Table of Contents
ISRN Soil Science
Volume 2012, Article ID 739051, 7 pages
http://dx.doi.org/10.5402/2012/739051
Research Article

Leaching of Fluoride from Biotite Mica in Soil: Implications for Fluoride in Shallow Groundwater

Department of Geology, Faculty of Science, University of Peradeniya, 20400 Peradeniya, Sri Lanka

Received 15 December 2011; Accepted 17 January 2012

Academic Editors: V. Ferro and L. S. van Overbeek

Copyright © 2012 K. U. K. S. Kularatne and H. M. T. G. A. Pitawala. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Leaching of F from biotite was investigated at room temperature by performing a series of short-term leach tests. The leaching of F from biotite structure strongly depends on its weathering stage. Results of this study suggest that high concentration of F is leached from highly weathered biotite, compared to fresh biotite. Results of dissolution experiments confirm that the organic acids in soil promote the leaching of F from biotite compared to inorganic acids. Citric acid which is a week organic acid enhances leaching of F from biotite structure compared to strong inorganic acid HNO3, independent of the weathering stage of biotite. Strong positive correlation between K+ and Fe2+ with F in biotite treated with citric acid suggests that F readily leachs into the solution through an ionic exchange and complex formation. Organic acids involve sorption and complex formation processes leading to release of F into the solution. Our studies suggest that in the presence of organic acids F is leached readily into water percolating through the soil. Therefore, shallow groundwater replenished by the water table may achieve high F concentrations by this leaching process.