一种求得纳滤膜荷电密度的快速方法

基于荷电纳滤膜中同离子浓度显著低于反离子浓度的特点,将Donnan-Steric Pore Model(DSPM)模型中的荷电密度近似表达为膜中反离子浓度与其化合价乘积,进而将其用于DSPM模型的简化,并通过与Spiegler-Kedem方程关联建立了纳滤膜荷电密度的计算方程.采用荷负电的NF270纳滤膜,实验研究了膜对NaCl溶液的截留特性,利用建立的荷电密度计算方程求得了NF270膜在NaCl浓度分别为2,8,21,50mol/m3时的荷电密度,并建立了该膜荷电密度与NaCl浓度间的关系式.将求得的荷电密度应用于DSPM模型,理论计算了膜对NaCl的截留性能,计算结果与实验结果相一致,表明所建立的荷电密度计算方程可作为一种求取纳滤膜荷电密度的快速方法.

Method for obtaining the charge density of nanofiltration membrane

Based on the characteristics that the concentration of co-ions is less than that of counter-ions in charged membrane,charge density value in the Donnan-steric pore model model(DSPM) can be expressed as the product of counter-ions concentration and ionic valence,then DSPM is simplified.Combining with the Spiegler-Kedem model,an equation for calculating the charge density of nanofiltration membrane has been established.Permeation experiments of aqueous solution of single electrolyte solute(NaCl) with negatively charged membrane(NF270) were conducted,and charge densities of NF270 membrane were obtained from the equation established when NaCl concentrations were 2,8,21,50 mol/m3.The relation between the charge densities and NaCl concentration was established and then was applied in DSPM for the calculation retention of NaCl.The calculation results are in agreement with experimental results,which shows that the equation established can be used as a rapid method for obtaining the charge density of nanofiltration membrane.