三醋酸纤维素/壳聚糖反渗透膜的制备及性能研究

Fabrication and Antibacterial Properties of Cellulose Triacetate/Chitosan Reverse Osmosis Membrane

以壳聚糖(CS)为抗菌剂和三醋酸纤维素(CTA)为基膜材料,通过液-液共混和相转化成膜技术制备了三醋酸纤维素/壳聚糖共混反渗透膜(CTA/CS-RO),以改善醋酸纤维素反渗透膜的抗菌性能.采用傅里叶红外光谱、X-射线光电子能谱、扫描电子显微镜、水接触角、X-射线衍射光谱等对其结构和性能进行表征.结果表明,CTA/CS-RO中CS与CTA之间存在氢键作用,并且CS随着双扩散过程向膜表面迁移;膜厚度随着CS含量的递增而减小,横断面结构由指状孔转变成海绵状.CS的添加有利于共混膜亲水性、水通量和力学性能的提高.当CS含量为0.75%~1.00%时,膜样品在保持较高的盐截留率(R>90%)的同时其断裂伸长率和结晶度没有显著变化.动态接触抗菌测试结果表明,CTA/CS-RO对大肠杆菌和金黄色葡萄球菌均具有抑菌作用.特别地,当CS含量为0.75%~1.00%时,膜样品对大肠杆菌和金黄色葡萄球菌的抑菌率分别为65%~72.5%和16%~51%.综合分析,CTA/CS共混反渗透膜制备过程中CS的加入量保持在0.75%~1.00%时膜的综合性能最优.

Compared with conventional reverse osmosis membrane （RO） materials, cellulose acetate （CA） reverse osmosis membranes have attracted considerable attention due to their unique chlorine resistance. However, r-glucose units in the cellulose backbone of CA molecule are vulnerable to erosion and degradation by aquatic microorganisms. To improve the antibacterial performance of cellulose triacetate reverse osmosis membrane, cellulose triacetate/chitosan blend reverse osmosis membrane （CTA/CS-RO） were designed and prepared with CS as the antibacterial agent by phase inversion. The homogeneous CTA solutions containning 20 g·L - CS in formic acid were casted with casting knife of 250 μm thickness and the asymmetrical CTA/CS-RO membranes were obtained after solvent evaporation, immersion precipitation process. The mass fractions of CS to CTA were selected to be 0.25%, 0.50%. 0.75%, 1.00% and 1.25%, respectively. The structure and performances of the obtained CTA/CS-RO membranes were characterized by various methods such as Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, water contact angle and X-ray diffraction spectroscopy. The red shift of the characteristic peak of C--O -- C in FTIR spectra indicated the presence of hydrogen bonding between CTA and C S. The characteristic peak of N1 s in XPS spectra indicated the migration of CS to the membrane surface during phase inversion. The SEM images showed that membrane thickness decreased with increasing CS concentration. The addition of CS improved the hydrophilicity, water flux and mechanical properties of CTA/CS-ROs. When the mass fraction of CS to CTA was within 0.75%-1.00%, CTA/CS-ROs showed high salt rejection （R 〉 90%） without siginificant changes in elongation at break and crystallinity. The dynamic contact antibacterial test results indicated that CTA/CS-ROs showed inhibitory effect on E. coli and S. aureus, which was improved by increasing the content of CS. When the mass fraction of CS to CTA was within 0.75% - 1.00%, CTA/CS-ROs possessed higher inhibition rate against E. coli （65% - 72.5%） than S. aureus （16% - 51%） due to the electrostatic attraction between the positive CS and gram negative E. coli.