Fluidized bed electrodes with high carbon loading for water desalination by capacitive deionization

Research progress of sodium super ionic conductor electrode materials for capacitive deionization

Maxing Out Water Desalination with MXenes

Various cell architectures of capacitive deionization: Recent advances and future trends

Activated carbon recycled from bitter-tea and palm shell wastes for capacitive desalination of salt water

Capacitive Deionization (CDI) has emerged as an energy-efficient and environmentally friendly technology for water desalination. This review provides a comprehensive analysis of CDI, covering both experimental and simulation approaches. It introduces the background, definition, and diverse applications of CDI, from water desalination to environmental monitoring and resource recovery. The review highlights CDI’s advantages, such as low energy consumption and operational simplicity, as well as its limitations, particularly its design-specific operating window favoring low-to-moderate salinity waters and sensitivity to organic-rich conditions. Strategies such as hybrid CDI systems and electrode surface functionalization are discussed to mitigate these challenges. Key working principles and advancements, including innovations in electrode materials, synthesis methods, and reactor design, are examined to improve ion removal efficiency, selectivity, energy use, and system durability. Material modification strategies are presented in the context of structure – performance relationships, emphasizing rational design principles. The review also explores simulation methods, including reactor modeling, computational fluid dynamics, molecular dynamics, and numerical approaches, and machine learning highlighting their synergy with experiments in optimizing CDI performance and guiding scale-up. Coupling CDI with other systems and its applications in water purification, particularly for ion and organic compound removal are also discussed. Finally, challenges in both experimental and simulation efforts, such as material cost, model complexity, computational demands, and scalability, are discussed. While CDI shows promise for sustainable water desalination and resource recovery, further research on hybrid configurations, predictive modeling, and pilot-scale validation is needed to address its limitations and enable large-scale adoption.

Desalination and disinfection of inland brackish ground water in a capacitive deionization cell using nanoporous activated carbon cloth electrodes

Understanding the percolation characteristics of multicomponent conducting suspensions is critical for the development of flowable (semi-solid) electrochemical systems for energy storage and capacitive deionization with optimal electrochemical and rheological performance. Despite its significance, not much is known about the impact of the selected particle morphology on the agglomeration kinetics and the state of dispersion in flowable electrodes. In this study, the impact of the conductive additive morphology on the electrochemical and rheological response of capacitive flowable electrodes has been systematically investigated. Critical viscosity limits have been determined for common carbon additives that offer slurry formulations with improved electrochemical and rheological performance. For instance, at the same electrical conductivity of 60 mS cm-1, higher aspect ratio particles, such as graphene and carbon nanotubes, offered 4 and 2.4 times lower viscosity compared to carbon black due to the improved packing and conformity of the high aspect ratio particles. On the other hand, thixotropic measurements showed that the flowable electrodes with carbon black exhibit the fastest agglomeration kinetics, offering 25 % less time to recover from the applied shear due to spherical morphology and facile agglomeration kinetics. Overall, our findings show that the particle morphology has a significant impact on the electrochemical and rheological performance of flowable electrodes with up to 40 % difference in capacitance for similar viscosity suspensions. Furthermore, a direct correlation between the rheological and the electrochemical properties was established, offering morphology-independent practical guidelines for formulating slurries with optimal performance. In this manner, particles that can achieve the highest density of packing before the critical limit were found to offer the optimal balance between electrochemical and rheological performance.

In recent years, more efforts have been made to improve new and more efficient non-membrane-based methods for water desalination. Capacitive deionization (CDI), a novel technique for water desalination using an electric field to adsorb ions from a solution to a high-porous media, has the capability to recover a fraction of the energy consumed for the desalination during the regeneration process, which happens to be its most prominent characteristic among other desalination methods. This paper introduces a new desalination method that aims improving the performance of traditional CDI systems. The proposed process consists of an array of CDI cells connected in series with buffer containers in between them. Each buffer, serve two purposes: 1) average the outlet solution from the preceding cell, and 2) secure a continuous water supply to the following cell. Initial evaluation of the proposed CDI system architecture was made by comparing a two-cell-one-buffer assembly with a two cascaded cells array. Concentration of the intermediate solution buffer was the minimum averaged concentration attained at the outlet of the first CDI cell, under a steady state condition. The obtained results show that proposed CDI system with intermediate solution had better performance in terms of desalination percentage. This publication opens new opportunities to improve the performance of CDI systems and implement this technology on industrial applications.

