Abstract
Water purification is the rendering of non-potable water into water good enough for human consumption and use. Capacitive deionization is a promising emerging water desalination technique; a close relative to the established desalination technology such as reverses osmosis (RO) etc. It operates at low pressure and can potentially utilize less energy for brackish water desalination.In a typical CDI cell, the feed water flows through the separator layer between two electrically charged carbon electrodes. This architecture results in significant performance limitations as electrodes are in solid state with limited exposed surface area of contact and pores for adsorption. Also, there is an inability to afford continuous mode of operation.Here, we describe an alternative architecture, where the feed electrode is in liquid state and flows semi-continuously on carved channels. Using this technique, we show that flow capacitive deionization enables significant reductions in desalination time and can desalinate higher feed solution. We show these benefits using commercially made powdered activated carbon and superfine activated carbon as electrode materials. The superfine carbon at a moderate carbon loading rival the performance of powdered activated carbon due to its reduced particle size. Furthermore, the physico-chemical and electrochemical properties of the solid and flow electrodes (pristine and modified electrodes) were characterized by low-temperature nitrogen adsorption measurement, scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infra-red (FT-IR), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS).We also present a strategy in reduction of concentration polarization of carbon based electrodes by utilization of electrospun nanofibers synthesized via electrospinning method and as a result, a notable improvement was made through experimental approaches by electrochemical impedance spectroscopy and cyclic voltammetry studies of the hybrid nanocomposites carbon electrodes. In furtherance, we demonstrate that our approaches are promising towards optimizing CDI/FCDI electrodes and in resolving some inherent challenges of carbon based electrodes.