Study Of Preparation And Application Of Poly (Phthalazinone Ether Sulfone) Separation Membranes

Recently, a series of novel poly (aryl ether sulfone) materials containing phthalazinone moiety are high-performance engineering thermoplastics with reasonable solubility and excellent thermal property. They possess high glass-transition temperature, membrane forming property, mechanical performance and chemical stability. Copoly (phthalazinone ether sulfone) (PPBES) which has good flexibility is a potential material for ultrafiltration (UF) membrane and support membrane of composite membrane. Positively charged QAPPESK nanofiltration membrane made in our laboratory has low rejection of high-valent cations, high flux and good thermal stability which possesses great potential in some wastewater treatment applications.PPBES UF membrane is prepared with phase inversion method and water is used in coagulation bath. The choice of solvent of the casting solution is based on solubility theory. Several solvents such as DMAc, NMP, DMF, Pyridine, DMSO and THF are tried to prepare casting solution. Only DMAc, NMP and Pyridine can be used according the solubility experiment. DMAc is chosen because the membrane formed has good performance. By using turbidity titration to study the effects of additives for the thermodynamic of the casting solution and the compatibility and precipitation capacity of five non-solvent additives on PPBES/DMAc solution are determined. Effect of different additives on membrane performance and morphology are studied. The polarity and volatility of the additive affect the membrane perfprmance and morphology obviously. Higher polarity causes the worse compatability with membrane material PPBES caused sponge-like structure and high flux. Additive with strong volatility is ready to escape and the membrane formed has dense skin, low flux and small pores.The influences of polymer concentration, coagulation temperature and evaporation time on UF membranes performance are studied. Under optimized condition, the flux of the membrane is 430 L/m2h and rejection of PEG 10000 is about 93% at 0.1 MPa and 20?. By using EGME as organic additive, LiCl as inorganic additive, a quaternary-system casting solution was prepared to make PPBES UF membrane with low molecular weight cut-off (MWCO). When the polymer content is 20%, EGME content is 8% and the LiCl content is 8% , the PPBES UF membrane with low MWCO is successfully prepared which has high flux of 122 L/m2h and high PEG1000 rejection rate of 100%. Because of the excellent mechanical performance and flexibility of PPBES, PPBES UF membrane is suited to be used as the substrate of PPBES composte NF membrane. In this work, Poly (piperazinamide) NF membrane is prepared on the PPBES UF membrane with interfacial polymerization method. Reaction conditions including monomer concentrations, immersion time in water phase, reaction time, post-treatment temperature and time are optimized. PPBES composite NF membrane prepared has high flux (75 L/m2h) and high rejection of Na2SO4 (97.5%). When tested with 1 g/L Na2SO4 solution, the membrane flux is increased from 61 to 290 L/m2h while the rejection decreases 3.8% only as the operation temperature elevated from 18?to 85??PPBES UF membrane with low MWCO has high rejection of organic material but can not reject inorganic salts, which will greatly decline the osmotic pressure. So it is suitable be ultilized in separation of salt and organic material, especially in treatment of dye production and dyeing wastewater. The simulative dye wastewater treatment is taken with the low MWCO PPBES UF membrane. The rejections of direct dye (Congo Red), anion dye (Gentian Violet) and sulfur dye (Sulfur Black B) are all 100%. The rejections of reactive dye (Reactive Yellow 86), disperse dye (Disperse Red 73) and cationic dye (Acid Chrome Blue K) are 79%, 54% and 43% , respectively. All the membrane fluxes are higher than 87 L/m2h except for disperse dye. In order to improve the rejection of Reactive Yellow 86, Disperse Red 73 and Acid Chrome Blue K, poly (piperzinamide) NF membrane is ultiliezd and shows good performance. The thermal stability of PPBES UF membrane and composite NF membrane is studied and the result demonstrates that they possess excellent themal resistance.Several NF membrane made in our laboratory are tried in the treatment of sulfur black dye wastewater of a Dalian factory. The negatively charged poly (piperzinamide)/PPBES NF membrane and SPPES/PPESK NF membrane show very low flux in operation while the positively charged QAPPESK NF membrane shows high flux and high dye rejection. The QAPPESK membrane has low rejection of divalent ions and can be used to separate and reuse dye and salts. At 60?and 0.6 MPa, the membrane flux is 14.5 L/m2h, rejection of sulfur black dye is 92.3% while salt rejection is only 10%. The membrane performance does not decline in 72 h operation at 60?. So the membrane is a suitable choice for this wastewater treatment and can accomplish the claim of separation of dye and inorganic salts.