电容去离子脱盐装置构型的研究进展

电容去离子(CDI)技术是一种新型的海水淡化技术,因其具有环境友好、操作简单和能耗低等优势而受到广大研究者的关注。在CDI技术中,电吸附的性能与装置的构型有着密切的联系。本文综述了目前常见的几种CDI装置,包括膜电容去离子(MCDI)、流动电极电容去离子(FCDI)、杂化电极电容去离子(HCDI)、反式电极电容去离子(i-CDI)以及脱盐电池(DB),对这几种装置的发展历程和装置构型进行介绍,最后,对CDI的装置构型在未来的研究发展方向进行了展望,以期为CDI装置在电脱盐领域的研究和应用提供参考。     

海水淡化用碳基电极材料及电容去离子技术研究进展

电容去离子技术(Capacitive Deionization,CDI)可以通过断电或电极反接方式使盐离子脱附,达到电极再生的目的,实现电极的可循环利用,其在海水淡化处理技术中具有独特的优势,逐渐成为一种缓和淡水资源紧缺和水污染的极具前景的技术手段。近年来,CDI处理技术正在向电极高效、无二次污染方向转变,未来将进一步聚焦碳基电极材料功能化(碳材料,钛碳化物MXenes,掺杂改性石墨烯材料)、装置和工艺设计优化等重要方向。为深入研究CDI海水淡化技术机理,进一步探索CDI方法在实际应用中的潜力,分别对CDI的脱盐机理、电极材料、装置和工艺设计对电吸附效率和性能的研究进展进行了总结,回顾CDI脱盐效果与电极材料、CDI电池装置设计等因素之间的密切关系,并对CDI技术在海水淡化中的研究发展提出展望。     

Relation between the charge efficiency of activated carbon fiber and its desalination performance

Four types of activated carbon fibers (ACFs) with different specific surface areas (SSA) were used as electrode materials for water desalination using capacitive deionization (CDI). The carbon fibers were characterized by scanning electron microscopy and N(2) adsorption at 77 K, and the CDI process was investigated by studying the salt adsorption, charge transfer, and also the charge efficiency of the electric double layers that are formed within the micropores inside the carbon electrodes. It is found that the physical adsorption capacity of NaCl by the ACFs increases with increasing Brunauer-Emmett-Teller (BET) surface area of the fibers. However, the two ACF materials with the highest BET surface area have the lowest electrosorptive capability. Experiments indicate that the charge efficiency of the double layers is a key property of the ACF-based electrodes because the ACF material which has the maximum charge efficiency also shows the highest salt adsorption capacity for CDI.     

电容去离子用功能化电极吸附材料的设计与构建

电容去离子(CDI)是近年来新兴的一种脱盐技术,由于其具有节能环保、实用性强等优势而倍受青睐。作为该技术核心的电极吸附材料,应具有高比表面积、良好导电性、亲水性、适宜孔隙结构、优异的稳定性等特点。这将有效保障该CDI器件不仅具有高CDI脱盐效率,而且拥有更强的循环稳定性。本文结合我们前期研究工作,针对吸附电极的制备、结构与性能构效关系的差异,综述了近年来多种功能化电极材料在CDI技术应用中的最新进展。     

Capacitive Deionization of Water (A Review)

Russian Journal of Electrochemistry - The literature on capacitive deionization (CDI) of water is discussed. The CDI is a new method of water desalination which consists of pumping water to be...     

Single module flow-electrode capacitive deionization for continuous water desalination

The search for novel desalination technologies has recently led to the introduction of flow-electrodes to capacitive deionization (CDI) processes, named as flow-electrode capacitive deionization (FCDI). Unlike classical CDI, which is a discontinuous or semi-continuous process due to the need for regeneration of the electrodes within the same module, flow-electrodes offer new design opportunities which enable fully continuous desalination processes as well as easily scalable systems. Here, we describe a novel system for the continuous desalination of water based on FCDI using a single flow-electrode and a single module. The flow-electrode is based on activated carbon powder suspended in water. During continuous operation of the system, a desalination rate of a 1 g/L NaCl solution of up to 70% is achieved at water recoveries of up to 80%. Additionally we report very good current efficiencies: in case of 80% water recovery, the current efficiency is 0.93. The single flow-electrode single module process might reduce energy and investment costs and lower the threshold to a large scale implementation.     

