多孔炭分子筛膜的应用研究

由于多孔炭分子筛膜具有均布的孔隙结构和较强的渗透通量,使其在生产和生活的诸多领域中得到了广泛应用。目前,国内外对多孔炭分子筛膜进行了大量研究,结果表明其可以根据分子筛分机理对混合物进行分离,特别对于分子直径较小气体的分离系数较高,在废水处理、气体分离、氢气回收等领域表现出优异的性能,具有广阔的发展前景。     

膜-生物硝化反应器处理含氨废水效能的研究

研究了膜 生物硝化反应器对含氨废水的处理效能以及分离膜的截留和渗透效能。膜_生物反应器启动迅速 ,在水力停留时间为 1d的情况下 ,反应器最高进水浓度达 80mmol(NH₄⁺-N)·L^-1 ,最高容积负荷达 1 12kg(NH₄⁺ -N)·m^-3·d^-1 ,氨氮去除率保持在 95%以上。试验证明 ,分离膜对微生物有良好的截留作用 ,50天内反应器的污泥浓度从 5g·L^-1 增长到 10g·L^-1 ,分离膜表面附着的生物层则对废水氨氮和亚硝氮有进一步的转化作用。在液位差低于 80cm时 ,提高液位差可增大膜渗透通量 ;液位差超过 80cm后 ,增大液位差的膜渗透通量效应很小 ;其中 ,当液位差为 2 0cm左右时 ,膜通量达 2 . 5 1L·m^-2 ·h^-1 ,阻力最小 [(2 . 6 3× 10^-5)m^-1]。该膜_生物硝化反应器可依靠液位差压力驱动出水 ,无需外加动力。     

应用中空纤维膜去除无细胞百日咳料液中的脱毒剂和色素

目的应用中空纤维膜洗滤技术去除无细胞百日咳料液中的脱毒剂和色素。方法采用不同浓度的盐溶液作为中空纤维膜洗滤液,通过洗滤过程的水通量衰减程度,洗滤后制品外观和蛋白回收率,原液戊二醛残留量,原液效价和毒力来确定洗滤液。用物理和化学清洗相结合的方式对使用后的膜进行清洗再生,以水通量恢复率对清洗效果进行评估。结果用盐溶液Ⅱ作为洗滤液,在洗滤过程维持跨膜压基本恒定的情况下,中空纤维膜水通量大、且衰减缓慢,洗滤后收集的制品外观呈淡黄色,蛋白颗粒均匀,蛋白回收率高,所制备原液的戊二醛残留量、效价和毒力检定结果均符合《中国药典》三部(2010版)要求。中空纤维膜使用后,用物理和化学清洗相结合的清洗方式使中空纤维膜的水通量恢复率分别达99.06%,98.11%,99.62%。结论中空纤维膜可用于去除无细胞百日咳料液中的脱毒剂和色素。     

葡萄糖淀粉酶在高压静电纺PEI/PVA纳米纤维膜上的离子吸附固定

旨在应用离子结合法将葡萄糖淀粉酶固定在PEI/PVA纳米纤维膜上并对其理化性质进行研究。采用高压静电纺丝技术制备聚乙烯亚胺(PEI)/聚乙烯醇(PVA)纳米纤维膜,采用热交联方法使其具备水稳定性后,再利用离子吸附法固定葡萄糖淀粉酶。结果显示,利用红外光谱(FT-IR)表征固定有葡萄糖淀粉酶的PEI/PVA纳米纤维膜,表明葡萄糖淀粉酶可成功固定在静电纺丝形成的PEI/PVA纳米纤维膜表面。通过固定化葡萄糖淀粉酶的酶学性质鉴定,发现固定化葡萄糖淀粉酶的最适反应温度为65℃,比游离的葡萄糖淀粉酶提高了6℃;固定化葡萄糖淀粉酶的适用p H值范围明显变宽;热稳定性和存贮稳定性显著增强且可以重复使用。利用离子吸附法能简便地将蛋白质分子固定于纳米纤维膜上,具有一定的应用前景。     

