【作者】 白雪；

【导师】 陈胜；

【作者基本信息】 四川大学 ， 纺织材料与纺织品设计， 2022， 硕士

【摘要】 水体污染是当今社会广泛关注的问题。每年纺织、造纸等行业都会产生大量有机合成染料废水,随之带来的水体污染问题愈加严重。大多数染料不仅具有高色度和高有机含量,还含有复杂的芳族结构和偶氮基团,在自然界中难降解,严重污染生态环境。此外,有毒有害染料还对人类健康和水生生物生长构成威胁。因此科研人员努力寻求简单高效的染料废水处理方法,例如离心、吸附、絮凝、光催化、化学氧化、膜分离等。其中,膜分离技术由于其具有能连续运行、适用广泛、成本低廉、截留效果好等优点,是广受欢迎的废水处理技术。静电纺丝纳米纤维膜以其高比表面积、高孔隙率、良好的机械强度以及形貌可控等优势成为废水处理技术中的一类新型的膜分离材料。本文以成本低、耐候性和耐化学性能好的聚丙烯腈作为主要原料,通过复合静电纺丝方法制备具有超细的纳米纤维,并通过均质化重组的方式进一步制备成纳米纤维膜,该膜在染料废水处理方面具有良好的应用前景。本文主要研究内容包括以下三个部分:(1)超低直径聚丙烯腈纳米纤维重组膜(re-u PAN)的制备及性能研究。通过溶剂选择性溶解和超声分散的方法去除复合电纺纤维中的海相组分(醋酸丁酸纤维素),得到直径约61 nm的超低直径聚丙烯腈纳米纤维(u PAN)的水分散液。所得u PAN纳米纤维直径仅有常规电纺PAN纤维直径的五分之一,比表面积高,吸附速率快,为制备性能优良的滤膜提供了可能。在真空辅助过滤的负压作用下,u PAN纳米纤维层层堆叠形成了具有良好力学性能的平板自支撑滤膜。综合孔隙率、通量以及力学性能对re-u PAN纤维膜进行了优化,得到了断裂强度为22.2 MPa,纯水通量为63.4 L/m2h的优化纤维膜。以亚甲基蓝为模型染料,探究了重组纤维膜对阳离子染料的过滤吸附作用,单位面积最大吸附量可达816.5 mg/m2。该膜在酸性乙醇溶液中能快速再生,并在10次循环后仍能保持优秀的过滤吸附性能(保持率99.99%)。(2)埃洛石纳米管(HNT)/超低直径聚丙烯腈纳米纤维复合膜(HNT/u PAN)的制备与性能研究。为进一步提高重组纳米纤维膜的通量和吸附效率,在u PAN水分散液中加入一定量的天然管状纳米材料HNT,通过真空抽滤得到HNT/u PAN复合膜。具有刚性特征和优秀吸附性能的HNT穿插在纳米纤维之间,构造具有疏松结构的复合薄膜,提升通量的同时吸附能力也能进一步提升。研究结果表明,在总质量相同的情况下,HNT:u PAN质量比为3:7时,复合膜平均通量可达到64.2 L/m2h,是同等质量下对应re-u PAN膜通量的两倍。得益于HNT的优秀吸附性能,优化条件下,复合膜对亚甲基蓝最大吸附量可达2424.6 mg/m2。但是循环过滤吸附实验表明,8次循环后染料去除率有所降低,循环性能较纯re-u PAN有所下降(保持率81.6%)。(3)聚多巴胺包覆埃洛石(HNT@PDA)/超低直径聚丙烯腈纤维复合膜(HNT@PDA/u PAN)的制备及性能研究。为改善HNT/u PAN复合膜的循环使用性能,在HNT表面包覆了聚多巴胺(PDA),改变其吸附机制,从而改善膜的循环使用性能,同时,利用PDA高吸附特性进一步提升滤膜的吸附能力。研究结果表明,HNT@PDA:u PAN质量比为3:7时,复合薄膜的平均通量为122.7L/m2h,是同等质量下re-u PAN膜的4倍。复合膜对亚甲基蓝的最大吸附能力达到3015.9 mg/m2,且对多种染料均具有良好的过滤吸附能力。该膜经10次循环后,去除率基本保持不变,循环使用性能得到提升(保持率95.8%)。更多还原

