Development of Cost-Effective Ion-Exchange Membranes for High Performance Reverse Electrodialysis

Abstract

Reverse electrodialysis (RED) is one of the promising processes for generating electricity from the salt concentration gradient between river and sea water. A RED stack contains alternately arranged anion- and cation-exchange membranes (AEMs and CEMs, respectively) which separate salt solutions of different concentrations. The power generation performance of REDs significantly depends on the characteristics of ion-exchange membranes (IEMs). The important membrane properties dominating the power generation in RED processes are the ion-exchange capacity, water swelling degree, electrical resistance, permselectivity, membrane thickness, and surface morphology etc. Moreover, the cost-effectiveness of IEMs is the most significant factor determining the successful commercialization of the RED process. In recent years, pore-filled IEMs (PFIEMs) in which an inert porous substrate provides excellent mechanical and chemical stabilities while a filling ionomer selectively transports ions through the membrane have been receiving great interests in the application to various energy conversion processes such as fuel cells and redox flow batteries. Simple and cheap mass production by a roll-to-roll process is one of the main advantages of the PFIEMs. In this work, we have investigated the optimum design parameters of the PFIEMs for successful application to a RED process. In addition, we have studied on the surface modification of the PFIEMs through facile methods for the improvement of the membrane properties. (This work was supported in part by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Korea government (MSIP) (2015R1A1A1A05001486) and the Technology Innovation Program funded by the Korea government (MOTIE) (No. 10047796).)