Possibility of Fluoride Removal Using Volcano Ash Soils and Bone Charcoal as Adsorbents

Tatsuhide Hamasaki

Faculty of Design Engineering, Osaka Sangyo University, Japan

Abstract: In some regions of Southern Asia and Western Africa, it has been observed that groundwater used as a drinking water source contains more than 1.5 mg/L of fluoride, which is the standard value approved by the World Health Organization. Adsorption is one of the methods widely used for easy fluoride removal; therefore, adsorption and flow tests were conducted using volcano ash soils and bone charcoal as adsorbents. Bone charcoal has already been examined as a fluoride adsorbent; however, volcano ash soils have not been studied previously. The following results were obtained using adsorption tests: the fluoride adsorption coefficients of bone charcoal, Kanuma volcano ash soil, and Akadama volcano ash soil were 1,500, 700, and 490 mL/g, respectively. As the first step for use in a water purification plant, flow tests were conducted assuming a fixed bed adsorption tower. For a water flow rate of

2.0 m/day, 1.8 mg/L of fluoride was reduced to 0.2 and 1.0 mg/L using bone charcoal and Akadama soil, respectively. However, for the water flow rates of 3.0 or 4.0 m/day, 1.8 mg/L of fluoride was reduced to 0.2 and 1.7 mg/L using bone charcoal and Akadama soil, respectively. Therefore, it was observed that the adsorption of the Akadama soil is strongly affected by the water flow rate.

Key words: fluoride, groundwater, volcano ash soil, bone charcoal, adsorption