渗透汽化膜在生物燃料分离中的应用

生物燃料作为一种重要的可再生能源,近年来引起了各国越来越多的重视。生物燃料的发展不仅依赖于生物质转化为生物醇的过程,也依赖于净化和分离技术的突破。在众多分离方案中,以膜渗透汽化为基础的混合工艺提供了最直接有效的方法。本文简述了渗透汽化技术的基本原理和混合工艺设计,并重点介绍了笔者近年来应用渗透汽化技术在生物燃料分离方面的研究工作,从膜材料和膜形态两方面阐述了膜设计和膜制造的具体方案,举例说明了渗透汽化膜在生物醇脱水和回收方面的应用,最后讨论了该领域的发展趋势以及未来挑战。     

聚己内酯/柚皮素纳米纤维膜对白介素1β诱导的体外骨关节炎的作用研究

目的探讨聚己内酯(PCL)/柚皮素纳米纤维膜对白介素1β(IL-1β)诱导SD大鼠软骨细胞退行性变修复作用。方法使用静电纺丝技术分别制作PCL纳米纤维膜,PCL/柚皮素纳米纤维膜,使用扫描电子显微镜(SEM)观察纳米纤维膜的表征。提取3～5 d的SD大鼠软骨细胞,分为空白对照组、骨关节炎(OA)组、骨关节炎加PCL(OA+PCL)组、骨关节炎加PCL/柚皮素(OA+PCL/柚皮素)组,分别处理24 h后进行CCK-8实验检测各组SD大鼠软骨细胞的增殖情况,并进行活/死细胞染色,观察各组SD大鼠软骨细胞的毒性。提取各组SD大鼠软骨细胞的总RNA,使用qRT-PCR检测炎症及软骨标志基因的表达。结果与OA组相比,PCL/柚皮素纳米纤维膜组大鼠的细胞活性较高,细胞数量明显增多,炎症标志基因表达明显降低,软骨标志基因表达明显增高(均P0.05)。结论 PCL/柚皮素能降低IL-1β诱导的SD大鼠体外骨关节炎症标志基因的表达,对SD大鼠关节炎有一定治疗作用,且能上调关节炎细胞中软骨标志基因COL2a1的表达。     

纤维素乙醇发酵液中复杂组分对乙醇渗透汽化传质过程的影响

考察了木质纤维素乙醇发酵液中各组分对乙醇透过聚二甲基硅氧烷(PDMS)-silicalite-1渗透汽化膜传质性能的影响。结果表明:酵母细胞、玉米秸秆残渣和发酵用无机盐可增加乙醇通过膜的通量和选择性;而葡萄糖和甘油的存在会对乙醇的透膜传质产生负面影响;木质纤维素水解后的产物如糠醛和羟基丙酮,表现出对膜分离乙醇轻微的抑制作用。本文建立了渗透汽化优先透醇与纤维素乙醇发酵集成过程,批次发酵20 h后乙醇产率从最初的12.95下降到10.22 g/(L·h),60 h后乙醇产率下降为0,葡萄糖消耗速率与乙醇消耗产率呈同样趋势;连续发酵过程中,乙醇产率较稳定地维持在13.30 g/(L·h)。实验证明,集成过程可及时地将产物乙醇分离出去,能够有效地消除产物抑制,提高乙醇生产速率和葡萄糖转化率。     

PLLA短纤维涂覆多孔HA支架的制备

细胞外基质的重要成分——胶原蛋白,主要以纳米纤维的形式存在并构成纳米纤维多孔网架,因此,构建具有类细胞外基质结构的仿生支架可能为细胞在体外的生长提供理想的微环境。本实验中,采用静电纺丝技术制备聚乳酸纳米纤维,并采用铜板切片法对纤维膜进行短切得到PLLA短切纤维,其中,单根纤维的长度在500μm左右。选用海藻酸钠作为PLLA短纤维的分散剂,将PLLA短纤维均匀的分散在海藻酸钠溶液中,形成短纤维的悬浊液,然后在多孔羟基磷灰石支架表面均匀的涂覆,用氯化钙交联海藻酸钠使纤维固定在支架表面。制得纤维复合支架。用扫描电镜观察复合支架微观形貌可观察到支架表面纤维分散均匀,并且未出现堵孔现象。     

