Year of Publication

2019

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Engineering

Department

Chemical and Materials Engineering

First Advisor

Dr. Dibakar Bhattacharyya

Abstract

Future nanofiltration (NF) membranes used for selective separations of ions and small organic molecules must maintain performance in environments where high concentrations of total dissolved solvents or foulants are present. These challenges can be addressed through the development of composite membranes, as well as the engineering of enhanced surface properties and operating conditions for existing commercial membranes.

In this work, ion transport through commercial thin film composite (TFC) polyamide NF membranes were studied in both lab-prepared salt solutions and industrial wastewater. The dependence of several variables on ion rejection was investigated, including ion radius, ion charge, ionic strength, and temperature. The impact of scaling and increasing ionic concentration on membrane performance during recovery of industrial wastewater was investigated. Fouling of the membrane surface was reduced by enhancing commercial NF membrane surfaces via aqueous-phase esterification of lignin sulfonate.

NF membranes were also created utilizing an ionic liquid solvent (1-ethyl-3-methylimidazolium acetate) to integrate composite materials into cellulose. Composite materials such as graphene oxide quantum dots, iron III particles, and lignin have been shown to be interact strongly with cellulose in solution with ionic liquid and bind together cellulose chains via hydrogen bonds following nonsolvent induced phase inversion. Studies suggest the composite materials modify membrane surface chemistry and improve selectivity of small organic molecules (~300 nm) while allowing for the complete passage of ions.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2019.114

Funding Information

My research was supported through NSF KY EPSCoR program (Grant number: 1355438) and NIH-NIEHS-SRC (Award number: P42ES007380). Industrial partners such as Southern Company, Chevron, and UOP Honeywell have also contributed valuable funding to make this work possible.

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