A review on capacitive deionization: Recent advances in Prussian blue analogues and carbon materials based electrodes

Capacitive deionization (CDI) technology is a challenge on an economical and effective electrosorption desalination method. The paper analyses the CDI current status and progress of carbon electrode materials, and describes the types of CDI and its performances of testing materials. The electrosorption capacities are summarized on the carbon electrode materials and the current hurdles. The reported numbers from the literature vary in a wide range between 0.25 and 26.42 mg/g of both electrodes CDI cell, we suggest that the CDI electrodes should have an adsorption of at least 9.0 mg/g NaCl when the applyed voltage is 2.0 V. The potential capacitive deionization technologies are proposed here.

Capacitive deionization, CDI, is considered as a versatile and promising electrochemical technology useful for both water desalination and remediation.1 CDI works under operational conditions equivalent to the charging/discharging steps in a generic electric double-layer capacitor (EDLC). Thus, it allows reducing ion concentration of an aqueous stream by the electrosorption of ions in porous electrodes and formation of the EDL, resulting in simultaneous salt withdrawal and energy accumulation. Once the deionization (charging) step is completed, the ions can be desorbed in regeneration (discharging) step. This leads to energy release and leaves the electrode surface available for the next deionization cycle. Accordingly, CDI is considered a simple, non-energy intensive method to produce clean water.2 In this work, a novel current collector-free electrode for CDI devices is designed based on electrodes consisting of a porous metal oxide (MOx) network interpenetrated into porous fibres of carbon nanotubes (CNTf). The fabrication of electrodes is based on the continuous impregnation of CNTf with MOx precursors in-line as they are spun from the chemical vapour deposition reaction. SiO2 and γ-Al2O3 were chosen, which have the following main benefits: i) developing an electrostatic EDL surface potential in the pH range of seawater and drinking water; ii) increasing specific surface area; iii) enabling wetting of electrodes by aqueous electrolytes.3 The content of MOx can be varied by adjusting the concentration of sol in the dispersion. γ-Al2O3/CNTf and SiO2/CNTf electrodes from 6 wt.% to 60 wt.% of MOx have been manufactured and characterized (TG-analysis, electrical conductivity, N2 adsorption isotherms, SEM and TEM images and RAMAN spectroscopy). The hybrid structure consisting of two interconnected porous networks with a uniform distribution of MOx on the supporting CNTf (see Fig 1a and Fig 1b) leads to high capacitance while reducing internal resistance (see Fig 1c), as confirmed by the electrochemical characterization (cyclic voltammetry, charge-discharge and electrochemical impedance spectroscopy). The use of a relatively simple fabrication process, particularly the infiltration of fabrics with sol particles in-line during fibre spinning, enables fabrication of large electrode samples and testing of a full CDI flow cell for brackish water desalination, 2.0 gNaCl L-1 (see Fig 1d). The full current collector-free CDI cell (see Fig 1e and Fig 1f), comprising a stack of γ-Al2O3/CNTf and SiO2/CNTf anodes and cathodes, respectively, has a large salt adsorption capacity of 6.5 mg g-1 and very high efficiency of 86%, which translates into a low energy consumption per gram of salt removed, 0.26 W h g-1. This is an 80% improvement compared with reference devices based on activated carbon and titanium foil current collector electrodes. The exceptional desalination properties (see Fig 1g) are directly linked to the interconnected nanoparticle MOx/CNTf hybrid network. Accordingly, we believe that these CNTf-based electrodes fabricated in a large scale could contribute to a significant improvement in the engineering manufacturing process of desalination reactors through more energy-efficient systems. Considering the high flexibility in bending of these hybrid electrodes, the possibility to build current collector-free desalination devices with complex non-planar shapes has also been opened up. References M. A. Anderson et al. Capacitive deionization as an electrochemical means of saving energy and delivering clean water. Comparison to present desalination practices: Will it compete?, Electrochim. Acta, 55, 3845–3856 (2010). http://dx.doi.org/10.1016/j.electacta.2010.02.012.M. E. Suss et al., Water desalination via capacitive deionization: what is it and what can we expect from it?, Energy Environ. Sci., 8, 2296–2319 (2015).http://dx.doi.org/10.1149/2.0271805jes.J. J. Wouters et al., Influence of Metal Oxide Coatings, Carbon Materials and Potentials on Ion Removal in Capacitive Deionization J. Electrochem.Soc., 165, 148–161 (2018). http://dx.doi.org/10.1149/2.0271805jes. Figure 1

