Study On The Performance Improvement Of Separation Membrane Using Carbon Nanomaterials

Polyethersulfone?PES?is one of the most widely used materials for membrane preparation.It has advantages of excellent thermal stability,mechanical stability,and dimensional stability.However,the intrinsic hydrophobic property of PES causes the membranes easily contaminated,which is the major challenge for the utilization of the membranes in industry.Nano-carbon materials become popular materials due to its excellent properties such as the mechanical properties and easy modification,and are good candidate for membrane modification.In this paper,the influence of sulfonated carbon nanotubes?SO₃-CNTs?and graphene oxide?GO?on PES membranes and their separation and permeation properties were investigated respectively.The effect of electric field characteristics on the properties of the mixed matrix membranes?MMMs?were tested by adding direct current?DC?electric field during the membrane preparation process to promote the migration of nano-additives to the membrane surface.The specific work is as follows:The PES membranes were prepared through immersion phase inversion using N,N-dimethylacetamide?DMAc?as solvent and polyvinylpyrrolidone?PVP?as porogen.The effect of preparation conditions of PES membranes was studied.The results showed that with the increase of PES concentration,the pure water flux of the membrane was significantly reduced and the methyl red dye separation performance of the membrane was increased.Under ambient humidity of 38%and temperature of 25 degrees,when the pre evaporation time was 1-5 minutes,the pure water flux of the membrane decreased and the dye separation performance obviously improved with time.The carbon nanotube?CNTs?was modified to obtain the sulfonated carbon nanotube?SO₃-CNTs?,and the SO₃-CNTs/PES MMMs were prepared by immersion phase inversion with adding it into the casting solution.It was found that with the increasing concentration of SO₃-CNTs,the viscosity of casting solution increased,and the flux of the MMMs decreased.But the addition of SO₃-CNTs increased the hydrophilicity and the charge density on the surface of the MMMs.Thus,the separation performance and antifouling performance of the MMMs were improved.It was found that the application of DC electric field during the membrane preparation enriched the SO₃-CNTs near the membrane surface,increased the hydrophilicity and the surface charge density of the MMMs,and further improved the separation performance and antifouling properties of the MMMs,but the active layer of the MMMs were thickened,the pore size decreased,and the pure water flux of the MMMs decreased.The graphene oxide?GO?was prepared by modified Hummers method,and the GO/PES MMMs were prepared by adding it into the casting solution.It was found that the addition of GO reduced the viscosity of the casting solution,improved the hydrophilicity,surface charge density,pure water flux,separation performance and antifouling performance of the MMMs.The MMMs were prepared by applying a direct current electric field during the pre-evaporation process.It was found that the application of electric field was beneficial to the aggregation of GO to the membrane surface,the hydrophilicity,negative charge density,pure water flux,separation performance and the antifouling ability of the MMMs were further improved.