【作者】 罗晓刚；

【导师】 张俐娜；

【作者基本信息】 武汉大学 ， 高分子化学与物理， 2010， 博士

【摘要】 高聚物吸附和分离树脂已广泛用于水处理、化工、生物医药、食品和环保等领域。不同大小和形貌的微球可用作微存储器、微反应器、微分离器和微结构单元。尤其,天然高分子微球由于可生物降解和生物相容,已广泛应用于色谱、分离科学、可控制载体和贮藏体、生物医药支撑体、环境和催化剂基体、食品方面和医药工业等领域,其中各类纤维素微球的需求量最大。然而,采用传统纤维素溶剂制备微球常常造成很大的环境污染,而采用纤维素衍生物制备微球则难以避免带有残留基团而影响性能。本工作主要是利用NaOH／尿素水溶液体系低温下直接溶解纤维素制备纤维素微球,并进行功能化修饰得到一系列尺寸由微米到毫米级以及不同功能的微球。同时,采用红外光谱(IR)、X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、振动样品磁强计(VSM)和凝胶渗透色谱-光散射联用(GPC-LS)等方法表征它们的结构和功能,并且评价它们在色谱、生物医用、水处理以及吸附和分离领域的应用。本工作主要创新点如下：(1)通过溶胶-凝胶转相法由纤维素溶液制备出粒径由微米到毫米级的再生纤维素微球；(2)利用纤维素微球的孔作为微反应器,通过原位法合成纳米的Fe304粒子,制备出新型磁性纤维素微球；(3)通过溶胶凝胶法创建生物催化剂载体微球,并有效固定化青霉素G酰化酶；(4)构建出包埋活性炭磁性纤维素珠粒吸附剂用于染料吸附；(5)构建出纤维素／甲壳素磁性复合微球吸附剂用于重金属离子吸附。本学位论文主要内容简述如下。纤维素溶解在预冷至-12℃的7wt%NaOH/12wt%尿素溶剂体系中,得到透明的纤维素溶液。通过溶胶-凝胶转相法由该纤维素溶液制备出再生纤维素微球(RCM)。这是一种利用可再生资源生产纤维素微球的绿色过程,而且使用后的纤维素微球可生物降解。通过改变制备工艺参数成功制备出粒径从5um到1mm的微球。随着分散剂的用量、油-水比和搅拌速度的增加,微球的尺寸迅速减小。RCM微球表现出较好的球形、纳米尺寸孔径,同时在它们水中具有良好的流动性能和染料吸附功能。装填此纤维素微球的制备型色谱柱具有很好的分级效率和较大的日分级产量。因此,RCM微球有望作为色谱填料材料,生物载体和生物吸附剂应用在实验室和工业上。利用湿态纤维素微球的孔作为微反应器,通过原位法合成了纳米级的Fe3O4粒子,制备出新型磁性纤维素微球。该方法简单、安全,而且制备的纤维素微球具有生物相容和生物降解性。结构分析表明Fe3O4纳米粒子均匀分布在纤维素基体中,这是由于纤维素与无机纳米粒子间具有强的相互作用。纤维素微球的孔作为微反应器能起到控制磁性粒子的生长及尺寸作用,这些磁性粒子对微球的磁诱导迁移和提高微球的靶向传递和释放均起重要作用。Fe3O4／纤维素复合微球表现出超顺磁性和灵敏的磁诱导迁移性。此外,该磁性微球具有对BSA优良的吸附性质,并符合Langmuir等温吸附模型。复合微球的pH敏感的BSA吸附和超顺磁性质在药物靶向传递和释放领域十分重要。通过溶胶-凝胶法成功制备了包埋Fe2O3纳米粒子的磁性纤维素复合微球,经过环氧氯丙烷修饰后用于配位固定化酶。青霉素G酰化酶(PGA)已成功地固定在这种多孔的磁性纤维素微球上。纤维素基体的微孔以及纤维素分子上-OH基的亲和力和磁性纳米粒子对酶的固定化起重要作用,它们协同作用保护了生物催化剂的结构和特性。固定化酶表现出较高的催化活性、热稳定性和pH值变化的容限,同时能重复利用。此外,固定化酶的磁性纤维素微球很容易通过磁场诱导作用从反应溶液中分离出来,便于重复使用。这种酶固定载体在生物催化剂领域具有应用前景。在浸没式撞击流反应装置中,通过共沉淀法成功合成了粒径为10nm的磁性γ-Fe203纳米粒子。同时,通过一种简单的滴落法包埋这种磁性纳米和活性炭粉末到纤维素基体中制备出吸附剂。利用二种含有不同电荷的染料(带正电荷的MB和带负电荷的MO)作为染料模型化合物评价此吸附剂的吸附效率。结果表明磁性纳米粒子和活性炭粉末有利于吸附剂球体的形成以及提高其吸附染料的能力。此纤维素复合吸附剂表现出对这两类染料有很高的吸附能力,且能更好地吸附MO。它们的吸附速率较快,在180min已完全达到吸附平衡,而且动态吸附数据可以通过伪二级动力学方程拟合。另外,此吸附剂能够再生和重复使用。它的磁学性质使它能够通过磁场诱导很容易从废液体系中移出。由此,这是一种可用于水处理的清洁和安全的“绿色”技术和方法。通过纤维素和甲壳素溶液在水体系共混制得甲壳素／纤维素混合溶液,然后加入磁性纳米粒子粉末(γ-Fe2O3),并且采用溶胶-凝胶转相法制备出磁性甲壳素／纤维素复合微球吸附剂。它们显示出磁诱导移动功能,而且该微球吸附剂具有多孔结构、较大的比表面积和对重金属离子的亲和力。它们对Pb2+、Cd2+和Cu2+有较高吸附率和回收率,它们吸附速度较快,在1-2h达到吸附平衡。温度对金属离子的吸附量影响不明显,而pH值对其影响较大。磁性甲壳素／纤维素复合微球用毕后可以通过磁场从反应溶液中分离出,重复使用。这种磁性复合微球吸附剂在工业水处理领域具有应用前景。总之,我们利用本实验室发明的新溶剂制备出纤维素溶液,然后用它构建不同粒径的纤维素微球。并且通过不同的方法,如原位生成无机纳米粒子、表面交联或活化、以及功能化创建功能化材料使它们适合应用于色谱填料、蛋白质的分离纯化、生物催化剂载体、染料吸附和重金属的吸附剂等领域。本论文为纤维素新型微球的制备及其结构和功能关系的建立提供了重要科学数据,因此不仅具有重要的学术价值和应用前景,而且符合国家可持续发展战略。更多还原

【Abstract】 Science and technology of polymeric microspheres (particularly natural polymer microspheres) and their dispersions have been developed rapidly for last three decades and the progress seems to be accelerated because the era demands fine materials, mesoscopic science, nanotechnology, etc. An important category of materials among natural polymers is polysaccharides. Among them, cellulose microspheres are the most widely applied to the maximum extent. Cellulose is the most abundant organic compound found on earth. Also, it is a renewable and a major biomass source. But almost all of these products have been prepared from toxic organic solvent or cellulose derivatives, leading it difficult to wash and to eliminate the residual groups, and then limited its bioapplication.In our laboratory, an environmental friendly novel cellulose solvent, namely NaOH/urea aqueous solution has been used. Cellulose could be rapidly dissolved in this solvent at low temperature. The aim of the present work was to investigate the cellulose microspheres from the cellulose solution.The novel development of this work is as follow:1. Regenerated cellulose microspheres (RCM) with diameter ranging from micro to millimeter were prepared successfully by sol-gel transition from the