SURFACE ION-EXCHANGE OF GEORGIA KAOLIN AN D RHEOLOGICAL PROPERTIES

Effect of surface ion-exchange of Georgia kaolin on the dispersion cha racteristics and the rheological properties were studied. The ion-exch ange was carried out individually with mono-valent cations (Li+, Na+, Kf), divalent cations (Mg2+, Ca2+, Sr2+, Ba2+, Co2+), and tri-valent c ations (Al3+, Fe3+), using corresponding chloride solution. The zeta p otential increased positively from -30 to +7 mV by the ion-exchange in the order of mono-<di-<tri-valent cations and simultaneously the visc osity of the slip increased, while the pH decreased from 6.2 to 3.7. T herefore, the zeta potential was considered to be strongly affected by the pH of slurry, but not by absorbed cations on the kaolinite partic le. The water him thickness was evaluated by both the measurement of w eight loss from 40 to 100 degrees C for the green body and the DSC mea surement. A positively linear relationship was observed on the values between the former and the later measurement, excluding trivalent cati ons, though the later values are about four-times higher than the form er values. The water film thickness was increased by the ion-exchange with di-valent cations rather than mono-valent cations. The water him thickness is found to be related with the hydration energy of ion-exch angeable cations.