A bipolar membrane-based cation electrolytic membrane suppressor for ion chromatography

Fabrication and application of a continuously regenerated cationic impurity removal device for ion chromatography

A continuously regenerated cationic impurity removal device (CR-CRD) has been fabricated and applied for ion chromatography (IC). The removal of cationic impurities is realized by electrodialytically replacing the cationic impurities with hydronium ions. The device is configured in a sandwich structure and the central eluent channel is respectively isolated from both electrodes by stacked cation exchange membranes and a bipolar membrane (BPM) plus stacked anion exchange membranes. The eluent channel is packed with cation exchange resins in hydronium form and their continuous regeneration can be achieved by electrodialysis. A desirable feature of the device is gas-free, and no degasser is required. It showed sufficient ability to remove cationic impurities, as indicated by > 99.9 % removal of 10 mL of 1 mM LiOH solution injected (∼10 μmol) or continuous removal of 1 mM LiOH solution at the flow rate of 1 mL/min (1 μmol/min). A useful application was for sample pretreatment in nuclear power industry, by eliminating strong matrix interference of the sample containing LiOH (1 mM) and boric acid (2000 mg/L) with trace anion analysis.

[Advances of electrodialytic technologies used in ion chromatography]

电渗析器件通常定义为在电场作用下操纵离子从一种溶液穿过离子交换膜迁移到另外一种溶液的一种设备。它可以通过电解水产生氢离子或氢氧根离子,从而用于离子色谱系统的淋洗液在线制备、抑制或检测。相较于人工配制淋洗液或再生液,电渗析技术具有绿色、高效、纯度高、自动化程度高等优势。因此基于电渗析器件的离子色谱系统应用范围越来越大。该文简要评述了近几年该器件的研究进展,具体包括电致淋洗液发生器、电致膜抑制器和电渗析样品前处理器。

Preparation of a polymer-based weak cation exchanger for ion chromatography via atom transfer radical polymerization

A novel polymer-based weak cation exchanger (WCX) for ion chromatography has been described. It was prepared by grafting tert-butyl acrylate and maleic anhydride onto the surface of poly(glycidyl methacrylate-divinylbenzene) microspheres via atom transfer radical polymerization, followed by hydrolytic treatment to produce acrylic and maleic acid groups. The obtained WCX showed better separation and higher selectivity for model cations relative to solely acrylic or maleic acid. Simultaneous separation of alkali and alkaline earth cations (including NH₄⁺) was achieved in a single isocratic run under suppressed mode, and ion exchange was found to dominate the separation process. Its utility was demonstrated for determination of several cations in a beer sample and the recovery was ranging from 98.4 to 109.9%.

Electrodialysis Pump Based on Enhanced Water Dissociation of Bipolar Membrane

We describe a novel micropump mode-electrodialysis pump (EDP), which is based on the recombination of hydrogen and hydroxyl ions generated by enhanced water dissociation of bipolar membrane (BPM). The pump is in a sandwich-like configuration in which the central production channel is spatially isolated from two outer regenerant chambers by a BPM, respectively. Both BPMs are put at the same direction, in which the anion exchange membrane (AEM) side is facing the anode with respect to the cation exchange membrane (CEM) side facing the cathode. Pure water as the feed solution flows through the regenerant chambers at a conventional flow rate (e.g., 0.2 mL/min). Under the electric field, enhanced water dissociation at the junction layer of BPM will occur, generating hydroxyl and hydrogen ions. Their electrodialytic migration into the central channel will recombine water and its flow rate is correlated with the applied current. The pump shows near-ideal Faradaic efficiency and at least 0.8 μL/min can be achieved by controlling the current. The produced water is near neutral and obvious enrichment of trace impurity anions is observed in the production channel.