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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 3109 from those obtained from both the untreated zeolitic mineral and the material treated with Na and Ca.

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The removal of phenol from aqueous solutions using surfactant-modified clinoptilolite-rich tuffs (SMZ) prepared from two Mexican zeolitic tuffs (Chihuahua and Oaxaca) was investigated. Sodium homoionization of the zeolitic rocks was performed before they were modified with the surfactants: hexadecyltrimethylammonium chloride or bromide and bencylcetildimethylammonium chloride. The surfactants in the modified zeolitic materials were determined considering the total carbon in the samples. The phenol removal was determined in a batch system taking into consideration the different quantities of surfactants in the zeolitic tuffs, contact time, pH and initial phenol concentration. The phenol was determined in the aqueous solutions by UV/Vis spectroscopy. Results showed that the formation of a hemimicelle or admicelle on the zeolites depended on the initial surfactant concentration and they were responsible for the type of interactions between the phenol and the surfactant-modified zeolites. Phenol adsorption by the surfactant-modified zeolites was carried out in approximately three hours. Phenol adsorption data was best adjusted to the pseudo-second order kinetic model. Both, surface properties of the surfactant-modified zeolites and pH of solution play an important role in the removal of this pollutant from aqueous solutions and they are responsible for the type of mechanism involved.

The adsorption of Brilliant Blue FCF from aqueous solution was evaluated using a Fe-zeolitic tuff. The adsorbent was characterized by scanning electron microscopy, IR spectroscopy and X-ray diffraction. Sorption kinetic, isotherms, dose and pH effects were determined and the adsorption behavior was analyzed. Kinetic pseudo-first order and linear isotherm models were successfully applied to the experimental results, indicating that the sorption mechanism is physisorption. Experiments in columns were performed and breakpoint was found in 100 min using a concentration of 5 mg/l.