Membrane arrangement influences time to steady state in FCDI with multi-ionic salt solutions

IF 8.3 1区工程技术 Q1 ENGINEERING, CHEMICAL

Desalination Pub Date : 2025-05-01 DOI:10.1016/j.desal.2025.118939

Lukas Mankertz , Meike Theis , Christian J. Linnartz , Matthias Wessling

{"title":"Membrane arrangement influences time to steady state in FCDI with multi-ionic salt solutions","authors":"Lukas Mankertz , Meike Theis , Christian J. Linnartz , Matthias Wessling","doi":"10.1016/j.desal.2025.118939","DOIUrl":null,"url":null,"abstract":"<div><div>Flow-electrode capacitive deionization (FCDI) is a promising technology for energy-efficient desalination, offering the potential to selectively remove ions from multi-ionic salt solutions. This study presents a comparative investigation of two FCDI modules with distinct ion-exchange membrane (IEM) arrangements, using cation-exchange membranes (CEM) and anion-exchange membranes (AEM): CEM-AEM-CEM (C <span><math><mo>∣</mo></math></span> A <span><math><mo>∣</mo></math></span> C) and AEM-CEM-AEM (A <span><math><mo>∣</mo></math></span> C <span><math><mo>∣</mo></math></span> A). Both modules achieved similar levels of desalination and concentration in steady state, but the time required to reach steady state varied significantly due to differences in the IEM arrangement and the ionic buffer-capacity of the flow electrode.</div><div>The results revealed that membrane selectivity is critical in systems with multiple ion species, particularly before achieving a steady state, where conductivity alone proves insufficient for characterizing salt composition. A higher selectivity for sulfate over carbonate was observed for AEMs, causing delayed stabilization of concentrations in the A <span><math><mo>∣</mo></math></span> C <span><math><mo>∣</mo></math></span> A module. Strategies to reduce the ionic buffer-capacity of the flow electrode, such as decreasing its volume as well as recognizing which ion should follow the flow-electrode path were identified as potential means to accelerate steady-state achievement.</div><div>Furthermore, experiments with varying carbonate-to-sulfate molar ratios in the diluate feed confirmed the inherent selectivity of AEMs for sulfate and established an upper limit for normalized transport ratios. These findings emphasize the need for complementary approaches, such as membrane coatings or tailored flow-electrode materials, to enhance process selectivity and efficiency. This work provides critical insights into the interplay of IEM arrangement and flow-electrode behavior, offering a foundation for optimizing FCDI systems in desalination applications involving complex salt solutions.</div></div>","PeriodicalId":299,"journal":{"name":"Desalination","volume":"613 ","pages":"Article 118939"},"PeriodicalIF":8.3000,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Desalination","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S001191642500414X","RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, CHEMICAL","Score":null,"Total":0}

引用次数: 0

Abstract

Flow-electrode capacitive deionization (FCDI) is a promising technology for energy-efficient desalination, offering the potential to selectively remove ions from multi-ionic salt solutions. This study presents a comparative investigation of two FCDI modules with distinct ion-exchange membrane (IEM) arrangements, using cation-exchange membranes (CEM) and anion-exchange membranes (AEM): CEM-AEM-CEM (C

∣

∣

C) and AEM-CEM-AEM (A

∣

∣

A). Both modules achieved similar levels of desalination and concentration in steady state, but the time required to reach steady state varied significantly due to differences in the IEM arrangement and the ionic buffer-capacity of the flow electrode.

The results revealed that membrane selectivity is critical in systems with multiple ion species, particularly before achieving a steady state, where conductivity alone proves insufficient for characterizing salt composition. A higher selectivity for sulfate over carbonate was observed for AEMs, causing delayed stabilization of concentrations in the A

∣

∣

A module. Strategies to reduce the ionic buffer-capacity of the flow electrode, such as decreasing its volume as well as recognizing which ion should follow the flow-electrode path were identified as potential means to accelerate steady-state achievement.

Furthermore, experiments with varying carbonate-to-sulfate molar ratios in the diluate feed confirmed the inherent selectivity of AEMs for sulfate and established an upper limit for normalized transport ratios. These findings emphasize the need for complementary approaches, such as membrane coatings or tailored flow-electrode materials, to enhance process selectivity and efficiency. This work provides critical insights into the interplay of IEM arrangement and flow-electrode behavior, offering a foundation for optimizing FCDI systems in desalination applications involving complex salt solutions.

Abstract Image

查看原文本刊更多论文

膜排列对多离子盐溶液中fdi的稳态时间有影响

流动电极电容去离子（FCDI）是一种很有前途的节能脱盐技术，它提供了从多离子盐溶液中选择性去除离子的潜力。本研究采用阳离子交换膜（CEM）和阴离子交换膜（AEM）对两种具有不同离子交换膜（IEM）排列的FCDI模块进行了比较研究：CEM-AEM-CEM （C∣a∣C）和AEM-CEM-AEM （a∣C∣a）。两个模块在稳定状态下都达到了相似的脱盐和浓度水平，但由于IEM排列和流动电极的离子缓冲容量的差异，达到稳定状态所需的时间有很大差异。结果表明，膜的选择性在多离子体系中是至关重要的，特别是在达到稳定状态之前，仅电导率不足以表征盐的组成。AEMs对硫酸盐的选择性高于碳酸盐，导致A∣C∣A模块中浓度的延迟稳定。减少流动电极的离子缓冲容量的策略，如减小其体积以及识别哪些离子应该遵循流动电极路径，被认为是加速实现稳态的潜在手段。此外，在稀料中不同碳酸盐与硫酸盐摩尔比的实验证实了AEMs对硫酸盐的固有选择性，并确定了归一化输运比的上限。这些发现强调需要补充的方法，如膜涂层或定制的流动电极材料，以提高工艺的选择性和效率。这项工作为IEM排列和流动电极行为的相互作用提供了重要的见解，为优化涉及复杂盐溶液的海水淡化应用中的FCDI系统提供了基础。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

求助全文

约1分钟内获得全文求助全文

来源期刊

Desalination 工程技术-工程：化工

CiteScore

14.60

自引率

20.20%

发文量

619

审稿时长

41 days

期刊介绍： Desalination is a scholarly journal that focuses on the field of desalination materials, processes, and associated technologies. It encompasses a wide range of disciplines and aims to publish exceptional papers in this area. The journal invites submissions that explicitly revolve around water desalting and its applications to various sources such as seawater, groundwater, and wastewater. It particularly encourages research on diverse desalination methods including thermal, membrane, sorption, and hybrid processes. By providing a platform for innovative studies, Desalination aims to advance the understanding and development of desalination technologies, promoting sustainable solutions for water scarcity challenges.