Functionalisation of polymer nanofibres and track-etched membrane removal of organic and and inorganic pollutants from water

Philosophiae Doctor - PhDOrganic and inorganic pollutants are two broad classes of pollutants in the environment with their main sources from waste waters that are indiscriminately dumped from chemical related industries. Among the organic pollutants are dyes that come as effluents from the textile industries. Toxic metals are the main inorganic pollutants with their sources from industries such as mining, electroplating, batteries etc. The presence of both classes of pollutants in the aquatic environment poses a serious threat to aquatic organisms and humans who depend on these waters for domestic purpose. Therefore, this research focused on the fabrication of materials and designing of methods for removal of both classes of pollutants from their aqueous solutions

Photocatalytic and antifouling properties of electrospun TiO2 polyacrylonitrile composite nanofibers under visible light

Polyacrylonitrile and its TiO2 composites were electrospun into nanofibers in N, N’-dimethylformamide for photocatalysis and antifouling experiments. The resultants nanofibers were characterized using field emission scanning microscope, Fourier transform infrared spectroscopy, x-ray diffraction, x-ray photoelectron spectroscopy and contact angle analyses. Fourier transform infrared spectroscopy confirmed the formation of polyacrylonitrile-TiO2 composite nanofibers with their diameter ranging from 10 to 340 nm. The x-ray photoelectron spectroscopy results indicate the formation of O–Ti–C bonds on polyacrylonitrile-TiO2 matrix. polyacrylonitrile-TiO2 and polyacrylonitrile nanofiber surfaces showed superhydrophobicity with water contact angle of 155 ± 1 and 154 ± 1, respectively at 120 s. The photocatalytic properties of polyacrylonitrile nanofibers and polyacrylonitrile-TiO2 nanofibers were investigated under a simulated visible light source of 1000 W/m2 using methylene blue. About 90% of methylene blue was degraded within 3 h of exposure using polyacrylonitrile-TiO2 nanofibers while 55% methylene blue degradation was achieved for polyacrylonitrile nanofibers

Fabrication and characterization of electrospun waste polyethylene terephthalate blended with chitosan: A potential single-use material

Textile single-use products are dominantly used for hygiene and personal care, many of which are non-biodegradable and are frequently discarded into sewerage systems, thus causing blockages. Thus, there is a need to move towards water-soluble textiles. This research study focuses on transforming or repurposing biomass material and synthetic reusable waste plastic materials to improve waste. Chitosan (CS) nanofibers could be used in single-use nonwoven fabric or biodegradable tissues, as the water-soluble properties of chitosan nanofibers make them the perfect material for single-use applications. Furthermore, CS was blended with polyethylene terephthalate (PET) polymer and PET-based waste plastic (CS-WPET) to slow the CS nanofibers’ water degradability and strengthen the durability of the nanofiber which could be used as air filters. The CS-TFA and CS-TFA/DCM nanofiber diameters were 95.58 ± 39.28 nm or 907.94 ± 290.18 nm, respectively, as measured from the HRSEM images. The CS-PET and CS-WPET hybrid nanofibers had fiber diameters of 246.13 ± 96.36 or 58.99 ± 20.40 nm, respectively. The thermal durability of the nanofibers was tested by TGA, which showed that CS-TFA/DCM nanofibers had sufficient thermal stability up to 150 ◦C, making them suitable for filter or fabric use at moderate temperatures. The blended nanofibers (CS-PET and CS-WPET) were thermally stable up to 160 ◦C. In the aqueous medium stability test, CS-PET and CS-WPET hybrid nanofibers had a slower degradation rate and were easily dissolved, while the CS nanofibers were rapidly and completely dissolved in an aqueous medium. Blending waste PET with CS allows it to be recycled into a useful single-use, non-woven textile, with greater water solubility than unmodified PET nanofibers but more durability than CS nanofibers on their own

Fabrication of silver‑coated PET track‑etched membrane as SERS platform for detection of acetaminophen

In this study, silver nanoparticles (AgNPs) were immobilized on the surface of polyethylene terephthalate (PET) membrane using diethylenetriamine (DETA) as a chemical linker. The molecule of DETA was attached to the surface of PET via an amide bond following scission of the polyester ester bond on the PET surface. The AgNPs were immobilized on the surface of diethylenetriamine-modifed PET membrane via a silver-nitrogen covalent bond. The silver-coated, DETA-modifed and unmodifed PET membranes were characterized by Fourier transform infrared (FTIR), x-ray photoelectron spectroscopy (XPS), ulltraviolet-visible spectroscopy (UV–Vis), and scanning electron microscopy (SEM). The results showed that the size of AgNPs also increased with time of immobilization. The percentage of elemental silver also increased with increase in time of immobilization of AgNPs on the surface of DETA-modifed PET membrane. The AgNP-coated PET membrane was used as SERS platform to detect acetaminophen in water. The SERS results showed that acetaminophen molecules could be detected with high Raman scattering intensity arising from adsorption of acetaminophen molecules on the silver nanoparticles of the SERS platform

Chitosan/PEO nanofibers electrospun on metallized track-etched membranes: fabrication and characterization

