Abstract
Desorption of Zn 2+ by montmorillonite in alkaline and earth alkaline environments was carried out at room temperature and at pH 6.0 using the following techniques: a combination of analytical methods to determine the variation of montmorillonite chemical composition, X-ray powder diffraction (at controlled relative humidity and at controlled temperature in the range 50°C≤ T≤400°C) and thermal analysis. The desorption isotherms clearly show that some of the Zn 2+ cations are retained in the layers, the proportion being greater when the montmorillonite is treated with Na + and smaller when treated with Mg 2+. The d (001) basal spacing, for samples teated with Na +-K + and Na +-Ca 2+ mixed solutions, appears to be mainly affected by the first appearance of K + and Ca 2+. Differential thermal analyses of Zn 2+-exchanged samples shows two dehydroxylation reactions at about 380 and 650°C which emphasized that Zn 2+ is differently bonded in the layers and hence differently released.
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