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A Desalination Battery Combining Cu3[Fe(CN)6]2 as a Na-Storage Electrode and Bi as a Cl-Storage Electrode Enabling Membrane-Free Desalination

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journal contribution
posted on 23.01.2019, 00:00 by Do-Hwan Nam, Margaret A. Lumley, Kyoung-Shin Choi
A desalination battery is an attractive route for seawater desalination because it couples ion removal with energy storage. In this work, we paired Cu3[Fe­(CN)6]2·nH2O as the Na-storage electrode with Bi as the Cl-storage electrode to construct a novel desalination battery that enables membrane-free desalination. Most current desalination technologies, with the exception of thermal distillation, rely on the use of membranes. Eliminating the need for a membrane can significantly simplify the construction and maintenance of desalination systems. After carefully examining the sodiation/desodiation reactions and cycle performance of Cu3[Fe­(CN)6]2·nH2O in both acidic and neutral saline solutions (0.6 M NaCl), we combined Cu3[Fe­(CN)6]2·nH2O with Bi, which was previously identified as a promising Cl-storage electrode, to construct a Cu3[Fe­(CN)6]2·nH2O/Bi desalination battery. The Cu3[Fe­(CN)6]2·nH2O/Bi desalination battery generates an electrical energy output during desalination, which is equivalent to discharging, and requires an electrical energy input during salination, which is equivalent to charging. We investigated optimum pH conditions to perform salination to minimize the energy necessary for charging so that the desalination/salination cycle could be achieved with a minimum overall energy input. The results obtained in this study suggest that with further optimization the Cu3[Fe­(CN)6]2·nH2O/Bi desalination battery will offer new possibilities for practical seawater desalination.