Influence of poly(ionic) liquid incorporation within resin wafer electrodeionization for reduced energy consumption in brackish water desalination

Abstract

Resin Wafer Electrodeionization (RW-EDI) is recognized as a promising technology for energy-efficient desalination of brackish water. However, RW-EDI is limited by energy requirements for the treatment of high-salinity feeds which prevent the large-scale deployment of this technology. Several material factors influence the resulting performance of RW-EDI. Current state-of-the-art wafers rely on a nonconductive polymer binder to ensure mechanical stability of resin wafers. However, a robust ionic polymer could improve resin wafer conductivity and energy efficiency of RW-EDI systems. Herein, this research studied the influence of ionic polymers within RW-EDI resin wafers. Specifically, polymer ionic liquid-based (PIL) ionic polymers were incorporated within ion exchange resin wafer formulations to enhance ion conductivity during RW-EDI operation. Two different resin wafer formulations were developed incorporating phosphonium-based PILs. These new resin wafer formulations were tested in a benchtop RW-EDI system at varied applied voltages. The results demonstrated that PIL loading had a major influence on the mechanical stability and conductive properties of the resin wafer as well as the RW-EDI performance. Resin wafers incorporating PILs exhibited an order of magnitude increase in ion conductivity (2.21 × 10-2 mS/cm) as compared to conventional polyethylene resin wafers (8.64 × 10-3 mS/cm). In the RW-EDI system, a 9.3 % decrease in specific energy consumption was achieved when PIL with 2.5 g loading of phosphonium-based PIL was employed, as compared to conventional polyethylene-based resin wafers. The results indicate that PIL ionic polymers can significantly improve energy efficiency within RW-EDI systems. The results also suggest that future studies should investigate additional ionic polymer materials for additional energy efficiency improvements within RW-EDI systems.