Chemical and Biomolecular Engineering - Research Publications

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Author: Chen, George × Author: Hassanvand, Armineh × Author: Webley, Paul ×

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    An investigation of the impact of fouling agents in capacitive and membrane capacitive deionisation
    Hassanvand, A ; Chen, GQ ; Webley, PA ; Kentish, SE (Elsevier, 2019-05)
    The effect of organic fouling on both capacitive deionisation (CDI) and membrane capacitive deionisation (MCDI) was studied using two model foulants, the sodium salt of alginic acid and humic acid. Fouling of the activated carbon electrodes in the CDI cell was significant. The salt adsorption fell to 75% and the charge efficiency to 90% of their initial values after 18 cycles of operation with 0.5 mM CaCl 2 and 60 mg L −1 of sodium alginate. Similarly, the salt adsorption fell to 70% and the charge efficiency to 65% of their initial values after 18 cycles of operation with 60 mg L −1 of humic acid. The effect on MCDI was much more limited with these two foulants. The ability to clean the CDI cell with alkali cleaning agents was also investigated. While this cleaning was effective in restoring the salt adsorption, the alkali solution caused erosion of the activated carbon electrode or its PVDF binder, evidenced by an accumulation of carbon within the cleaning solution. Alternative electrode designs or alternative cleaning solutions will be needed if this approach is to be used in systems with similar foulants.
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    A comparison of multicomponent electrosorption in capacitive deionization and membrane capacitive deionization
    Hassanvand, A ; Chen, GQ ; Webley, PA ; Kentish, SE (PERGAMON-ELSEVIER SCIENCE LTD, 2018-03-15)
    In this study, the desalination performance of Capacitive Deionization (CDI) and Membrane Capacitive Deionization (MCDI) was studied for a wide range of salt compositions. The comprehensive data collection for monovalent and divalent ions used in this work enabled us to understand better the competitive electrosorption of these ions both with and without ion-exchange membranes (IEMs). As expected, MCDI showed an enhanced salt adsorption and charge efficiency in comparison with CDI. However, the different electrosorption behavior of the former reveals that ion transport through the IEMs is a significant rate-controlling step in the desalination process. A sharper desorption peak is observed for divalent ions in MCDI, which can be attributed to a portion of these ions being temporarily stored within the IEMs, thus they are the first to leave the cell upon discharge. In addition to salt concentration, we monitored the pH of the effluent stream in CDI and MCDI and discuss the potential causes of these fluctuations. The dramatic pH change over one adsorption and desorption cycle in CDI (pH range of 3.5-10.5) can be problematic in a feed water containing components prone to scaling. The pH change, however, was much more limited in the case of MCDI for all salts.