Capacitive deionization (CDI) can remove ionic contaminants from water. However, concentrations of background ions in water are much higher than target contaminants. In this study, we demonstrate a selective CDI process tailored for removal of SO42- using composite electrodes containing a sulfate-selective polymer coating, which allows preferential transport of SO42- over Cl-. The total salt adsorption capacity and charge efficiency of the resin/QPVA coated electrode was as high as 29.2 meq/m2 and 65.6%, respectively, compared with 20.6 meq/m2 and 46.2% for uncoated electrodes (Figure 1A&B). The resin/QPVA coated electrode also achieved a SO42- selectivity of 2.22 over Cl- (Figure 1C), which was achieved by selective transmission of SO42- through the ion exchange resin layer rather than preferential absorption onto the resin. In addition, the SO42- selectivity, salt adsorption capacity, and charge efficiency were enhanced by increasing thickness of resin coating, and considerable selectivity was still achieved even at an Cl-:SO42- ratio of 20:1 (Figure 1D). The resin/QPVA coated CDI system was stable over more than 50 adsorption and desorption cycles. To the best of our knowledge, this was the first attempt to selective remove SO42- over Cl- in CDI system. By coating a resin functional layer on electrode, the CDI excellently enhanced desalination efficiency, charge efficiency, and SO42- selectivity over Cl- at various conditions, suggesting a generally applicable route for selective removal of target ions and contaminants using CDI.

Resin-modified capacitive deionization for selective uptake and removal of sulfate

256th National Meeting (2018)

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