Preparation And Characterization Of High Flux Aromatic Polyamide Ultrafiltration Membrane Doped With Graphite Phase Carbon Nitride（g-C₃N₄）

As one of the membrane separation technologies,ultrafiltration（UF）has been widely used in protein concentration and removal of organic matter in textile wastewater.There are many kinds of membrane materials,and poly（m-phenylene isophthalamide）（PMIA）is a promising membrane material because of its good heat resistance and chemical resistance.In order to improve the performances of the membranes,the membrane is usually optimized by means of modification.Membrane modification is often used to improve the performances of membranes,Blending is an easy kind of membrane modification method,Membranes are prepared by doping inorganic nanoparticles in the organic polymer.Graphite phase carbonitride（g-C₃N₄）is a two-dimensional nanomaterial with good application prospects in membrane modification.In this paper,the preparation method of PMIA UF membrane is discussed.PMIA UF membrane is prepared by doping PMIA as membrane material and DMAc as organic solvent,as well as PVP and Li Cl as additives.The effect of concentration（PMIA,Li Cl and PVP）and evaporation time on the microstructure and separation performances of the membranes were investigated.The performances of UF was investigated by observing the microstructure and testing the mechanical properties so as to obtain a better membrane performances and manufacturing process.A better permeation performance is obtained with the composition of 13 wt.%of PMIA,4 wt.%of Li Cl and 1 wt.%of PVP,and the pure water flux is 191 L/（m²·h）,and the molecular weight cut off is 148.7 k Da.in order to further optimize the membrane properties,PMIA/g-C₃N₄ UF membranes with PMIA as the membrane material and graphite phase carbonitride（g-C₃N₄）as additive were prepared.The UF membranes were characterized by contact angle,SEM,permeability,porosity and tensile test.The effects of g-C₃N₄ addition on the performances of the membranes were investigated.The results showed that with the increase of g-C₃N₄ content,the membranes became thinner,and the finger-like pores became longer,and the surfaces of membranes were denser.The addition of g-C₃N₄ increases the hydrophilicity of the membrane surface and reduces the pores of the membrane.A certain proportion of g-C₃N₄can effectively increase the flux of the membranes,but excessive addition will affect the separation performances of the membrane.When the addition amount of g-C₃N₄ is 5%of PMIA mass fraction,the performances of the membrane is optimal.At this time,the pure water flux reaches 542 L/（m²·h）,which is 284%of the membrane without g-C₃N₄.g-C₃N₄shows a promising prospect in the field of membrane separation.