The rheological characteristics of purified bentonite suspensions as a function of exchangeable cation $({\text{Ca}}^{2+},{\text{NH}}_4^{+},{\text{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.

Ceramic tile production by the wet route requires clay suspensions with a high solid content and low viscosity. In this work the deflocculation of clays in aqueous suspensions was investigated by varying the type of clay and additive. Three kaolinitic and two illitic clays were characterized and dispersed with deflocculants based on lithium, sodium and potassium silicates and polyacrylates. The clays were characterized by chemical and mineralogical analyses, particle size distribution, zeta potential, organic carbon content, cation exchange capacity (CEC) and specific surface area (BET). Deflocculation curves were determined by measuring the viscosity for 50 wt.% clay slips. The results indicate that additive consumption is closely related to CEC and BET, which correspond respectively to the chemical and physical characteristics of the clay mineral's surface. Moreover, viscosity values at the deflocculation point are closely related to BET.