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首页> 外文期刊>Environmental Science & Technology >Junction Potentials Bias Measurements of Ion Exchange Membrane Permselectivity
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Junction Potentials Bias Measurements of Ion Exchange Membrane Permselectivity

机译：离子交换膜通透性的结电位偏置测量

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摘要

Ion exchange membranes (IEMs) are versatile materials relevant to a variety of water and waste treatment, energy production, and industrial separation processes. The defining characteristic of IEMs is their ability to selectively allow positive or negative ions to permeate, which is referred to as permselectivity. Measured values of permselectivity that equal unity (corresponding to a perfectly selective membrane) or exceed unity (theoretically impossible) have been reported for cation exchange membranes (CEMs). Such nonphysical results call into question our ability to correctly measure this crucial membrane property. Because weighing errors, temperature, and measurement uncertainty have been shown to not explain these anomalous permselectivity results, we hypothesized that a possible explanation are junction potentials that occur at the tips of reference electrodes. In this work, we tested this hypothesis by comparing permselectivity values obtained from bare Ag/AgCl wire electrodes (which have no junction) to values obtained from single-junction reference electrodes containing two different electrolytes. We show that permselectivity values obtained using reference electrodes with junctions were greater than unity for CEMs. In contrast, electrodes without junctions always produced permselectivities lower than unity. Electrodes with junctions also resulted in artificially low permselectivity values for AEMs compared to electrodes without junctions. Thus, we conclude that junctions in reference electrodes introduce two biases into results in the IEM literature: (i) permselectivity values larger than unity for CEMs and (ii) lower permselectivity values for AEMs compared to those for CEMs. These biases can be avoided by using electrodes without a junction.
机译：离子交换膜（IEM）是与多种水和废物处理，能源生产和工业分离过程相关的通用材料。 IEM的定义特征是它们选择性允许正离子或负离子渗透的能力，这被称为渗透选择性。对于阳离子交换膜（CEM），已经报道了等于1（相当于完全选择性的膜）或超过1（理论上不可能）的渗透选择性的测量值。这样的非物理结果使我们质疑正确测量此关键膜性能的能力。由于已显示称重误差，温度和测量不确定性不能解释这些异常的渗透选择性结果，因此我们假设可能的解释是在参比电极尖端出现的结电位。在这项工作中，我们通过比较从裸露的Ag / AgCl线电极（无结）获得的渗透选择性值与从包含两种不同电解质的单结参比电极获得的渗透选择性值来检验该假设。我们表明，使用带有结的参比电极获得的渗透选择性值大于CEM的单位。相反，没有结的电极总是会产生低于1的磁导率。与没有结的电极相比，具有结的电极还导致人为的AEM渗透选择性值低。因此，我们得出的结论是，参考电极中的结在IEM文献中为结果引入了两个偏差：（i）CEM的渗透选择性值大于1，（ii）AEM的渗透选择性值低于CEM。通过使用无结的电极可以避免这些偏压。

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  • 来源
    《Environmental Science & Technology》 |2018年第8期|4929-4936|共8页
  • 作者

    Ryan S. Kingsbury; Sophie Flotron; Shan Zhu; Douglas F. Call; Orlando Coronell;

  • 作者单位

    Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States;

    Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States;

    Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States;

    Department of Civil, Construction, and Environmental Engineering, College of Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States;

    Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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