Knowledge and Technology Used in Capacitive Deionization of Water

Abstract

The demand for water and energy in today’s developing world is enormous and has become the key to the progress of societies. Many methods have been developed to desalinate water, but energy and environmental constraints have slowed or stopped the growth of many. Capacitive Deionization (CDI) is a very new method that uses porous carbon electrodes with significant potential for low energy desalination. This process is known as deionization by applying a very low voltage of 1.2 volts and removing charged ions and molecules. Using capacitive principles in this method, the absorption phenomenon is facilitated, which is known as capacitive deionization. In the capacitive deionization method, unlike other methods in which water is separated from salt, in this technology, salt, which is a smaller part of this compound, is separated from water and salt solution, which in turn causes less energy consumption. With the advancement of science and the introduction of new porous materials, the use of this method of deionization has increased greatly. Due to the limitations of other methods of desalination, this method has been very popular among researchers and the water desalination industry and needs more scientific research to become more commercial.

Recent Progresses in Adsorption Mechanism, Architectures, Electrode Materials and Applications for Advanced Electrosorption System: A Review

“…To ensure the safety of industrial and domestic water supply, desalination technology has attracted the attention of many researchers. This concept of “electrochemical desalination” was put forward by Evans and Hamilton [ 90 ]. Compared with reverse osmosis (RO) and multi-stage flash (MSF), the electrosorption desalination technology shows low energy consumption, easy operation, and so on.…”

Development of Composite Nanostructured Electrodes for Water Desalination via Membrane Capacitive Deionization

“…Therefore, the development of water desalination technologies to convert the abundant saline water, which covers more than 70% of the Earth's surface into freshwater is more necessary than ever. [1,2] In recent decades, new techniques for desalination of brackish and seawater have emerged, including reverse osmosis (RO), electrodialysis (ED), distillation, and others. These methods produce clean water but are either expensive or inefficient in terms of energy consumption.…”

“…These methods produce clean water but are either expensive or inefficient in terms of energy consumption. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Capacitive deionization (CDI) is considered an emerging technique for the removal of ions from aqueous solutions that can be effectively used in water desalination and water treatment processes. In CDI, the electrochemical cell consists of the electrodes, the current collectors, and the nonconductive spacer.…”

“…[1,19] Moreover, unlike other desalination techniques, CDI removes dissolved ions as a minority component from the solvent (i.e., water), thus enabling desalination of water even at low salinity (e.g., brackish water) without extreme energy consumption. [1,2] However, a crucial issue of CDI is related to the phenomenon of co-ion expulsion, especially when carbon-based materials are exclusively used as electrodes, which significantly reduces the energy efficiency of the system. This is caused by ions of the same polarity that are continuously adsorbed and subsequently desorbed from the pores of the electrodes, reducing the number of counter-ions that can be removed from the feed water.…”

Optimizing the Micro/Mesoporous Structure of Hierarchical Porous Carbon Synthesized from Petroleum Pitch Using the Solvent-Free Method for Ultra-Fast Capacitive Deionization

“…When the voltage is removed, ions release from the electrodes back into the solution. In this case, CDI requires electrodes with high salt adsorption capacity (SAC) and salt adsorption rate (SAR) to store plentiful ions as quickly as possible during the deionization process. , In order to achieve those traits, the CDI electrodes should possess several characteristics: (i) large specific surface area for ion adsorption; (ii) high electrical conductivity; (iii) high electrochemical stability; and (iv) appropriate pore structure for rapid ion adsorption–desorption. − …”