壳聚糖絮凝纯化香菇多糖的研究

研究了壳聚糖对香菇多糖提取液的沉降作用,考察了壳聚糖用量、沉降时间、溶液酸度对吸附色素、沉降蛋白质和多糖损失的影响,同时考察了壳聚糖对超滤膜分离初始膜通量的影响。实验结果表明壳聚糖对香菇多糖提取液中色素和蛋白质具有较好的絮凝沉降效果,当壳聚糖的用量为5.0mg/mL,絮凝沉降时间为40min,溶液pH为5.0时,60r/min的转速搅拌条件下,色素含量降低了约28%,蛋白质含量降低了42%左右,而多糖含量只损失8.9%左右,溶液粘度降低了11.8%,采用超滤分离时,经壳聚糖沉降的多糖溶液初始膜通量增加了14%左右。     

耦合中空纤维膜超滤分离游离细胞催化合成ATP

对耦合中空纤维膜超滤分离进行游离细胞催化合成ATP过程进行了实验研究,考察了细胞的催化效率和膜组件的操作稳定性。结果显示,中空纤维超滤膜的耦合分离能有效地截留反应液中的游离酶,其中乙醇脱氢酶(ADH)和已糖激酶(HK)的稳态截留效率在95%以上。耦合膜分离的酵母细胞催化ATP合成反应可重复使用2.5～3.0次,酶的利用率比普通分离的细胞提高2.0～2.5倍。中空纤维超滤膜于0.1Mpa工作压力下连续11批耦合分离操作,膜的渗透性无明显下降,过滤速率保持在初速率的95%以上。在稀释速率0.25h-1下,反应体系保持了连续5h的ATP高转化率合成与分离耦合的拟稳态操作。     

Ultrafine polysaccharide nanofibrous membranes for water purification

Ultrafine polysaccharide nanofibers (i.e., cellulose and chitin) with 5-10 nm diameters were employed as barrier layers in a new class of thin-film nanofibrous composite (TFNC) membranes for water purification. In addition to concentration, the viscosity of the polysaccharide nanofiber coating suspension was also found to be affected by the pH value and ionic strength. When compared with two commercial UF membranes (PAN10 and PAN400), 10-fold higher permeation flux with above 99.5% rejection ratio were achieved by using ultrafine cellulose nanofibers-based TFNC membranes for ultrafiltration of oil/water emulsions. The very high surface-to-volume ratio and negatively charged surface of cellulose nanofibers, which lead to a high virus adsorption capacity as verified by MS2 bacteriophage testing, offer further opportunities in drinking water applications. The low cost of raw cellulose/chitin materials, the environmentally friendly fabrication process, and the impressive high-flux performance indicate that such ultrafine polysaccharide nanofibers-based TFNC membranes can surpass conventional membrane systems in many different water applications.     

Surface modification of nanofibrous poly(acrylonitrile-co-acrylic acid) membrane with biomacromolecules for lipase immobilization

In this work, poly(acrylonitrile-co-acrylic acid) (PANCAA) was electrospun into nanofibers with a mean diameter of 180 nm. To create a biofriendly microenvironment for enzyme immobilization, collagen or protein hydrolysate from egg skin (ES) was respectively tethered on the prepared nanofibrous membranes in the presence of 1-ethyl-3-(dimethyl-aminopropyl) carbodiamine (EDC)/N-hydroxyl succinimide (NHS). Confocal laser scanning microscopy (CLSM) was used to verify the surface modification and protein density on the nanofibrous membranes. Lipase from Candida rugosa was then immobilized on the protein-modified nanofibrous membranes by covalent binding using glutaraldehyde (GA) as coupling agent, and on the nascent PANCAA nanofibrous membrane using EDC/NHS as coupling agent, respectively. The properties of the immobilized enzyme were assayed. It was found that different pre-tethered biomacromolecules had distinct effects on the immobilized enzyme. The activity retention of the immobilized lipase on ES hydrolysate-modified nanofibrous membrane increased from 15.0% to 20.4% compared with that on the nascent one, while it was enhanced up to more than quadrupled (activity retention of 61.7%) on the collagen-modified nanofibrous membrane. The kinetic parameter, K_m and V_max, were also determined for the free and immobilized lipases. Furthermore, the stabilities of the immobilized lipases were obviously improved compared with the free one.     

