【作者】 张晓光；

【导师】 杨基明； 高大勇；

【作者基本信息】 中国科学技术大学 ， 工程热物理， 2007， 博士

【摘要】 膜分离技术广泛应用于血液透析，血液净化等生物医学相关领域。常用膜组件的形式为中空纤维式的透析器，结构与管壳式的换热器非常类似。研究也主要集中在三个方面，中空纤维膜本身的研究、膜组件的传质过程的研究以及新的膜分离应用领域的开发。本文的研究工作也围绕这样一条主线完成。(1)本文首先制备中空纤维膜。浸没沉淀相转化法是最主要的制备中空纤维膜的方法，采用相转化干-湿纺丝工艺，以PAN／DMF／水(聚丙烯腈／二甲基甲酰胺／水)为三元制膜体系，以聚乙二醇PEG400作为成孔添加剂，运用自行加工设计的芯液桶、喷丝头等关键部件，实验制备了可以用于血液透析的聚丙烯腈中空纤维膜。通过显微镜观察中空纤维膜内径、外径、壁厚等宏观结构：用扫描电镜观察膜横断面及表面其他微观结构。探讨了纺丝液的压力、喷丝头尺寸、芯液压力以及卷绕速率等对中空纤维膜宏观结构(外径和壁厚)的影响。结合相转化法成膜理论，分析目前存在大孔缺陷的原因，找到改良中空纤维膜结构，避免缺陷的基本方法。结果表明：喷丝头尺寸对膜宏观结构起决定性影响，喷丝头尺寸越大，所得的中空纤维膜的尺寸也越大；纺丝液压力增大，纤维膜的内、外径、壁厚均增加；芯液压力增大，纤维膜的内外径增加，壁厚减少；适当增大喷丝头尺寸，减小纺丝液和芯液压力，可以减少纤维表面的穿孔，改善纤维膜的结构性能。(2)本文其次使用Matlab软件，同时考虑透析器外壳内壁面的影响和中空纤维随机排布的影响，通过假定恒定中空纤维表面浓度和恒定浓度流量两种类比传热问题中经常采用的边界条件，数值模拟了管外流场充分发展情况下，中空纤维透析器的管外传质，计算了透析器管外流场及浓度场分布以及不同填充密度情况下透析器管外传质系数，考察了壁面、中空纤维的随机排布方式、填充密度、管外流体的平均流速等对管外传质的影响，并与忽略壁面影响的结果进行比较。模拟结果表明：受中空纤维随机排布的影响，管外流场存在沟流现象，局部填充密度的不同导致流场分布不均匀；随机排布的方式对传质系数有较大的影响，但相比忽略壁面影响时的影响要小；管外流速越大，传质系数也越大；在所研究的中空纤维填充密度范围内(10％～50％)，随着填充密度的增大，透析器的管外传质系数先增大，后减小，变化幅度均较小，存在一个最佳的填充密度；与忽略壁面影响时的值比较发现，在填充密度较小时，壁面对传质有促进作用，填充密度较大时，则相反。(3)本文最后将透析膜分离方法应用到低温生物学领域，特别是细胞低温保存过程中低温保护剂的去除。成功搭建实验装置，研究各种因素对细胞溶液中渗透压变化的影响，结果表明：透析液侧预填充亚高渗的低温保护剂溶液或者高渗的盐水溶液，能够有效减缓初始时的渗透压突变。随着清洗过程进行，逐步加速血液和透析液的流速可以增大清洗效率，缩短清洗所需要的时间。两者结合可以得到最佳的清洗程序。分别运用透析法和常规离心方法做了去除红细胞低温保护剂甘油的实验，新方法冰冻-复温-洗涤后的红细胞计数回收率(％)为89.71±2.46(平均值±标准偏差)，血红蛋白回收率(％)为84.93±4.64，上清游离血红蛋白的含量(g／L)为0.66±0.13，所得冰冻-复温-洗涤后的红细胞悬液的渗透压(残余甘油的含量)为340.33±20.56mOsm，与传统离心方法所得结果相当，均达到了国家对冰冻洗涤红细胞的质量标准要求。清洗一个单位冰冻红细胞需要用时30-40分钟，远小于离心方法所需要的约2个小时。结果表明：与常规的离心洗涤法比较而言，本文方法能够快速有效安全地去除低温保存细胞悬浮液中的低温保护剂。设计自动控制的清洗系统，初步调试结果验证了其可行性和潜力，表明该系统将在医院、血液中心和细胞库等部门有很广阔的应用前景。更多还原

