Defluoridation with Locally Produced Thai Bone Char

The fluoride sorption ability of a locally available bone char is quantified. Both a synthetic solution and natural groundwater samples from several sites are studied and compared to Indian bone char, which is widely accepted and used successfully in India and elsewhere. The Freundlich and Langmuir sorption isotherms were used to quantify sorption properties. Results show that the Thai bone char is as effective as the Indian bone char for removing fluoride from contaminated water, despite the more rigid physical and social constraints found in rural Thailand. Sorption studies with fluoride-contaminated natural groundwater samples also show that chlorides, nitrates, and sulfates had little effect on the removal of fluoride by the homemade bone char. 1. Introduction Fluoride contamination of groundwater is a common environmental problem worldwide. The allowable drinking water standard for fluoride is 1.5？mg？L？1 [1]. Concentrations of fluoride higher than this level affect both teeth and bone, resulting in dental or skeletal fluorosis. In rural Thailand, fluoride concentrations in groundwater range from 1 to 20？mg？L？1 and dental fluorosis has been recorded since 1960 [2]. Studies have also documented liver and kidney damage [3] and a bone cancer called osteosarcoma found in young boys exposed to high levels of fluoride [4]. Continuous intake of fluoride may also cause damage to the nervous system [5]. Fluoride removal at point of use is still an ongoing research area since the major water source in most rural areas around the world is groundwater. Rural areas use groundwater for drinking and household use. Centralized methods, such as the village-centered reverse osmosis systems installed in about 1250 villages in Thailand between 2004 and 2008 for fluoride removal, are costly, require high maintenance, and are simply not available to many rural areas. Effective fluoride removal methods such as reverse osmosis [6, 7] and membrane technology [8–10] are applied in many countries; however the high installation and maintenance costs of these methods generally preclude their use in poor countries. Low cost fluoride removal technologies, such as coagulation [11] and adsorption [12], are more acceptable in developing countries. Adsorption is a very popular method because of its simplicity in preparation, operation, and maintenance. Recently, many attempts have been made to use waste or low cost materials as the absorbent. The materials studied include bauxite [13], montmorillonite [14], activated water treatment sludge [15], waste mud [16], red mud [17], granular