Electrospun chlorinated carbon nanotubes/Fe2O3/PVA nanocomposite fibrous material for the removal of oil in aqueous solutions
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Date
2023-03-16
Authors
Motlokoa, Teboho Ridwell
Journal Title
Journal ISSN
Volume Title
Publisher
Vaal University of Technology
Abstract
In general water pollution worldwide is alarming, hence wastewater treatment is becoming a very paramount area of scientific research. Oil spills are a major source of contamination for sea and coastal waters and results in the death of marine animals. A variety of solid adsorbents are available for removal of organic and inorganic pollutants from water. However most absorbents are not recoverable and reusable, while some become a source of secondary pollution after use. A variety of solid absorbents are available for removal of organic and inorganic pollutants from water.
In this study, four sorption materials were developed to be applied as sorbents for the removal of diesel oil in aqueous solutions. The sorption material consisted of chlorinated carbon nanotubes (Cl-CNTs) loaded with iron oxide nanoparticles that are embedded in a Polyvinyl Alcohol (PVA) polymer matrix. The sorption capacity of the materials was evaluated in the separation of a mixture containing diesel oil and water.
The chlorinated carbon nanotubes were synthesized using chemical vapour deposition and thereafter iron oxide nanoparticles were added using co-precipitation methods. Transmission Electron Microscope (TEM) images showed that the Cl-CNTs had a spaghetti-like morphology. Secondary growth of nanofibers on the outer walls of the main CNTs was also observed in some nanoparticles. The outer diameter size of the CNTs were between 21.8 nm and 28.3 nm. The iron oxide nanoparticles that formed in the presence of the CNTs were spherical in shape with a size of 20.0 nm and uniformly distributed on the CNTs surface. X-Ray Diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis indicated that the iron oxide phase was Fe2O3. Fourier Transform Infra-Red (FTIR) analysis showed that the CNTs were made of sp2-hybridised carbon and their surface contained carbonyl groups.
Nanofiber composite mats were prepared by electrospinning Cl-CNTs and Cl-CNTs/Fe2O3 suspended in PVA polymer solutions. The amount of Cl-CNTs and Cl-CNTs/Fe2O3 added to the PVA matrix were varied resulting in morphology changes in the polymer fibres as determined by Scanning Electron Microscopy (SEM). The PVA polymer had a fibre size of 371 nm which increased to 580 nm with the addition of 0.1 wt.% Cl-CNTs. The fibre size decreased to 413 and 211 nm with the addition of 0.2 wt.% and 0.5 wt.% Cl-CNTs, respectively. The addition of the Cl-CNTs prevented the bead formation, which was observed in the pure PVA fibres. The average diameters of the fibres were 366, 275, 219 and 169 nm, for 0.1, 0.5, 0.7 and 1 wt.% Cl-CNTs/Fe2O3, respectively. High amounts of inter-fibre fusing were observed for the 0.1 wt.% Cl-CNTs/Fe2O3/PVA matrix. The amount of inter-fibre fusing decreased with addition of higher concentrations of Cl-CNTs/Fe2O3. The Fe2O3/Cl-CNTs/PVA nanofibers was crosslinked using either glutaraldehyde or heat to improve their stability in water. The crosslinking process also caused changes in the morphology of the fibres; for instance, inter-fibre fusions were observed when glutaraldehyde was used.
The Cl-CNTs/PVA nanofibers mat had the highest oil sorption capacity of 9.9 g/g. The Fe2O3/Cl-CNTs/PVA nanofibers mat had the lowest capacity of 7.6 g/g but it increased to 9.2 g/g after crosslinking with heat at 40 °C. Thus far, our findings suggest that the synthesized nanofiber mats can be suitable for use as absorbents for floating oil in aqueous solutions with the use of an easily degradable polymer matrix. Further study can be employed using Brunauer – Emmett – Teller (BET) analyses to understand the porosity and surface area of the material which will help more in understanding the sorption capacity of the material.
Description
M. Tech. (Department of Biotechnology and Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology.
Keywords
Water pollution, Wastewater treatment, Solid adsorbents, Removal of organic and inorganic pollutants, Nanocomposite fibrous material, Oil absorbents, Removal of diesel oil, Nanoparticles