Research On Preparation Of Carbon Nanotube Composite Nanofiltration Membrane And Treatment Of Dye Wastewater

The traditional textile industry usually produces a large amount of wastewater which will have harmful effects on the ecosystem if directly discharged.However,nanofiltration membrane technology,as an efficient water purification treatment method,can be used for the decolorization of dye wastewater,which can meet the necessary standards for wastewater treatment.In the field of water treatment,the wide application of membrane technology is mainly limited by two aspects:membrane separation performance and membrane fouling.Therefore,the research for new composite membrane materials and new membrane materials have important academic value and practical significance.In this paper,a composite nanofiltration membrane based on buckypaper membrane was proposed and applied to the treatment of dye wastewater.Buckypaper membrane has a great influence on the overall performance of the membrane.Therefore,it is necessary to study the physical and chemical properties and water treatment performance of buckypaper membranes.The microstructure,physicochemical properties and permeability/selectivity of composite nanofiltration membranes should be further studied.It is also necessary to study the purification effect of the carbon nanotube composite nanofiltration membrane on textile wastewater.Moreover,it is necessary to evaluate the separation performance of composite nanofiltration membrane and discuss its separation mechanism.and study its separation mechanism.First,a series of buckypaper membranes with different CNT load were prepared using vacuum filtration method,and buckypaper membranes were characterized by various means.The results showed that the buckypaper membranes had similar non-woven fiber structure;CNT load had effects on the zeta potential,hydrophocility,pore size distribution,mechanical strength,and so on;however,the surface roughness and porosity did not change significantly.It was found that the permeability of the BP membrane was about 210 LMH/bar,and the retention for humic acid was more than 90%.Second,since the original BP membrane has poorer mechanical strength,and its high hydrophobicity and surface roughness,which adverse to the interfacial polymerization reaction,it is necessary to dip the BP membrane in polyvinyl alcohol（PVA）solution to prepare BP-PVA membrane.The results showed that BP-PVA membranes had smaller pore size and porosity,improved hydrophilicity,weak zeta potential,lower roughness,and better mechanical strength.Carbon nanotube composite nanofiltration membrane（BP-PVA-PA）was prepared by interfacial polymerization on BP-PVA membrane.With piperazine（PIP）immersion time,PIP concentration,reaction time,heat treatment time and PVA impregnation time as independent variables,and the permeability and salt cutting performance of nanofiltration membrane as dependent variables,the interinterface polymerization reaction conditions were adjusted.The rejection for divalent salt and permeability of the prepared composite nanofiltration membrane were above 98%and 7.1 LMH/bar.Finally,the physical and chemical properties,permeability and salt rejection performance of BP-PVA-PA membrane,BP-PA membrane and PVDF-PA membrane were compared comprehensively.The results showed that compared with BP-PA membrane,BP-PVA-PA membrane has better salt rejection performance and mechanical strength.Compared with PVDF-PA membrane,the surface potential of BP-PVA-PA membrane is greatly weakened and the mechanical strength is greatly increased.At last,the purification effect of textile wastewater was studied.The treatment effect and antifouling ability of BP-PVA-PA membrane on four kinds of simulated dye wastewater,including Congo red,methyl orange,methylene blue and rhodamine B,were tested.NF90 commercial nanofiltration membrane was used as the control membrane.The results showed that BP-PVA-PA composite nanofiltration membrane could retain more than 93%of dye.Its rejection ability was affected by steric hindrance and Donnan effect,and showed better antifouling performance than NF90membrane,especially for cationic dye wastewater.Similarly,the performance of BP-PVA-PA membrane is slightly better than that of NF90 membrane in the treatment of lignin wastewater.By investigating the retention perfomance of composite membrane for four kinds of inorganic salts（Na₂SO₄,Mg SO₄,Mg Cl₂,Na Cl）,it was found that compared with NF90 commercial nanofiltration membrane,BP-PVA-PA composite nanofiltration membrane has better permeability and selective separation performance for inorganic salts.Besides,"Donan effect"played a dominant role in the selective separation of inorganic salts by BP-PVA-PA composite nanofiltration membrane.