采用Desal-DK有机纳滤膜分别对低浓度范围(1～50 mol/m3)的KCl、NaCl、Na2SO4、K2SO4、MgCl2水溶液进行纳滤实验,考察盐的浓度及类型对截留率的影响,结合道南细孔-介电DSPM-DE模型计算等效荷电密度(Xd),孔内介电常数(εp),采用DSPM模型计算等效膜孔半径(rp),研究不同类型盐的截留率变化和Xd、εp、rp的关系.结果表明,Na2SO4、K2SO4的截留率变化趋势和KCl、NaCl相同,随着盐浓度的增加而降低,其原因归结于随着浓度的增加| Xd|增加,电荷屏蔽作用增强,道南电势减弱;MgCl2的截留率随着盐浓度的增加而升高,原因是浓度的增加Mg2+与膜的羧基不断发生特性结合,| Xd| 升高,εp降低,静电排斥作用变大和介电排斥作用增强的双重作用.
Salt solutions(KCl,NaCl,Na2SO4,K2 SO4,MgCl2) were filtrated with a commercially available DK nanofiltration membrane to evaluate effects of concentration and type of salt in the feed side on the membrane performance,the concentration of them was in the range from 1 to 50 mol/m3.The Donnan steric pore and dielectric exclusion (DSPM-DE) model and DSPM model were applied to calculate volumetric membrane charge values,dielectric constant,and pore radius,to analyze the relationship between the parameters and rejection of salt.In the low concentration range,the results showed that the rejection of Na2SO4 and K2SO4 showed the same changing rule as the KCl and NaCl,the membrane charge density(|Xd |) increased when the concentration of salt solutions increased,the rejection decreased duo to charge screening.The rejection of MgCl2 increased with increasing of the concentration,the | Xd | of salt solution decreased first and then increased,duo to special combination of Mg2+ with carboxyl.The electrostatic repulsion and the dielectric exclusion influenced the rejection of MgCl2 together.
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