Study On The Structure And Performance Of Polyethersulfone Membrane

Asymmetric polyethersulfone (PES) ultrafiltration membranes were prepared by phase inversion process. The composition of casting solution and membrane forming condition were studied. DMAc,NMP and DMF were used as casting solvents and organic alcohol (ethyl alcohol, ethylene glycol and glycerol) were used as additives while considering the casting solution composition. The character of polymer solution was studied. Proper solvent was chosen, and the rules that additives influencing the character of solution were observed and analyzed. The temperature of water bath and sodium dodecylsulfate (SDS) concentration in the bath were changed while considering the membrane forming condition.Experiment results showed that the order of intrinsic viscosity is: PES-NMP > PES-DMAc >PES-DMF system, the order of dense solution viscosity is: PES-NMP > PES-DMF >PES-DMAc system. PES-NMP membrane has relatively higher flux but not stable against pressure. PES-DMF membrane has relatively lower flux and stability against pressure because of a lot of finger-like pores. PES-DMAc membrane with some macro voids has medium flux and good stability against pressure.Increase of the additive content weakened the thermodynamic stability of the casting solution, which results in the decrease of cloudy point, and results in the increase of zero shearing viscosity and flow activation energy. Corresponding membranes became more porous. The pure water flux increased and the rejection of BSA decreased when more additives were added. Sponge-like membrane structure without macro voids was obtained while the ratio of additives were strictly controlled and the gradient of structure was improved .The membranes are stable under pressure and have low water resistance.As bath temperature increase, the top layer of membrane become thick and pores at bottom become larger and flux increase. Proper addition of SDS can improve rejection and flux of membrane.The SEM photograph and test of flux at different pressure and comparesupported-unsopported membrane show that the membranes we prepared maintain good performance against pressure.