Ion Separation Utilizing Crosslinkable Zwitterionic Amphiphilic Copolymeric Membranes

There is a growing need for valuable mineral resources like lithium and heavy metals. While these resources exist in aqueous sources like wastewater and brines, they are difficult to extract and differentiate. Polymeric membranes provide a sustainable, cost-effective, and scalable method to recover these resources in ion form from these aqueous sources. However, current commercial membrane technology is inadequate in achieving this selectivity, especially while maintaining reliability and fouling resistance. Previous work in our group has investigated the self-assembly of zwitterion based polymers in fabricating fouling resistant, thin film composite membranes that can achieve exceptional anion separation coined crosslinkable zwitterionic amphiphilic copolymeric membranes (x-ZACS). These x-ZACs readily self-assemble into a network of nanochannels where the zwitterions line the pore walls. Previous work suggests the ion selectivity is driven by the selective interactions between the zwitterions lining these x-ZAC nanochannels and the ions traversing through the ~1nm confined, self-assembled nanochannels. To date, only one commercially available zwitterion chemistry has been investigated for ion selectivity. My current work expands on the anion selectivity achieved to synthesize x-ZAC membranes that focus on other zwitterionic repeat units. The goal is to create membranes with cation-cation selectivity for use in the recovery and selective extraction of lithium and valuable metal ions from brines and wastewater.<b> </b>To accomplish this, different zwitterionic chemistries have been synthesized to fabricate alternate x-ZAC membranes which were analyzed for selectivity between cations. Preliminary results show some selectivity differences between zwitterion chemistries, with promise in cation selectivity with a commercially available zwitterion.This work suggests that pressure-driven membranes with well-selected x-ZAC chemistries and crosslink densities can separate similarly sized and charged ions which enables more scalable and energy-efficient recovery of metal and mineral resources.