Natural zeolites from Ethiopia for elimination of fluoride from drinking water

Zeolites and fluoride-rich groundwaters are both usually associated to volcanic regions, and hence in this work we study natural zeolites as fluoride-adsorbents in order to develop a cheap and locally-available fluorosis mitigation technology. The defluoridation capacities of eleven samples originally from Ethiopia are studied as raw materials, without any treatment. Results show that one of the samples, containing mainly analcime and mordenite zeolites, has a maximum defluoridation capacity of 0.47 mg(F-)/g; interestingly, this adsorbent is able to reduce the fluoride concentration beyond the safe limit established by the World Health Organization of 1.5 mg/L. In addition, desorption of fluoride from the adsorbent is easily and quantitatively achieved by subjecting the fluoride-loaded solid to a mild treatment of NaOH 0.001 M; such regenerated adsorbent retains 56% of the initial defluoridation capacity. Experiments carried out with real groundwaters show that this sample preserves its high defluoridation capacity in an actual case. Therefore, our study reports a promising cost-effective and locally-available new adsorbent for defluoridation of fluoride-rich groundwaters. (C) 2013 Elsevier B.V. All rights reserved.