A novel apparatus has been developed for the electrophoretic clarification
of concentrated colloidal suspensions. The laboratory equipment is capable
of being scaled up to much larger capacity. The apparatus was designed to p
rocess suspensions in either batch or semicontinuous operation, and it has
been used to demonstrate the removal of coal/clay colloidal matter from the
effluent of a coal-washing facility. In addition, a parametric study of so
dium-bentonite suspensions in batch operation was performed to elucidate th
e effects of initial colloid and electrolyte (NaCl) concentrations on the r
ate of clarification and the instantaneous power requirements. It was found
that an increase in either the initial particle or electrolyte concentrati
on (up to 50 mg of NaCl/L) caused a decrease in the instantaneous power lev
els but increased the time necessary to reach a given solution clarificatio
n. Typical electrophoretic clarification experiments resulted in 99.9% remo
val of the colloidal matter. In semicontinuous operation it was shown that
a 0.2 wt % sodium-bentonite suspension could he clarified to 2.6 x 10(-4) w
t % in 13.5 h without the addition of flocculants or other chemicals.