【Abstract】 Membrane separation has been widely used in biomedical related areas such as hemodialysis and hemopurification. The most commonly used membrane system is hollow fiber module whose configuration is similar to that of tube-shell heat exchanger. Investigations were mainly focused on the hollow fiber membrane preparation, mass transfer of hollow fiber modules and extending of its application. All the research work in this thesis will be explored around this topic.(1) Firstly, immersion precipitation is one of the most important methods for the production of hollow fiber membranes. In this paper dry-wet spinning technique was used during the preparation of dialysis hollow fiber membranes, three-component solution PAN/DMF/Water was chosen as the basic materials, PEG400 was chosen as the pore forming agent. The macro-morphology such as inner and outer diameter and wall thickness of the hollow fibers were observed by microscopy; the micro-morphology of the membrane surface and cross-section ware observed by SEM. The influence of some important spinning parameters such as spinning pressure, nonsolvency pressure, spinneret aperture and rolling rate were investigated. The appearance of some big bores in the hollow fiber surface was discussed based on phase transition theory. Some suggestions for avoiding the defects were presented and the optimized conditions for membrane formation were obtained.The results show that: the spinneret aperture is the key factor that determines the membrane macro-structure, the bigger the spinneret aperture the bigger the fiber size; the membrane inner ,outer diameter and it’s wall thickness increase with the spinning pressure; the membrane inner ,outer diameter increase and the wall thickness decrease with the nonsolvency pressure; with proper spinneret aperture, spinning and nonsolvency pressure, satisfactory fibers were obtained.(2) Secondly, Mass transfer coefficient is an important parameter to evaluate the performance of hollow fiber modules. With the help of Matlab software, the shell-side flow field was simulated numerically under the condition of well developed fluid flow. The theoretical model considers the effects of both the inner wall of the module shell and the random distribution of the hollow fibers on the shell-side mass transfer performance. For different packing density of hollow fibers, the concentration field and the shell-side mass transfer coefficients of dialyzers were obtained with the concentration boundary conditions of constant wall flux and constant wall concentration which are similar to the boundary conditions often used in heat transfer problems. Also the influence of flow rate to the mass transfer coefficient was studied. It was found that, because of the random distribution of hollow fibers channel flow exists in the shell-side flow field, The mass transfer coefficient increases with flow rate. Different packing patterns of hollow fibers result in different mass transfer coefficient values. This effect comes out more remarkable when neglecting the module wall effect. By varying the packing density from 10% to 50%, mass transfer coefficient increases first and then decreases experiencing a maximum value. Comparing to that with no wall effect, we found that, the wall effect promotes the mass transfer in a relatively low packing density but comes to the contrary as the packing density getting higher.(3) Lastly the dialysis membrane separation process is used in the field of cryobiology, especially in the process of removal cryoprotective agents(CPA) from cryopreserved cells.The experimental setup was established successfully to study the factors that affect the osmolality change(residual CPA concentration) in the cell suspension. The experimental results show that: i) during the initial time period, the sudden decrease of the osmolality can be avoided by prepriming the dialysate side with sub-hypertonic CPA solution or hypertonic saline solution. ii) As the washing process goes on, the residual CPA decreases slower and the washing efficiency decreases, this problem can be solved by increasing the blood flow rate and the dialysate flow rate. Through experiments the optimum procedure for removing CPA was found which can decrease both the osmotic shock to the cells and the wahing time.Further more experiments of the removal of glycerol from cryopreserved RBCs were done using the novel hollow fiber module dialysis method and traditional centrifugal method. Using the new method the Freeze-Thaw-Wash(FTW) RBC count recovery(%) is 89.71±2.46 (Mean±SD), hemoglobin recovery(%) is 84.93±4.64, the free hemoglobin concentration (g/L) is 0.66±0.13, and the osmolality of the FTW RBC suspension(the residual glycerol concentration) is 340.33±20.56mOsm .There is no significant difference between the results of centrifugal method. All these results satisfy the requirements of the national quality standards for freeze-thaw-wash RBCs . It takes only 30-40 minutes to wash one unit of frozen RBCs using the new method, which is much less than the 2 hours of the centrifugal method. The results show that compared to the traditional centrifugal method, this method is more efficient and safe.An automated washing system was designed based on the above progress. It was demonstrated that the new device has great potential to be used in hospitals, blood centers and cell banks et.al.更多还原