Date of Graduation

12-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Chemical Engineering

Advisor/Mentor

Qian, Xianghong

Committee Member

Wickramasinghe, S. Ranil

Second Committee Member

Clausen, Edgar C.

Third Committee Member

Chang, Yung

Fourth Committee Member

Hestekin, Christa N.

Keywords

HIC membranes; IEX membranes; polymer density; polymer chain length; binding capacity; protein purification

Abstract

Electrospun membranes are an attractive alternative to flat sheet membranes as absorbent with numerous advantages like high porosity, large specific surface area and ease of functionalization. This doctoral dissertation focuses on fabricating novel polymeric membrane adsorbents for protein separations and ammonium ion removal. Three distinctly different preparation methods including UV-initiated polymerization, atom transfer radical polymerization, and mixed-matrix formation, have been employed to fabricate the electrospun membranes. Overall, this study aimed to develop electrospun membranes with excellent separation efficiency for application in protein purification and ammonium ion removal.

Chapter 2 details the stepwise development of weak anion exchange membranes and subsequent application in protein purification. The static and dynamic binding capacities of functionalized electrospun PAN and PSf membranes are reported to be ~100 mg/mL and ~200 mg/mL, respectively. Further experimental investigation reveals that surface modification of electrospun membranes by grafting polymeric ligands can enhance protein adsorption due to increased surface area-to-volume ratio.

Chapter 3 details development of responsive electrospun membranes for hydrophobic interaction chromatography (HIC). The responsive HIC ligand explored in the scope of this study leverages the switch between hydrophobic to hydrophilic state depending on salt concentrations. Moreover, experimental results reveal substantial improvement in dynamic binding capacity and recovery by controlling the effects of polymer density and polymer chain length relative to flat-surface membranes.

Chapter 4 details a stepwise development of mixed-matrix membranes fabricated using an electrospinning method for ammonia removal. Moreover, fabrication of novel zeolite embedded electrospun membrane is also provided in detail. In the scope of this study, a maximum binding capacity of ~30 mg/gzeolite for the ammonium ions was obtained using the mixed-matrix membrane. Overall, more than 90% of total ammonia nitrogen (TAN) removal is reported from aquaculture wastewater with high water flux and excellent regeneration using 2 M NaCl solution.

Chapter 5 details a systematic study on the effects of feed conditions on viral clearance for different commercially available media. Experimental results using design of experiment methodology and provide an understanding of the mechanism of adsorption between different commercial products through charge density and porosity.

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