Removal of Fluoride from Aqueous Solution by Ettringite

Abstract

In order to purify waste water containing fluoride, the calcium additive method has usually been used to recover fluoride ions in the form of refractory calcium fluoride. In this case, the removable fluoride concentration is limited to be 10-15 mg/l due to the solubility of calcium fluoride. In this study, we report 3CaO•Al₂O₃•3CaSO₄•32H₂O (ettringite) as a highly absorbent substance for the fluoride. The fluoride concentration of the water treated with the ettringite was achieved to be less than 8 mg/l without sludge.