Adsorption on calcium-montmorillonite

Stadler, M., and P. W. Schindler. 1993a. Modeling of H+ and Cu2+ adsorption on calcium-montmorillonite. Clays Clay Miner. 41 288-296. 

FIGURE 5.41 HPAM adsorption on calcium-montmorillonite (25°C). Molecular weight curve 1, 6 million curve 2, 9 million curve 3, 10 million and curve 4, 15 million. Source Yang et al. (2002a). 

As seen in the figure, the sorbed quantity of valine strongly depends on the quality of the cation in the interlayer space. Calcium-montmorillonite shows a rather low valine adsorption (about 10 7 mol valine/g Ca-montmorillonite) compared to the other montmorillonites (10 3 mol valine/g Cu-, and Zn-montmorillonites). 

Here, the adsorption of valine on different cation-exchanged montmorillonites is described (Nagy and Konya 2004). A discussion of the kinds of interactions that are possible in the ternary system of montmorillonite/valine/metal ions will be presented, and a description how the metal ions can affect these interactions. The interlayer cations (calcium, zinc, copper ions) were chosen on the basis of the stability constants of their complexes with valine. The adsorption of valine on montmorillonite is interpreted using a surface-complexation model. 

Fig. 9. Distribution coefficients for adsorption of Sr" and Ba" on the calcium form of Wyoming montmorillonite, loading of Sr-H- 7x10-5 to 4.5x10-3 mole/kg, loading of Ba 5x10 to 7.6x10 mole/kg, pH 5, acetate buffer (O.OIM Ca(Ac)2 + HAc), equilibration time 30 to 70 hours.

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