Capacitive deionization (CDI) is an emerging technology for fresh water production from brackish-level saline sources. In the same manner as a capacitor, CDI uses an applied potential difference (&lt;1.5 V) across usually carbon-based electrodes to attract ions of the opposing polarity (counter-ions) to their respective electrodes, thereby creating a desalinated stream. Once the electrodes are charged to capacity, they are regenerated by short-circuiting, reducing or reversing polarity, while simultaneously producing a concentrated saline stream. However, CDI continues to suffer from inefficiencies and longevity issues caused by charge leakage from unwanted electrochemical reactions including coupled carbon oxidation and oxygen reduction reactions at applied potential &gt;0.8 V. Furthermore, the mismatch between the chemical charge afforded by surface groups such as hydroxyl, phenolic, and carboxyl groups and the polarity and magnitude of the applied potential can lead to further inefficiencies. Some of the short-comings of CDI can be ameliorated by affixing ion-exchange membranes (IEMs) to the porous electrode for more selective ion adsorption and desorption in a process called membrane capacitive deionization (MCDI). Increases in the charge efficiency from &lt;50% for CDI to &gt;80% for MCDI are typically seen. However, performance can still be severely diminished from mismatches between the chemical charge properties of the electrodes and the IEMs.<br/>Through this work, the effect of synergistically coupling the surface charge properties of the electrode to those of the IEMs will be shown to result in a more effective desalination process. Also, the opportunities available for utilizing single membranes as a cost reduction strategy without sacrificing performance will be detailed. Results will be based on commercially available electrodes that possess surface hydroxyl and phenolic groups and their nitric acid treated analog that contain carboxylic groups.<br/>

Effective operation of capacitive deionization using annexed membranes

2019 Spring National Meeting

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