摘要
【目的】电控离子选择渗透(electrochemically switched ion permselectivity, ESIP)是一种新型的离子选择性膜分离技术,已成功应用于低浓度目标离子的高效、连续、选择性分离。然而,离子在膜内传质不符合Nernst-Planck理论,建立ESIP离子传质模型有助于人们理解ESIP分离过程。【方法】在ESIP膜分离系统中,为研究离子在膜上双脉冲电势与极室槽电压耦合动态场中的传质行为,提出了修正的Nernst-Planck模型。根据唐南(Donnan)平衡以及电中性假设等,建立了ESIP膜分离过程的离子传递稳态模型。通过数值模拟考察了电流密度、膜厚、膜内离子活性位点浓度对膜分离系统中离子浓度和电阻分布的影响。【结果】在原料侧扩散层和膜相内,膜厚和离子活性位点浓度对离子浓度分布影响较大,降低膜厚、提高离子活性位点浓度是提高离子传质的主要方式。在高电流密度、低膜厚和高离子活性位点浓度下,原料侧扩散层电阻在整体电阻中占主导作用,通过增加流体流速或减小腔室厚度以提高离子传质速率。在低电流密度、较高膜厚下,Donnan层电阻占主导作用,通过增加膜的离子活性位点来提高离子传质速率。【结论】在高电流密度、低膜厚和高离子活性位点浓度下,减弱扩散层电阻(增加流体流速、减少腔室厚度)是实现ESIP性能优化的主要途径。
【Purposes】Electrochemically switched ion permselective(ESIP)is a novel ion selective membrane separation technology,which has been applied for the efficient,continuous and selective separation of low-concentration target ions.However,the ion transfer in the ESIP membrane is disobedient to the Nernst-Planck theory,and the development of mass transfer model of ESIP contributes to the understanding of ESIP separation process.【Methods】In the ESIP membrane separation system,a modified Nernst-Planck model was proposed to study the mass transfer behavior in the dynamic field coupled with the double pulse potential on the membrane and the cell voltage on the electrode compartment.According to Donnan equilibrium and electroneutrality hypothesis,the steady state model of ion transfer in ESIP membrane separation process was established.The effects of current density,membrane thickness and ionic active site concentration on ion concentration and resistance distribution in membrane separation system were investigated by numerical simulation.【Findings】The results show that in the diffusion layer of feed solution and the membrane phase,the membrane thickness and the ionic active site concentration have great influence on the ion concentration distribution,and reducing the membrane thickness and increasing the ionic active site concentration are the main ways to improve the ion mass transfer.Under the influence of high current density,thin membrane and ionic active site concentration,resistance in the diffusion layer of feed solution plays a dominant role in the overall resistance,and the ion mass transfer rate can be increased by increasing the flow rate or decreasing the chamber thickness.【Conclusions】At low current density and thick membrane,the resistance of Donnan layer plays a dominant role,and the ion mass transfer rate is improved by increasing the ionic active sites of the membrane.
作者
高凤凤
张雪锋
张忠林
郝晓刚
GAO Fengfeng;ZHANG Xuefeng;ZHANG Zhonglin;HAO Xiaogang(College of Chemical Engineering and Technology,Taiyuan University of Technology,Taiyuan 030024,China)
出处
《太原理工大学学报》
CAS
北大核心
2023年第4期609-618,共10页
Journal of Taiyuan University of Technology
基金
国家自然科学基金资助项目(22108188,U20A20141)。
关键词
电控离子选择渗透膜分离
离子传质
数值模拟
浓度分布
电阻分布
Electrochemically switched ion permselective membrane
ion mass transport
numerical simulation
concentration distribution
resistance distribution