【Abstract】 Water pollution is a widespread concern of the society.With the increasing demand for organic synthetic dyes in textile and papermaking industries,the water pollution becomes more and more serious.Most dyes have not only high chroma but also high organic contents.Due to the complex aromatic structures and azo groups,dyes are difficult to degrade under various natural conditions,leading to serious environmental problems.More seriously,dye wastewater threatens human’s health and aquatic life due to its toxicity.Researchers are exploring simple yet efficient treatment methods,several strategies(e.g.,centrifugation adsorption,flocculation,photocatalytic,oxidation,membrane filtration,etc.)have been applied to remove dyes from wastewater.Among those techniques,membrane separation technology has been widely investigated and regarded as a most efficient one because of its continuous operation,low cost,and superior removal effect.Electrospinning nanofiber membrane has become a new way of water treatment technology because of its advantages of high specific surface area,high porosity,good mechanical property and controllable morphology.In this paper,as the main research object,the common polymer polyacrylonitrile with low cost,weather resistance and good chemical resistance was easy used to prepare nanofibers by electrostatic spinning.It’s an ideal material for making filter membrane for water treatment.The main research content of this paper includes the following three parts:(1)Preparation and characterization of re-u PAN membranes.In this paper,an ultra-low diameter polyacrylonitrile nanofibers(u PAN)with a diameter of about 61 nm was prepared by removing the Marine component(cellulose acetate butyrate)of composite electrospun nanofibers through solvent selective dissolution.And the water dispersion solution of u PAN was obtained by ultrasonic dispersion.The u PAN nanofibers were only one-third of that of ordinary electrostatic spinning,with high specific surface area and rapid adsorption capacity,which provided possibilities for the preparation of filter membrane.The u PAN nanofibers were overlapped and deposited layer by layer under negative pressure assisted with vacuum filtration,forming a flat and self-supported reconstituted membrane with good mechanical properties.Considering porosity,flux and mechanical properties,re-u PAN-12 membrane was selected as the final optimization with a strength of 22.2 MPa and an average flux of63.4 L /m2 h to achieve higher water treatment efficiency under the condition that the membrane strength was sufficient to be used under high operating pressure.Using methylene blue dye as the model,the filtration and adsorption of cationic dyes by reu PAN-12 membrane was investigated.The maximum adsorption capacity per unit area was up to 816.5 mg/m2.The membrane can be rapidly desorbed in acidic ethanol solution and had excellent cycling performance(99.99%)that the adsorption capacity basically remains unchanged after 10 cycles.(2)Preparation and characterization of HNT/u PAN composite membranes.In order to further improve the flux and adsorption efficiency of the reconstituted nanofiber membrane,a certain amount of natural nanomaterials HNT was added into the u PAN aqueous dispersion to obtain HNT/u PAN composite membranes by vacuum extraction and filtration.Under the condition of the same total mass,HNT:u PAN=3:7was the best ratio,and its average flux was 64.2 L/m2 h,which was twice that of reu PAN films with the same mass.Using methylene blue as the model,the adsorption capacity of HNT/u PAN-3 membrane on cationic dyes was investigated.The maximum adsorption capacity per unit area was 2424.6 mg/m2,which increased 374 mg/m2.The removal rate of HNT/u PAN-3 membrane was decreased after 8 cycles that meant the cycling performance(81.6%)decreased compared with re-u PAN.(3)Preparation and characterization of HNT@PDA/u PAN composite membranes.To improve the recycling performance of HNT/u PAN membrane,PDA was coated on HNT surface to change its adsorption mechanism so that improving the desorption effect.Meanwhile,PDA’s high adsorption performance could also be used to increase the adsorption capacity.After blending with u PAN dispersion,different proportions of HNT@PDA/u PAN membranes were prepared with the same total mass.In terms of comprehensive performance,HNT@PDA:u PAN=3:7 was the best ratio.The average flux of HNT@PDA/u PAN-3 membrane was 122.7 L/m2 h,which was 4 times that of re-u PAN membrane with the same mass.Using methylene blue as the model,the maximum adsorption capacity of HNT@PDA/u PAN-3 membrane to dye was 3015.9mg/m2,and HNT@PDA/u PAN-3 membrane had good adsorption effect on various dyes.After 10 cycles,the removal rate(95.8%)was almost unchanged,indicating that the cycling performance had been improved.更多还原