Papers by Nomso C Hintsho-Mbita
Journal of Environmental Chemical Engineering, 2016
This work describes the synthesis of carbon nanofibers (CNFs) which was functionalized with b-cyc... more This work describes the synthesis of carbon nanofibers (CNFs) which was functionalized with b-cyclodextrin (b-CD). The resultant composite, b-CD@CNFs, was then used for the extraction of selected nitro-based explosive compound pollutants from aqueous solutions. The extraction was through an off-line solid-phase extraction (SPE) procedure followed by high-performance liquid chromatography with ultraviolet detection. Scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were used to characterize the synthesized materials. Three independent variables: SPE elution solvent, sample pH and sample volume were investigated to determine their influence on the adsorption of the explosive compounds from aqueous samples. The breakthrough volume of 40 mL was considered as optimum. Under the optimized conditions, good calibration linearities were obtained in the range 30-150 mg L À1 with coefficients of determination (R 2 ) > 0.997 for 3-nitrotoluene (3-NT), 1,3-dinitrobenzene (1,3-DNB), 2,6-dinitrotoluene (2,6-DNT), 4-nitrotoluene (4-NT), nitrobenzene (NB) and 2-nitrotoluene (2-NT). Low limits of detection of 3.3, 7.1, 8.6, 9.7, 23.1 and 13.0 mg L À1 were found for the respective compounds. The applicability of the developed method using b-CD@CNF as a sorbent was investigated using spiked real water samples collected within the vicinity of an operational gold mine and recoveries of 36.6-102.2% were obtained. 2016 Published by Elsevier Ltd.
Journal of Nanoscience and Nanotechnology, 2016
Various reducing and inert gases have been used in the catalytic chemical vapour deposition (CCVD... more Various reducing and inert gases have been used in the catalytic chemical vapour deposition (CCVD) synthesis of carbon nanomaterials (CNMs). In this paper we report on the effects that hydrogen and nitrogen gases have on the production of CNMs from acetylene on fly ash catalysts. Parameters such as temperature and gas environments were investigated. Transmission electron microscopy (TEM) revealed that CNMs of various morphologies such as carbon nanofibers (CNFs) and carbon nanospheres (CNSs) were formed. When hydrogen was used the carbonaceous products were formed in higher yields as compared to when nitrogen was used. This could be due to the multifunctional roles that hydrogen plays as compared to nitrogen. Laser Raman and Mössbauer spectroscopy measurements revealed that three types of products were formed, namely: amorphous carbon, graphitic carbon and iron carbide. Significantly cementite (Fe 3 C) was identified as the main intermediate carbide species in the catalytic growth of well-ordered CNMs.
RSC Advances, 2015
Carbon nanomaterials (CNMs) can be derived from waste materials such as: coal fly ash and CO2, wi... more Carbon nanomaterials (CNMs) can be derived from waste materials such as: coal fly ash and CO2, with CO2 and C2H2 as carbon sources respectively.
Nanoscale Research Letters, 2014
Carbon nanofibers (CNFs), cylindrical nanostructures containing graphene, were synthesized direct... more Carbon nanofibers (CNFs), cylindrical nanostructures containing graphene, were synthesized directly from South African fly ash (a waste product formed during the combustion of coal). The CNFs (as well as other carbonaceous materials like carbon nanotubes (CNTs)) were produced by the catalytic chemical vapour deposition method (CCVD) in the presence of acetylene gas at temperatures ranging from 400°C to 700°C. The fly ash and its carbonaceous products were characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), laser Raman spectroscopy and Brunauer-Emmett-Teller (BET) surface area measurements. It was observed that as-received fly ash was capable of producing CNFs in high yield by CCVD, starting at a relatively low temperature of 400°C. Laser Raman spectra and TGA thermograms showed that the carbonaceous products which formed were mostly disordered. Small bundles of CNTs and CNFs observed by TEM and energy-dispersive spectroscopy (EDS) showed that t...
Nanoscale Research Letters, 2014
Carbon nanofibers (CNFs), cylindrical nanostructures containing graphene, were synthesized direct... more Carbon nanofibers (CNFs), cylindrical nanostructures containing graphene, were synthesized directly from South African fly ash (a waste product formed during the combustion of coal). The CNFs (as well as other carbonaceous materials like carbon nanotubes (CNTs)) were produced by the catalytic chemical vapour deposition method (CCVD) in the presence of acetylene gas at temperatures ranging from 400°C to 700°C. The fly ash and its carbonaceous products were characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), laser Raman spectroscopy and Brunauer-Emmett-Teller (BET) surface area measurements. It was observed that as-received fly ash was capable of producing CNFs in high yield by CCVD, starting at a relatively low temperature of 400°C. Laser Raman spectra and TGA thermograms showed that the carbonaceous products which formed were mostly disordered. Small bundles of CNTs and CNFs observed by TEM and energy-dispersive spectroscopy (EDS) showed that the catalyst most likely responsible for CNF formation was iron in the form of cementite; X-ray diffraction (XRD) and Mössbauer spectroscopy confirmed these findings.
Photo-catalytic noble metallic and bimetallic nano-composites (Ag or Pd/-TiO 2 /CNT) were synthes... more Photo-catalytic noble metallic and bimetallic nano-composites (Ag or Pd/-TiO 2 /CNT) were synthesized using a commercial source of multi-walled carbon nanotubes via a modified dry-mix metal-organic chemical vapour deposition method (MOCVD). The titania loading was varied from 10-40 wt.%, and the optimum TiO 2 /CNT photo-catalyst was determined using methylene blue degradation as a model probe reaction. Furthermore, acid-treated nanotubes and non-acid treated nanotubes were compared as a substrate for the synthesis of various titania nano-composites, and it was found that the acid treatment decreased the photo-catalytic activity of the titania CNT nano-composites. The 20 wt.% titania on CNT samples were then further modified with silver, palladium, and a combination of both metals using the MOCVD technique. It was found that the silver titania CNT nano-composites were the most effective photo-catalyst for the degradation of methylene blue. The deposition of 2% Ag on 20% TiO 2 /MWCNT resulted in 92% degradation of 50 mg/L MB in 4 h with 1 g/L of photo-catalyst. Palladium had little effect in altering the photo-catalytic activity of the titania CNT nano-composites, and the combination of both metals suppressed the photo-catalytic activity of the titania CNT nano-composites.
Carbon nanofibers (CNFs), cylindrical nanostructures containing graphene, were synthesized direct... more Carbon nanofibers (CNFs), cylindrical nanostructures containing graphene, were synthesized directly from South African fly ash (a waste product formed during the combustion of coal). The CNFs (as well as other carbonaceous materials like carbon nanotubes (CNTs)) were produced by the catalytic chemical vapour deposition method (CCVD) in the presence of acetylene gas at temperatures ranging from 400°C to 700°C. The fly ash and its carbonaceous products were characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), laser Raman spectroscopy and Brunauer-Emmett-Teller (BET) surface area measurements. It was observed that as-received fly ash was capable of producing CNFs in high yield by CCVD, starting at a relatively low temperature of 400°C. Laser Raman spectra and TGA thermograms showed that the carbonaceous products which formed were mostly disordered. Small bundles of CNTs and CNFs observed by TEM and energy-dispersive spectroscopy (EDS) showed that the catalyst most likely responsible for CNF formation was iron in the form of cementite; X-ray diffraction (XRD) and Mössbauer spectroscopy confirmed these findings.
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Papers by Nomso C Hintsho-Mbita