纳米碳管改性聚哌嗪酰胺复合纳滤膜的制备

Preparation of Polypiperazine Amide Composite Nanofiltration Membrane Modified by Carbon Nanotubes

采用混酸(H2SO4/HNO3=3/1(V/V))处理多壁碳纳米管(MWNTs)制备了羧基化碳管(Carboxylated MWNTs),并与哌嗪(PIP)反应,制备了胺化的多壁纳米碳管(Amine functionalized MWNTs)。以聚砜(PSf)超滤膜为基膜,以均苯三甲酰氯(TMC)为油相单体和胺化的多壁纳米碳管与哌嗪(PIP)为水相单体,采用界面聚合法制得多壁碳纳米管改性聚哌嗪酰胺复合纳滤膜。采用傅里叶红外光谱(FT-IR)、拉曼光谱(RAM)、X射线光电子能谱(XPS)和扫描电子显微镜(SEM)和静态接触角表征了改性前后碳纳米管和复合膜的结构,结果表明哌嗪成功氨化改性了碳纳米管,基膜表面复合了一层聚哌嗪酰胺膜。重点考察了碳管在水相中添加量、TMC浓度、聚合时间对复合膜性能的影响,结果显示,在有机相单体浓度为1 g?L?1,水相单体浓度为2 g?L?1,水相中多壁碳纳米管的浓度为0.1 g?L?1,反应时间为45 s,复合膜的纯水通量为85.6 L?m?2?h?1,Na2SO4的截留率达到98%,对不同盐溶液的截留效果分别为:Na2SO4>MgSO4>MgCl2>NaCl。水相中碳纳米管的加入,能有效改善膜的分离性能。

Carboxylated multi-wall carbon nanotube was prepared by treating the multi-wall carbon nanotube （MWNTs） with mixed acid （H2SO4/HNO3=3/1（V/V））. Amine functionalized MWNTs was obtained by reacting the carboxylated MWNT with piperazine （PIP）. Using the polysulfone （PSf） ultrafiltration membrane as the support, the PIP and amine functionalized MWNTs as aqueous monomer and trimesoylchloride （TMC） as organic monomer, the polypiperazine-amide composite nanofiltration membranes were prepared by interfacial polymerization. The structures of the membrane before and after modification were characterized by the spectra of Fourier transform infrared spectrophotometry （FT-IR）, Raman spectrophotometry （RAM）, Scanning electron microscope （SEM）, X-ray photoelectron spectroscopy （XPS） and contacting angle. The results show that the MWNT is amine-functionalized by PIP, and a thin layer composed of polypiperazine-amide is formed on the support. The effects of MWNT adding amount in the aqueous phase, TMC concentration and reaction time on the composite membranes were investigated. The results show that when the concentration of organic phase monomer is 1 g·L-1, the concentration of water phase monomer is 2 g·L-1, the concentration of MWNTs in water phase is 0.1 g·L-1, the time of reaction is 45 s, the pure water flux is 85.6 L·m-2·h-1, which are the optimum condition, the retention ratio of Na2SO4 can reach 98%. The salt rejection order of the composite membrane is Na2SO4﹥MgSO4﹥MgCl2﹥NaCl. The separation performance of composite membrane could be improved by adding the MWNTs into the water phase.