BRGM, French Geological Survey, 45060 Orléans, France; Department of Earth Sciences, Uppsala University, 75236 Uppsala, Sweden.
Department of Geophysics, Steinmann Institute, Bonn University, 53115 Bonn, Germany.
J Colloid Interface Sci. 2017 Nov 1;505:1093-1110. doi: 10.1016/j.jcis.2017.06.071. Epub 2017 Jun 21.
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.
蒙脱石（Mt）粘土具有高比表面积和表面电荷，这使它们具有显著的吸附性能。然而，由于其微观结构和界面性质的复杂性，其电化学和聚集行为尚未完全阐明。在这项工作中，首次使用光谱感应极化法研究了重量分数为 0.5-5.2%的 Na-Mt 悬浮液的导电和分散性能。四电极系统用于减少电极极化和接触电阻引入的误差。使用 Mt 基面的三层模型和考虑扩散层传导和 Stern 层极化的复导电性模型，成功地描述了低频范围为 0.1Hz 至 45kHz 的复导电性谱。从反转弛豫时间分布推断出聚集尺寸分布。我们发现，Na-Mt 基面的负永久表面电荷控制其正交（虚部）电导率，该电导率在 100Hz 至 45kHz 频率范围内对 pH 值和盐度（NaCl）不敏感。对于较低的频率，在最高盐度下正交电导率的突然增加可以通过考虑 Na-Mt 颗粒的凝聚来解释。
