Doctoral Dissertations

Orcid ID

http://orcid.org/0000-0002-2775-1563

Date of Award

12-2020

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Natural Resources

Major Professor

Siqun Wang

Committee Members

Timothy M. Young, David P. Harper, Terry Liles

Abstract

Particulate matter (PM) pollution has become a global environmental issue because it poses threat to public health. To protect individuals from PM exposure, one common method is using air filters for indoor air purification. However, conventional air filters have various drawbacks, such as high air resistance, the filters are not fabricated with environmentally friendly technology, and they cannot be easily regenerated. In this dissertation, a new electrospun poly(vinyl alcohol) (PVA)/cellulose nanocrystals (CNCs) composite nanofibrous filter was successfully developed. This PVA/CNCs composite material was demonstrated as air filter for the first time. The CNCs improved the filtration performance by increasing the surface charge density of the electrospinning suspension and thereby reducing diameter of fibers. High PM2.5 removal efficiency was achieved (99.1%) with low pressure drop (91 Pa) at a relatively high airflow velocity (0.2 m s-1), under extremely polluted condition (PM2.5 mass concentration >500 μg m-3). The integral effect of various electrospinning suspension properties on filtration performance was also investigated using response surface methodology. With a face-centered central composite design, the operating parameters for fabricating PVA/CNCs air filters were optimized, and the optimum conditions were a suspension concentration of 7.34% and a CNCs percentage of 20%. Additionally, the water-soluble PVA/CNCs composite was converted to be completely water-resistant when the electrospun material was heated at 140 oC for only 5 min. The mechanism of the change of water solubility of the fibers was investigated systematically. Our results revealed that increased crystallinity is the key factor for improving the aqueous stability, and CNCs provided additional nucleation sites for PVA crystallization during both electrospinning and heating process. The heated filters were effectively regenerated by water washing and the filtration performance was satisfactorily maintained. Because both PVA and CNCs are nontoxic and biodegradable, no organic solvents or crosslinking agents were used in the whole fabrication process, and the heating process is facile, the method proposed in this dissertation for fabricating electrospun PVA/CNCs nanofibrous filters is environmentally friendly and cost-effectively. This new cellulose-based air filter, which possesses high removal efficiency for PM, low pressure drop, and long lifetime, is very promising.

Comments

Portions of this document were previously published on ACS Sustainable Chemistry & Engineering and Chemical Engineering Journal

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