Investigation of a novel high-efficiency ion-permselective membrane module based on the electrochemically switched ion exchange scheme

Abstract

Electric field-accelerated ion-permselective membrane (EISM) separation has attracted significant attention in recent years. Thus, herein, to further investigate the ion transport mechanism and optimize the separation efficiency, five types of ion-permselective membrane modules (IPMM I–V) based on the electrochemically switched ion exchange (ESIX) scheme were designed. Compared with the traditional ion separation systems, the in situ membrane-based ion separation system was set up with an extra pulse potential applied to the PPy/PSS/SSWM (polypyrrole/polystyrenesulfonate/stainless steel wire mesh) membrane. The continuous permselective separation of K⁺ as target ions was performed from dilute aqueous solution through the IPMM system. The pulse potential combined with the regulated cell voltage was functionalized synergistically to create an “ion-sieving effect” and effectively guide the target cations from the source cell to the receiving cell. Moreover, the formation of an equal potential volume in IPMM-V suppressed the reverse migration of the target ions and the detected ion flux across the membrane was 100 times that of the IPMM-I system. The ion transport mechanism was also analyzed in detail based on the equivalent circuit of the system, and the optimized operation parameters were obtained for the high-efficient ion separation system. These results can provide some beneficial information for the design and practical operation of novel EISM systems.