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Divalent Ion Selectivity in Capacitive Deionization with Vanadium Hexacyanoferrate: Experiments and Quantum‐Chemical Computations
Author(s) -
Singh Kaustub,
Li Guanna,
Lee Juhan,
Zuilhof Han,
Mehdi B. Layla,
Zornitta Rafael L.,
Smet Louis C. P. M.
Publication year - 2021
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.202105203
Subject(s) - capacitive deionization , materials science , electrode , selectivity , vanadium , divalent , inorganic chemistry , prussian blue , electrochemistry , chemical engineering , chemistry , organic chemistry , metallurgy , engineering , catalysis
Selective removal of ions from water via capacitive deionization (CDI) is relevant for environmental and industrial applications like water purification, softening, and resource recovery. Prussian blue analogs (PBAs) are proposed as an electrode material for selectively removing cations from water, based on their size. So far, PBAs used in CDI are selective toward monovalent ions. Here, vanadium hexacyanoferrate (VHCF), a PBA, is introduced as a new electrode material in a hybrid CDI setup to selectively remove divalent cations from water. These electrodes prefer divalent Ca 2+ over monovalent Na + , with a separation factor, β Ca/Na ≈3.5. This finding contrasts with the observed monovalent ion selectivity by PBA electrodes. This opposite behavior is understood by density functional theory simulations. Furthermore, coating the VHCF electrodes with a conducting polymer (poly‐pyrrole, doped with poly‐styrenesulphonate) prevents the contamination of the treated water following the degradation of the electrode. This facile and modular coating method can be effortlessly extended to other PBA electrodes, limiting the extent of treated water contamination during repeated cycling. This study paves the way for tunable selectivity while extending the library of electrodes that can be successfully used in (selective) CDI.