Changes in induced polarization associated with the sorption of sodium, lead, and zinc on silica sands

• Published in: Journal of colloid and interface science 2011-08, Vol.360 (2), p.739-752
• Main Authors: Vaudelet, P., Revil, A., Schmutz, M., Franceschi, M., Bégassat, P.
• Format: Article
• Language: English
• Subjects: cations; Chemistry; Colloidal state and disperse state; Conductivity; dielectric spectroscopy; Double layer; Earth Sciences; electric current; electric field; Electrical double layer; Exact sciences and technology; General and physical chemistry; Geomorphology; Induced polarization; Lead; lead nitrate; Low-frequency dielectric spectroscopy; Mathematical models; phase transition; Polarization; Porosity; Porous materials; Resistivity; Sand; Sands; Sciences of the Universe; Silica; sodium; sodium chloride; sorption; Surface conductivity; Surface physical chemistry; TLM; Zinc; zinc sulfate
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2011.04.077

Phase lag between the current and the voltage for different types of cations sorbed onto silica. [Display omitted] ► Induced polarization is sensitive to sorption of metallic cations on silica. ► The main polarization mechanism is related to the polarization of the Stern layer. ► A Stern layer polarization model coupled with a complexation model can explain the induced polarization data. Low-frequency dielectric spectroscopy can be measured in terms of a conductance and a phase lag between the electrical current and the electrical field. This conductance and phase lag can be written as into a complex conductivity with both an in-phase and quadrature components that are frequency dependent. In sands, the low-frequency (10mHz–40kHz) spectra of the complex conductivity are dominated by the polarization of the electrical double layer (especially the internal part of the electrical double layer called the Stern layer) and the Maxwell–Wagner polarization (typically above 100Hz). We present a polarization that is able to explain the complex conductivity spectra including the grain size distribution, the porosity, and the complexation of the mineral surface with the ions of the pore water. To test this model, we investigate the sorption of various cations (Na, Pb, Zn) characterized by different affinities with the surface of silica. Sand column experiments were carried out to see the change in the complex conductivity during the advective/dispersive transport of a lead nitrate solution and a zinc sulfate solution, replacing a sodium chloride solution in the pore space of the sand. The complex conductivity model is able to explain the change of the phase over time.