Low-Cost Manufacturing of High-Performance Ion Exchange Membranes for Electrodialysis using Initiated Chemical Vapor Deposition

Electrodialysis and other membrane-based, electro-driven desalination methods offer advantages over current prominent methods for desalination including low costs, reduced energy consumption, low plant footprints and minimal feed pretreatment. However, the high cost and poor selectivity of ion exchange membranes, as well as their susceptibility to scaling, still prevent electro-driven desalination technologies from being applied to their fullest potential across all salinity regimes. In the proposed work, GVD Corporation will use its proprietary polymer deposition method, called iCVD, to develop a roll-to-roll- compatible manufacturing process for ion exchange membranes for approximately $10/m2 – a factor of 5-30x less than conventional methods. iCVD allows the deposition of a crosslinked, ultrathin and defect free ion-conducting polymer film directly onto a porous support in a single step, circumventing the typical slow, multistep process used for IEMs which is responsible for their high cost. In addition, iCVD is perfectly suited to fabrication of bilayer membranes with high monovalent selectivity. Monovalent selective membranes will have better scaling resistance and greater utility in recovery of valuable minerals, such as magnesium and calcium fertilizers, manganese and lithium for rechargeable batteries and heavy metals for industrial processes, helping to offset the operating costs of desalination. Lower-cost membrane manufacturing of membranes with monovalent selectivity will allow a dramatic reduction in levelized cost of water for electrodialysis of both low- and high-salinity feed waters. The consequent widespread adoption of ED for the treatment of natural feeds and waste water streams will help to combat water scarcity, reduce energy consumption for water treatment, and create novel sources of critical minerals and more efficient reuse of industrial chemicals. In Phase I, GVD will demonstrate the fabrication of anion- and cation-exchange membranes using its iCVD technology. Conditions for batchwise depositions will be optimized to obtain conductivities equal to or greater than that of existing commercial IEMs at the lowest possible cost in an eventual roll-to-roll system. GVD will also fabricate monovalent selective bilayer membranes that will be more scaling resistant and useful in mineral separations. In this work, GVD is partnering with Prof. Chinmayee Subban and the University of Washington (UW) to perform measurements of membrane selectivity and conductivity and real measurements of electrodialysis efficiency using iCVD membranes.