Fluoride sorption using morringa indica –based activated carbon
Fluoride is an important micro nutrient for the production and maintenance of healthy bones and teeth. Although a certain amount of fluoride gives good protection against dental decay, excess intake of fluoride ions cause dental fluorosis. When the concentration of fluoride is more than 4 mg/L it causes softening of bones, ossification of tendons and ligaments and neurological damage in severe cases (Karthikeyan, 2005). Fluoride can be removed from water by several methods. Most prevalent defluoridation technologies involve precipitation, adsorption and ion exchange mechanisms. Different adsorbent materials employed for defluoridation include activated carbon obtained from several sources, bone charcoal, tricalcium phosphate, activated alumina, alum and lime. Precipitation of fluoride with calcium, aluminum salts and lime can be done but the treated water have high pH resulting in a supplementary difficulty of eliminating excess chemicals (Fan, 2003). Adsorption is another technique in which fluoride is adsorbed onto a membrane or a fixed bed packed with resin or other mineral particle. Many techniques such as reverse osmosis, electrodialysis, Donnan dialysis, etc also have been reported to be successful defluoridation methods.(Elniidaoui, 1 998).In recent years a large number of cost effective adsorbents have been reported to possess fluoride removal capacity. Few are flyash (Singh, 1990), bauxite (Express India, 1998), silica gel (Wang, 1995) zeolites (Mayadevi, 1996), spent catalyst (Liu, 1996), natural soil (Balkema, 1998) and clay minerals which were established to remove fluoride from aqueous medium through adsorption. The fluoride adsorption efficiency of these materials mainly depends on the nature of adsorbents. Fluoride adsorption capacity of activated carbon prepared from agriculture waste is experimentally verified. Activated carbon obtained by burning and carbonization of the Iviorringa Indica bark, possess appreciable defluoridation efficiency.