Promoting water-splitting in Janus bipolar ion-exchange resin wafers for electrodeionization
Promoting water-splitting in Janus bipolar ion-exchange resin wafers for electrodeionization
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DOI：
10.1039/c9me00179d
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发表时间：
2020-06-01
影响因子：
3.6
通讯作者：
Arges, Christopher G.
中科院分区：
文献类型：
--
作者：
Jordan, Matthew L.;Valentino, Lauren;Arges, Christopher G.
随着应用范围的不断扩大，电化学分离工艺正在经历复兴，因为与传统分离技术相比，它们提供了提高能效和可持续性的机会。现有的平台，如电渗析和电去离子（EDI）正在经历显著的改进，并且目前正在部署用于处理不同的液体流（例如，水和废水处理、有机酸分离等）。此外，电化学分离的相对较低的固有电力需求可以通过与可持续的可再生能源的整合来满足。为了实现真正可持续的电化学分离过程，最重要的是通过最大限度地减少这些单元内的所有电阻源来提高电化学分离的能量效率。这项工作报告了一类新的对称和不对称的Janus双极树脂晶片（RW），其增加了EDI中的间隔通道离子电导率，同时具有将水分裂成质子和氢氧根离子的额外功能。后一个属性在需要pH调节的利基应用中是重要的，例如从液体流中去除二氧化硅和有机酸。Janus双极RW由单个离子传导RW设计而成，这些RW连接在一起以形成紧密的聚阳离子-聚阴离子结。有趣的是，在低盐浓度下的单离子传导RW的电导率被观察到依赖于RW转移的抗衡离子的离子迁移率。使用单一的离子传导RWs来构建Janus双极RWs，使得能够将水裂解催化剂（氢氧化铝纳米颗粒）并入到多孔离子交换树脂床中。据我们所知，这是第一次在EDI的离子交换树脂床中使用水解离催化剂。双极结中的水解离催化剂使水预极化，使得其更容易在施加的电场下经由第二维恩效应分裂成水合氢离子和氢氧根离子电荷载体。新的分子层状Janus RW在实验室规模的EDI装置中表现出令人满意的水分解和盐去除，并且这些材料可以改善甚至取代现有的双极膜电渗析装置，该装置目前需要大的电解质进料浓度。
Electrochemical separation processes are undergoing a renaissance as the range of applications continues to expand because they offer opportunities for increased energy efficiency and sustainability in comparison to conventional separation technologies. Existing platforms such as electrodialysis and electrodeionization (EDI) are seeing significant improvement and are currently being deployed for treating a diverse set of liquid streams (e.g., water and wastewater treatment, organic acid separation, etc.). In addition, the relatively low inherent electricity requirement for electrochemical separations could potentially be satisfied through integration with sustainable sources of renewable energy. In order to achieve a truly sustainable electrochemical separations process, it is paramount to improve the energy efficiency of electrochemical separations by minimizing all sources of resistances within these units. This work reports of a new class of symmetric and asymmetric Janus bipolar resin wafers (RWs) that augment the spacer channel ionic conductivity in EDI while having the additional functionality of splitting water into protons and hydroxide ions. The latter attribute is important in niche applications that require pH modulation such as silica and organic acid removal from liquid streams. The Janus bipolar RWs were devised from single ion-conducting RWs that were interfaced together to create an intimate polycation-polyanion junction. Interestingly, the conductivity of the single ion-conducting RWs at low salt concentrations was observed to be dependent on the ionic mobilities of the counterions that the RW was transferring. Using single ion-conducting RWs to construct Janus bipolar RWs enabled the incorporation of a water-splitting catalyst (aluminum hydroxide nanoparticles) into the porous ion-exchange resin bed. To the best of our knowledge, this is the first time a water dissociation catalyst has been implemented in the ion-exchange resin bed for EDI. The water dissociation catalyst in bipolar junctions pre-polarizes water making it easier to split into hydronium and hydroxide ion charge carriers under applied electric fields via the second Wien effect. The new molecularly layered Janus RWs demonstrate both satisfactory water-splitting and salt removal in bench scale EDI setups and these materials may improve, or even supplant, existing bipolar membrane electrodialysis units that currently necessitate large electrolyte feed concentrations.