Active Fouling Removal from Electrically Conductive Membranes with an Interdigitated Pattern

Membrane processes are among the most effective technologies for treating traditional as well as alternative sources of water, but membrane fouling remains a major challenge. Electrically conductive membranes (ECMs) offer a promising alternative to traditional fouling cleaning methods, using surface localized electrochemical reactions to disrupt and remove all types of foulants. This paper investigates an alternative design for ECMs where an interdigitated pattern of carbon nanotubes is deposited on the membrane surface. The design colocates both the working and counter electrodes on the membrane surface and enables an easy way to vary membrane surface coverage by the conductive material. A systematic investigation into electrode width and spacing revealed that self-cleaning efficiency ranged from 20% to 60%, as the surface coverage was increased from 25% to 66%. Surprisingly, membranes with 25-49% coverage showed no significant differences in self-cleaning, suggesting a nonlinear relationship between surface coverage and fouling removal. SEM images and testing with a different electrolyte shed light into the reasons behind the limited self-cleaning and how it could be improved. Beyond electrode design, using membrane fouling index (MFI) analysis and time-of-flight secondary ion mass spectrometry (ToF-SIMS), we identified fouling rate and fouling location as critical factors controlling electrochemical self-cleaning.