Doctoral Dissertations

Date of Award

5-2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemical Engineering

Major Professor

Thomas A Zawodzinski

Committee Members

Joseph Bozell, Robert Counce, Arthur Ragaskas

Abstract

The use of biomass as a viable, renewable feedstock for the production of energy and as a surrogate for the petrochemical industry has generated a tremendous amount of research over the last 40 years. With lignin comprising 25- 35% by weight of the dry mass of much of that material, much time and energy has been devoted to investigating a viable, scalable value-added proposition for the use of lignin and lignin pre-cursor materials. The bulk of lignin produced today comes as a by-product of the de-pulping process in the production of paper – most of which is used as a combustion fuel by these paper plants to offset their carbon footprint. Considering that lignin has a heating value generally considered to be about half that of most industrial combustion fuels and that the heterogeneous nature of lignin lends itself well to chemical production, the burning of lignin is an inelegant use of its potential.

With this premise in mind, we have functionalized unmodified organosolv lignins to attempt to utilize them as a structural scaffold to increase the chemical and mechanical durability of various polymer materials for usage as anion exchange membranes (AEMs). The modifications, which can be selective based on the native reactivity of the modification sites, not only impart structural support to the polymer matrix, but also ionic character to increase the ion exchange capacity (IEC) of the polymer. By altering the concentration of the modified lignin, as well as other ionic and cross-linking constituents, we can the improve the mechanical and chemical properties of the polymer to make a strong case for the premise that the addition of lignin increases the polymer’s ability to accept a higher loading of charge sites before precipitation. By measuring conductivity, water uptake, IEC and the number of water molecules per ion, we are able to make determinations regarding the link between synthetic modifications and performance properties of the membrane.

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