具有阴阳离子插入行为的电容去离子电极设计

具有离子嵌入/脱嵌能力的离子插层型电容去离子(CDI)电极材料是一类具有很高比容量的新型CDI电极,可以有效改善传统碳材料电极离子存储容量有限、电极易腐蚀的缺点。本文以金属氧化物、过渡金属/碳/氮/碳氮化物(MXenes)、钠超离子导体(NASICON)型磷酸盐材料等为分类,综述了近几年具有代表性的基于离子嵌入/脱嵌的电极材料的设计及在CDI方面的应用,以期深入理解构效关系,开发出性能更强的电极材料。     

电容去离子除氯电极的构建及其脱盐性能研究进展

电容去离子技术(Capacitive deionization,CDI)是一种新兴的脱盐技术,通过在电极两端施加较低的外加电场除去水中的带电离子和分子,由于其较低的能耗和可持续性而备受关注。基于储能电池领域近年来的迅猛发展,CDI电极材料实现了从以双电层作用机理为代表的碳材料到法拉第电极材料的跨越,使得脱盐性能有了大幅度提升。Na⁺的去除与Cl^-的去除同等重要,然而,CDI中针对氯离子高效去除的电极材料研究关注较少。本文从CDI装置的构型演变发展出发,系统地归纳与梳理了CDI中关于脱氯电极材料的分类,对比了不同类型脱氯电极材料的特点,并总结了Cl^-去除的机理,分别为基于双电层的电吸附、转化反应、离子插层和氧化还原反应。本文是首篇关于CDI阳极材料的进展综述和展望,为CDI除氯电极的后续研究提供理论基础和研究思路。     

磺化石墨烯/活性炭复合电极的制备及其不对称电容器脱盐

在还原剂NaBH₄存在下, 采用对氨基苯磺酸重氮盐与氧化石墨(GO)表面共价键合制备磺化石墨烯(GP-SO₃H). 傅里叶变换红外光谱(FTIR)证明磺酸基团在石墨烯表面接枝. 采用扫描电子显微镜(SEM)研究了磺化石墨烯的表面形貌. 以磺化石墨烯为添加剂, 制备了磺化石墨烯/活性炭(GP-SO₃H/AC)复合电极. 循环伏安及阻抗分析结果表明, 该复合电极的电容特性及导电性有明显改善. 以活性炭电极为对电极组装了不对称电容器(GP-SO₃H/AC|AC), 研究了该不对称电容器的电化学脱盐性能. 与对称电容器(AC|AC)相比, 不对称电容器中由于电极内磺酸基团对反离子的屏蔽作用, 电容器的电流效率达到89.4%以上, 脱盐量提高2.4倍, 单个循环脱盐量达到10.87 mg/g.     

高回收率膜法苦咸水淡化工艺的应用研究进展

膜法苦咸水淡化过程中,符合环境保护要求的浓排水处理方法成本高昂,所以只有当回收率达到较高值时,在实际运行中才具有经济可行性。目前,在不加剧膜污染的条件下进一步提高苦咸水淡化系统回收率的方法已成为该领域研究热点。本文详细综述了高回收率膜法苦咸水淡化工艺的应用研究进展,包括基于反渗透、纳滤、正渗透、膜蒸馏、电渗析和电容去离子化淡化工艺过程,以及这些过程面临的热点问题,并对此提出了建议。     

石墨烯基电极材料的设计和构建及其在电容去离子中的应用

电容去离子(CDI)是一种通过静电力作用将离子从水中去除的技术,电极是整个装置中为最为核心的部件,石墨烯因具有优异的导电性和巨大的比表面积等优势成为当前CDI电极材料的研究热点之一。目前对于CDI石墨烯电极的研究主要集中于石墨烯电极的合成,然而有关CDI性能与石墨烯电极制作工艺及电极材料自身结构之间的关系,缺少相关综述。本文系统介绍了CDI的基本原理与性能指标,综述了石墨烯电极材料的研究进展与电极制作工艺,重点分析、归纳和总结了石墨烯材料的特性(孔隙结构、导电性、亲疏水性)对CDI性能的影响,最后对CDI中石墨烯电极材料今后的发展进行了总结和展望。     

Role of titania incorporated on activated carbon cloth for capacitive deionization of NaCl solution

Adsorption isotherms of NaCl on activated carbon cloth (ACC) and titania-incorporated activated carbon cloth (Ti-ACC) under an electric field were investigated to deduce the role of titania in capacitive deionization (CDI) of NaCl. Electrosorption of NaCl on the ACC was significantly increased by titania incorporation, whereas its physical adsorption was considerably decreased, resulting in an improved performance of the Ti-ACC as a CDI electrode. Langmuir isotherms based on a localized and fixed amount of adsorption were suitable for the simulation of electrosorption and physical adsorption of ions on the ACC electrodes. The variances of q(m) and b of Langmuir isotherms with electric potential indicate increases in the number of ions per adsorption site and in electrosorption strength of ions by titania incorporation. A cyclic voltammetric study for ion adsorption on ACC electrodes confirms the reversibility between electrosorption and desorption of ions, regardless of titania incorporation.     

