pH响应性乙烯-乙烯醇共聚物分离膜的纳滤特性

Nanofiltration Property of pH-Responsive Ethylene-co-Vinyl Alcohol Copolymer Membrane

具有纳滤特性的pH响应性膜在小分子分离体系中具有广泛应用前景。文中以铸膜液浓度为25%的乙烯-乙烯醇共聚物(EVAL)超滤膜为基膜,接枝具有pH响应性的功能单体甲基丙烯酸二甲氨基乙酯,制备pH响应性EVAL膜,通过考察膜对标准物聚乙二醇(PEG)与无机盐的截留性能,研究其纳滤特性。结果表明,当pH小于pKa时,pH响应性EVAL膜对聚乙二醇(PEG)与无机盐的截留效果均明显高于未接枝膜,接枝率6%的接枝膜对PEG 800、PEG 1000及PEG 2000的截留率均达到90%以上,对二价阳离子的截留率达到80%以上,无机盐的截留顺序为:CaCl_2>MgCl_2>MgSO_4>NaCl>Na2SO_4。当pH大于pKa时,PEG及无机盐截留率明显下降,膜对PEG 1000的截留率由95.6%降至62.9%,对MgCl_2截留率降至30.6%,截留率及膜水通量变化存在显著的pH响应性。

The pH-responsive membrane with nanofiltration property has wide prospect for separating mixtures with low-molecular-weight. In this paper, the pH-responsive ethylene-co-vinyl alcohol copolymer （EVAL） membrane was prepared by grafting dimethylaminoethyl methacrylate onto EVAL ultrafiltration membrane, of which the polymer concentration is 25%. The nanofiltration property （the rejection of PEG and inorganic salt） was investigate＆ The results show that the rejection of PEG and inorganic salt are both higher than unmodified membrane when pH is lower than pK,. The rejection of PEG 800, PEG 1000 and PEG 2000 of membrane with GD 6 % is higher than 90 %. The rejections of bivalent cations are higher than 80 %. The rejection order of inorganic salt is CaCl2 〉MgCl2 〉MgSO4 〉NaCl 〉 Na2SO4. The rejection of PEG and inorganic salt decrease significantly when the pH value is higher than pK,. The rejection of PEG 1000 decreases from 95.6% to 62.9%. The rejection of MgCl2 decreases to 30.6%. The pH-responsive properties of rejection and flux are observed.