Reaktionen von Ca‐Montmorillonit und Ca‐Vermiculit mit Kohlensäure

• Published in: Zeitschrift für Pflanzenernährung und Bodenkunde
• Main Authors: Veith, J., Schwertmann, U.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1972
• Subjects: Carbonic acid
• Online Access: http://dx.doi.org/10.1002/jpln.19721310105; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjpln.19721310105; https://onlinelibrary.wiley.com/doi/pdf/10.1002/jpln.19721310105

Reaction of Ca‐Montmorillonite and Ca‐Vermiculite with CO 2 The treatment of Ca‐montmorillonite and Ca‐vermiculite with carbonic acid (Pco 2 = 2 atm) has shown the following results: In the pH range of ± 3.9–6.0 Ca is exchanged by H directly only on pH dependent (variable) charge sites (Cav), whereas, Ca on permanent charge sites (Ca p ) is exchanged only by lattice cations mainly Al released by proton attack. Therefore, with regard to proton uptake from carbonic acid the two Ca‐clays behave as extremely weak acids. The exchange of Ca v proceeds rapidly that of Ca p much more slowly, the first one is essentially reversible the latter at least not within a short period of time. The proportion of Ca v is found from a graphical extrapolation of the Ca saturation‐pH‐function (fig. 3). Al released during the initial stage of the reaction is non exchangeable, prevents the expandable minerals partly from collapsing on K tratement (verm. much more than mont.) and has an OH/Al ratio of about 2. On treating the same clay sample several times or at low suspension concentrations exchangeable Al with OH/Al = O occurs. Exchangeable hydrogen was never detected. Vermiculite is less resistent against carbonic acid than montmorillonite. The results were discussed in respect to the mechanism of release of lattice constituents and in respect to Al release under the influence of CO 2 ‐concentrations of soils.