离子交换膜传质过程中电化学特性的研究

Investigations on electrochemical properties in mass transport of ion exchange membrane

电化学阻抗谱和直流方法均可用来评价离子交换膜传质过程中的电化学性质,而前者可用于分析膜本身、双电层和扩散边界层的电阻值.通过比较两个等效电路的拟合效果及其物理化学意义,选择了最优的等效电路来定量分析离子交换膜体系的各个分层,并考察了不同流速和浓度下两种膜的电化学性质变化.研究发现,直流方法测定的电阻值等于电化学阻抗谱测定的各个分层的电阻值之和;随着流速的增大,膜本身和双电层的电阻变化较小,而扩散边界层的电阻明显降低;随着浓度的增大,传质体系的电阻均显著降低;阳离子交换膜和阴离子交换膜具有不同的电化学传质特性.研究结果对于优化离子交换膜的电化学评价技术及离子交换膜的制备和应用具有重要意义.

Electrochemical impedance spectroscopy （EIS） and direct current method （DC） can be used to investigate the electrochemical properties in the mass transport of ion exchange membrane （IEM ）. The resistance of membrane？ electrical double layer （EDL） and diffusion boundary layer （DBL） can be analyzedseparately by EIS. With the comparison of two equivalent circuits and in terms of their physical and electrochemical interpretations？ a better equivalent circuit was selected？ and the effects of flow rate on electrochemical properties of two membranes were investigated. I t is found that the resistance determined from DC was equal to the sum of each sublayer’s resistance in IEM systems from EIS; when the flow rate increased,the resistance of membrane and EDL did not change significantly？ while the DBL resistancedecreased obviously; with the increase of concentration, the resistance of mass transport system decreased significantly; the transport properties in cation exchange membrane and anion exchange membrane were different. Research results are of major importance for developments of characterization techniques on membrane transport properties and applications of IEMs.