A simple approach to constructing antibacterial and anti-biofouling nanofibrous membranes

In this work, antibacterial and anti-adhesive polymeric thin films were constructed on polyacrylonitrile (PAN) nanofibrous membranes in order to extend their applications. Polyhexamethylene guanidine hydrochloride (PHGH) as an antibacterial agent and heparin (HP) as an anti-adhesive agent have been successfully coated onto the membranes via a layer-by-layer (LBL) assembly technique confirmed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), energy-dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The antibacterial properties of LBL-functionalized PAN nanofibrous membranes were evaluated using the Gram-positive bacterium Staphylococcus aureus and the Gram-negative Escherichia coli. Furthermore, the dependence of the antibacterial activity and anti-biofouling performance on the number of layers in the LBL films was investigated quantitatively. It was found that these LBL-modified nanofibrous membranes possessed high antibacterial activities, easy-cleaning properties and stability under physiological conditions, thus qualifying them as candidates for anti-biofouling coatings.     

Fabrication of gelatin/calcium phosphate composite nanofibrous membranes by biomimetic mineralization

Based on the principles of biomimetic mineralization, biocomposite nanofibrous membranes were fabricated by the growth of CaP crystals on electrospun gelatin nanofibers to mimic both the physical architecture and chemical composition of natural bone ECM. Plenty more CaP crystals formed on the nanofibrous membrane containing Ca(2+) ion precursors, in which these crystals were also observed on the inner side of membrane. The release rate of Ca(2+) ion precursors from the nanofibrous membrane was slower than that of PO(4)(3-) ion precursors, suggesting the existence of more strong intermolecular interaction between gelatin and Ca(2+) ions. ATR-FTIR and XRD results clearly revealed the formation of CaP crystals mixed with apatite and CaCO(3), or apatite and TCP on the membranes. The Ca/P molar ratio of crystals obtained from the XPS data was 2.03 and 1.60, which depended on the mineralization conditions. Higher amount of CaP crystals significantly accelerated the deposit rate of bone-like apatite on the surface of composite membrane, meaning to the improved in vivo bone bioactivity.     

Chitosan-modified poly(acrylonitrile-co-acrylic acid) nanofibrous membranes for the immobilization of concanavalin A

Lectin affinity membranes have been receiving much attention for the separation and detection of various glycoconjugates. In this work, we present a simple and efficient method for the preparation of lectin affinity nanofibrous membranes. Chitosan-modified poly(acrylonitrile-co-acrylic acid) (PANCAA) nanofibrous membranes were first prepared by a coupling reaction between the primary amino groups of chitosan and the carboxyl groups of PANCAA electrospun membranes. Surface characterizations by attenuated total reflectance Fourier transform infrared spectroscopy (FT-IR/ATR), X-ray photoelectron spectroscopy (XPS) and field-emission scanning electron microscopy (FESEM) confirm the chemical and morphological changes of the studied nanofibrous membranes. Fluorescence-labeled concanavalin A (FL-Con A) was then immobilized on these membranes via noncovalent binding. Analyses by fluorescence spectrophotometer (FS) and confocal laser scanning microscopy (CLSM) reveal that the immobilization of Con A onto the modified nanofibrous membranes has been successfully achieved on the basis of the electrostatic interaction and the specific recognition between Con A and chitosan. The results show that the amount of adsorbed FL-Con A increases dramatically with the increasing coupling degree of chitosan (CDC) on the nanofibrous membrane. Moreover, Con A immobilized on the chitosan-modified nanofibrous membranes (CMNMs) can remain relatively stable at pH 5.3. Therefore, it is believed that this work may provide a new kind of material for affinity application.     

Application of electrospun poly(ethylene terephthalate) nanofiber mat to apple juice clarification

Electrospinning was used to produce self-supporting nanofibrous poly(ethylene terephthalate) membranes with good mechanical properties and straightforward handling. The application of this type of membranes in apple juice clarification process was investigated. Processing characteristics and quality parameters of apple juice were analyzed in order to compare the proposed method to traditional clarification techniques. In general, the apple juice obtained from electrospun nanofiber membrane filtration revealed physico-chemical characteristics comparable to those from juice clarified by ultrafiltration or by conventional clarification using filtering aids. Nevertheless, the new process showed a high flux performance and revealed to be much faster, simple and more economical than the traditional processes. This work demonstrated the filtration potential of an electrospun PET membrane thus introducing a new concept of clarification and opening new approaches for the juice processing industry or even for other food industry fields.     

