【作者】 王乃鑫；

【导师】 纪树兰；

【作者基本信息】 北京工业大学 ， 应用化学， 2013， 博士

【摘要】 致密复合膜具有超薄选择性分离层和多孔支撑层，在膜分离领域具有广阔的应用前景。在复合膜制备领域，选择性分离层的超薄化和运行过程中的稳定性是其中的主要难题。利用交替沉积的层层吸附自组装（LbL）是解决分离层超薄化最具前途的技术之一，而将有机/无机纳米杂化材料用于复合膜制备可以有效提高膜的机械强度和热稳定性，极大地丰富膜材料体系。本论文采用动态自组装技术分别在有机和无机基底上制备了聚电解质及纳米杂化多层膜，通过现代分析手段揭示了多层膜的微观结构、形貌与分离性能之间的构效关系，并将其用于渗透汽化和纳滤等分离领域，对复合膜的分离性能及其稳定性进行了研究。首先，将动态自组装技术和热交联技术相结合在中空纤维陶瓷基底的内表面制备了聚电解质多层膜，并将聚电解质间的静电力转化为共价键，制备出高稳定性的渗透汽化复合膜。采用EDX，SEM和Zeta电位等对复合过程中膜表面的形貌和结构变化进行了表征。所制备的有机/无机中空纤维复合膜对95wt.%乙醇/水体系显示出优异的渗透汽化分离性能。考察了组装层数，进料液温度和进料液水含量对复合膜渗透汽化性能的影响。当复合层数达到5层时，复合膜的渗透通量可达1050g/m2h，而透过液中的水含量仍可保持在97.5wt.%。相比于以有机聚合物为基底制备的复合膜，有机/无机中空纤维复合膜的渗透通量有了显著提高，并且提高了复合膜的机械强度。对复合膜的稳定性测试表明，有机/无机中空纤维复合膜在30h内可稳定运行。其次，采用超声破碎和静电分散技术制备了氧化石墨烯/聚电解质纳米杂化复合物，形成了稳定分散的纳米杂化物溶液。TEM结果表明同步超声破碎和静电分散作用可使氧化石墨烯的尺寸从微米级降低到纳米级尺度，从而与聚丙烯腈基膜孔径相匹配，有利于在基膜表面自组装形成纳米杂化复合物多层膜。进一步采用动态自组装技术组装氧化石墨烯/聚电解质纳米杂化复合物多层膜，通过SEM，FTIR，AFM和Zeta电位对组装过程进行了跟踪表征。采用纳米压痕仪和热重分析对组装后的氧化石墨烯/聚电解质纳米杂化多层膜表面进行了分析，研究结果表明，氧化石墨烯/聚电解质多层膜的杨氏模量和纳米硬度分别从1.3GPa和0.16GPa增加到1.9GPa和0.24GPa，分解温度升高，分解速率下降，表明杂化多层膜的机械强度和热稳定性均有较大程度的提高。将所制备的氧化石墨烯/聚电解质纳米杂化多层复合膜用于染料脱除，一价和二价离子的分离以及乙醇/水体系的渗透汽化分离，均取得较好的分离效果。纳米杂化多层膜对刚果红和甲基蓝的截留率均可达99%以上，对Mg2+和Na+的截留率分别为92.9%和44.1%，用于渗透汽化分离乙醇/水体系时透过液中的水含量可达98.1wt.%，渗透通量为156g/m2h。这表明纳米杂化多层膜可被用于不同体系的分离领域。最后，采用动态负压自组装技术制备了聚乙烯醇/氧化石墨烯纳米杂化复合物“孔填充”复合膜。研究结果表明，杂化氧化石墨烯后的聚乙烯醇复合膜的杨氏模量、纳米硬度和热稳定性均有较大程度的提高。将聚乙烯醇/氧化石墨烯纳米杂化复合物膜用于甲苯/正庚烷体系的渗透汽化分离，分别对组装过程中的聚乙烯醇浓度，氧化石墨烯含量，动态复合时间和动态复合压力进行了考察，结果表明复合膜对芳烃/烷烃混合体系具有较好的分离性能。当进料液为50wt.%的甲苯/正庚烷时，复合膜的分离因子可达12.9，渗透通量为27g/m2h。由于复合膜的“孔填充”结构，可以在保证复合膜分离性能的同时有效抑制有机溶剂对复合膜的过度溶胀，从而增强了复合膜的稳定性。将复合膜浸泡在50wt.%的甲苯/正庚烷溶液中480h后，复合膜的渗透汽化性能基本保持不变，有被用于分离芳烃/烷烃体系分离的潜在可能性。更多还原

