Effect of Convective Flow on the Current Efficiency of an lon-Selective Membrane

本文探討在電析操作中，加入一壓力降以加強流動效應，以及在薄膜與溶液的界面上Donnan平衡的假設對電流效率的影響。我們考慮的固定電荷分佈包括線性函數與正弦函數兩大類。在固定電荷總量固定的條件下，若溶液與界面上不假設Donnan平衡，則固定電荷為線性分佈的電流效應較正弦函數分佈的為高。若流動效應小於某一數值，在固定的流動效應下，電流效率會隨著電位降的增加而增加，但當流動效率大於某一數值以後，在固定的流動效應下，隨著電位降的增加，電流效率反而會下降。假設Donnan平衡的結果，與不假設時的結果在定性上相同，但假設Donnan平衡時電流效率較高。

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並列摘要

The effect of convective flow on the current efficiency of an ion-selective membrane is investigated by solving the general Nernst-Plank equation simultaneously with Poission equation. We found that assuming Donnan equilibrium at liquid-membrane interfaces leads to a positive deviation in the current efficiency of a membrane. The qualitative behavior of the membrane remains the same, however, regardless of whether this condition is assumed. For a fixed electrical potential drop across a membrane, the current efficiency increases with the applied current density. It is interesting to observe that, for a fixed applied current density, the higher the electrical potential drop the lower the current efficiency. If the electric Peclet number is small, the current efficiency is mainly controlled by the electrical potential drop, and if it is large, the current efficiency is controlled by the pressure drop across the membrane. It is found that the large the electric Peclet number the more serious the concentration polarization near liquid-membrane interfaces.

並列關鍵字

lon-selective membrane ； Pressure gradient ； Convective flow ； Current efficiency

國際替代計量

Effect of Convective Flow on the Current Efficiency of an lon-Selective Membrane

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