Preparation And Characterization Of CA Hollow Fiber Nanofiltration Membrane

In this paper, CA hollow fiber membranes were prepared by NIPS method at a high temperature. The membranes were characterized by water flux, rejection rate, pore size distribution, tensile properties, scanning electron microscopy (SEM) and other methods.Firstly, the acetate content of the cellulose acetate was determined, and the results showed that it meets the need of experiment. Then cellulose acetate hollow fiber membranes were prepared through self-made equipment. The effects of polymer concentration, the CTA/CA ratio on the structure and the performance of the membranes were investigated. The results showed that with the increase of total polymer content, the pure water flux decreased while the retention of salt and PEG increased. With a constant polymer concentration, the effect of CTA/CA ratio on the membrane performance was studied and the result showed that the optimal CTA/CA ratio is 10:0. The optimal membrane had a pure water flux of 2.8 L·m-2h-1 with a retention of MgSO4 and PEG 2000 was 82.8% and 93.3% respectively.Secondly, the effects of types and concentrations of additives on membrane performance were investigated by mechanical properties, pore size distribution and the permeability of the membrane. The results showed that the properties of the membrane were better with the non-solvent content being 4% than others. The membrane with A1 as an additive showed a better performance with a pure water flux of 4.5 Lm-2·h-1and a rejection rate of PEG2000 and magnesium sulfate at 91.6% and 60.1% respectively.The effects of operation parameters including operation pressure, concentration and temperature of feed solution on membrane performance and rejection rate were investigated with the optimal membranes. The results showed that with the feed solution concentration increasing, the retention of MgSO4 decreased while the flux changed slightly. The permeate flux of magnesium sulfate increased while the retention decreased with the temperature of the feed solution increasing. With the operating pressure increased, the magnesium sulfate flux increased significantly, while the magnesium sulfate retention rate increased slightly.Finally, membrane separation performance was studied by inorganic salts solutions and the retention follow the order of MgSO4>MgCl2>Na2SO4>NaCl. The membrane was used to separate dyes. The result showed that the retention of dyes all reached 93% at least.