution. The separation performance was evaluated in terms of mass transfer and energy consumption. It was obtained that the separation performance increased when the equivalent ratios of chloride to fluoride and sulfate to fluoride were increased. After 13 min of operation time, 63% of fluoride was removed from the solution when a binary mixture of F− : Cl− (1 : 25) was employed. In the case of a binary mixture of F− : (1 : 25), removal of fluoride was 93% in 16 min. For a ternary mixture of F− : Cl− : (1 : 25 : 25), fluoride was separated from the mixture with a 96% of removal in 20 min.