微孔膜限界電流値法によるイオン交換膜の動的輸率測定法  [in Japanese] Measurement of Dynamic Transport Number in Ion-exchange Membrane by Limiting Current Method with Microhole Filter  [in Japanese]

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Author(s)

    • 須藤 雅夫 SUDOH Masao
    • 静岡大学工学部物質工学科 Department of Materials Science and Chemical Engineering, Shizuoka University
    • 居波 永治 INAMI Eiji
    • 静岡大学工学部物質工学科 Department of Materials Science and Chemical Engineering, Shizuoka University

Abstract

Nafionの陽極側表面に微孔膜を合わせることにより, 境膜厚みを固定して限界電流値の測定を行い, カチオンの動的輸率を算出した.様々な測定件に対して限界電流値は以下のような影響を受けた.液境膜の定常状態保つためには電圧の走査速度は10mV/s以下にする必要があり, また膜の両側に濃度差を防ぐには3mV/s以上が必要であった.微孔膜の孔径については, 0.05μm以下になると空隙率も0.01以下になり微孔膜自身が抵抗として働いてしまった.逆に0.2μm以上になると膜の陽極側が律速であるという条件が満たされなくなった.また攪拌により拡散が乱れ膜が振動するために限界電流値が増加することが分かった.以上より限界電流法による動的輸率の測定には, 微孔膜孔径: 0.08μm, 走査速度: 5mV/sとして攪拌を行わない状態が最適条件であるという結論になった.この測定条件での結果, 共に外部溶液濃度増加に伴う副イオンの侵入により輸率は減少する傾向を示した.またこの結果を二相イオン輸送モデルにより考察することにより不均質度βは0.1~0.2となった.またアニオン収着量による不均質度は0.4と高い値を示したが, これはアニオン収着量ではイオンクラスターの空孔部が支配的になるのに対して, 動的輸率ではチャンネル部が支配的になるためだと考察できた.

The dynamic transport number of counter-ions in Nafion-117 was measured by the limiting current method with a microhole filter. The microhole filter was attached onto the anode side of the Nafion surface in order to fix the thickness of the fluid film. The limiting currents were affected by various conditions of the measurement. A scanning rate of below 10mV/s was required to maintain a steady-state concentration in the laminar film. A scanning rate of above 3mV/s was required to prevent concentration differences between opposite sides of the membrane. Since the porosity of microhole Nuclepore filters decreases with a decrease in pore diameter, the electrical resistance of the microhole filter significantly affected the voltage difference in cases where the pore diameter was below 0.05μm (the porosity below 0.01). Mean while, in case where the pore diameter was above 0.2μm, ionic transport through the microhole filter was not rate-determining. The limiting current was increased by stirring the external solution, because the flux was disturbed and the membrane vibrated. In conclusion, a pore diameter (microhole filter) of 0.08μm, a scanning rate of 5mV/ s and no stirring are the most optimum conditions. The transport number of counter-ions (H<SUP>+</SUP> or Na<SUP>+</SUP>) through Nafion-117 decreased by the intrusion of co-ions with increasing external concentration. Non-homogeneity β was obtained as from 0.1 to 0.2 by analyzing the two phase model of ionic transport of H<SUP>+</SUP>and Na<SUP>+</SUP>, respectively. The measurement of the anion sorbed concentration yielded high non-homogeneity (β= 0.4). It is believed that the large volume of ion-clusters of Nafion was related to the anion-sorbed concentration and the small channels between ion-clusters controlled the transport of the counter-ion.

Journal

  • Bulletin of the Society of Sea Water Science, Japan

    Bulletin of the Society of Sea Water Science, Japan 52(6), 359-366, 1998-12-01

    The Society of Sea Water Science, Japan

References:  13

Cited by:  1

Codes

  • NII Article ID (NAID)
    10008283044
  • NII NACSIS-CAT ID (NCID)
    AN0018645X
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    03694550
  • NDL Article ID
    4614049
  • NDL Source Classification
    ZM44(科学技術--地球科学--海洋・陸水・火山) // ZP8(科学技術--化学・化学工業--無機化学・無機化学工業)
  • NDL Call No.
    Z15-47
  • Data Source
    CJP  CJPref  NDL  J-STAGE 
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