ABSTRACT
Fluorine, Chlorine, Bromine, and Iodine are usually present as anions and hence, are adsorbed on anion exchange resins. Fluoride is readily adsorbed on strongly basic anion exchange resins in the hydroxide, chloride and acetate forms from solutions adjusted to pH 5 to 9. Fluoride can be adsorbed directly from samples of natural waters, air and ammoniacal solutions. On strongly acid cation exchange resins fluoride is not retained from acid, neutral, or alkaline media. The separation of fluoride from accompanying elements on cation exchange resins may be incomplete in the presence of metals forming stable anionic fluoride complexes such as Al and Zr. Separation from most co adsorbed anions, especially from sulfate, phosphate, and nitrate, can be achieved by elution of the adsorbed fluoride with 0.025 to 0.5 M ammonium chloride solutions adjusted with ammonia to pH ~ 9 or with 0.1 to 0.5 M NaOH solutions.
