Effect of taurate surfactant and polyvinylpyrrolidone on kaolinite suspension

The adsorption of sodium lauroyl taurate (SLT) onto polyvinylpyrrolidone (PVP) in aqueous solution had the first transition point (T1) at 5 mM and the second transition point (T2) increased with increasing the concentration of PVP (9 mM for 0.1% PVP, 11 mM for 0.5% PVP and 12 mM for 1.0% PVP). The relative viscosity of the solution (SLT and PVP in water) increased with increasing SLT but reduced viscosity decreased with SLT. The high concentration of a kaolinite suspension (20 g/30 ml-medium) was greatly affected by the presence of SLT and PVP with respect to its flow property. Suspension flow curves at low shear rate (1–15 s−1 by cone-and-plate method) showed a non-Newtonian behavior. Plastic and relative viscosities, along with the Bingham yield, were derived from these flow curves. Characteristic dispersion and fluidity were explained in terms of the Bingham yield value, effective volume fraction and void fraction of the dispersion. The presence of PVP affected the suspension properties as a flocculant at concentration <0.1% and as a dispersant at higher concentrations. The SLT surfactant plays an important role in the Bingham yield value, the suspension viscosity and the effective volume fraction at concentrations above 5 mM. The combination of PVP (≤0.1%) and SLT improves the dispersion ability of kaolinite, but it boosts flocculation with a maximum at 5 mM SLT with PVP greater than 0.1%.