Study On The Preparation And Property Of PPES Ultrafiltration Membrane With Low Molecular Weight Cut-off

Poly(phthalazinone ether sulfone) (PPES) is a novel material for ultrafiltration (UF) membrane with high glass-transition temperature, good solubility, well membrane-forming ability, good mechanical performance and chemical stability. By using PPES as membrane material, NMP as solvent and organic substance and inorganic substance mixture as additive, the UF membranes with low molecular weight cut-off are prepared with a phase inversion technique, and then prepared on the support of non-woven fabric with a casting machine. The chemical stability and treating conditions for dry-membranes are also studied. The membranes are applied into the desalination-purification for dye PCSD-BK at last.The phase separation behavior of mixture additives in PPES casting solution is studied by means of cloud - point titration. The results show that the addition of LiCl decreases the thermodynamic stability of the casting system. By increasing the amount of additive LiCl, the needed amount of organic substance decrease when the casting solution reaches the cloud-point; Different additives have the same effect on the phase separation behavior of the casting solution.The effects of polymer concentration and the content of two substances in additive on membranes' structure and performance are studied. The results show that pure water flux of the membrane decrease with the increasing of polymer concentration, while the rejection rate increase accordingly; with the content of Glycol 6%, LiCl 1.5% as additive, the membrane with high water flux 299L·m^-2·h^-1 and high PEG1000 rejection rate 93% is prepared.The influences of coagulation temperature, evaporation time and thickness of membrane on UF membranes performance are also examined. the results show that with the increasing of the evaporation time, the pure water flux firstly decrease then increase and the rejection decreases; with the increasing of coagulation temperature, the pure water flux increase and the rejection decrease; Additionally with the increasing off membranes' thickness, the pure water flux decrease.PPES UF membranes with high water flux 409L·m^-2·h^-1 and high PEG1000 rejection rate 96% are prepared on the support of non-woven fabric with a casting machine. By using glycerol and SDS solution as treating agents, the dry-membranes are prepared. the results show that when it is soaked in the solution of 20% glycerol for 3 h, the water flux recovery rate can reach 90% and the rejection rate has no obvious change; when it is soaked in the solution of 0.2% SDS or glycerol, SDS mixture, the water flux could keep satisfactory, but the rejection rate decrease obviously; after the dry-membranes were stored 48days, the performance have no obvious change.The chemical stability of PPES is also studied, the results show that PPES UF membranes show excellent free chlorine-resistant ability, oxidation-resistant ability, acid-resistance ability, alkali-resistant ability. In process of desalination-purification for dye PCSD-BK, the permeate flux of the membrane increase with the increasing of operating temperature, while the rejection rate has no obvious change. It proves that the membranes have excellent heat-resistance. The dye PCSD-BK solution is almost desalinized through 5 times cycle.