UNDERSTANDING THE PROPERTY-PERFORMANCE RELATIONSHIPS OF MEMBRANE ACTIVE LAYERS CONTAINING POROUS NANOPARTICLES Public Deposited

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  • March 21, 2019
Creator
  • Perry, Lamar
    • Affiliation: College of Arts and Sciences, Department of Applied Physical Sciences, Materials Science Graduate Program
Abstract
  • Thin-film nanocomposite (TFN) membranes for water purification have emerged in the last decade as a class of membranes that can provide increased water productivity over traditional thin-film composite (TFC) membranes, but still maintain the same level of contaminant rejection. The mechanisms by which the increased water permeability is achieved are not well understood as there are no comprehensive studies on the relevant structure-performance relationships. Accordingly, the overall objective of this study was to advance the understanding of the property-performance relationships of TFN membranes containing porous nanoparticles in their active layers. Towards achieving my overall objective, I pursued the following specific objectives: (i) to develop a method to measure charge density in active layers of polyamide-based TFC and TFN membranes; (ii) to characterize the effect of LTA zeolite loading on the physico-chemical properties of the active layers of zeolite TFN membranes, and investigate their corresponding structure-performance relationships; and (iii) to characterize the effect of ZIF8 nanoparticle loading, surface area, and size on the performance of ZIF8-TFN membranes, and investigate their corresponding structure-performance relationships. Overall, the results obtained in this study showed that zeolite and ZIF8 nanoparticle incorporation into active layers results in higher water productivity, and unchanged salt rejection up to a zeolite loading threshold above which salt rejection decreases (~0.15 wt% in the organic TMC solution used to cast the active layer). Results and analyses also showed that the observed changes in the physico-chemical properties of the active layer polymer did not explain the observed changes in membrane performance. Therefore, it is concluded that the increased water productivity of TFN membranes over the control TFC membranes is the result of water transport through the porous structure of LTA zeolite and ZIF8 nanoparticles, or along the polymer-nanoparticle interface. Alternatively, nanoparticle incorporation may have changed properties of the active layer polymer not characterized in this study (i.e., water diffusivity, or microstructure) in such a way such that it led to greater water permeability.
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  • In Copyright
Advisor
  • Coronell, Orlando
  • You, Wei
  • Superfine, Richard
  • Lind, Mary Laura
  • Lopez, Rene
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2017
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