Pva Hydrophilic Ultrafiltration Membrane

Membranes fouling is the main problem for ultrafiltration process and so become a focus on research presently. PVA was chosen to prepare ultrafiltration membranes by way of phase transition because of its hydrophilic nature in this article .And these membranes are expected to minimize membrane fouling.The preparing of ultrafiltration membranes by use of unmodified PVA was studied with different additives and solvents. The membrane had an asymmetrical structure consisting of a dense skin layer and a cellar porous sublayer measured by SEM. Under pressure of 0.1 Mpa, the flux was measured that no pure water permeated through the membrane. Conversely, the membrane presented ultrafiltration properties when the membrane was prepared from a heterogeneous casting solution of PVA by immersing them in Na2SO4/H2O as coagulant medium. Experiments showed that strong action of hydrogen bond in PVA blocked the formation of PVA ultrafiltration membranes.PVA was partly modified with aldehyde by way of hydroxy-protected in the following experiments. The membranes were prepared from a casting solution of poly(vinyl acetal), N,N-dimethylacetamide as solvent by immersing them in coagulation bath. Finally, the membranes were hydrolyzed to remove aldehyde under acid condition with glutaradehyde and the membranes were crosslinked at the same time. Thus the results showed that the strength of membrane was enforced and the hydrophilicity remained. Experiments were performed on the influences of the concentration of poly(vinyl acetal) and temperature on pure water flux and rejection of membranes. The temperature of casting solution and coagulation was found to have a marked influence on the flux. When temperature was elevated, the flux increased much. And the trend to the effect of ratio of the content of additive( PEG-600) to poly(vinyl acetal) on the flux exhibited a parabola. When the ratio was 1.5, the flux reached the peak, and vvith the ratio increased, the flux reduced instead. The important results showed that the membranes had smaller contact angle than other types of membranes and minimized membrane fouling considerably. The SEM photographs showed that the morphology of membranes were finger and sponge.