Effects of the Nature of the Exchangeable Cation and Clay Concentration on the Rheological Properties of Smectite Suspensions

Abstract

The rheological characteristics of purified bentonite suspensions as a function of exchangeable cation (Ca2+,NH4+,Li+)$({\rm{C}}{{\rm{a}}^{2 + }},{\rm{NH}}_4^ + ,\;{\rm{L}}{{\rm{i}}^ + })$ are studied at three different clay concentrations (40 gL−1, 60 gL−1, 80 gL−1). A Herschel-Bulkley model is used to determine rheological parameters such as yield value, consistency and fluidification index. The flow curves are typical for shear thinning fluids but differ on two points; presence of yield stress and/or thixotropy. The Li suspensions are not yield stress fluid, and the thixotropy is weakly expressed only for the 80 gL−1 suspension. On the contrary, Ca-clay suspension flow curves always present yield stress and a large thixotropic area. The NH4-clay suspensions exhibit an intermediate behavior as there is no thixotropy, but a yield stress appears for the most concentrated suspension. These differences in macroscopic mechanical properties are discussed with reference to the suggested microscopic clay organization in suspension.

Evaluation of the organization of the homoionic smectite layers (Na+ or Ca2+) in diluted dispersions using granulometry, microscopy and rheometry

“…Many parameters can modify the smectite layer association: the properties of the smectite sheets (mineralogy, size, structural charge, exchangeable cations…) [12] [13] [14 [15] [16] [17] [18] [19], the ionic environment [20] [21] [22] [23] [24] [25] [26], the solid/liquid ratio [20] [27], the solution chemistry [28], the organic matter [29], and the dispersion preparation.…”

Application of montmorillonite in bentonite as a pharmaceutical excipient in drug delivery systems

“…from autoionization of water easily infiltrates into the interlayer (Song et al 2005 montmorillonite. The physical state of montmorillonite changes from an anhydrous solid to a hydrated material, semi-rigid plastic, gel, and suspension with increasing water content (Norrish 1954;Low 1979Low , 1980Malfoy et al 2003). The change in physical state from an anhydrous solid to a gel is called swelling Ogata 1994, 1996).…”

Rheological Behavior of Smectite Dispersions: The Influence of Suspension Concentration and Exchangeable Cation

“…However, its efficiency may vary according to the clay properties [9,15]. The saturation rates were deduced from the exchangeable cations, by comparing the content of the saturating cation with the sum of all cations.…”

“…Smectite layers, that have negative charge, are surrounded by a double diffuse layer (DDL), containing cations to balance the negative charge. The calcium smectite platelets are aggregated into quasicrystals with a thin DDL, in contrast sodium saturated smectites often are isolated platelets with large DDL [2][3][4][5][6][7][8][9][10][11]. Despite this knowledge, the comparison of rheological parameters, even for similar materials like sodium bentonite, as determined by different authors is difficult because experimental conditions are slightly different and also because the cation exchange is not a simple answer.…”