Currently, shortage of the water resources is a global issue. Water desalination is a solution that can be used to solve the water shortage problem. Capacitive deionization (CDI) is an effective water desalination method. CDI offers relatively low energy consumptions and low initial costs. This paper improves energy exchange between CDI units used in efficient CDI systems. Traditionally, hysteresis control is employed for transferring energy through power converters; this control method induces switching losses. Converter losses cause CDI systems not to operate in nominal voltage. In this paper, a buck converter and a CDI selector are proposed to compensate the losses. The maximum switching frequency is limited to prevent high switching losses. Simulation results validate the proposed scheme.

본 연구에서 광산수의 재활용을 위해 축전식 탈염공정을 적용하였다. 이를 위해 이온교환폴리머를 코팅한 탄소 전극을 활용하였는데 본 성능을 관찰하기 위해 이온교환폴리머를 코팅하지 않은 탄소 전극으로 광산수의 탈염 운전을 수행하고 비교분석하였다. 또한, 광산수의 높은 농도가 축전식 탈염공정에 미치는 영향을 조사하기 위해 저농도의 기수(NaCl 200 ppm)를 활용한 운전 성능 비교 역시 수행하였다. 연구 결과 이온교환폴리머를 코팅한 탄소 전극을 활용한 광산수 탈염 효율 및 제거양 모두 그렇지 않은 전극에 비해 높았고 에너지 소모량은 더 적게 나타났다. 이는 높은 비패러데이 전류, 높은 염농도에 따른 낮은 용액 저항, 전극 기공 내에서의 이중층 중첩효과에 기인하는 것으로 판단되었다. 또한, 이온교환폴리머를 코팅한 전극을 활용한 기수 탈염 운전 결과 낮은 염농도에 따라 용액의 저항이 높아지고, 제거 대상의 염의 양이 낮아 광산수에 비해 매우 높은 효율을 보였으나, 제거양은 매우 낮음을 알 수 있었다. In this study, capacitive deionization (CDI) was introduced for desalination of mining water. Ion-exchange polymer coated carbon electrodes (IEE) were used in CDI to desalt mining water. The CDI performance using the IEE for desalination of mining water was carried out and then was compared with that using general carbon electrodes without ion-exchange polymer coating (GE). Moreover, to investigate the effect of the concentration of influent solutions on CDI performance, the CDI performance using the IEE for desalination of brackish water (NaCl 200 ppm) was also performed and analyzed. As a result, the higher salt removal efficiency, rate and the lower energy consumption in the CDI process using the IEE and mining water were obtained compared with those using the GE and mining water. It is mainly due to higher non-Faradaic current, low ohmic resistance of the influent, overlapping effect of electric double layers in micropore of the electrode. In addition, the CDI process using the IEE and brackish water shows much higher salt removal efficiency and lower salt removal rate than that using the IEE and mining water. This results from the lower concentration (i.e., higher ohmic resistance) and salt amount of the influent.

Capacitive deionization (CDI) is a promising water purification technology which works by removing salt ions or charged species from aqueous solutions. Currently, most of the research on CDI focuses on the desalination of water with low or moderate salt concentration due to the low salt adsorption capacity of the electrodes. The electrosorption capacity of CDI relies on the structural and textural characteristics of the electrode materials. The cost of electrode materials, the complicated synthesis methods, and the environmental concerns arising from material synthesis steps hinder the development of large-scale CDI units. By considering the good electrical conductivity, high specific surface area (SSA), porous structure, availability, mass production, and cost, porous carbon derived from biomass materials may be a promising CDI electrode material. This review presents an update on carbon nanomaterials derived from various biomasses for CDI electrodes. It covers different synthesis methods and the electrosorption performance of each material and discusses the impact of the SSA and porous structure of the materials on desalination. This review shows that a variety of biomass materials can be used to synthesize cost-effective CDI electrode materials with different structures and good desalination performance. It also shows that diverse precursors and synthesis routes have significant influences on the properties and performance of the resulting carbon electrodes. Additionally, the performance of CDI does not depend only on BET surface area and pore structure but also on the applied voltage, initial concentration of the feed solution, and mass, as well as the capacitance of the electrodes.

Influence of particle size distribution on carbon-based flowable electrode viscosity and desalination efficiency in flow electrode capacitive deionization