Effect of humic acid adsorption on the rheological properties of sodium montmorillonite suspensions

in this work we analyze the rheological behavior of Na-montmorillonite (NaM t) suspensions in the presence of humic acid. The analysis starts from the fact that the electric charges on plate and edge surfaces of clay particles largely determine the formation of three-dimensional structures in suspens ions. Zeta potential data of NaMt as a function of humic acid HA) concentra tion suggest that its adsorption takes place preferentially on the edges of the particles. A good correlation between the parameters describing the vi scosity-shear rate or viscosity-shear stress dependencies and the product o f the; potentials of edges and faces, edge) face is demonstrated. It indica tes that the rheological behavior of NaMt suspensions is largely controlled by electrostatic interactions, Adsorption of HA also changes the viscoelas tic properties of the suspensions significantly as determined by both oscil lometric and creep-recovery tests. A trend of NaMt suspensions from approxi mately solid like when no HA is adsorbed, to almost liquid like when the HA concentration is in the range of 50-100 mg/l is observed. (C) 2001 The Soc iety of Rheology.