Grzegorczyn Sławomir, Slezak Andrzej
Department of Biophysics, Medical University of Silesia, Zabrze.
Polim Med. 2006;36(2):57-69.
In order to characterize processes proceeded in concentration boundary layers (CBLs), divided by neutral and horizontally mounted membrane, the electromotive force (EMF) during and after turning off mechanical stirring of aqueous KCl solutions was measured. The EMF was measured by means of Ag / AgCl electrodes and electrometer connected with a microcomputer. Aqueous solutions of KCl with fixed and lower concentration Cl = 10(-5) mol x l(-1) was over the membrane, while KCl concentration under the membrane Ch > Cl was changed. Such configuration of membrane system caused stable reconstruction of CBLs after turning off mechanical stirring of solutions in electrochemical cell. On the basis of time dependencies of EMF the concentration dependencies were performed and it was stated that dependencies of EMF = f(Ch/Cl) are nonlinear. It was found that maximal value of EMF, equal to 175 mV, was observed during mechanical stirring of solutions for Ch/Cl = 400. In order to interpret experimental results, the model of EMF changes in time after turning off mechanical stirring was elaborated on the basis of Kedem-Katchalsky model equations for transport of electrolytes through the membrane. The transport number of K+ ions (t+), appointed for the membrane, depended nonlinearly on Ch/Cl and for Ch/Cl = 50 was maximal and amounted to t(+max) = 0.7. Besides, concentration dependence of relaxation time of CBLs reconstruction after turning off mechanical stirring was appointed. For Ch/Cl < 500, increase of Ch/Cl caused considerable decrease of relaxation time, while for Ch/Cl > 500 the relaxation time was small and did not change considerably with increase of Ch/Cl, in this range.
为了表征在由中性且水平安装的膜分隔的浓度边界层（CBLs）中发生的过程，测量了KCl水溶液机械搅拌开启期间及关闭后的电动势（EMF）。EMF通过Ag/AgCl电极和与微型计算机相连的静电计进行测量。固定且较低浓度Cl = 10(-5) mol·L(-1)的KCl水溶液位于膜上方，而膜下方的KCl浓度Ch > Cl是变化的。这种膜系统配置在关闭电化学池中溶液的机械搅拌后导致CBLs的稳定重建。基于EMF的时间依赖性进行了浓度依赖性研究，并表明EMF = f(Ch/Cl)的依赖性是非线性的。发现在溶液机械搅拌期间，当Ch/Cl = 400时观察到EMF的最大值，等于175 mV。为了解释实验结果，基于Kedem-Katchalsky模型方程中电解质通过膜的传输，阐述了关闭机械搅拌后EMF随时间变化的模型。指定给膜的K+离子迁移数（t+）非线性地依赖于Ch/Cl，并且当Ch/Cl = 50时最大，达到t(+max) = 0.7。此外，还确定了关闭机械搅拌后CBLs重建的弛豫时间的浓度依赖性。对于Ch/Cl < 500，Ch/Cl的增加导致弛豫时间显著降低，而对于Ch/Cl > 500，弛豫时间较小，并且在该范围内随着Ch/Cl的增加变化不大。
