International Journal of Ecology and Environmental Sciences
Elimination of Fluoride from Water using Limestone and Common Laboratory Acids
Abstract
An efficient and simple defluoridation method has been evaluated using locally available limestone and some acidic chemicals. For efficient fluoride removal, it requires more time, about 20 hr, because limestone dissolutes in small amounts at neutral pH. In this work, two common laboratory acids were added to the fluoride water before filtration through the limestone column and it was found that in the presence of acid, the removal capacity of limestone not only increased but also became quicker. It was possible to bring down the fluoride level from 10-15 mg/L to below 1 mg/L. High dissolution of limestone in the presence of acids generates a high amount of calcium ion in the water, which precipitates the fluoride as calcium fluoride. The dissolution process by the acids creates new surfaces of the limestone which also helps in adsorption of fluoride onto the surface of the limestone. These two phenomena, precipitation and adsorption of fluoride, were proved as the mechanism of fluoride removal in this process. The limestone has been analyzed before and after the treatment process and it was found that it retains its quality for reuse in the defluoridation process.
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References
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