双分离层复合纳滤膜的制备及其性能

以改性后的聚丙烯腈(PAN)超滤膜为基膜，依次采用层层自组装(LBL)和界面聚合的方法制备了具有双层分离层的复合纳滤膜。以间苯二胺(MPD)为水相单体，均苯三甲酰氯(TMC)为有机相单体，聚乙烯亚胺(PEI)为阳离子聚电解质，聚(4-苯乙烯磺酸钠)(PSS)为阴离子聚电解质，探索了LBL条件对双分离层复合纳滤膜性能的影响，考察了通过不同制备方法获得的纳滤膜对硫酸镁(MgSO4)的分离性能，得到了最佳的LBL制备条件：PEI溶液的浓度为1.00 g·L-1，pH为7；PSS溶液的浓度为1.00 g·L-1，pH为10，支撑电解质氯化钠(NaCl)浓度为1.00 mol·L-1，单一聚电解质(PEI或PSS)的沉积时间为20 min。与仅通过界面聚合法制得的聚酰胺纳滤膜相比，在界面聚合反应之前，先通过LBL沉积1.5层的聚电解质层时得到的复合纳滤膜分离性能优异稳定，在0.80 MPa的压力下，过滤2.00 g·L-1 MgSO4溶液时的通量为18.6 L·(m2·h)-1，截留率达到99.07%。

Preparation and performance of double-separation-layer composite nanofiltration membrane

Composite nanofiltration membrane with double separation layers was prepared through combined layer-by-layer (LBL) self-assembly and interfacial polymerization methods using hydrolyzed polyacrylonitrile (PAN) ultrafiltration membrane as support. M-phenylenediamine(MPD) and trimesoyl chloride (TMC) were used as aqueous monomer and organic monomer, respectively. Polyethyleneimine (PEI) and sodium polystyrene sulfonate(PSS) were chosen as cationic polyelectrolyte and anionic polyelectrolyte, respectively. The effects of LBL self-assembly conditions on the performance of double-separation-layer composite nanofiltration membranes were investigated. The separation characteristics of nanofiltration membranes which prepared through different fabrication methods for MgSO4 were evaluated. The optimum LBL conditions were the concentration of 1.00 g·L-1 and pH of 7 of PEI solution, respectively. The concentration and pH of PSS solution were 1.00 g·L-1 and 10, respectively. Supported electrolyte (NaCl) concentration was 1.00 mol·L-1. The deposition time of one kind of polyelectrolyte (PEI or PSS) was 20 min. Compared with polyamide nanofiltration membrane prepared by using simple interfacial polymerization method, the double-separation-layer composite nanofiltrationmembrane which prepared through firstly depositing 1.5 polyelectrolyte layers and followed by interfacial polymerization had better and stable separation properties. Under the pressure of 0.80 MPa, the flux of double-separation-layer composite nanofiltration membrane was 18.6 L·(m2·h)-1 and the retention rate reached 99.07% when filtering 2.00 g·L-1 magnesium sulfate solution