Because of the high operational costs required to perform water purification, radical new treatment approaches are being considered beyond traditional pressure-driven membrane separations. The development of electrified membranes is one promising approach toward improving performance, as applied voltages can be used to mitigate biofouling while simultaneously enhancing the removal of ions and other charged contaminants. Many processes have been explored to leverage applied voltages for separations, such as in: (1) electrofiltration, where conductive membrane surfaces are charged to mitigate the adhesion of contaminants, (2) capacitive deionization, where high surface area electrodes electrophoretically draw contaminants from water, or (3) ion concentration polarization / shock deionization, where faradaic currents generate a depletion of ions near an ion exclusion membrane, creating a pure water stream.<br/><br/>Despite the rapidly growing potential for these and other technologies that rely upon electrified membranes, there is a significant need for an improved understanding of the effect of ion and water electrostatics within these porous materials while under the effects of an electric field. In particular, the origin of exotic transport behaviors of ions within micro- and nanoporous channels, such as high streaming mobilities, overlimiting currents, and the competition between surface conduction and electro-osmotic flow, is still relatively unexplored. In this presentation, we discuss the many factors that affect the use of electric fields to enhance separations, focusing on the fundamental transport of ionic species and our work to leverage those effects for improved separations. First, we describe our own work to make existing membrane materials conductive using organic and inorganic coatings combined with laser pyrolysis. The resulting laser-induced graphene-based membranes show excellent conductivity, an important characteristic for reducing electrical resistance losses, and can be scalably and cost-competitively produced when compared to current membrane technologies. We also describe our work to further enhance the separation of charged contaminants by leveraging surface coatings to create trans-membrane electric fields. Together, these works demonstrate how electrified porous materials can be used to enhance separation processes and highlight the need for improved fundamental understanding of the transport behaviors involved in their operation.

Electrified membranes for water treatment: Toward new experimental and theoretical tools

2019 Fall National Meeting

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