| In this paper,the aromatic polyamide（PMIA）ultrafiltration membranes were fabricated via phase inversion method,The effects of additives type and content on the structure and performance of ultrafiltration membranes were studied.Then the ultrafiltration membranes were used as substrate to prepare the PA-PMIA composite nanofiltration membranes via interfacial polymerization.The effect of water phase monomer piperazine（PIP）concentration,oil phase monomer trimesoyl chloride（TMC）concentration and reaction time on the performance of composite nanofiltration membranes were systematically investigated.Besides,the ultrafiltration membranes and composite nanofiltration membranes were characterized by means of analysis techniques such as field emission scanning electron microscopy（FF-SEM）,atomic force microscopy（AFM）and contact angle measurement.Results were obtained as follows:（1）Additives have a great influence on the structure and performance of the ultrafiltration membranes.The addition of LiCl led PMIA ultrafiltration membranes to form tunnel-like pores,and the size of tunnel-like pores decreased with the addition of LiCl increasing,while the addition of PVP made the macro-voids of membranes decrease and thickness of skin-layer increase.The increasing of both of them made ultrafiltration membranes porosity and pure water flux decrease and BSA rejection increase.Due to the addition of PEG,the macro-voids of PMIA ultrafiltration membranes increased first and then decreased,the pure water flux increased first and then decreased,and the BSA rejection decreased first and then increased.（2）When LiCl/EtOH was used as mixed additive,the structure and performance of ultrafiltration membranes were remarkably improved and pure water flux was enhanced significantly.With the addition of EtOH,macro-voids of ultrafiltration membranes were suppressed and finger-like pores became longer,the addition of LiCl made finger-like pores longer and sponge-like pores increase,sponge-like pores became thicker and denser with the increasing of PMIA concentration.The increasing of three additives mentioned above led to decreasing of porosity and average effective pore size,which led its pure water flux to decrease and BSA rejection to increase.When PMIA concentration was 10wt.%,LiCl content was 7wt.%andα=0.6,PMIA ultrafiltration membranes presented vertical finger-like and loose sponge-like pores structure,their pure water flux was as high as 905.2L/（m2·h）,and the BSA rejection was 98.53%.（3）The PMIA ultrafiltration membranes exhibited excellent resistance in alkanes,alcohols,ketones,esters,benzenes and acid-base solvents.（4）The surface of PMIA ultrafiltration membranes was covered with an ultra-thin and hydrophilic PA layer successfully through interfacial polymerization whose thickness was about 40nm and the low contact angle was 44.77°.when PIP concentration was 0.5%（w/w）,TMC concentration was 0.1%（w/v）and the reaction time was 30s,PA-PMIA composite membranes had the best performance whose pure water flux was 55.03L/（m2·h）and Na2SO4rejection was 98.12%.The rejection effect of composite membranes for different inorganic salts as follow:Na2SO4>MgSO4>MgCl2>NaCl,and the composite membranes exhibited excellent resistance in alkanes,alcohols,ketones,esters,benzenes and acid-base solvents. |
