Date of Graduation

12-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Biological and Agricultural Engineering

Advisor/Mentor

Jin-Woo Kim

Committee Member

Danielle J. Carrier

Second Committee Member

Joshua Sakon

Third Committee Member

Ed Claussen

Fourth Committee Member

Thomas A. Costello

Keywords

Cellulose Nanocrystals, Cellulose Nanofibers, Hardwoods, Lignocellulosic Biomass, Nanocellulose, Softwoods

Abstract

Production of nanocellulose from a variety of naturally abundant, locally available and industrially significant wood species provides an opportunity for diversifying the portfolio of traditional pulp and paper industries. The U.S. has a prolific forest products industry with a well-established infrastructure that could be utilized for optimized and customized production of cellulose nanomaterials. However, to achieve that, it is important to a) understand how biorefining strategies for complete fractionation of biomass affect the downstream processing of pulp into nanocellulose, b) maximize the yields of cellulose nanocrystals and nanofibers (CNCs and CNFs) from pretreated raw materials, and c) evaluate if the yields and properties of CNCs vary based on the wood species used as the starting material. In the first objective, effect of pre-extraction prior to kraft pulping on the yields and properties of CNCs and CNFs was evaluated, using loblolly pine as a model substrate. Differences between cellulose nanomaterials obtained from pre-extracted vs non-extracted pulp were found with respect to their yield, crystallinity index, surface charge, particle size and thermal stability. Overall, kraft pulp purity was found to be a significant factor impacting the quality and quantity of nanocellulosic materials. In the second objective, strong acid strong acid hydrolysis-based production of CNCs and CNFs from pre-extracted and fully bleached loblolly pinewood kraft pulp was optimized using response surface methodology. Conditions, with respect to acid concentration, temperature, duration and pulp particle size, that maximized CNC and CNF yields were identified. In the third objective, four wood species were evaluated for CNC production using strong acid hydrolysis conditions that were previously optimized for pinewood. Differences in the yield of CNCs among the four species was found to be strongly correlated with pulp purity. Differences in the morphological, thermal and mechanical properties were also observed, highlighting the tuning potential of CNCs based on raw material selection. This research will advance the production and targeted application of nanocellulose derived from wood biomass.

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