The development of next-generation adsorption, separation, and filtration materials is growing with an increased research focus on polymer composites. In this study, a novel blend of chitosan (CS) and polyethylene oxide (PEO) nanofiber mats was electrospun on titanium (Ti)-coated polyethylene terephthalate (PET) track-etched membranes (TMs) with after-treatment by glutaraldehyde in the vapor phase for enhancing the nanofiber stability by crosslinking. The prepared composite, titanium-coated track-etched nanofiber membrane (TTM-CPnf) was characterized by Fourier transform infra-red (FTIR), water contact angle, and scanning electron microscopy (SEM) analyses. Smooth and uniform CS nanofibers with an average fiber diameter of 156.55 nm were produced from a 70/30 CS/PEO blend solution prepared from 92 wt. % acetic acid and electrospun at 15 cm needle to collector distance with 0.5 mL/h flow rate and an applied voltage of 30 kV on the TTM-CPnf. Short (15 min) and long (72 h)-term solubility tests showed that after 3 h, crosslinked nanofibers were stable in acidic (pH = 3), basic (pH = 13), and neutral (pH = 7) solutions. The crosslinked TTM-CPnf material was biocompatible based on the low mortality of freshwater crustaceans Daphnia magna. The composite membranes comprised of electrospun nanofiber and TMs proved to be biocompatible and may thus be suitable for diverse applications such as dual adsorption–filtration systems in water treatment

Surface-modified polyacrylonitrile nanofibers as supports

Polyacrylonitrile nanofibers (PAN-nfs) are one of the most studied nanofibres because of their excellent characteristics, such as good mechanical strength, chemical resistance, and good thermal stability. Due to the easy dissolution in polar organic solvents, PAN-nfs are mostly produced via electrospinning technique. The electrospun PAN-nfs surfaces are relatively in-active and hydrophobic, and, therefore, hinder some potential applications; however, chemical surface modification reactions, such as amination, reduction, hydrolysis, and amidoximation, have been carried out on them. These reactions bring about functional groups, such as amine, hydroxyl, carboxylic, imine etc, to the surface PAN-nfs and invariably make their surfaces active and hydrophilic. The surface-modified PAN-nfs have been used as supports for organic compounds, enzymes, and antibodies in biological studies. They have also been used for immobilization of various organic ligands for adsorption of metal ions in water. Furthermore, because of their ability to complex metal ions, several surface-modified PAN-nfs have also been used as supports for transition metal catalysts in Fenton’s chemistry.IS

Metal Specific Functionalized Nanofibers

Functionalized nanofibers made by electrospinning technique. [...

Adsorptive Recovery of Cu²⁺ from Aqueous Solution by Polyethylene Terephthalate Nanofibres Modified with 2-(Aminomethyl)Pyridine

The accumulation of plastic waste products in the environment has adversely affected wildlife and human beings. Common plastics that accumulate in the environment are plastics that are made of polyethylene terephthalate (PET) polymer. PET plastic waste products can be recycled for beneficial use, which would reduce their negative impacts. In this study, modified PET or waste PET (WPET) from plastic bottles was blended with powder commercial 2-(aminomethyl)pyridine (SiAMPy) resin and electrospun into composite nanofibres and applied for Cu2+ adsorption. PET-SiAMPy or WPET-SiAMPy composite nanofibres fibre diameters from the HRSEM images were 90–140 nm and 110–155 nm, respectively. In batch adsorption experiments, PET-SiAMPy or WPET-SiAMPy composite nanofibres achieved Cu2+ adsorption equilibrium within 60 secs of contact time with 0.98 mmol/g (89.87%) or 1.24 mmol/g (96.04%) Cu2+ adsorption capacity. The Cu2+ complex formation rate (k) with WPET-SiAMPy was 0.0888 with the mole ratio of Cu2+ and WPET-SiAMPy nanofibres 1:2. The complex molecular formula formed was Cu(WPET-SiAMPy)2 with a square planar geometry structure. The WPET-SiAMPy nanofibres’ adsorption was best fitted to the Freundlich isotherm. WPET-SiAMPy composite nanofibres were considered highly efficient for Cu2+ adsorption from aqueous solution and could be regenerated at least five times using 5 M H2SO4

Fabrication and Characterization of Electrospun Waste Polyethylene Terephthalate Blended with Chitosan: A Potential Single-Use Material

Textile single-use products are dominantly used for hygiene and personal care, many of which are non-biodegradable and are frequently discarded into sewerage systems, thus causing blockages. Thus, there is a need to move towards water-soluble textiles. This research study focuses on transforming or repurposing biomass material and synthetic reusable waste plastic materials to improve waste. Chitosan (CS) nanofibers could be used in single-use nonwoven fabric or biodegradable tissues, as the water-soluble properties of chitosan nanofibers make them the perfect material for single-use applications. Furthermore, CS was blended with polyethylene terephthalate (PET) polymer and PET-based waste plastic (CS-WPET) to slow the CS nanofibers’ water degradability and strengthen the durability of the nanofiber which could be used as air filters. The CS-TFA and CS-TFA/DCM nanofiber diameters were 95.58 ± 39.28 nm or 907.94 ± 290.18 nm, respectively, as measured from the HRSEM images. The CS-PET and CS-WPET hybrid nanofibers had fiber diameters of 246.13 ± 96.36 or 58.99 ± 20.40 nm, respectively. The thermal durability of the nanofibers was tested by TGA, which showed that CS-TFA/DCM nanofibers had sufficient thermal stability up to 150 °C, making them suitable for filter or fabric use at moderate temperatures. The blended nanofibers (CS-PET and CS-WPET) were thermally stable up to 160 °C. In the aqueous medium stability test, CS-PET and CS-WPET hybrid nanofibers had a slower degradation rate and were easily dissolved, while the CS nanofibers were rapidly and completely dissolved in an aqueous medium. Blending waste PET with CS allows it to be recycled into a useful single-use, non-woven textile, with greater water solubility than unmodified PET nanofibers but more durability than CS nanofibers on their own