Pulsed electrophoretic filter-cake release in dead-end membrane processes

The application of electric fields can be a very effective means of removing deposits from membrane surfaces. Such a means of process improvement has usually been applied to cross-flow filtration, allowing efficient operation at low cross-flow velocities. In the limiting case of dead-end filtration (zero crossflow) it is possible to use electric-field pulses to release the filter cake for collection. Experimental data are presented for the dead-end ultrafiltration of silica colloids and the protein bovine serum albumin and for the dead-end microfiltration of titania dispersions taking as variables the magnitude of the applied field, the pulse interval the pulse duration, and the feed conditions (pH, ionic strength, concentration). The data identify the conditions when pulsed electric fields can be used as an efficient means of releasing filter cakes for collection. A force balance model is developed to predict the filtration rate at the end of the release process, taking into account electrophoretic, electroosmotic, and hydrodynamic forces. The model shows excellent agreement with the experimental data for ultrafiltration and reasonable agreement with the experimental data for microfiltration. The use of pulsed electric fields to release filter cakes in dead-end membrane processes is a promising technique that is most likely to find application in the clarification of process feeds containing low dispersed solutes.