【作者】 杨伟；

【导师】 王宇新；

【作者基本信息】 天津大学 ， 膜科学与技术， 2011， 博士

【摘要】 自2004年石墨烯(Graphene)被成功制得以来,因具有特殊的物理、化学及力学性质,使其成为备受瞩目的国际研究前沿和热点,在众多领域有着潜在的巨大应用价值。本文首先制备了氧化石墨烯和石墨烯,然后以它们为原料制备了聚合物功能复合膜,并对复合膜的性能进行了研究。首次利用浓硫酸作为脱氧剂脱氧还原氧化石墨烯制备了石墨烯。研究结果表明,随反应温度和反应液中硫酸浓度的增大,石墨烯的还原程度增强。硫酸浓度是决定还原程度的关键因素,只有浓度大于70wt%时,氧化石墨烯才能被还原的比较彻底。利用制得的石墨烯制备了PVDF/Graphene导电复合膜。研究结果显示,随石墨烯含量的增加,复合膜的断面出现越来越多鳞片状断茬结构。复合膜的断裂强度在石墨烯添加量为0.5wt%时达到最大值,比纯膜增大34.2%。石墨烯添加量为1wt%时达到复合膜的导电渗流阀值,电导率为0.001S/m。首次将氧化石墨烯片层掺杂到较高磺化度(DS=67%)的SPEEK中制备了复合质子交换膜。研究表明,氧化石墨烯的加入,提高了复合膜的尺寸稳定性,并且复合膜的阻醇性能和可使用温度都得到显著地提高。使用温度的提高使SPEEK高电导率的特性得以发挥。利用甲基磺酸作溶剂,采用浸没沉淀相转化法首次制备了不同磺化度的SPEEK超滤膜。研究发现,膜的含水率、溶胀度及膜表面孔径随磺化度的升高而增大。膜的纯水通量随磺化度的升高明显增加,磺化度为60%的膜的纯水通量比磺化度为12%的膜提高了220.9%。超滤膜对BSA有较高的截留性能,而PEG-20K及Rose Bengal的截留率却随磺化度的增大而明显下降。在过滤BSA溶液过程中,由于BSA分子在过程驱动力的作用下沉积在SPEEK超滤膜的表面或进入膜孔内,从而使膜的渗透通量与纯水通量相比下降非常明显。此外,膜的渗透通量还与进料液的pH有关。碱性环境下,BSA与SPEEK超滤膜的电荷排斥作用增强,使得BSA不易在膜表面沉积,从而使膜保持较高的渗透通量。首次制备了磺化度为7%的SPEEK纳滤膜,并表征了其纳滤性能。研究发现,通过调节铸膜液的浓度、成膜凝固浴的温度及组成,可以制得性能优异的SPEEK纳滤膜。低磺化度的SPEEK膜具有良好的热稳定性,可以在较高温下工作。制备了SPEEK/GO复合纳滤膜,并对复合膜的性能进行了初步的研究。实验发现,随GO添加量的增大,复合膜的渗透性能下降,截留性能提高。并且GO的添加使复合膜的尺寸稳定性得到显著提高。更多还原

【Abstract】 Graphene, which was first prepared in2004, has attracted tremendous attention andbecome the leading edge and hotspot in various relative fields. Due to many intriguingphysical, chemical and mechanical properties, graphene has great potential appliedvalue. In this paper, we prepared graphene oxide (GO) and graphene firstly, and thenprepared them-based composite membranes and explored their performance.We provide a facile approach using graphene oxide colloidal suspension to preparegraphene nanosheets with concentrated sulfuric acid (H2SO4) as deoxidizing agent forthe first time. Results show that the higher the reaction temperature and the H2SO4concentration, the more complete the reduction. According to these two impactparameters, we found that the concentration of H2SO4is the key factor to determinethe degree of reduction. Only the concentration of sulfuric acid more than70wt%, thedegree of reduction would be more thoroughly.PVDF/Graphene composite membranes were prepared by a solution mixingmethod. As the content of graphene increased, the cross-section of the membranesshowed more and more scale-like stubble structure. The breaking strength of thecomposite membranes reached the maximum value as graphene content of0.5wt%,which increased34.2%compared to the pure PVDF membrane. The compositemembranes show low percolation threshold around1wt%graphene loading, theconductivity is0.001S/m.Graphene oxide was incorporated into the SPEEK matrix with relative high DS(67%) to prepare novle composite membranes for the first time. The strong interactionbetween the GO nanosheets and SPEEK molecular chains helps to reduce the swellingand methanol permeability of the composite membranes, and improve thedimensional stability. For the composite membranes, high conductivity can beachieved as the applicable temperature is improved.SPEEK ultrafiltration (UF) membranes with different DS were prepared byimmersion phase inversion method, methylsulfonic acid was used as solvent toaccommodate SPEEK. The water uptake, swelling and surface pore size wereincreased with the DS. Water flux was increased dramatically with the DS, flux of themembrane with60%DS was3.2times that of12%DS. For all the membranes,rejections of BSA were much higher, however, the rejections of PEG-20K and Rose Bengal were decreased with the DS dramatically. During the filtration of BSAsolution, all the SPEEK membranes showed lower permeate fluxes due to membranefouling, which produced by the protein molecules entrapping in the pores and blockthe channels under the trans-membrane pressure. Besides, the permeate flux wasrelevant to the feed pH. When feed pH was higher than7, the repulsion of chargesbetween BSA and membrane surface was enhanced, which suppressed the depositionof BSA, thus keep the permeate flux at a higher level.We prepared SPEEK nanofiltration (NF) membranes with7%DS and studiedtheir NF performance. The effects of several basic factors on performances, such asSPEEK concentration, coagulation-bath temperature and component, were explored.SPEEK NF membranes with excellent thermal stability can be used in hightemperature circumstance. In addition, we also prepared SPEEK/GO compositemembrane. Results show that the permeate flux decreases, the rejection and thedimensional stability increased with the rise of GO content.更多还原