Electro-spinning and electro-blowing of hyaluronic acid

In this study, hyaluronic acid (HA) was electro-spun and electro-blown to prepare nonwoven nanofibrous membranes. Critical parameters for processing and corresponding effects on the membrane morphology were investigated using the methods of rheology and scanning electron microscopy (SEM). During electro-spinning, the optimal HA concentration window for nanofibrous formation was determined within a narrow range of 1.3-1.5 w/v %, corresponding to a solution viscosity range of 3-30 Pa s at a shear rate of 1 s(-1). SEM results indicated that, with increases in (1) the total concentration by blending of low molecular weight HA, (2) the evaporation rate by the addition of ethanol, and/or (3) the feeding rate of solution, the electro-spinning performance for creating nanofibers was improved. However, the improvement was not sufficient to achieve a consistent production of high quality nonwoven nanofiber membranes. This problem was overcome by a new electro-blowing process using the combination of air flow and electro-spinning. Although air blowing at room temperature around the spinneret orifice did not exhibit a remarkable enhancement of nanofiber formation of HA, the performance was significantly improved with an increase in the air blowing rate. SEM results showed that the temperature of air-blowing was the most effective parameter in ensuring HA nanofiber formation. As the temperature of the blown air increased from 25 to 57 degrees C, the nanofiber formation became consistent and uniform. A high quality HA nonwoven membrane of nanofibers was successfully produced by blowing air at 57 degrees C with a 70 ft(3)/hr flow rate.     

Electrospun poly(lactic acid)/chitosan core-shell structure nanofibers from homogeneous solution

The core-shell structure nanofibers of poly(lactic acid)/chitosan with different weight ratios were successfully electrospun from homogeneous solution. The preparation process was more simple and effective than double-needle electrospinning. The nanofibers were obtained with chitosan in shell while poly(lactic acid) in core attributing to phase separation, which were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). The electrospun nanofibrous membrane was evaluated in vitro by using mouse fibroblasts (L929) as reference cell lines. Cell culture results indicated that these materials were good in promoting cell growth and attachment, thus they could be used for tissue engineering and wound healing dressing.     

微小毛霉凝乳酶的分离纯化研究

研究微小毛霉(HL-1)凝乳酶的分离纯化条件及方法。研究酶的最适浸提温度、酶的浸提pH值和最适浸提时间,探讨离子浓度、加水量对浸提效率的影响,利用高速冷冻离心法、有机溶剂沉淀法,膜分离法和层析法等对粗酶液进行了分离。利用光谱法对纯化样品进行检测。酶的最适浸提温度为30℃;最适pH为6.0;浸提10 h活力最高;1%的氯化钠有利于酶的分离,加水比例为15时有利于提取,在10 000 r/min下离心10min澄清效果最好,95%的酒精沉淀效果最好,利用0.2μm的微滤膜可除去发酵液中的菌体,8 000的超滤膜可拦截凝乳酶蛋白,S300的填料可有效分离凝乳酶,纯度达95%以上。     

Core-shell structured PEO-chitosan nanofibers by coaxial electrospinning

Core-shell structured PEO-chitosan nanofibers have been produced using a coaxial electrospinning setup. PEO and chitosan solutions, both in an aqueous acetic acid solvent, were used as the inner (core) and outer (shell) layer, respectively. Uniform-sized defect-free nanofibers of 150-190 nm diameter were produced. In addition, hollow nanofibers could be obtained subsequent to PEO washing of the membranes. The core-shell nanostructure and existence of chitosan on the shell layer were confirmed by TEM images obtained before and after washing the PEO content with water. The presence of chitosan on the surface of the composite nanofibers was further supported by XPS studies. The chitosan and PEO compositions in the nanofibrous mats were determined by TGA analysis, which were similar to their ratio in the feed solutions. The local compositional homogeneity of the membranes and the efficiency of the washing step to remove PEO were also verified by FTIR. In addition, DSC and XRD were used to characterize the crystalline structure and morphology of the co-electrospun nonwoven mats. The prepared coaxial nanofibers (hollow and solid) have several potential applications due to the presence of chitosan on their outer surfaces.