Relationship between the colloidal and rheological properties of mineral suspensions

The electrokinetic and rheological behaviour of lateritic aqueous suspensio ns has been analyzed as a function of samples chemical composition, pH of s uspensions, and nature and concentration of electrolyte added to the aqueou s suspensions. First, it was determined that the isoelectric point (IEP) of suspensions in the presence of non-adsorbing electrolytes is a function of the ratio serpentine/ goethite present in samples. The flow properties of the suspensions are strongly dependent on pH, reaching the highest values o f apparent viscosity at values around the isoelectric point. Specific adsor ption of silicate and magnesium species on particles surface was revealed b y a shift in the IEP In particular, silicate anions shifted the IEP value t o acidic pH whilst magnesium cations shifted the value to basic pH. A simil ar trend was displayed in the rheological behaviour of suspensions where th e highest viscosity values were shifted to the same direction.