Study on defluoridation of drinking water using zirconium ion impregnated activated charcoals

Abstract

Activated charcoals which are effective for fluoride removal, when impregnated with zirconium metal ions have an increase in their fluoride adsorption capacity by 3 to 5 times to that of plain activated charcoal. Continuous down flow adsorption mode at room temperature was adopted to defluoridate drinking water. Three columns were prepared by the impregnation of ZrOCl₂ in groundnut shell, coconut shell and coconut fiber activated charcoals. The column was run at a constant rate of 0.6-0.7 L/h with known fluoride influent water and a constant level of water was maintained. Treated water samples were analysed by the ion selective electrode method. In this study zirconium ion impregnated coconut fiber charcoal (ZICFC) showed maximum fluoride uptake and proved to be the most effective defluoridating agent followed by groundnut shell and coconut shell charcoals. ZICFC was effective for 21 liter lots of (8.0 mg F- ion/L) test solution and 6 liter lots of (2.47 mg F ion/L) tap water, where the fluoride concentration in each of these liter lots is less than 1.5 mg/L.