【Abstract】 Dense composite membrane has the ultrathin selective separation layer and a poroussupport layer. It can improve the separation performance and stability of the compositemembrane. Therefore, the dense composite membrane has board application prospects in thefield of membrane separation. The key factor for the industrial application of the compositemembrane was excellent performance and stable operation. One of the main approaches islayer-by-layer self-assembly technical. The organic-inorganic hybrid and compositemembrane can combine the advantages of both polymeric and ceramic membranes, whichposs great theoretical and practical sigificance. In this work, nanohybrid membrane wasdeposited onto the organic and inorganic substrate by dynamic self-assembly. Therelationship between the microstructure, morphology and separation performance of themultilayers was investigated by modern analytical tools. The composite membrane was usedon pervaporation and nanofiltration. The separation performance and stability of thecomposite membrane was investigated.Firstly, the organic-inorganic composite hollow fiber membrane was prepared bydynamic layer-by-layer self-assembly and heat cross-linking technology. Static electricitybetween the polyelectrolyte was converting to covalent bond. The composite membrane hasan excellent pervaporation performance with high stable. The formation of multilayers on thehollow fibers was characterized with an EDX, SEM and electrokinetic analyzer. Thecomposite membrane has an excellent separation performance on95wt.%ethanol/watermixtures. The effects of layer number, feed temperature and water content in the feed on thepervaporation performance have been investigated. The membrane obtained with fivebilayers had a permeate flux of1050g/m2h, while the water content in permeate was97.5wt.%. Compared with an organic polymer based membrane, the permeate flux wassignificantly improved while the selectivity still remained at a relatively high level whenusing the ceramic hollow fiber substrate. Furthermore, the mechanical, chemical and thermalstability of the composite membrane can be enhanced. The composite membrane wasoperated over30h for pervaporation separation of95wt.%ethanol/water mixtures and had arelatively good long-term stability.Secondly, a stable, well-dispersed graphene oxide/polyelectrolyte nanohybrid complexwas prepared by sonication and electrostatic dispersion. The size of graphene oxide sheetdecreased from micronmeters to nanometers, which could match the pore size of the substrate.The nanohybrid complex was assembled onto the surface of PAN membrane. The assemblyprocess was systemtically investigated by SEM, FTIR and an electrokinetic analyzer, anano-indenter and TGA. The nanoindentation and thermogravimetric experiments in particular indicated that the GO incorporation greatly improved the Young’s modulus,hardness and thermal stability of the membranes. The Young’s modulus and hardnessincreased from1.3GPa and0.16GPa to1.9GPa and0.24GPa, respectively. The nanohybridmembrane show comparable nanofiltration and pervaporation performances in the dyeremoval, separation of monovalent and divalent ions, and dehydration of solvent-watermixtures. The retention of nanohybrid membrane for congo red and methyl blue could reach99%. The retention for Mg2+and Na+was92.9%and44.1%, respectively. For separation ofethanol/water mixtures, the water content in permeate could reach98.1wt.%and thepermeate flux was156g/m2h. The results suggested that the nanohybrid multilayermembrane can be used on varies separation fields.Lastly, a poly(vinyl alchol)/graphene oxide nanohybrid complex was prepared bysonicated. The nanohybrid complex was assembled onto an asymmetric PAN ultrafiltrationmembrane to form “pore-filling” composite membrane by dynamic pressure-driven assembly.The nanoindentation and thermogravimetric experiments in particular indicated that the GOincorporation greatly improved the Young’s modulus, hardness and thermal stability of themembranes. The composite membrane was used on pervaporation of toluene/n-heptanemixtures. The effects of pressure, filtration time, polymer, and GO concentration onpervaporation performance were investigated. When the feed solution was50wt.%toluene/n-heptane mixtures, the separation factor of the composite membrane was12.9andthe permeate flux was27g/m2h。The composite membrane was immersed into50wt%toluene/n-heptane solution for480h. Results of the swelling experiment suggest thatassembly of the nanohybrid membrane by molecular-level dispersion of GO in PVA led toenhanced affinity of the membrane to aromatic compounds and thus improved thepervaporation performance. Meanwhile, the pore-filling structure could effectively reduceswelling of the nanohybrid membrane to make the composite stable.更多还原