Electroosmotic dewatering of bentonite suspensions

Electroosmotic dewatering of Bentonite suspensions under conditions of constant DC voltage and constant DC current was investigated experimentally in a column 5 cm in diameter. The suspensions were prepared with CaCl$ sb2$ in distilled water with concentrations up to 1 M. The initial solid content was between 9.1 wt% and 26 wt% and the initial bed height ranged from 1.0 cm to 5.2 cm. Constant voltages from 4.0 V to 8.0 V and constant currents from 90 mA to 110 mA were used.Electroosmosis removed 20-60% of the water with energy expenditures well below the energy required to vaporize the water. Higher voltages or currents removed more water. Removal rates were increased by the addition of CaCl$ sb2$. The lowest bed height (1 cm) gave the lowest energy of dewatering, but the final water removal was low. For constant voltage experiments with an initial field strength of 2.8 V/cm, bed heights around 2 cm gave the highest water removal. The initial solid content had little effect on the final solid content. The Helmholtz/Smoluchowski theory did not predict correctly the effects of electrolyte concentration, solid content and bed height on the rate of electroosmotic dewatering