Electrospun and Vapor-Phase Deposited Electroactive Polymer Nanocomposites for Water Purification via Photocatalysis

The industrial revolution and the increase in commercial goods have resulted in significant environmental pollution. Synthetic dyes, especially azo dyes, are produced in millions of kilograms for use in textile and dyeing industries [3]. Amounts as low as <1 ppm of these organic pollutants can be fatal for aquatic ecosystems [4] and pose significant threat to humans considering the global drinking water scarcity that has been increasing for the past two decades. Existing techniques used to remove organic pollutants from water are adsorption, reductive and oxidative processes, bioremediation, separation by membranes, phytoremediation, catalysis and liquid-liquid extraction [1, 5]. These technologies are however limited due to inefficient mineralization of synthetic dyes, excessive production of sludge, dense solution disposal, high energy requirements and high operational costs [6]. Low-cost decontaminating materials that can be powered through naturally existing energy sources are desperately needed to reduce water contamination. Current research for the degradation of organic azo dyes focuses on advanced oxidative processes (AOPs). AOPs comprise a range of newly developed efficient techniques for conversion of toxic and resistant organic contaminants into less environmentally harmful minerals [7]. Oxidative catalysis is a method which produces active radicals under mildly reactive conditions [7]. These active oxidizing radical species then react with organic pollutants to break them down into harmless species [7, 8]. Photocatalysis is one of the most promising AOPs. Photocatalysis, when mediated by the right materials, can take place under ultraviolet (UV) and visible wavelengths of sunlight for breakdown of organic molecules. Photocatalysis mediated through visible light avoids the need for large and expensive UV lamps in areas lacking drinking water purification facilities. In the present work, we electrospun the commodity polymer polyacrylonitrile (PAN) to form the supportive structure of photocatalytic membranes. The role of PAN as carrier polymers or commodity polymer is to provide mechanical strength and robustness as nanocomposite electrospun fibers. Titanium dioxide (TiO2) nanoparticles were embedded within the nanofibers to act as photocatalysts. Electroactive polymers (EAPs) were then coated onto the PAN/TiO2 nanofibers, resulting in photocatalytic composites that offer a lower the bandgap. This adjustment of bandgaps enables absorption of visible light, requiring less energy to promote photocatalysis [9]. The results of this dissertation are divided into three main goals: (1) Electrospinning of Composite Nanofibers. A high molecular weight commodity polymer i.e., PAN, was used to produce nanofibers mats. The photocatalyst titanium dioxide (TiO2) as was incorporated into PAN solution for electrospinning to result in nanocomposite fiber mats with photocatalyst. The morphology and elemental composition of electrospun nanofibers were investigated using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS), respectively. (2) Coating of EAPs onto Composite Nanofibers. The second goal involved oxidative polymerization of electroactive polymers onto electrospun nanofibers, first via solution-phase as proof of concept, and later using the more scalable process of vapor-phase deposition (VPD). That is, once TiO2-loaded PAN nanofiber mats were developed, EAP precursors of choice i.e., 3,4-ethylenedioxythiophene (EDOT), pyrrole (Py), 2,2- bithiophene (BT) and 3-hexylthiophene (3HT) were polymerized onto them. Evaluation of obtained VPD coupons was carried out with scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDS). Functional group analysis performed using Fourier transform infrared spectroscopy (FTIR). (3) Evaluation of Dye Removal Performance of EAP-Coated Nanofiber Composites. The ability of the EAP-coated nanofibers to remove dyes was evaluated using a solar simulator system. Two organic dyes were chosen for dye removal studies of contaminated water: methylene blue (MB) and methyl orange (MO). Selection of one cationic (MB) and other anionic (MO) dye was intentional to help discriminate between photocatalysis and ionic exchange processes that might be occurring because of interactions between the EAP coating and the dyes. To evaluate dye removal, a series of dilutions of aqueous MB and MO solutions was produced to prepare calibration curves, and eventually MB and MO were placed in contact with VPD-electrospun nanofiber coupons and irradiated under a solar simulator to evaluate the ability of EAP-coated PAN/TiO2 nanocomposite to act as photocatalyst. UV-Vis spectroscopy was utilized to monitor dye removal. Our novel idea aims to facilitate remote water purification (requiring no artificial UV lamps) using merely natural resources (i.e., via solar-based photo-catalysis) and avoiding the need for artificial light resources. The choice of fabrication techniques like electrospinning and vapor-phase deposition is intentional as both techniques are scalable at industrial level. The proposed water purification system via photocatalysis takes advantages of each of the materials’ properties with PAN as the inexpensive, easy-to-electrospin commodity polymer, TiO2 as the naturally available photocatalyst, and easily applied EAPs to enable visible light activation. This nanocomposite material is ideally suited and will be important for textile industry-heavy places like in South Asia and others.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Materials Science, Engineering, and Commercialization

Grantor

Texas State University

Year dc:date.issued

2026

Author dc:creator

• ur Rehman, Junaid

Advisors dc:contributor.advisor

• Betancourt, Tania
• Irvin, Jennifer

Committee members dc:contributor.committeemember

• Kerwin, Sean
• Hwang, Sangchul
• Anderson, Joyce

• electrospinning
• vapor-phase deposition
• electroactive polymers
• water purification

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10877/24477

OAI identifier oai:identifier

oai:digital.library.txst.edu:10877/24477