Nickel hexacyanoferrate electrodes for high mono/divalent ion-selectivity in capacitive deionization

Kaustub Singh, Zexin Qian, P. M. Biesheuvel, Han Zuilhof, Slawomir Porada, Louis C.P.M. de Smet*

*Corresponding author for this work

    Research output: Contribution to journalArticleScientificpeer-review

    57 Citations (Scopus)
    7 Downloads (Pure)

    Abstract

    Selective ion removal has been a point of focus in capacitive deionization because of its industrial applications such as water purification, water softening, heavy metal separation and resource recovery. Conventionally, carbon is used as electrode material for selectivity. However, recent developments focus on intercalation materials such as Prussian Blue Analogues, due to their size-based preference towards cations. Selectivity of nickel hexacyanoferrate electrodes from a mixture of Na+, Mg2+, and Ca2+ ions was studied in this work. Here, a CDI cell with two identical NiHCF electrodes was operated in two desalination modes: (a) cyclic, in which ions are removed from and released into the same water reservoir and thus, the ion concentration remains the same after one cycle, and (b) continuous, in which ions are removed from one water reservoir and released back in a different reservoir. An average separation factor of ≈15 and 25, reflecting the selectivity of the electrodes, was obtained for Na+ over Ca2+ and Mg2+ from an equimolar solution of Na+, Ca2+ and Mg2+ in both, cyclic and continuous desalination. It was concluded that NiHCF, used in a symmetric CDI cell, is a promising material for highly selective removal of Na+ from a multivalent ion mixture.

    Original languageEnglish
    Article number114346
    Number of pages7
    JournalDesalination
    Volume481
    DOIs
    Publication statusPublished - 2020

    Keywords

    • Capacitive deionization
    • Ion-selective intercalation
    • Mono/divalent selectivity
    • Prussian blue analogues

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