纳滤膜截留特性与膜基本特征之间关系的研究

选择DF10、DF30、DF90 3种纳滤膜对无机盐(NaCl和CaCl_2)、微量有机物(药物及个人护理品)、富里酸溶液进行纳滤实验,考察具有不同物理化学特性的膜对不同种类溶质的截留能力差异.结果表明,膜孔大小和带电量共同决定了纳滤膜对无机物的截留率,而微量有机物和天然有机物的截留率主要由膜孔径决定.膜活性层厚度很大程度上影响了膜的透水系数;膜的透水系数与NaCl截留率呈现负相关;膜的截留分子量越小,其对有机物的截留率越高;脱盐(NaCl)能力不一定正相关于有机物截留率,也不正相关于CaCl_2截留率.研究发现,DF30具有低无机物截留、高有机物截留的特性,这与其截留分子量适中、膜表面电荷密度低、活性层厚度小等物化性质密切相关.

Relating the rejection behaviors with the physico-chemical properties of nanofiltration membranes

Three types of nanofiltration membranes, i.e. DF10, DF30, and DF90, were chosen to test the rejection of inorganic salts (NaCl and CaCl₂), trace organic compounds (pharmaceutical and personal care products), and fulvic acid, in order to study the effects of physico-chemical properties of membrane on the rejection performance. Results showed that the membrane pore radius and surface charge jointly determined the rejection of inorganic salts, while the rejection of trace organic compounds and natural organic matter primarily relied on the membrane pore size. The membrane active layer thickness had a great impact on the water permeability. The membrane water permeability had a negative correlation with the ability in rejecting NaCl. A small molecular weight cut-off generally corresponded to a high rejection of organic substances. There was no clear relationship between the desalting ability and rejection of organic substances, nor the rejection of NaCl and that of CaCl₂. The DF30 membrane exhibited a high rejection of organic substances and a low rejection of inorganic salts, which was attributed to its moderate molecular weight cut-off, low surface charge density, and small active layer thickness.