Rheology of aqueous suspensions of montmorillonite/ gum arabic /electrolyte

The rheological properties of purified Na-montmorillonite (Na-MTp)-Water-NaCl- Gum arabic (GA) mixture have been investigated. Montmorillonite and the GA from the south of Mauritania were purified and characterized by several physical and chemical methods: X-ray fluorescence (XRF), X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), and size exclusion chromatography (SEC). The results showed that both the plastic and elastic parameters increased with the clay fraction. The sol-gel transition was detected at the volume fraction between 0.012 and 0.016. These two parameters increased with the amount of NaCl added, at low NaCl concentrations, due to the decrease in the double layer thickness, before the system collapsed at NaCl concentrations above 20 mmol. L⁻¹. In the presence of GA, the variation of the yield stress and the elastic modulus shows a progressive reduction of both parameters as the amount of gum increased. The order of mixing of the different components used is also studied. The results of the MTp-NaCl-GA mixture, called the first order of the mixture, shows that the yield stress and the elastic modulus decreased as the concentration of NaCl increases. The MTp-GA-NaCl mixture, called the second order of the mixture, shows that the yield stress and the elastic modulus increased progressively with the increase in NaCl concentration. The connection between physicochemical interactions and the observed behaviors is detailed.