Measurement of electrokinetics in cake filtration

This paper addresses the role of the free surface charge in cake filtration with main emphasis on a new method to study electrokinetic effects in cake filtration by streaming current measurement. The method is based on the assumption that electrolyte- and cake resistance are purely ohmic, which allow a relationship between streaming current and measured current to be established. It is shown that streaming current can be found from the slope of the inverse measured current vs. the filtrate volume. The streaming current in combination with the theory of irreversible thermodynamics permits the effect of free surface charge on cake filtration to be quantified in terms of phenomenological filtration parameters, which allow electrokinetic filtration phenomena like electroviscous flow reduction to be distinguished from flow reduction cause by structural changes in the filter cake. In the present study the method is demonstrated on filtration of anatase titanium oxide particles.