cellulose dope dissolved in NaOH/urea aqueous system at low temperature.2. Novel magnetic cellulose microspheres were prepared successfully by in situ synthesis of Fe3O4 in the cellulose pores as reaction micro-chamber. The Fe3O4/cellulose microspheres were found to exhibite sensitive magnet-inducted delivery and superparamagnetic properties.3. Magnetic cellulose microspheres (MCM) containing y-Fe2O3 were functionalized successfully by using epoxy chloropropane to promote the covalent immobilization of Penicillin G acylase (PGA).4. The magnetic nanoparticles and activated carbon were embedded in cellulose matrix to fabricate a dye sorbent via simple and "green" process.5. An efficient biodegradable heavy metal adsorbent, magnetic cellulose/chitin microspheres consiting of magneticγ-Fe2O3 nanoparticles (MCCM), were succesfully prepared by using sol-gel transition (SGT) method from cellulose and chitin drops in NaOH/urea aqueous solution.Regenerated cellulose microspheres with diameters from micro to millimeter were prepared successfully by sol-gel transition from the cellulose dope dissolved in NaOH/urea aqueous system at low temperature. It was a "green" process for the production of the regenerated cellulose microspheres from renewable raw materials, and the used microspheres were safe and biodegradable. By changing the process parameters, the spherical regenerated cellulose microspheres and beads which possessed the celluloseⅡcrystal structure and with diameters range from 5 um to 1 mm, could be created, and can be used both at laboratory and industrial scale. With a decrease in the dispersant dosage, oil-water ratio and stirring speed, the size of the microspheres increased rapidly. Moreover, the nano-scale pore of the microspheres could be easily regulated by physical dehydration method. The RCM microspheres exhibited good spherical shape, nano-scale pore, as well as better flow properties and adsorption capacity for the dyes. The preparative chromatographic column packed with these cellulose microspheres exhibited good fractionation efficiency and large throughput. Therefore, the RCM microspheres have promising applications as chromatographic packing, biocarrier and biosorbent materials.Novel magnetic cellulose microspheres were prepared successfully by in situ synthesis of Fe3O4 in the cellulose pores as reaction micro-chamber. This was a new, simple, and safe method for the preparation of the magnetic cellulose microspheres having biocompatibility and biodegradability through a "green" pathway. The Fe3O4 nanoparticles were dispersed uniformly in the cellulose matrix, as a result of a strong interaction between Fe3O4 and the cellulose. The micro-chamber in the cellulose microspheres facilitated to retain the shape and size of the Fe3O4 nanoparticles, which play an important role in both the creation of the magnet-induced transference, and the improvement of the targeting delivery and release. The Fe3O4/cellulose microspheres exhibited sensitive magnet-inducted delivery and superparamagnetic properties. Moreover, the magnetic microspheres possessed excellent adsorpton capacity on BSA, and could be described well by the Langmuir isotherms. The pH sensitivity of the BSA adsorption loading and the superparamagnetic properties of the magnetic microspheres will be very important for the bioapplications in the drug targeting delivery and release areas.Magnetic cellulose microspheres were functionalized successfully by using epoxy chloropropane to promote the covalent immobilization of enzyme. Penicillin G acylase was immobilized successfully in the porous structure of the magnetic cellulose microspheres. The