Abstract
Electrochemical water desalination has been a major research area since the 1960s with the development of capacitive deionization technique. For the latter, its modus operandi lies in temporary salt ion adsorption when a simple potential difference (1.0–1.4 V) of about 1.2 V is supplied to the system to temporarily create an electric field that drives the ions to their different polarized poles and subsequently desorb these solvated ions when potential is switched off. Capacitive deionization targets/extracts the solutes instead of the solvent and thus consumes less energy and is highly effective for brackish water. This paper reviews Capacitive Deionization (mechanism of operation, sustainability, optimization processes, and shortcomings) with extension to its counterparts (Membrane Capacitive Deionization and Flow Capacitive Deionization).
Highlights
The looming and upsurge of unavailable/insufficient freshwater resources is one of the major problems confronting humans and there is no denying that human activities and unprecedented environmental disasters are a contributing factor to this.In total, 98% of the water present on Earth is either sea or brackish water which is not readily available for direct use by humans [1]
When an external direct voltage is applied onto a system containing saline solution, the electric field created electrostatically drives the solvated ions in the solution into their different polarized poles where they are adsorbed in the pores of the electrodes and the process continues until the pores are saturated
The phenomenon of ions adsorption lies on the electrical double layer (EDL) created when an accumulation of ions is formed at the electrode–electrolyte interface due to the electrical potential
Summary
The looming and upsurge of unavailable/insufficient freshwater resources is one of the major problems confronting humans and there is no denying that human activities and unprecedented environmental disasters are a contributing factor to this. The material aspect of this technology (electrode materials) is one of the key factors or backbone of this electrochemical desalination process. Carbon as a cheap material has served as a precursor for electrode formation due to its availability, porosity, large surface area, amidst other factors. It does not possess all the suitable properties needed to make it a standalone material leading to myriad of research in new hybrid electrodes development [6]. The operation mode, energy utilization, advantages, and shortcomings of reverse osmosis and electrodialysis are briefly highlighted
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