Electrode Materials for Desalination of Water via Capacitive Deionization

Abstract

Recent years have seen the emergence of capacitive deionization (CDI) as a promising desalination technique for converting sea and wastewater into potable water, due to its energy efficiency and eco‐friendly nature. However, its low salt removal capacity and parasitic reactions have limited its effectiveness. As a result, the development of porous carbon nanomaterials as electrode materials have been explored, while taking into account of material characteristics such as morphology, wettability, high conductivity, chemical robustness, cyclic stability, specific surface area, and ease of production. To tackle the parasitic reaction issue, membrane capacitive deionization (mCDI) was proposed which utilizes ion‐exchange membranes coupled to the electrode. Fabrication techniques along with the experimental parameters used to evaluate the desalination performance of different materials are discussed in this review to provide an overview of improvements made for CDI and mCDI desalination purposes

MXene‐Based Capacitive Deionization–Strong Competitor Among Faradaic Electrode Systems: Current Status and Future Perspectives

“…The measurement of maximum SAC is based on the arrival of desalination process at the equilibrium stage when the effluent conductivity remains unchanged with time. The formula used to calculate gravimetric SAC in the SP and BM operations are shown in equation 1 and 2: [8,[33][34][35] SAC SP ¼ n R DC: dt m (1)…”

“…with the desalination/electrosorption or total cycling time (t, min) according to the equation 3. [8,[33][34][35] ASAR SP=BM ¼ SAC SP=BM t…”

“…Equation 4 and 5 represent the formula associated with the calculation of Λ in the SP and BM experimental conditions, respectively. [33][34][35]…”

“…[33,34] Moreover, the ratio of SAC at the initial and final cycles reflects the electrode regeneration efficiency (ERE) and can be obtained by equation 8, where SAC i /SAC n is the SACs at the initial/n th cycling process. [35] There are many factors, such as electrode corrosion, disintegration, self-passivation, volume change, and chemical reaction, which resulted in loss of SAC or low ERE after prolonged cycling activity.…”

“…Although salty water desalination by using MXene-based electrode materials are very promising and has been covered briefly in a broad domain of electrode materials/water treatment, [30,[33][34][35][37][38][39]72,[128][129][130][131][132][133][134] there are only a few review article that are majorly focused on MXene-based CDI application. [135,136] Moreover, state-of-the-art comparative study for the desalination performance of MXene-based electrodes with other Faradaic electrodes is lacking in the previous review articles.…”