The electrochemistry of activated carbonaceous materials: past, present, and future

Carbonaceous materials are widely used in electrochemistry. All allotropic forms of carbons??graphite, glassy carbon, amorphous carbon, fullerenes, nanotubes, and doped diamond??are used as important electrode materials in all fields of modern electrochemistry. Examples include graphite and amorphous carbons as anode materials in high-energy density rechargeable Li batteries, porous carbon electrodes in sensors and fuel cells, nano-amorphous carbon as a conducting agent in many kinds of composite electrodes (e.g., cathodes based on intercalation inorganic host materials for batteries), glassy carbon and doped diamond as stable robust and high stability electrode materials for all aspects of basic electrochemical studies, and more. Amorphous carbons can be activated to form very high specific surface area (yet stable) electrode materials which can be used for electrostatic energy storage and conversion [electrical double-layer capacitors (EDLC)] and separation techniques based on electro-adsorption, such as water desalination by capacitive de-ionization (CDI). Apart from the many practical aspects of activated carbon electrodes, there are many highly interesting and important basic aspects related to their study, including transport phenomena, molecular sieving behavior, correlation between electrochemical behavior and surface chemistry, and more. In this article, we review several important aspects related to these electrode materials, in a time perspective (past, present, and future), with the emphasis on their importance to EDLC devices and CDI processes.     

Modeling of electrochemical deionization across length scales: Recent accomplishments and new opportunities

Theoretical models have recently been used to simulate deionization technology by capturing electrochemical processes at atomistic, electrode, and plant length scales in electrodialysis, capacitive deionization using electric double layers, and Faradaic deionization using intercalation materials and redox-active polymers. We review the salient features of such models, identifying their major accomplishments in quantifying energy consumption and ion removal, analyzing the feasibility of large-scale systems, and discovering new electrode materials and understanding their deionization mechanisms. After summarizing strengths and weaknesses of recent modeling strategies, we identify research directions to expand modeling capabilities that can be used to inform electrode material/microstructure design, to assign energy losses to electrode-scale mechanisms, to bridge length scales, and to capture Faradaic kinetic/diffusion processes.     

Development of high quality Fe_3O_4/rGO composited electrode for low energy water treatment

Electrochemical water treatment is an attractive technology for water desalination and softening due to its low energy consumption. Especially, capacitive Deionization(CDI) is promising as a future technology for water treatment. Graphene(rGO) has been intensively studied for CDI electrode because of its advantages such as excellent electrical conductivity and high specific surface area. However, its 2D dimensional structure with small specific capacitance, high resistance between layers and hydrophobicity degrades ion adsorption efficiency. In this work, we successfully prepared uniformly dispersed Fe_3O_4/rGO nanocomposite by simple thermal reactions and applied it as effective electrodes for CDI. Iron oxides play a role in uniting graphene sheets, and specific capacitance and wettability of electrodes are improved significantly;hence CDI performances are enhanced. The hardness removal of Fe_3O_4/rGO nanocomposite electrodes can reach 4.3 mg/g at applied voltage of 1.5V, which is 3 times higher than that of separate r GO electrodes.Thus this material is a promising candidate for water softening technology.     

Graphene–carbon 2D heterostructures with hierarchically-porous P,N-doped layered architecture for capacitive deionization

Exploring a new-family of carbon-based desalinators to optimize their performances beyond the current commercial benchmark is of significance for the development of practically useful capacitive deionization (CDI) materials. Here, we have fabricated a hierarchically porous N,P-doped carbon–graphene 2D heterostructure (denoted NPC/rGO) by using metal–organic framework (MOF)-nanoparticle-driven assembly on graphene oxide (GO) nanosheets followed by stepwise pyrolysis and phosphorization procedures. The resulting NPC/rGO-based CDI desalinator exhibits ultrahigh deionization performance with a salt adsorption capacity of 39.34 mg g⁻¹ in a 1000 mg L⁻¹ NaCl solution at 1.2 V over 30 min with good cycling stability over 50 cycles. The excellent performance is attributed to the high specific surface area, high conductivity, favorable meso-/microporous structure together with nitrogen and phosphorus heteroatom co-doping, all of which are beneficial for the accommodation of ions and charge transport during the CDI process. More importantly, NPC/rGO exhibits a state-of-the-art CDI performance compared to the commercial benchmark and most of the previously reported carbon materials, highlighting the significance of the MOF nanoparticle-driven assembly strategy and graphene–carbon 2D heterostructures for CDI applications.

MOF nanoparticle-driven assembly on 2D nanosheets produces the graphene–carbon heterostructure with hierarchically-porous P,N-doped layered architecture.     

The Surge of Metal–Organic-Framework (MOFs)-Based Electrodes as Key Elements in Electrochemically Driven Processes for the Environment

Metal–organic-frameworks (MOFs) are emerging materials used in the environmental electrochemistry community for Faradaic and non-Faradaic water remediation technologies. It has been concluded that MOF-based materials show improvement in performance compared to traditional (non-)faradaic materials. In particular, this review outlines MOF synthesis and their application in the fields of electron- and photoelectron-Fenton degradation reactions, photoelectrocatalytic degradations, and capacitive deionization physical separations. This work overviews the main electrode materials used for the different environmental remediation processes, discusses the main performance enhancements achieved via the utilization of MOFs compared to traditional materials, and provides perspective and insights for the further development of the utilization of MOF-derived materials in electrified water treatment.