圆盘式膜组件中浓差极化现象研究

Study of concentration polarization in disc-type membrane module

采用圆盘式膜组件,使用DK纳滤膜对KCl溶液进行纳滤截留实验,并通过计算流体动力学(CFD)模拟、VVM数学方法以及道南-筛分-介电孔(DSPM-DE)模型对实验结果进行拟合与分析。结果表明:通过CFD模拟,KCl真实截留率要明显高于表观截留率,且跨膜压差对膜面切向流速的影响可忽略不计,因此VVM直接适用于圆盘式膜组件中浓差极化现象的模拟;主体溶液浓度、通量及膜面切向流速的变化会对浓差极化产生影响,通过DSPM-DE模型拟合发现,膜内荷电密度(Xd)随主体溶液浓度的变化有较大变化;在通量及膜面流速不变的条件下,浓差极化层厚度不变,体系中溶质浓度的升高会增强浓差极化现象。

Disk-type membrane module and DK membrane were used to characterize the retention of KCl solution.Computational fluid dynamics （CFD） simulation,velocity variation method （VVM）,and Donnan steric pore＆dielectrical exclusion （ DSPM-DE） model were used to fit and analyze experimental results. Results showed that the real retention of KCl was obviously higher than the observed one. transmembrane pressure feeble effected tangential velocity in disc-type membrane module,so VVM could be directly used to simulate the phenomenon of concentration polarization （ CP ） . The deviation between real and observed retention are mainly effected by solute concentration,permeate volume flux and tangential velocity on the membrane.Fitting results from DSPM-DE model showed that the change of Xd was followed by solute concentration,permeate volume flux variation. Under the situation of unchanged tangential and permeate volume flux, solute concentration increase would enhance the phenomenon of CP, but the CP layer remained the same.