Browsing by Author "Tarus, Bethwel"
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Item Electro-spun transparent film from banana pseudo-stem native cellulose using N-methylmorpholine-N-oxide solvent system(Elsevier, 2025-04-21) Livifile, Silla; Tarus, Bethwel; Kisula, Lydia; Kivevele, Thomas; Thomas, YusufuThe study-utilized electrospinning to prepare a transparent film from native cellulose extracted from banana pseudo stems. The process of electrospinning was performed at room temperature conditions, after which the cellulose film was obtained through water coagulation. Dimethyl sulfoxide and dimethylformamide were added to the electrospinning solution to adjust the surface tension, viscosity, and conductivity of the prepared solutions. The formed thin film was characterized using Infrared spectroscopy (IR) and X-ray crystallography tests to confirm the elimination of non-cellulosic materials during extraction. It was revealed that the banana fibers were dominated by crystallinity and converted from cellulose-I to cellulose-II after dissolution in N-methyl morpholine N-oxide (NMMO). Scanning electron microscopy images revealed that fiber and electro-spun film morphologies could be achieved by varying sodium hydroxide solution concentration and solution parameters during fiber treatment and electrospinning. Concentration of 17.5 % (wt./v)of the alkaline solution showed to be more effective in changing the surface morphology of the fiber. The structure and mechanical characteristics of the films were influenced most by the concentration of banana native cellulose, process stability, and the solidification of the electro-spun fibers. The film exhibited an initial degradation temperature of 165°C, a light transmittance of 83.3 % in the visible UV range, and a tensile strength ranged from 5.83 MPa to 8.13 MPa. This performance highlights its potential applications in various fields, including packaging and biomedical engineering.Item Electro-spun transparent film from banana pseudo-stem native cellulose using N-methylmorpholine-N-oxide solvent system(Elservier, 2025-06) Livifile, Silla; Tarus, Bethwel; Kisula, Lydia; Kivevele, Thomas; Jande, YusufuThe study-utilized electrospinning to prepare a transparent film from native cellulose extracted from banana pseudo stems. The process of electrospinning was performed at room temperature conditions, after which the cellulose film was obtained through water coagulation. Dimethyl sulfoxide and dimethylformamide were added to the electrospinning solution to adjust the surface tension, viscosity, and conductivity of the prepared solutions. The formed thin film was characterized using Infrared spectroscopy (IR) and X-ray crystallography tests to confirm the elimination of non-cellulosic materials during extraction. It was revealed that the banana fibers were dominated by crystallinity and converted from cellulose-I to cellulose-II after dissolution in N-methyl morpholine N-oxide (NMMO). Scanning electron microscopy images revealed that fiber and electro-spun film morphologies could be achieved by varying sodium hydroxide solution concentration and solution parameters during fiber treatment and electrospinning. Concentration of 17.5 % (wt./v)of the alkaline solution showed to be more effective in changing the surface morphology of the fiber. The structure and mechanical characteristics of the films were influenced most by the concentration of banana native cellulose, process stability, and the solidification of the electro-spun fibers. The film exhibited an initial degradation temperature of 165°C, a light transmittance of 83.3 % in the visible UV range, and a tensile strength ranged from 5.83 MPa to 8.13 MPa. This performance highlights its potential applications in various fields, including packaging and biomedical engineering.Item Electrospun carbon nanofibers for use in the capacitive desalination of water(Elsevier, 2022-12) Tarus, Bethwel; Jande, Yusufu; Njau, KaroliCapacitive deionization (CDI) has rapidly become a promising approach for water desalination. The technique removes salt from water by applying an electric potential between two porous electrodes to cause adsorption of charged species on the electrode surfaces. The nature of CDI favors the use of nanostructured porous carbon materials with high specific surface areas and appropriate surface functional groups. Electrospun carbon nanofibers (CNFs) are ideal as they have a high specific surface area and surface characteristics for doping/grafting with electroactive agents. Compared with powdered materials, CNF electrodes are free-standing and don't require binders that increase resistivity. CNFs with an appropriate distribution of mesopores and