Study On PAN Electrospun Nanofiber Membrane Modified By Polydopamine And Its Properties On Oil/Water Separation

While for thousands of years of human history, water has been a plentiful resource all around the world and almost a free good, nowadays, the situation is going to be reversed. Water scarcity is gradually becoming the single greatest threat to food security, human health, and natural ecosystems. Nanofiber material has been widely used because of the high specific surface area and other advantages. Electrospinning is a versatile and simple techniques, which has been applied to fabricate nanofibers. There is a question:electrospun membranes are usually difficult to keep excellent in both water flux and emulsion rejection rate. Therefore, the PAN nanofiber, which is usually used in oil water treatment, was modified by dopamine. The filtration properties of oily wastewater were tested, then the membranes were further multi-functionalized. It shows the application of electrospun nanofiber membrane has been optimized and extended.Firstly, polydopamine nanoparticles were prepared, then the PDA particles blended PAN composite membrane was further prepared. The result showed that although the pure water flux increased, emulsion rejection rate was no significant changed and mechanical properties decreased.Secondly, polydopamine coated PAN electrospun nanofiber membrane was prepared, then effect of the dopamine concentration and modified time on oil/water separation was also tested. The results showed that the oil/water separation performance of the membrane was significantly improved after coating modification. With the increase of dopamine concentration, nanofiber diameter increased, pore size decreased, the tensile strength of membrane also improved, elongation is basically stable which maintained at more than 40%; the pure water flux increased first and then decreased, when dopamine concentration is lmg/mL, water flux of membrane up to 14656L/（m²·h）, which is 63% higher than the unmodified membrane; the pore size distribution of membrane obviously narrowed, when dopamine concentration is 1.5mg/mL, membrane got the smallest pore size and the emulsion rejection rate reached the best value of 96.1%; additionally, antifouling performance also improved. As the coating time prolonging, the nanofiber diameter increased then basically unchanged, tensile strength first increased rapidly and then tends to be stable, after 8h coating procedure, tensile strength was 77% higher compared to unmodified membrane, elongation was basically stable which remained around 40%; the pure water flux increased first and then decreased, reached the maximum after 20h coating, increased 52% compared with the unmodified membrane; emulsion rejection rate continued to improve, after 16h coating, oil/water flux of the membrane was invariable. In summary, membrane achieve the best performance on oil/water separation when dopamine concentration was 1.5mg/mL, coating time 20 h.Finally, based on the adhesion properties of poly dopamine, TiO₂ nanoparticles were attached on the surface of polydopamine coating membrane, and the multi-functional nanofiber membrane was prepared, the neat PAN membrane was used as a reference. As a result, the addition of TiO₂ can improve antifouling property of membranes; under the condition of the presence of polydopamine layer, composite membrane （TiO₂ concentration0.1w/v%） possessed both excellent performance of oil/water separation and TiO₂ binding. Photocatalytic MB test results showed that TiO₂/PDA/PAN film had more active TiO₂ participated in the photocatalytic process and showed a good degradation ability of MB dye.