Fouling Mitigation of Ion Exchange Membranes in Energy Conversion Devices

Abstract

In this study, three different environmentally friendly fouling mitigation technologies are suggested and are investigated in reverse electrodialysis (RED) to develop the most appropriate fouling mitigation technology for RED: applying direct current, flowing a solution with high salt concentration, and periodically switching river and seawater streams in RED. The quantitative level of anion exchange membrane fouling mitigation is evaluated in terms of the power density and the amount of power generation of RED. Applying a direct current electric field with higher voltage than 8 V was not allowed for fouling mitigation in the two-cell-pair bench RED stack due to decomposition of the redox couple. In comparison of the RED operations with two different fouling mitigation methods using firstly 40-min power generation during in-operation and 40-min fouling mitigation stage during out-of-operation as a cycle for 80 min and secondly 80-min forward power generation and 80-min backward power generation as two cycles. It was found that, over five cycles, the amount of the RED power generation using the former fouling mitigation method is 1.7 times higher than RED power generation using the latter fouling mitigation method.

Fouling and Mitigation Behavior of Foulants on Ion Exchange Membranes with Surface Property in Reverse Electrodialysis

“…Figure 5 shows the variation of electrical resistance of the four different IEMs immersed in 0.1 wt.% foulant + 0.017 M NaCl solutions. The foulants were introduced only in river water (0.017 M NaCl) to foul the IEMs effectively since the previous studies have reported the mitigation behavior of IEMs’ fouling in a NaCl solution of high concentration such as seawater (0.513 M NaCl) [ 18 , 19 ]. As shown in Figure 5 a,b,e,f, the anionic foulant, SDBS_348_AS, causes only the AEMs to increase electrical resistance and the cationic foulant, CC_340_CS, results in an increase in electrical resistance only for the CEMs.…”

“…Finally, the fouling mitigation of the IEMs with different surface properties used in this study was investigated. The previous studies reported that the high concentration of a NaCl solution such as seawater effectively mitigated the membrane fouling formed by electrostatic attraction between ionic foulants and IEMs [ 18 , 19 ]. Thus, the flowing of a concentrated NaCl solution into a dialysate and a concentrate between RED operations was used as a fouling mitigation method in this study.…”

“…Since AEMs and CEMs have negatively and positively charged functional groups, respectively, oppositely charged foulants could be electrostatically attracted to their surfaces [ 17 ]. In a recent study, several types of organic foulants, i.e., charged and non-charged species, were investigated to confirm three different fouling pathways, i.e., electrostatic attraction, electromigration and the macromolecule interaction between IEMs and foulants in a RED system [ 18 , 19 ]. Foulants exist in rivers and seawater with low and high salt concentrations, respectively, in RED.…”

“…Finally, the effect of the surface property of IEMs on fouling and mitigation behavior is investigated. The flowing method of concentrated NaCl solutions is used for fouling mitigation technology as suggested in the previous study [ 18 , 19 ].…”