Polyamide Composite Nanofiltration Membranes Prepared By Interfacial Polymerization

Nanofiltration is a pressure-driven process which has a separationproperty between ultrafiltration and reverse osmosis. The nanofiltrationmembrane has good separation properties to bivalent and multivalent ions,and has wide applications in separating the molecular weight between200and2000. Composite membrane technique is the most effective method toprepare nanofiltration membrane. The nanofiltration membrane prepared bythis method is composed of two parts: a porous support (usuallymicrofiltration membrane or ultrafiltration membrane), and an active denselayer which is prepared by interfacial polymerization. In this paper, thecomposite nanofiltration membranes were prepared through interfacialpolymerization on supports with different structure, and choosing differentamides as reaction monomers. The main works contents as following:The composite nanofiltration membranes used polypropylene films assupport, and were prepared though interfacial polymerization withpiperazine (PIP) and trimesoyl chloride (TMC) on the supports. In order toenhance the membrane hydrophilicity so that PIP can be adsorbed on the surface to enable the interfacial polymerization, acrylic acid was first graftedon PP membrane by UV-induced grafting polymerization, and the research isconcentrated on the effect of the grating degree and the hydrophilicity,caused by the BP concentration, monomer concentration and UV irradiationtime. Combined with ATR-FTIR to analyze the difference of chemicalcontents on the membrane surfaces, and used SEM to characterize thesurface morphology and the cross-section structures. Meanwhile, theseparation properties of composite membranes which prepared on modifiedPP membrane with different grating degree were studied. The results showedthat the membrane hydrophilism got better while the grafting degree ofsupports became higher, the formation of dense and complete functionallayer was easier, and the rejection of composite membrane to smallmolecules became higher.In addition, a novel composite nanofiltration membrane was studied inthis paper. The polyacrylonitrile membrane which produced by nanofibrouselectro-spinning method was choosn as support, PEI and TMC were activemonomers. In this part, with different PEI concentration and the pH of feedconditions, the differences of separation property among membranes weregiven. And the structures and the morphology of composite nanofiltrationmembranes were characterized by ATR-FTIR and SEM. At the same time,the separation properties of two kinds of composite nanofiltrationmembranes, which were different only in the PEI molecular weight of600 and1800, were contrasted. The results showed that when PEI molecularweight was increased from600to1800, the flux of composite nanofiltrationmembrane became smaller, but the relative rejection became much higher.Nowadays, there is few report about interfacial polymerization on thesurface of non-hydrophilic support. In this study, polyaminde compositenanofiltration membrane was successfully prepared on the surface of PPmembrane, a non-hydrophilic support, via surface hydrophilic modificationfollowed by interfacial polymerization. Meanwhile, compared to usingsupport prepared by traditional L-S method, by choosing a novel structuresupport, which has high porosity and the structure of through pores formedby fibers joint with each other, composite nanofiltration membrane withhigher flux and higher rejection was successfully prepared.