Complex conductivity of water-saturated packs of glass beads

• Published in: Journal of colloid and interface science 2008-05, Vol.321 (1), p.103-117
• Main Authors: Leroy, P., Revil, A., Kemna, A., Cosenza, P., Ghorbani, A.
• Format: Article
• Language: English
• Subjects: Chemistry; Colloidal state and disperse state; Complex conductivity; Double layer; Exact sciences and technology; General and physical chemistry; Induced polarization; Particle size distribution; Porous materials; Porous media; Spectral impedance; Surface physical chemistry
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2007.12.031

The low-frequency conductivity response of water-saturated packs of glass beads reflects a combination of two processes. One process corresponds to the polarization of the mineral/water interface coating the surface of the grains. The other process corresponds to the Maxwell–Wagner polarization associated with accumulation of the electrical charges in the pore space of the composite medium. A model of low-frequency conductivity dispersion is proposed. This model is connected to a triple-layer model of electrochemical processes occurring at the surface of silica. This model accounts for the partition of the counterions between the Stern and the diffuse layers. The polarization of the mineral/water interface is modeled by the electrochemical polarization model of Schurr for a spherical grain. We take into account also the DC surface conductivity contribution of protons of the sorbed water and the contribution of the diffuse layer. At the scale of a macroscopic representative elementary volume of the porous material, the electrochemical polarization of a single grain is convoluted with the grain size distribution of the porous material. Finally, the Maxwell–Wagner polarization is modeled using the complex conductivity of a granular porous medium obtained from the differential effective medium theory. The predictions of this model agree well with experimental data of spectral induced polarization. Two peaks are observed at low frequencies in the spectrum of the phase. The first peak corresponds to the distribution of the size of the beads and the second peak is due to the roughness of the grains. Phase of the complex conductivity as a function of the frequency for a pack of glass beads with a rough surface at different salinities and comparison with the prediction of the model.