Study on the fluoride removal characteristics of mineral (fluorapatite)

Abstract

The effectiveness of low grade fluorapatite bearing mineral on fluoride removal has not been examined earlier. For identification of such mineral, a preliminary assessment of performance of mineral is essential in order to know which aspect is necessary to carry out further research for development of mineral based defluoridation technology. In this study batch adsorption study was performed to evaluate the fluoride removal potential of low cost rock phosphate (fluroapatite) mineral at pH 4, 5 and 6. The optimum dose was determined to be 1.5, 2.5 and 3.5 g mineral at pH 4, 5 and 6, respectively. The first order adsorption rate constants derived by Lagergren equation at different pH, clearly indicates the fast removal kinetics at pH 4. The comparatively high solubility of mineral and an increase of calcium concentration at pH 4 appears to be the main reason for fast removal reaction. There was no effect of mineral quantity on fluoride removal after solution pH became alkaline. The various aspects of the study including recyclability of mineral are discussed.