【作者】 邱实；

【导师】 高从堦； 冯献社；

【作者基本信息】 浙江大学 ， 化学工程， 2011， 博士

【摘要】 碳纳米管自问世以来因其卓越的性能而备受关注。将碳纳米管与聚合物复合从而提高聚合物的力学、电学及其它性能,具有广泛的研究和实际应用前景,尤其是将碳纳米管添加到高聚物中制备成膜,利用其独特的一维管状结构和超疏水能力,可以提高传统分离膜对复杂体系的分离效果。获得到结构完整,性能优良的碳纳米管／聚合物分离膜,首先需要提高碳纳米管在聚合物基体中的分散性。通过对碳纳米管改性接枝活性基团,提高界面相容性可使整个体系保持稳定,发挥混合杂化膜中碳纳米管的独特性能。本论文针对上述目标,采用不同功能化方法提高原始碳纳米管的纯度、稳定性和分散性,然后将功能化的碳纳米管与几种聚合物材料分别进行复合,分别制备超滤、反渗透和渗透汽化膜,研究添加碳纳米管后膜分离性能的变化。主要包括以下四个方面的内容：(1)原始多壁碳纳米管(multi-walled carbon nanotube)的纯化及表面功能化。首先采用在硫酸/硝酸组成的混酸中超声处理以纯化碳纳米管。针对不同聚合物的结构特点采用两种不同的方法对纯化碳纳米管进行功能化以提高成膜后的性能：一是利用5-异氰酸酯-异酞酰氯(5-isocyanato-isophthaloyl chloride, ICIC)与碳纳米管反应实现多壁碳纳米管表面酰氯化；二是利用丁二酸酐过氧化物(diisobutyryl peroxide)与碳纳米管反应实现碳纳米管表面的羧酸化。通过功能化改性后,极大的提高了多壁碳纳米管在水中和各种有机溶剂中的分散性,也显著提高其在各种聚合物基质中的分散能力和界面相容性。(2)碳纳米管/聚砜超滤杂化膜的制备及性能研究。将表面酰氯化的碳纳米管与聚砜基质共混,采用相转化的方法制备得到表面孔径约为30 nm的超滤膜。通过扫描电镜(SEM)和透射电镜(TEM)观察膜表面和截面结构；采用元素分析(XPS),红外光谱(IR)及接触角对膜表面的化学成分和亲疏水性分析。以纯水和聚乙二醇(PEG,分子量20000)为原料液分别测试超滤膜的通量和截留性能,结果表明,碳纳米管的加入改善了膜的微结构并提高了膜表面的亲水性,纯水通量由原来的40 L/m2-h上升到180 L/m2·h,分离性能得到显著增强。另外,通过对BSA蛋白质分子的静态吸附实验,证明加入碳纳米管的聚砜超滤膜可以有效降低蛋白质引起的膜污染。(3)碳纳米管/壳聚糖渗透汽化复合膜的制备及性能研究。将表面羧酸化的碳纳米管与壳聚糖共混制备得到表面致密的渗透汽化复合膜。通过SEM和TEM观察到膜的形貌以及碳纳米管在壳聚糖中的分散状况；通过红外光谱和X射线衍射(XRD)比较了混有碳纳米管的壳聚糖复合膜和纯壳聚糖复合膜结构的差异。通过膜在乙醇和水中的溶胀实验,考察了膜中碳纳米管含量对乙醇和水在膜中溶解系数和扩散系数的影响,与Fick定律推导出的理论扩散系数进行比较,证实膜中的碳纳米管更有利于提高水分子的扩散速率。最后将膜应用与渗透汽化实验中,考察料液温度和碳纳米管含量对分离性能的影响,结果表明,含碳纳米管的混合膜可以降低分子穿透膜的活化能,从而大幅度地提高水通量和膜的总通量及其他分离性能。(4)碳纳米管/聚酰胺反渗透复合膜的制备及性能研究。首先考察界面聚合反应条件对以间苯二胺(MPD)和均苯三甲酰氯(TMC)为单体的反渗透复合膜性能的影响,并经过单因素和正交实验优化膜制备条件。研究了向水相中添加相转移催化剂和小分子醇类后对反渗透复合膜性能的影响,合理的解释了相转移催化剂和小分子醇作为水相添加剂能提高复合膜通量的原因。随后,将羧酸化的碳纳米管分散到MPD水溶液中制备得到碳纳米管/聚酰胺反渗透复合膜。SEM、TEM的表征结果证明：加入碳纳米管后膜表面比纯聚酰胺膜粗糙,而且加入碳纳米管后由于微相分离会造成膜的分离层出现微小的空隙,降低了膜表面的致密程度。另外,碳纳米管/聚酰胺复合膜的表面更亲水,表面的电负性也大于纯的聚酰胺复合膜。与纯聚酰胺复合膜分离性能相比,碳纳米管/聚酰胺反渗透复合膜对纯水和盐溶液的渗透通量增加近一倍,同时,膜抗污染性和耐氧化性也得到了一定的提高,对活性氯的耐受力提高到3000 ppm·h。综上所述,本论文所制备的含碳纳米管有机/无机复合膜比单纯的有机高分子膜在结构和性能上有明显提高,该膜制备方法为制备高性能杂化膜提供了新的思路。更多还原