micropores have better desalination performance. Compositing CNFs with faradaic materials improves ion storage by adding pseudocapacitance to the electric double layer capacitance. The use of electrospun CNFs as electrodes for CDI is summarized with emphasis on the major precursor materials used in their preparation and structure modification, and their relations to the performance in salt electrosorption.Item Fabrication of porous carbon nanofiber webs from polyacrylonitrile and cellulose acetate for NaCl removal from water using capacitive deionization(IWA Publishing, 2024-01-01) Tarus, Bethwel; Jande, Yusufu; Njau, KaroliCapacitive deionization (CDI) has shown potential in addressing freshwater scarcity. CDI's electrode design is a key to better performance as it determines the extent of water purification. For carbon electrodes, the pore structure is an important factor influencing removal kinetics and ion storage. Herein, porous carbon nanofibers with diameters ranging from 277 to 348 nm were fabricated from blends of polyacryloni- trile (PAN) and cellulose acetate (CA) through electrospinning and carbonization. Surface area and pore properties were adjusted by varying the proportions of the precursors while ensuring no adverse alteration to the products’ tangible properties. Enhanced pore structure and specific surface area were evident in the blend-based carbon nanofibers. The blend ratio of 2:8 (CA:PAN) had a high specific surface area of 925.47 m2 /g and a pore volume of 0.7884 cm 3 /g. Correspondingly, a high specific capacitance of 177.5 F/g was attained. Desalination per- formance was determined in batch mode using 500 mg/L NaCl solution. A salt adsorption capacity of 6.57 mg/g and charge efficiency of 0.46 was obtained for the blend that had 20% CA. The carbon nanofibers demonstrated good desalination stability when used repetitively indi- cating their excellent potential for practical applicationItem Water Desalination By Capacitive Deionization Using Electrospun Micro-Mesoporous Ultrafine Carbon Fibres(NM-AIST, 2024-08) Tarus, BethwelCapacitive deionization is a promising method for desalination of low-to-moderate salinity water. Electrode pore structure is an important factor influencing performance in this technology. For the majority of carbon materials including ultrafine carbon fibres used as electrodes for capacitive deionization, excessive microporosity has hampered optimal performance. In this study, mesoporous ultrafine carbon fibres (277–700 nm diameters) were fabricated from polyacrylonitrile blended with cellulose acetate or terephthalic acid through electrospinning and carbonization for use as capacitive deionization electrodes. Fibre surface and pore attributes were adjusted by varying the proportions of the blended polymers while ensuring no adverse change in their tangible attributes. Fibre structure was further modified by embedding or hydrothermally coating MoS2 nanoparticles to enhance desalination performance through faradaic means. The produced blend-based fibres attained a specific surface area of 925.47 m2/g and a pore volume of 0.7884 cm3/g. Electrochemical tests revealed increasing specific capacitance and reducing charge transfer resistance with increase in surface area and mesopore volume. For MoS2-loaded fibres, hydrothermally-grown MoS2 yielded enhanced charge transfer and higher diffusion-controlled capacitance than the embedded MoS2. Desalination performance was evaluated under various configurations including conventional setup, single and multi-channel asymmetric cells, and multi-channel battery deionization setups. A specific adsorption capacity of 8.03 mg/g was achieved in the plainltrafine carbon fibres using 20 mM NaCl in batch mode at 1.2 V. The highest specific adsorption capacity attained was 32.11 mg/g using 20 mM NaCl in a four-channel battery deionization cell at ±0.8 V. In energy utilization, the MoS2-coated ultrafine carbon fibres when used in a battery deionization cell demonstrated over 3.7 times higher thermodynamic energy efficiency than in the asymmetric setups and 50 times higher than in conventional setups, while maintaining consistent desalination performance. The electrodes in the battery deionizationcells benefited from the coupled effects of electrosorption/intercalation and ion exchange membranes in symmetric conformation to effectively utilize charge. These findings promote the use of cellulose acetate and terephthalic acid as excellent pore templates in mesoporous ultrafine carbon fibre fabrication for capacitive deionization and provide insight into process engineering for improved electrochemical desalination and enhancement in ion intercalation based desalination configurations.