原位离子交联聚电解质络合物纳滤膜的制备与表征

Fabrication and performance of in-situ ionic cross-linking polyelectrolyte complex nanofiltration membranes

为获得高渗透选择性的聚电解质络合物纳滤膜(PECNFMs),以聚乙烯亚胺(PEI),海藻酸钠(SA)和羧甲基纤维素钠(CMC)为原料,通过原位离子交联的方式制备了一系列新型PECNFMs。分别采用傅里叶变换红外光谱(ATR-FTIR),场发射扫描电镜(SEM)和接触角实验(CA)对PECNFMs的化学组成、结构和亲水性进行表征。考查聚电解质的配比、聚阴离子的种类、无机盐的种类及操作温度等因素对PECNFMs性能的影响。结果表明,当PEI质量比相同时,PEI/SA原位离子交联PECNFMs较PEI/CMC膜具有更高的水通量;且随着PEI质量比的增加,PECNFMs的荷电性由荷负电转变为荷正电;当PEI质量比为0.9时(PEI/SA 0.9)具有最佳的纳滤分离性能,其对MgCl_2的截留率为94.0%,水通量为13.4L·m^(-2)·h^(-1)(在25℃和0.6 MPa下,对1 g·L^(-1)MgCl_2水溶液进行测试),表现出较高的Na^+/Mg^(2+)分离性能(分离因子为10.4)。采用原位离子交联法,成功制备了高渗透选择性的新型PECNFMs,该方法具有一定的普适性,为高性能纳滤膜的制备开辟了新途径。

In order to obtain high water flux and salt rejection polyelectrolyte complex nanofiltration membranes （PECNFMs）, a novel type of PECNFMs is prepared with the polyethyleneimine （PEI）, the sodium alginate （SA） and the carboxymethyl cellulose （CMC） via the in-situ ionic cross-linking method. The chemical compositions, structures, and hydrophilicity of the PECNFMs are characterized by the Fourier transform infrared spectroscopy （FTIR）, the field emission scanning electron microscope （FESEM）, and the water contact angle （CA）, respectively. The effects of the PEI mass ratios, the polyanionic types, the feed inorganic salts, and the operating temperature on the nanofihration performance of the PECNFMs are investigated. It is shown that the in-situ ionic cross-linking PEI/ SA PECNFMs enjoy a higher water flux as compared to the PEI/CMCs with the some PEI mass ratio, and the surface charge of the PECNFMs could be turned from negative to positive by increasing the PEI mass ratio. With the optimized PEI/SA value of 0.9, a water flux of 13.4 L· m^-2· h^-1 is obtained with the MgCl2 rejection being maintained at around 94.0% （with 1 g. L ^-1 aqueous MgCl2 solution at 25% and 0.6 MPa）. Moreover, with the PEI/SA value of 0.9, the best Na^＋/Mg^2＋ selectivity （ aMg2＋^Na^＋ =10 4） is secured. Thisstudy provides an approach for fabricating PECNFMs with high water flux and salt rejection via an in-situ ionic cross-linking method and opens new avenues for fabricating high performance nanofihration membranes.