【Abstract】 Since the carbon nanotubes (CNTs) was first discovered in 1991, it has been of great interest in chemistry physics and materials science rapidly, and has a lot of potential applications in many fields, especially applying in preparation of new mixed matrix membranes (MMM), due to its peculiar mechanical, electronic, chemical properties. The constraints of separation performance of traditional membrane would be conquered by CNTs because of its unique one-dimensional and superhydrophobic tubal structure. However, how to fabricate a well-performance CNT mixed matrix membrane (CNTs-MMM) is really a tough task since the bad dispersibility of CNTs. If CNTs would be grafted by active group and thus create no void with polymers, the CNTs-MMM would exhibit more advantages than original polymer membrane. So the task of this thesis is first to exploit two different methods for functionalizing CNTs to improve its purity, stability and dispersion in polymers, and then mix the functionalized CNTs with polymers to fabricate three well-performance CNTs-MMMs which can be applied in ultrafiltration, pervaporation and reverse osmosis. The main contents include the following four parts:(1) The purification and functionalization of pristine multi-walled carbon nanotubes (MWNTs). First, the pristine MWNTs were treated by mixed acid in ultrasonic bath for purification. After that, according to the chemical structure of polymers, two different functionalized methods were used. One was acyl-chlorination (MWNTs-COC1). MWNTs were treated by 5-isocyanato-isophthaloyl chloride (ICIC) and acyl-chloride group was successful grafted on it. The second was carboxylation (MWNTs-COOH). MWNTs were treated by diisobutyryl peroxide and carboxyl group was successful grafted on it. After functionalziation, not only the dispersibility of MWNTs in water and organic solvents was remarkably improved, but also well dispersed in different polymer matrix.(2) Preparation and property of MWNTs/polysulfone (PSF) ultrafiltration hybrid membranes. Blends of polysulfone and different composition of MWNTs-COC1 to prepare a series of ultrafiltration membranes by phase-inversion method. According to the SEM and TEM, it was found that the content of functionalized MWNTs was an important factor influencing the morphology and permeation properties of the blend membranes. In addition, SEM images of the blend membrane surface and cross-section showed that the average pore size and pore structure of the blend membranes changed with the content of functionalized MWNTs up to 0.19%, then decreased. The static water contact angle of membrane surface showed that the hydrophilicity was improved with increasing content of functionalized MWNTs in blends. In separation experiments, pure water flux of the blend membranes increased from 40 L/m2·h to180 L/m2·h with the content of functionalized MWNTs, until up to 0.19%, and then gradually decreased. Finally, protein adsorption performance of membrane indicated that MWNTs content suppressed the adsorption of protein on membrane, and thus alleviated membrane fouling.(3) Preparation and property of MWNTs/chitosan pervaporation hybrid membranes. A series of MWNTs-COOH incorporated chitosan membranes were prepared by phase-inversion method. The morphology of surface and cross-section of membrane were observed by SEM and TEM. XRD and IR were employing to analyse chemical structure of membrane surface. In swelling experiment, the swelling degree of hybrid membranes in ethanol/water mixtures was 6 times than that of the pristine chitosan membrane. According to the Fick’s law, the solubility and the diffusion coefficient of membranes in water, ethanol, and 90% ethanol/water mixtures were obtained. Compared with the calculated diffusion coefficient (D90), the measured diffusion coefficient (D90T) in 90% ethanol/water mixtures was higher, which indicated the functionalized MWNTs were more prone to increased water permeation when ethanol and water penetrated into the membrane simultaneously. In pervaporation experiment, the permeation flux of the membranes increased significantly with increasing functionalized MWNTs content in hybrid membrane in pervaporation. The effect of MWNTs content in the membrane matrix and operating temperature on pervaporation performance was investigated. After introducing functionalized MWNTs, the Arrhenius activation parameters for the total permeation decreased from 28.15 to 12.91 kJ/mol, which indicated that the carbon nanotubes filled membranes were easier to penetrate and exhibited higher flux performance than a pristine membrane.(4) Preparation and property of MWNTs/polyamide reverse osmosis composite membranes. Reverse osmosis composite membrane was prepared by interfacial polymerization of MPD with TMC on the surface of polysulfone support. The effects of monomers concentration, reaction time of IP, time and temperature of heat treatment on the separation performance of composite membranes were investigated. From the orthogonal experiment results, the optimum condition was obtained. In addition, the effects of phase-transfer catalyst and several alcohols as additions in water phase during IP on membrane performance were investigated, and the reason was also discussed. After that, MWNTs/polyamide reverse osmosis composite membranes were prepared by interfacial polymerization under the optimum condition. By comparing of structures, the surface of MWNTs/polyamide membrane was rougher than pure polyamide membrane, and some gaps occurred in polyamide layer because of micro-phase separation. Moreover, membrane surface became more hydrophilic and was decorated by more negative charges. In addition, after testing, the water flux of MWNTs/polyamide membrane was doubled than original polyamide membrane, and MWNTs/polyamide membrane could inhibit membrane fouling caused by organic or inorganic substances. The most important thing is the oxidation resistance of composite membrane has also been improved, the tolerance of active chlorine was up to 3000 ppm-h.In summary, the structure and performance of CNT mixed matrix membrane have more advantages than the original polymer membranes, and such hybrid membrane can break through the constraints of separation performance of traditional membrane, which provides an idea and method for the development of membrane technology.更多还原