Preparation Of Functionalized Cellulose Acetate Porous Fiber Membranes And Its Application In Wastewater Treatment

Water,as the basis of life,is an important resource for the survival of human beings,animals,and plants.With the advancement of society,a large amount of industrial sewage and domestic wastewater are discharged into clean water,which seriously pollutes water sources and poses a great threat to human health.In this regard,adsorption separation technology is considered to be one of the effective methods to remove pollutants in wastewater due to its simplicity,high efficiency and low cost.Although a large number of adsorption materials have been developed,traditional materials have limitations during the actual separation process,such as expensive,weakened ability,complex post-treatment and easy to cause secondary pollution with the increasing depletion of non-renewable resources and the increasingly serious global environmental problems.Therefore,it is of practical significance to exploit a cheap,efficient,and environment-friendly material for sewage purification.In this paper,cellulose acetate(CA),which is abundant in nature and has the advantages of inexpensiveness,environmental friendliness,biodegradation and workability,had been used as the matrix.The water-soluble polyethyleneimine(PEI)rich in amine groups,the polydopamine(PDA)with strong adhesion and the visible light catalyst titanium dioxide(TiO2)had been introduced that continuously improved the preparation ideas and methods to obtain three kinds of CA-based porous fiber membranes to achieve high-efficiency adsorption of Cr(Ⅵ)and oil-water separation.The main research results are as follows:(1)The amine functionalized CA-c-PEI porous fiber membrane was successfully prepared by blending PEI and CA through electrospinning technology and cross-linking reaction.The micromorphological characterization exhibits that there are a large number of pores on the single fiber of the CA-c-PEI.The adsorption performance test shows that the CAc-PEI porous fiber membrane exhibits good adsorption capacity for Cr(Ⅵ),and the maximum adsorption capacity is 285.7 mg/g(25℃).Moreover,the adsorbent can highly efficiently reduce the concentration of Cr(Ⅵ)to 0.03 mg/L from the initial concentration of 50 mg/L,satisfying the requirement of the drinking water recommended by the World Health Organization.Furthermore,the CA-c-PEI membrane exhibits excellent adsorption performance under the interference of coexisting ions and reuse performance.It is worth noting that the adsorption mechanism of CA-c-PEI to Cr(Ⅵ)is mainly complexation and electrostatic interaction.The experimental results also prove that the amine groups is both the adsorption site and the reduction site.(2)CA/PEI(CAP)porous fiber membrane with different diameters was prepared through electrospinning by controlling the outflow rate of spinning solution.The effects of the introduction of PEI and diameter distribution of fiber on the microscopic morphology,surface wettability,and porosity of the fiber membrane were studied.The contact angle test found that the introduction of PEI effectively improved the hydrophilicity of CA,and the CAP membrane exhibits the characteristics of superoleophobicity under water and superhydrophobicity under oil.It is found that CAP-0.03 porous fiber membrane could separate oil/water mixtures of the oil-in-water or water-in-oil emulsion systems with high separation efficiency and ultra-high flux only driven by gravity.(3)Using CA as the matrix material,PEI,PDA and TiO2 as the modified materials,the CA/PEI@PDA@PEI(CTPP)fiber porous membrane was prepared by the combination of electrospinning technology and cross-linking reaction.The adsorption performance examination displays that comparing with the CA-c-PEI sample,the CTPP sample exhibits better adsorption performance with an adsorption capacity of 357.14 mg/g.Further studies have shown that the CTPP-20 membrane has good reusability.The study of adsorption mechanism shows that the loading of PEI increases after PDA pre-modification of CA,which indicating that the content of amine groups also increases,implying that the CTPP-20 membrane would generate more protonated amine groups when adsorping Cr(Ⅵ).In other words,the electrostatic interaction,reduction and complexation between CTPP-20 membrane and Cr(Ⅵ)are enhanced.In particular,the results shows that the CTPP-20 sample reduces about 72.1%of Cr(Ⅵ)to Cr(Ⅲ).