Preparation And Properties Of SPPBES Composite Nanofiltration Membranes

Copoly(phthalazinone biphenyl ether sulfone)(PPBES) is a kind of thermoplastic functional materials with perfect mechanical strength, temperature resistance and film forming properties. Accordingly, sulfonated copoly(phthalazinone biphenyl ether sulfone)(SPPBES) is a good choice for being functional layer material of composite nanofiltration membrane, which can improve the hydrophilicity as well as optimizing comprehensive performance of the material.In this work, two kinds of sulfonated copoly(phthalazinone biphenyl ether sulfone)(SPPBES) compoise nanofiltration membranes were prepared with copoly(phthalazinone biphenyl ether sulfone)(PPBES) and polyether sulfone(PES) as ultrafiltration support membranes, respectively. The influence of conditions on the structure and performance of composite nanofiltration membrane were studied, including sulfonated degree, polymer concentration, heat treatment time and temperature. It was found that the salt removing rate increased and the water flux decreased with the increasing of polymer concentration, heating time and heating temperature. The composite nanofiltration membrane achieved good comprehensive performance, which was prepared from SPPBES with sulfonated degree of 0.9 and heated for 0.5h at 90?.The morphology, hydrophilicity and surface chemical composition of the composite nanofiltration membrane were investigated by scanning electron microscope, static contact angle measurement and infrared total reflection. The oxidation stability was studied by free chlorine immersion method. The effects of operating temperature and pressure on the performance of composite nanofitration membrane were investigated. When the operating pressure increased from 0.4 MPa to 1.2 MPa, the rejection of inorganic salt maintained at 85% and the flux of the SPPBES/PPBES membrane increased from 26 L/m2h to 60 L/m2h. Under the same operating conditions, the flux of the SPPBES/PES membrane rised from 18L/m2h to 62 L/m2h and the rejection of inorganic salt kept steadily at 79%. When the operating temperature increased from 20? to 95?, the flux of SPPBES/PPBES membrane enhanced from 46 L/m2h to 130 L/m2h and its rejection of inorganic salt decreased by 3%, while the flux of SPPBES/PES membrane elevated from 31 L/m2h to 90 L/m2h with salt removing rate decreased by 2%. Compared with commercial nanofiltration membranes, the SPPBES/PPES and SPPBES/PES membranes showed better thermal stability while they had the comparable performance under same conditions.In this work, SPPBES-LiCl, SPPBES-NaCl and SPPBES-KC1 nanofiltration membranes were prepared, which were made from PPBES as support layer and SPPBES as functional layer with LiCl, NaCl and KC1 as different inorganic salt additives. The membranes showed rejection of inorganic salt in the order of Na2SO4> NaCl?MgSO4>MgCl, and the SPPBES-LiCl showed highest salt removing rate while SPPBES-KCl exhibited highest flux among the three membranes. The effects of inorganic salt additive on their structure and morphology, hydrophilicity and surface chemical composition of membranes handled by different inorganic salts were investigated by FTIR, SEM and contact angle. The results suggested that they have same chemical composition and similar structure and hydrophilicity. The properties including thermal stability, chemical stability and oxidation resistance were investigated in detail. It was found that the membranes showed good high temperature resistance, excellent chemical stability and oxidation resistance. Besides, SPPBES-LiCl composite nanofiltration membrane showed good resistance to acid, alkali and free chlorine.