Date of Graduation

12-2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Chemical Engineering

Advisor/Mentor

Audie Thompson

Committee Member

Ranil Wickramasinghe

Second Committee Member

Xianghong Qian

Third Committee Member

Jamie Hestekin

Fourth Committee Member

Paul Millett

Keywords

Fouling, Green solvents, Membranes, Ultrafiltration

Abstract

Membrane fouling and sustainable production of membranes are two of the most important challenges in membrane science. Chapter 1 of this dissertation introduces these challenges and covers previous research that has been done in those areas. Additionally, the objectives of this dissertation are stated. In chapter 2, a study was done in which polyethersulfone ultrafiltration membranes were functionalized with copper oxide nanoparticles and zwitterions for the purpose of reducing fouling on the membrane surface. Characterization confirmed the attachment of each component to the membranes. Dead-end filtration was performed with water and bovine serum albumin solution and showed that the functionalization reduced flux decline caused by organic fouling. The copper oxide nanoparticles were stable, with minimal copper leached. In chapters 3 and 4, two different green solvents, Cyrene and gamma-valerolactone, were investigated for fabricating polysulfone ultrafiltration membranes. The solvents are potential replacements for toxic solvents, such as n-methylpyrrolidone, that are commonly used in membrane fabrication. Ultrafiltration membranes were successfully fabricated, characterized, and tested by dead-end filtration. For both solvents, casting membranes into coagulation baths with mixtures of water and ethanol led to membranes with better flux and rejection than casting membranes into coagulation baths of pure water or pure ethanol. The mechanisms of how coagulation bath composition influences membrane morphology were analyzed. In chapter 5, dissipative particle dynamics simulations were performed to test the effect of solvent viscosity on the dynamics of phase inversion during membrane formation. Solvent viscosity impacted the speed of phase inversion and final degree of agglomeration of polymer. In chapter 6, conclusions are drawn and recommendations for future work are given.

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