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Advanced imaging as a novel approach to the characterization of membranes for microfiltration applications.

机译：先进的成像技术是微滤应用中膜表征的一种新颖方法。

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摘要

The primary objectives of my dissertation were to design, develop and implement novel confocal microscopy imaging protocols for the characterization of membranes and highlight opportunities to obtain reliable and cutting-edge information of microfiltration membrane morphology and fouling processes.;After a comprehensive introduction and review of confocal microscopy in membrane applications (Chapter 1), the first part of this dissertation (Chapter 2) details my work on membrane morphology characterization by confocal laser scanning microscopy (CLSM) and the implementation of my newly developed CLSM cross-sectional imaging protocol. Depth-of-penetration limits were identified to be approximately 24 microns and 7-8 microns for mixed cellulose ester and polyethersulfone membranes, respectively, making it impossible to image about 70% of the membrane bulk. The development and implementation of my cross-sectional CLSM method enabled the imaging of the entire membrane cross-section. Porosities of symmetric and asymmetric membranes with nominal pore sizes in the range 0.65-8.0 microns were quantified at different depths and yielded porosity values in the 50-60% range. It is my hope and expectation that the characterization strategy developed in this part of the work will enable future studies of different membrane materials and applications by confocal microscopy.;After demonstrating how cross-sectional CLSM could be used to fully characterize membrane morphologies and porosities, I applied it to the characterization of fouling occurring in polyethersulfone microfiltration membranes during the processing of solutions containing proteins and polysaccharides (Chapter 3). Through CLSM imaging, it was determined where proteins and polysaccharides deposit throughout polymeric microfiltration membranes when a fluid containing these materials is filtered. CLSM enabled evaluation of the location and extent of fouling by individual components (protein: casein and polysaccharide: dextran) within wet, asymmetric polyethersulfone microfiltration membranes. Information from filtration flux profiles and cross-sectional CLSM images of the membranes that processed single-component solutions and mixtures agreed with each other. Concentration profiles versus depth for each individual component present in the feed solution were developed from the analysis of the CLSM images at different levels of fouling for single-component solutions and mixtures. CLSM provided visual information that helped elucidate the role of each component on membrane fouling and provided a better understanding of how component interactions impact the fouling profiles.;Finally, Chapter 4 extends the application of my cross-sectional CLSM imaging protocol to study the fouling of asymmetric polyethersulfone membranes during the microfiltration of protein, polyphenol, and polysaccharide mixtures to better understand the solute-solute and solute-membrane interactions leading to fouling in beverage clarification processes. Again, cross-sectional CLSM imaging provided information on the location and extent of fouling throughout the entire thickness of the PES membrane. Quantitative analysis of the cross-sectional CLSM images provided a measurement of the masses of foulants deposited throughout the membrane. Moreover, flux decline data collected for different mixtures of casein, tannic acid and beta-cyclodextrin were analyzed with standard fouling models to determine the fouling mechanisms at play when processing different combinations of foulants. Results from model analysis of flux data were compared with the quantitative visual analysis of the correspondent CLSM images. This approach, which couples visual and performance measurements, is expected to provide a better understanding of the causes of fouling that, in turn, is expected to aid in the design of new membranes with tailored structure or surface chemistry that prevents the deposition of the foulants in "prone to foul" regions. (Abstract shortened by UMI.).
机译：本论文的主要目的是设计，开发和实施新颖的共聚焦显微镜成像方案，以表征膜，并突出机会获得可靠的尖端微滤膜形态和结垢信息。共聚焦显微镜在膜应用中的应用（第1章），本论文的第一部分（第2章）详细介绍了我通过共聚焦激光扫描显微镜（CLSM）进行膜形态表征的工作以及我新开发的CLSM截面成像协议的实现。对于混合的纤维素酯和聚醚砜膜，渗透深度极限分别约为24微米和7-8微米，因此无法对约70％的膜体积成像。我的横截面CLSM方法的开发和实施使整个膜横截面成像成为可能。在不同深度对标称孔径在0.65-8.0微米范围内的对称膜和不对称膜的孔隙率进行定量，得出的孔隙率值在50-60％的范围内。我希望并期望在本部分的工作中开发出的表征策略将能够通过共聚焦显微镜对未来的不同膜材料和应用进行研究。在展示了如何使用CLSM截面来完全表征膜的形态和孔隙率之后，我将其用于表征含有蛋白质和多糖的溶液在处理聚醚砜微滤膜时发生的结垢（第3章）。通过CLSM成像，可以确定在过滤包含这些材料的流体时，蛋白质和多糖在整个聚合物微滤膜中的沉积位置。 CLSM能够评估湿的，不对称的聚醚砜微滤膜内单个成分（蛋白质：酪蛋白和多糖：葡聚糖）的结垢位置和程度。来自处理单组分溶液和混合物的膜的过滤通量分布图和CLSM横截面图像信息相互一致。通过分析单组分溶液和混合物在不同结垢水平下的CLSM图像，可以得出进料溶液中每种单独组分的浓度曲线与深度的关系。 CLSM提供了可视信息，有助于阐明每个组件在膜结垢中的作用，并更好地了解了组件之间的相互作用如何影响结垢轮廓。最后，第4章将我的横截面CLSM成像方案的应用范围扩展到研究结垢的结垢。在蛋白质，多酚和多糖混合物的微滤过程中使用不对称聚醚砜膜，以更好地理解溶质-溶质和溶质-膜相互作用，从而导致饮料澄清过程中结垢。同样，横截面CLSM成像提供了有关PES膜整个厚度上结垢的位置和程度的信息。截面CLSM图像的定量分析提供了沉积在整个膜上的污垢质量的测量。此外，使用标准污垢模型分析了酪蛋白，鞣酸和β-环糊精的不同混合物收集的通量下降数据，以确定处理不同污垢组合物时的污垢发生机理。将通量数据的模型分析结果与相应CLSM图像的定量视觉分析进行了比较。这种将视觉和性能测量结合起来的方法有望更好地了解结垢的原因，从而有望帮助设计出具有定制结构或表面化学特性的新膜，从而防止污垢沉积在“容易犯规”的区域。 （摘要由UMI缩短。）。

著录项

  • 作者

    Marroquin, Milagro.;

  • 作者单位

    Clemson University.;

  • 授予单位 Clemson University.;
  • 学科 Engineering General.;Engineering Chemical.;Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 244 p.
  • 总页数 244
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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