Low-frequency dielectric properties of three bentonites at different adsorbed water states

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:411

Article

Kaden, Heike^1,2  Koeniger, Franz^1,2  Stromme, Maria³  Niklasson, Gunnar A.³  Emmerich, Katja¹ 

[1] Karlsruhe Inst Technol, Competence Ctr Mat Moisture, D-76021 Karlsruhe, Germany

[2] Karlsruhe Inst Technol, Inst Funct Interfaces, D-76021 Karlsruhe, Germany

[3] Uppsala Univ, Angstrom Lab, Dept Engn Sci, Uppsala, Sweden

关键词: Clay mineral;    Layer silicate;    Smectite;    Bound water;    Permittivity;    Equivalent circuit;   

DOI  :  10.1016/j.jcis.2013.08.025

来源: Elsevier

【 摘 要 】

Three bentonites of varying smectite content were investigated by dielectric spectroscopy in the frequency range 10(-4) to 10(6) Hz after storage at well-defined humidities. The identification of relaxation processes from complex permittivity measurements was difficult, since conductivity effects were superimposed on the underlying relaxations. Relaxation peaks revealed by the dissipation factor indicated the occurrence of interfacial processes between 10(2) and 10(6) Hz. The intensity of the polarization of the electrochemical double-layer at the clay-water interface was promoted by increasing water content and was shifted to higher frequencies the higher the water content in the bentonites. Below similar to 1 Hz, electrode polarization (EP) was shown to be a participating process with capacitance values ranging from 0.6*10(-3) to 7.3*10(-3) F due to the accumulated charges. An equivalent circuit model was introduced that successfully described the low-frequency dielectric behavior of bentonites at low moisture levels. An included series R-CPE connection was used to describe the double-layer relaxation. At water contents up to 17%, the bulk resistivity was mainly influenced by smectite content and cation exchange capacity, whereas at water contents of >= 19%, interlayer occupation and hydration state became more important. (C) 2013 Elsevier Inc. All rights reserved.

【 授权许可】

Free