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Title: A bioinspired eco-friendly plant protein-based porous nanofibrous aerogels for multifunctional applications in water purification and oil/water separation
Authors: Wei, Xueqin
Advisors: Wang, Yi (ABCT)
Yao, Zhongping (ABCT)
Keywords: Water -- Purification
Oil pollution of water
Issue Date: 2019
Publisher: The Hong Kong Polytechnic University
Abstract: Oil-absorption plays an important role in many fields such as oil-spill cleanup, oil/water separation, and environmental remediation. Physical absorption using absorbent materials is generally considered to be one of the most effective countermeasures because it is simple, efficient, and fast. Porous materials with hydrophobicity are good candidates for oil absorption because the porous structure helps them to absorb oil in the presence of water. While hydrophobicity and oleophilicity are primary determinants of successful sorbents, biodegradability is also an important factor. Natural materials are biodegradable and environment friendly, avoiding secondary pollution. Corn zein is an abundant and reproducible biopolymer with excellent biodegradability and hydrophobicity in specific conditions. In this study, the bio-inspired zein scaffolds and gelatin/zein fibers were fabricated to obtain enhanced properties for applications in water purification and oil-water separation. In Chapter 3, zein nanofibers were fabricated using a facile and cost-effective method. Bio-inspired by the natural spider silk fibers, the scaffolds were formed from the dispersion of zein nanofiber in tert-butanol and their oil absorption capacities were investigated. Various fiber to solvent ratios, 1:0, 1:150, 1:125, 1:100, 1:75, were selected and the scaffolds, E0, E150, E125, E100, and E75, respectively, were obtained after freeze-drying. The zein scaffolds as well as the spider silk fiber scaffold (SSFS) were characterized using attenuated total reflection-fourier transform infrared spectroscopy (ATR-FTIR), water contact angle (WCA) goniometer, and scanning electron microscopy (SEM). The WCAs of the scaffolds E75, E100, E125, E150, E0, and SSFS were 106.120°, 100.233°, 103.125°, 98.265°, 110.743°, and 106.674°, respectively, which indicated that they were hydrophobic. The scaffolds exhibited enormously high absorbing capacities for organic liquids. The absorption capacity of the E0 in motor oil, diesel oil, pump oil, and olive oil was 91 g/g, 152 g/g, 77 g/g and 147 g/g respectively. The oil absorption capacity of the SSFS in motor oil, diesel oil, pump oil, and olive oil was 53 g/g, 29 g/g, 52 g/g and 31 g/g respectively. It was lower than that of the E0, but higher than that of most oil absorbents. The porosities of E150, E125, E100, E75 were much higher than that of E0 but the oil absorption capacities of these scaffolds were lower than that of E0. Hence, porosity has limited influence on oil absorption capacities and the organic solvent absorption capacity is related to the density of solvent. E0 and SSFS had good reusability for 30 cycles while other scaffolds were broken in absorption-squeezing cycles. It is thought that the formation of hydrophobic surface was mainly contributed by the enriched β-sheet content. E0 has similar molecular structure, hydrophobicity and oil absorption capacity to SSFS.
In Chapter 4, gelatin/zein nanofibers at various ratios in two different solvents 80% acetic acid and solution mixed by water/ethanol/acetic acid in the ratio of 6/2/2 were fabricated using electrospinning. The nanofibers exhibited excellent organic liquids absorption capacities with the highest oil absorption 109 g/g for olive oil, 48 g/g for diesel oil and 166 g/g for motor oil, approximately 4-6 times that of natural sorbents and nonwoven polypropylene fibrous mats. The morphology, diameter distribution, and porosity of the nanofibers were investigated. Their chemical structure, mechanical strength, hydrophobicity and thermal property were characterized using ATR-FTIR, mechanical test, water contact angle measurements and thermogravimetric analysis. The hydrophobicity of the fibers was increased by the increase of gelatin/zein and obtained the highest WCA (114.3°) with GZ ratio equals to 1:1. With a further increasing of zein or gelatin, WCAs were decreased. The gelatin/zein nanofibers in 80% acetic acid with weight ratios of 1:3 and 1:2 showed much higher elongation at break of 16.4% and 11.0%, according to mechanical tests. It indicated these nanofibers had good deformability and flexibility. The gelatin/zein composite nanofibers were also in high potential for emulsion separation and heavy metal ion absorption. This work suggested that the zein based scaffolds and composite gelatin/zein nanofibers have potentials as materials for oil absorption and filtration applications.
Description: xi, 87 pages : color illustrations
PolyU Library Call No.: [THS] LG51 .H577M ABCT 2019 Wei
Rights: All rights reserved.
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