Graduation Year

2015

Document Type

Thesis

Degree

M.S.E.E.

Degree Name

MS in Electrical Engineering (M.S.E.E.)

Department

Electrical Engineering

Degree Granting Department

Electrical Engineering

Major Professor

Sylvia Thomas, Ph.D.

Committee Member

Norma Alcantar, Ph.D.

Committee Member

Andrew Hoff, Ph.D.

Keywords

Arsenic, Cactus Mucilage, Electrospinning, Life Cycle Analysis, Polystyrene, Poly Vinyl Alcohol

Abstract

This work investigates the fabrication, characterization and testing of Opuntia ficus-indica mucilage nanofibers to be utilized in water filtration systems. These mucilage nanofibers are formed using different polymers through a process called electrospinning. The polymers used to promote the formation of nanofibers are poly vinyl alcohol (PVA) and polystyrene (PS). The mucilage is a jelly like substance extracted from the pads of the cactus plant. It is a mixture of proteins, complex polysaccharides and monosaccharaides. It is an inexpensive, non-toxic, biodegradable and biocompatible material which is present in abundance. The mucilage extracted from the pads is mixed with acetic acid to form the mucilage solution. The mucilage solution is then mixed by volume with co-spinning polymers, PVA and PS. PVA is a synthetic polymer that is water-soluble, and this work considers two types of PVA differentiated based upon molecular weight, such as low molecular weight PVA and high molecular weight PVA. Polystyrene is a synthetic polymer extracted from a monomer styrene, and it is inexpensive, biodegradable, and abundant. The polystyrene, in its solid form, is further decomposed using a solvent called D-Limonene. D-Limonene is a biodegradable, non-toxic solvent formed from the citrus extract of orange peelings. The PVA and PS solutions are mixed in several different volume ratios with the mucilage solutions. These solutions were electrospun and consistent nanofibers were obtained using the low molecular weight PVA solutions and the polystyrene solutions. The fibers and polymeric solutions were characterized by scanning electron microscopy (SEM), contact angle measurements, viscosity, and FTIR. Resulting mucilage nanofiber membranes were characterized by atomic fluorescence spectrometry (AFS) filtration testing. In addition, a life cycle analysis using the SimaPro software was performed to understand the environmental impact of solutions used to fabricate the mucilage nanofiber membranes. Characterization results confirm the formation of PVA:mucilage and PS:mucilage nanofibers. Filtration testing of the nanofiber membranes indicates better performance with membranes formed by PS: mucilage solutions as compared to PVA: Mucilage solutions. Overall, this work has shown that natural materials, such as cactus mucilage, can be synthesized with polymeric solutions to form environmentally friendly water filters.

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