Critical issues in the determination of the bentonite cation exchange capacity
| Autor: | Francesco Mazzieri, Mario Manassero, Nicolò Guarena, Evelina Fratalocchi, Andrea Dominijanni |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Materials science
Clays fabric/structure of soils geosynthetics Solid particle 0211 other engineering and technologies Swelling pressure Charge density 020101 civil engineering 02 engineering and technology geosynthetics Geotechnical Engineering and Engineering Geology 0201 civil engineering Chemical engineering fabric/structure of soils Bentonite cardiovascular system Earth and Planetary Sciences (miscellaneous) Cation-exchange capacity Clays Geosynthetics 021101 geological & geomatics engineering |
| Zdroj: | Géotechnique Letters. 9:205-210 |
| ISSN: | 2045-2543 |
| DOI: | 10.1680/jgele.18.00229 |
| Popis: | The swelling pressure and transport properties of bentonites are controlled by the electric charge density of solid particles, which is commonly estimated from the laboratory measurement of the cation exchange capacity (CEC). However, the standard ammonium displacement method for CEC determination does not take into account the fabric changes that occur in bentonites under exposure to high salt concentration solutions. A series of laboratory tests was conducted to assess the relevance of such a critical issue, by varying the concentration of the extracted potassium chloride (KCl) solution with respect to that of the standard test. The obtained results show that the release of the adsorbed ammonium cations depends on the bentonite fabric, which is controlled by the potassium chloride concentration. As a consequence, the ammonium displacement method may provide an unrepresentative estimate of the CEC of bentonites. The methylene blue titration method, despite its apparently more limited accuracy, instead, seems to provide a more reliable estimation of the CEC, as the bentonite fabric is maintained dispersed during the test. |
| Databáze: | OpenAIRE |
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