Transport processes during electrowashing of filter cakes

Abstract

Applications of electric fields during washing of filter cakes increases the removal rate of ions from the cake mother liquor, and under appropriate conditions the field also increases the wash flow rate by electroosmosis. Experimental data that show the key effects of the fields on the rates of ion mass transfer are presented: with the downstream electrode acting as a cathode, cation removal rates are increased whilst the removal rate of the anions is decreased. The concentration profile of the cations with washing time shows an increase in concentration to a value above that of the mother liquor, before it decreases due to displacement by the fresh wash liquor. A model is formulated that describes the advection, dispersion, ion migration and electroosmosis transport processes in the cake. Numerical solution of the model gives cation concentration profiles at the exit of the cake that are in qualitative agreement with the experimental observations. Experimentally measured wash liquor flow rates tend to be lower than what traditional colloid science principles predict by a factor of 5 to 10: reasons for this difference, supported by experimental work from other researchers, are discussed.

A periodic array of nano‐scale parallel slats for high‐efficiency electroosmotic pumping

“…Electroosmosis in a porous media has become important due to its applications in removal of soil contaminants , dewatering , electrochromatography , hot embossing , micropumping , and separation . Porous media may consist of parallel fibers such as that in a filter.…”