WATER DEFLUORIDATION BY MEXICAN HEULANDITE–CLINOPTILOLITE

Abstract

Fluorosis is caused by excess ingestion of fluoride. In this work, a natural Mexican zeolite (heulandite–clinoptilolite from Sonora) was evaluated for the sorption of fluoride ions from aqueous solutions and well-water. The effects of sodium, calcium, lanthanum, and europium in the crystalline network of this aluminosilicate, as well as, the effects of pH and particle size of the zeolite on the fluoride sorption were determined. It was found by x-ray diffraction, electronic microscopy, and IR that the structure of the material does not change after the retention of fluoride ions, and fluoride retention is not substantially affected by the cations (Na, Ca, La, and Eu) in the zeolite, the initial pH, or the particle size of the material studied. The K _d values obtained from the zeolitic mineral treated with La and Eu are slightly different from those obtained from both the untreated zeolitic mineral and the material treated with Na and Ca.

Keywords:

• Fluoride ions
• Sorption
• Mexican heulandite–clinoptilolite

ACKNOWLEDGMENTS

The authors thank CONACYT (Project 35322-E) for their financial support, I. García-Sosa, B. Y. Moreno-Gutiérrez, and M. Rivera-Garza for their collaboration to the zeolite characterization, Departamento de Análisis Químicos del Instituto Nacional de Investigaciones Nucleares for the colorimetric fluoride determinations and V. Martínez-Miranda for her suggestions.