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选用截留分子量40 000 Da表面没有固有电荷的PVDF中性超滤膜,重点考察了离子吸附对超滤膜表面电性能和渗透性能的影响.选用4种电解质溶液为考察对象,按阴阳离子价态可分为KCl(1∶1),K2SO4(1∶2),MgCl2(2∶1)和MgSO4(2∶2).基于溶度积的计算,5mM的镁离子会在pH9.52处开始产生沉淀,因而选择pH3~9为考察范围.膜在1 mM4种电解质溶液中的等电点分别为pH7.4(MgCl2),7.0(MgSO4),6.9(KCl),5.5(K2SO4),这可由离子迁移速率来解释.膜的盐截留率在等电点附近为零,并往两侧逐渐增大。通量则在等电点处最大,而往两侧逐渐减小.
The effect of ion adsorption on the surface electrical properties and permeability of ultrafiltration membrane was investigated by using a PVDF neutral ultrafiltration membrane with 40,000 Da molecular weight cut off and no intrinsic charge on the surface of the ultrafiltration membrane.The four electrolyte solutions were selected as the investigation object, Can be divided into KCl (1: 1), K2SO4 (1: 2), MgCl2 (2: 1) and MgSO4 (2: 2) Based on the solubility product, 5 mM of magnesium starts to be produced at pH 9.52 Precipitation, so choose the pH range of 3 to 9. The isoelectric point of the membrane in 1 mM 4 kinds of electrolyte solution were pH7.4 (MgCl2), 7.0 (MgSO4), 6.9 (KCl), 5.5 (K2SO4), which can be ion Migration rate to explain the membrane salt rejection rate in the vicinity of the isoelectric point is zero, and gradually increased on both sides. Flux at the isoelectric point of the largest, while gradually decreasing on both sides.