Capacitive deionization (CDI) has drawn attention as a promising electrochemical technology to remove ions from water. To further improve desalination performance, ion-exchange membranes can be placed in front of the electrodes, referred to as membrane capacitive deionization (MCDI). It is well-known that the electrosorption capacity in CDI is mainly determined by ion charge and hydrated size. However, only a few researchers have investigated the competitive electrosorption of different ions in MCDI. The objective of this study is to improve the removal performance of phosphate using MCDI with a resin modified carbon composite electrode. Herein, we prepared an activated carbon-based electrode coated with a heterogeneous anion-exchange layer. The surface morphology and structural characterization of the resultant composite materials were investigated carried out by a scanning electron microscope, Fourier transform infrared spectroscopy, and X-ray photoelectron spectra. The electrochemical analysis was performed by electrochemical impedance spectroscopy, galvanostatic charge-discharge and cyclic voltammetry. To have a better understanding of competitive electrosorption, the experiments on phosphate removal were carried out in single-pass MCDI mode. As demonstrated, the resin/carbon composite electrode has good capacitive properties for charge storage via electrical double layer formation. According to the experiments on phosphate removal (H2PO4-), MCDI with the resin/carbon composite electrode shows a higher charge efficiency (42.4%) and larger electrosorption capacity (0.072 mmol/g-carbon) at 1.2 V, as compared to CDI. More importantly, the electrosorption selectivity of phosphate over chloride can be significantly increased from 0.174 to 0.512. This reflects the fact that by coating an anion-exchange layer in front of the activated carbon electrode, the removal of phosphate can be improved due to less coion repulsion and charge-promotion transport.

Enhanced removal of phosphate using an activated carbon electrode coated with an ion exchange layer in membrane capacitive deionization

256th National Meeting (2018)

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