Spectral induced polarization of Na-montmorillonite dispersions

Abstract

Montmorillonite (Mt) clays have a high specific surface area and surface charge, which confer them remarkable adsorption properties. Nevertheless, their electrochemical and aggregation behavior are not completely elucidated because of the complexity of their microstructural and interfacial properties. In this work, the conductive and dispersive properties of Na-Mt suspensions of weight fractions 0.5-5.2% were investigated for the first time using the spectral induced polarization method. A four-electrode system was used to reduce errors introduced by electrode polarization and contact resistances. Complex conductivity spectra in the low-frequency range of 0.1Hz to 45kHz were successfully described using a triple layer model of the basal surface of Mt and a complex conductivity model that considers conduction of the diffuse layer and polarization of the Stern layer. Aggregate size distributions were inferred from inverted relaxation time distributions. We found that the negative and permanent surface charge of the basal plane of Na-Mt controls its quadrature (imaginary) conductivity, which is not very sensitive to pH and salinity (NaCl) in the 100Hz to 45kHz frequency range. For lower frequencies, the sudden increase of the quadrature conductivity at the highest salinities was explained by considering coagulation of Na-Mt particles.

Influence of smectite and salinity on the imaginary and surface conductivity of volcanic rocks

“…; Leroy et al . ). Clay minerals usually have a smaller particle diameter than other minerals – typically in the range 0.1–10 µm (e.g.…”

“…type of ions, concentration, pH, temperature) influences the imaginary and surface conductivity as well Weller et al 2011;Weller, Zhang and Slater 2015b). It is also suggested that the presence of clay minerals may cause an increase in polarization effects, in addition to an increased surface conductivity (Vinegar and Waxman 1984;Weller et al 2015a;Leroy et al 2017). Clay minerals usually have a smaller particle diameter than other minerals -typically in the range 0.1-10 µm (e.g.…”

Low-frequency dielectric response of a periodic array of charged spheres in an electrolyte solution: The simple cubic lattice

“…The anomalous low-frequency dielectric response of charged particles immersed in an electrolyte has been observed in various types of systems, from suspensions of polystyrene latex particles, emulsions of fat particles [1], and suspensions of clay particles [12,13] to complicated rock formations [42]. Often, the explication of this phenomenon begins with the single-particle polarization response, similar to that given in Eq.…”

Tracking Magmatic Hydrogen Sulfur Circulations Using Electrical Impedance: Complex Electrical Properties of Core Samples at the Krafla Volcano, Iceland

“…Rock polarization is also sensitive, to a lesser extent, to the pore size, the presence of clay minerals, and the electrolyte conductivity, especially in the case of sandstones (Binley et al, 2005;Klein & Sill, 1982;Kruschwitz, 2007;Kruschwitz et al, 2010;Leroy et al, 2017;Lesmes & Frye, 2001;Revil & Skold, 2011;Slater & Sandberg, 2000;Weller & Slater, 2012;Weller et al, 2013). Similarly to connected metallic particles, connected clay minerals may also prevent polarization and cause conduction instead.…”