【摘要】 将N,N′-二甲基乙酰胺(DMAc)作为共试剂添加在间苯二胺水溶液中参与界面聚合反应,以改善聚酰胺复合反渗透膜(PA-RO-x, x代表添加DMAc的质量分数)的性能. X射线光电子能谱(XPS)和衰减全反射傅里叶红外光谱(ATR-FTIR)分析表明,随着DMAc含量的增加,复合膜结构中交联聚酰胺含量相对于线性羧基部分有所增加;场发射扫描电子显微镜(FE-SEM)和原子力显微镜(AFM)表征结果显示,随着DMAc含量的增加,膜表面的粗糙程度逐渐增大;静态水接触角测试结果表明,添加DMAc后,膜的亲水性增强.结合上述测试结果发现,添加DMAc可以有效降低水油两相的不相溶性,提高水相中间苯二胺向正己烷中扩散的速率,这有助于加快间苯二胺与均苯三甲酰氯反应;同时,聚酰胺结构中交联酰胺含量的增加可以提供更多的氢键位点,有助于水分子快速渗透通过复合膜而不损失截盐率;膜表面的粗糙程度变大,有助于提高水通量.在2 g/L的氯化钠溶液和1.6 MPa测试压力条件下, PA-RO-5.2(DMAc添加质量分数为5.2%)的渗透通量和截盐率分别为66.1L/(m~2·h)和98.7%,与未添加DMAc的聚酰胺复合反渗透膜相比,通量增加115%,截盐率仅下降0.9%.更多还原

【Abstract】 In a bid to improve the performance of polyamide composite reverse osmosis membranes(PA-ROx,x represents DMAc concentration),N,N′-dimethylacetamide(DMAc)was applied as co-reagent added into the aqueous m-phenylenediamine solution for interfacial polymerization reaction with trimesoyl cloride.Characterization of the PA-RO-x membranes by X-ray photoelectron spectroscopy(XPS)and attenuated total reflectance Fourier transform infrared(ATR-FTIR)spectroscopy confirmed that with the increase of DMAc concentration,the content of cross-linked amide linkages in PA-RO-x membranes increased relative to the liner pendant carboxylic acid groups. By the field emission scanning electron microscope(FE-SEM)and atomic force microscope(AFM),it is obviously showed that the surface morphology gradually changed and the surface roughness of composite reverse osmosis membranes increased as the increase of DMAc content. The static water contact angle measurement with sessile drop method revealed that the hydrophilicity of the composite reverse osmosis membranes was enhanced after DMAc was added. According to the above mentioned characterization results,it was confirmed that DMAc play a key role that could effectively reduce the immiscibility between aqueous phase and oil phase,and help to improve the diffusion rate of m-phenylenediamine from aqueous phase to n-hexane for accelerating the reaction between m-phenylenediamine and trimesoyl cloride. At the same time,the increase of the linkages of cross-linked amide can be as hydrogen-bond sites,which can be beneficial for water molecules penetrate through the polyamide composite reverse osmosis membranes quickly without considerable losing the salt rejection. The higher the surface roughness of the membranes,the higher the permeate flux. The water permeate flux and NaCl rejection of PA-RO-5.2(DMAc concentration is 5.2%,mass fraction)reached 66.1 L/m~2·h and 98.7%,respectively,for 2 g/L NaCl under 1.6 MPa. Compared with the polyamide reverse osmosis composite membrane without DMAc addition,the permeate flux of PA-RO-5.2 increased by 115% and the desalination rate decreased by 0.9%.更多还原