Effect of polyvinylpyrrolidone and sodium dodecyl sulphate on the dispersity and fluidity of concentrated kaolinite suspension

Abstract

Flow curves for the concentrated suspension of kaolinite (20 g/30 ml-medium) were obtained in the presence of polyvinylpyrrolidone (PVP) and sodium dodecyl sulphate (SDS) by means of a Couette-type rotary viscometer. The flow curves were Newtonian or non-Newtonian, depending on the concentration of PVP and SDS added. From these curves, the plastic viscosity (r/vL) and Bingham yield value (F0) were obtained. The relative viscosity (Gel) of r/PL with respect to the medium viscosity (r/0) were calculated and the contour lines for Fo and for 17rel obtained as a function of the concentration of SDS and PVP added. The feature of these contour lines was qualitatively similar to that for the mean diameter (din) of the secondary particles in a dilute suspension of kaolinite. It was concluded that both the increase in drain the dilute suspension and the increase in r/to1 and F 0 in the concentrated suspension were brought about by the interpartide bridging effect of PVP. The increase in r/re1 was due to the formation of bulky flow units of large void volume. The increase in F 0 reflected the growth of gel structure caused by the bridging effect. It was shown that PVP behaved as a flocculating agent at lower concentrations, but behaved as a dispersing agent at higher concentrations, while SDS at any concentration behaved as a dispersing agent for kaolinite suspension.

Effect of Polyvinylpyrrolidone and Sodium Lauroyl Isethionate on Kaolinite Suspension in an Aqueous Phase

“…The polymer behaves as dispersant when the concentration increased, resulting in diminishing the Bingham yield value as well as plastic viscosity. In contrast to SDS 20) and cetyltrimethyl ammonium bromide 13) at high shear rate, Bingham yield values declined linearly with an increase in the surfactant concentration at a constant concentration of polymer. They decreased to near zero at high concentrations of surfactant, resulting in Newtonian flow.…”

“…According to the results of Shimabayashi et al, 20) gradual increasing of the concentration of SDS with constant concentration of PVP in kaolinite suspension gets better dispersing effects; and gradual increasing in the concentration of PVP with constant concentration of SDS obtains the maximum values of relative viscosity, effective volume fraction, Bingham yield value and void fraction at high shear rates. That was owing to the fact that PVP acts as an aggregating agent at a low concentration (Ͻ0.1%), but a dispersing agent at a high concentration.…”

“…SDS depressed flocculation in dilute kaolinite suspension at any concentrations. 20,21) Shimabayashi's prior study 20) on combination of SDS and PVP in kaolinite suspension concluded that flocculating effect and mean diameter of secondary particles of kaolinite declined with the increase in concentration of SDS. Complex formations between SDS and PVP and their adsorption onto kaolinite surface enhanced the dispersing effect.…”