existence of the cavity in the cellulose matrix and affinity forces from-OH groups and the Fe2O3 nanoparticles played an important role in the improvement of the enzyme immobilization, leading to the preservation of the structure and nature of biocatalyst. The immobilized PGA exhibited highly effective activity, thermal stability and enhanced tolerance to pH variations, as well as good reusability. Moreover, the cellulose magnetic microspheres loaded with PGA could be conveniently and easily separated from reaction solution, leading to recovery of the catalysts. The new immobilization carriers prepared from safe, low cost and biocompatible cellulose will have wide applications in the development of biocatalysts.Magnemite (y-Fe2O3) nanoparticles of about 10 nm were prepared in a submerged circulation impinging stream reactor. The magnetic nanoparticles and activated carbon were embedded in cellulose matrix to fabricate a sorbent via simple and "green" process. Two dyes including positively charged methylene blue (MB) and negatively charged methyl orange (MO) as models of organic dyes were adsorbed effectively by the MCB-AC beads. The Fe2O3 nanoparticles and AC in the MCB-AC could play an important role in both the formation of spherical shape beads and the improvement of the adsorption capacity. The MCB-AC beads exhibited high adsorption capacity for the two dyes, and could more strongly adsorb MO. The adsorption kinetics was fast with 180 min to reach equilibrium time, and the kinetic data were well fitted by a pseudo-second-order model. Furthermore, the sorbent could be regenerated and used repeatedly. The magnetic properties of the beads allow their separation from the effluent by applying a magnetic field, leading to the development of a clean and safe process for water pollution remedy. This work provided a new pathway for the preparation of the MCB-AC beads including theγ-Fe2O3 nanoparticles and AC, and this process is promising on a large scale production.Magnetic chitin/cellulose microspheres were successfully prepared by coagulating a blend of cellulose, chitin andγ-Fe2O3 nanoparticles in 7wt% NaOH/12wt% urea aqueous solution by sol-gel transition. This adsorbent has a porous structure, larger surface area and the affinity for heavy metal ions. The magnetic microspheres possessed excellent adsorpton capacity on heavy metal ions (Pb2+、Cd2+ and Cu2+). The adsorption kinetics was fast with 3-5h to reach equilibrium, and the kinetic data were well fitted by a pseudo-second-order model. The magnetic properties of the beads allow their separation from the effluent by applying a magnetic field, leading to the development of a clean and safe process for water pollution remediation. Moreover, the microspheres could be regenerated by treating with 1 mol/L HC1 aqueous solution. Therefore, we developed new environment-friendly microspheres prepared by a simple process for removal and recovery of heavy metals.This thesis is comprised of studies on pure cellulose microspheres and functionalized microspheres with different particle size created from cellulose in NaOH/urea aqueous solution by different method, such as sol-gel transition, surface modification, and physical and chemical blending. A series of scientific and technological problems were resolved. Through these studies, we developed a low-cost, nontoxic and "green" process for fabrication of cellulose microspheres materials on a large scale production. Therefore, we anticipate were great scientific significance and prospects for application of these materials which are used for out country and play a major role for a sustainable development.更多还原