聚多巴胺/聚乙烯亚胺共沉积中间层增强薄膜复合正渗透膜性能

以聚多巴胺/聚乙烯亚胺(PDA/PEI)共沉积于三醋酸纤维素(CTA)多孔支撑膜表面形成中间层,再结合界面聚合法获得聚酰胺薄膜,构建了PDA/PEI共沉积中间层改性薄膜复合(TFC)正渗透(FO)膜.通过傅里叶变换衰减全反射红外光谱法、扫描电子显微镜、原子力显微镜、溶质截留法、水接触角仪等研究了PDA/PEI共沉积中间层对CTA膜和TFC膜的表面结构和性质的影响.研究结果表明,PDA/PEI共沉积使得CTA膜表面变得更为平滑,表面孔径减小至(30.0±4.1) nm,且表面孔径分布趋于均一.同时,在PDA/PEI共沉积改性CTA膜表面界面聚合得到的聚酰胺层呈现出更均匀的叶片状结构和优异的亲水性.基于此,具有PDA/PEI共沉积中间层的TFC正渗透膜显著提高了水通量(FO模式:(7.1±2.3) L/(m^2·h)),较空白TFC膜提升了57.6%.同时,中间层改性TFC膜具有更低的反向盐通量(FO模式:1.4±0.1 g/(m^2·h))和"净盐通量"(FO模式:(0.2±0.06) g/L),与空白TFC膜相比分别下降了83.9%和90.6%.说明PDA/PEI共沉积中间层不仅能有效提升TFC正渗透膜的水渗透性,而且大幅提升了膜的截盐性和渗透选择性.

High-performance Thin Film Composite forward Osmosis Membrane with Polydopamine/Polyethyleneimine (PDA/PEI) Co-deposition Interlayer

Forward osmosis(FO), as a promising membrane separation technology, has attracted much attention,whose performance is strongly dependent on the structure and property of FO membrane. Thin film composite(TFC) FO membrane, consisting of a thin film and a porous substrate, is commonly used for FO process due to its high water permeability. Nevertheless, TFC FO membrane still suffers from a trade-off between water permeability and salt rejection, which limits the further application of FO process. Recently, constructing an interlayer between the thin film and the porous substrate has been reported as an effective way to improve the performance of TFC membranes. Herein, a novel TFC FO membrane was prepared by using a polydopamine/polyethyleneimine(PDA/PEI) co-deposition interlayer on cellulose triacetate(CTA) porous substrate followed by an interfacial polymerization. The surface structures and properties of CTA substrates and TFC membranes were systematically investigated by FTIR/ATR spectroscopy, scanning electron microscopy,atom electron microscopy, solute rejection method, and water contact angle test. Compared with CTA substrate and PDA modified CTA substrate, the surface of CTA substrate deposited by PDA/PEI interlayer becomes smooth and has a narrow surface pore size distribution as well as small surface pore size of(30.0 ± 4.1) nm. Meanwhile,the polyamide film formed on the PDA/PEI co-deposition interlayer presents a uniform leaf-like structure and excellent hydrophilicity. Therefore, TFC FO membrane with PDA/PEI co-deposition interlayer achieves an improved water flux of(7.1 ± 2.3) L/(m^2·h), rising by 57.6% compared with nascent TFC FO membrane;a low reverse salt flux of(1.4 ± 0.1) g/(m^2·h), and a small specific salt flux of(0.2 ± 0.06) g/L, decreasing by 83.9% and 90.6%, respectively. It means that PDA/PEI co-deposition interlayer facilitates to improve both water permeability and selectivity of TFC FO membrane. This work proposes an effective modification method for improving the performance of TFC FO membrane by using PDA/PEI co-deposition interlayer.