Preparation And Characterization Of PVC Hollow Fiber Nanofiltration Membrane

Nanofiltration is a membrane process with separation characteristic between ultrafiltration and reverse osmosis, which has achieved great progress in recent years. In this paper our research is main about preparation of PVC hollow fiber nanofitration membrane. Using PVC hollow fiber ultrafiltration membrane, we tried to prepare PVC hollow fiber nanofiltration membrane by second hole shinkage method, UV-induced grafting polymerization method and interfacial polymerization method. The possibility of every method was evaluated. The main contents and results are summarized as follows:The blends of PVC and P(VC-MAA) copolymer are used to prepare PVC flat membrane with carboxyl groups on the surface by using non-solvent immerse phase inversion method. With the catalysis effect of DCC the amine group of m-phenylenediamine reacts with the carboxyl group to form an amide bond, so as to shrink the hole. The result shows the modification is effective. After modified the chemical composite and the zeta potential of the membrane change significantly, the water flux decreases, the retention of BSA and dextran100,000rises. But the retention of MgSO4decreases. However, this method is not successful on PVC hollow fiber membrane due to its lack of carboxyl group.PAAc are grafted onto the outer surface of PVC hollow fiber membranes to prepare PAAc grafting membrane by UV-induced grafting polymerization method. The study finds that in order to avoid the destruction effect of UV irradiation on the membrane, the irradiation time should be less than3min. With the irradiation time and the concentration of monomer increased, the grafting yield increases. After grafting, the water flux and the BSA retention both increase. After treatment of NaOH solution, the water flux of the modified membrane increases, because the carboxyl group is converted to carboxylic acid ion. The water flux reduces after the treatment of HCl solution.PVC hollow fiber composite nanofiltration membrane is successfully prepared by interfacial polymerization using PVC ultrafiltrion membrane as support membrane. m-phenylenediamine(MPD) as the water phase monomer, trimesoyl chloride(TMC) as the oil phase monomer. The study finds that a series of nanofiltration membranes with different MWCO can be obtained by controlling the reaction conditions. The optimized conditions for nanofiltration membrane preparation are obtained:the concentration of MPD is1%, the concentration of surfactant SDS0.05%, the concentration of acid absorbent0.6%, the concentration of TMC0.3%, the drying time40min, and the reaction time1min. Under0.3MPa the water flux of the membrane reaches17.8L/m2-h, and the retention of congo red, methyl orange and MgSO4is more than99%,90%and60%, respectively.