32 research outputs found
Methane decomposition : characterization of the carbon produced and possible use in direct carbon fuel cells
Ph.D, Faculty of Science, University of the Witwatersrand, 2011Investigations into methane conversion (both catalytic and non-catalytic) and
characterization of the carbon produced for use in high efficiency DCFCs were
performed. Under non-catalytic processes, a high methane conversion (> 80%) was
achieved at 1200 oC at flow rates of between 10-60 ml/min. Analysis of the carbon
using Raman spectroscopy showed that the carbon was highly disordered and the
degree of disorder increased with increase in methane flow rate (from aD/aG = 1.54
at 10 ml to aD/aG = 2.24 at 60 ml/min). Further analysis of the carbon using
thermogravimetric analysis (TGA) demonstrated that the carbon produced at higher
flow rates e.g. 100 ml/min were easily oxidized (746 oC) compared with those
produced at lower flow rates (10 ml/min, 846 oC). Therefore, a high temperature
coupled with high flow rates (60-100 ml/min) produced carbon with desired qualities
(high disorder, low crystallinity and more thermally reactive) for DCFC uses.
In the catalytic decomposition of methane, Ni supported on TiO2 and a 1:1 mixture
of TiO2/Al2O3 gave high and stable methane conversions of about 60% at only 600
oC compared to 1200 oC required for the non-catalytic conversion. These catalysts
were found to be the best catalyst systems of the tested catalysts.
Considering the thermal oxidation and crystallinity data which are some of the
properties of the carbon required for direct carbon fuel cells (DCFCs), the carbon
produced can potentially be used in DCFC systems
Cyclodextrin polyurethanes polymerised with carbon nanotubes for the removal of organic pollutants in water
Organic compounds are some of the major pollutants of water worldwide. They can be toxic or carcinogenic even at low concentrations. The non-reactivity of these species makes it difficult to remove them from water, particularly when present at concentration levels of nanograms per litre (ng·ℓ-1) or lower. Reasonably inexpensive yet effective methods for the removal of these organic pollutants to below ppb levels are therefore required.Insoluble cyclodextrin polyurethanes have demonstrated the ability to remove organic species from water at concentration levels of nanograms per litre. Carbon nanotubes have also been reported to efficiently adsorb some organic molecules such as dioxins and polychlorinated dibenzo-furans. However, these nanotubes are currently too expensive to be used on their own in water treatment.An investigation into the use of cross-linked cyclodextrin polyurethanes copolymerised with functionalised multiwalled carbon nanotubes as adsorbents for organic pollutants has yielded very useful results which may have an impact in future water treatment applications.Keywords: multiwalled carbon nanotubes, cyclodextrins, polymer composites, adsorption, trichloroethylene, endocrine disruptor
Sorption of Ochratoxin A from Aqueous Solutions Using β-Cyclodextrin-Polyurethane Polymer
The ability of a cyclodextrin-polyurethane polymer to remove ochratoxin A from aqueous solutions was examined by batch rebinding assays. The results from the aqueous binding studies were fit to two parameter models to gain insight into the interaction of ochratoxin A with the nanosponge material. The ochratoxin A sorption data fit well to the heterogeneous Freundlich isotherm model. The polymer was less effective at binding ochratoxin A in high pH buffer (9.5) under conditions where ochratoxin A exists predominantly in the dianionic state. Batch rebinding assays in red wine indicate the polymer is able to remove significant levels of ochratoxin A from spiked solutions between 1–10 μg·L−1. These results suggest cyclodextrin nanosponge materials are suitable to reduce levels of ochratoxin A from spiked aqueous solutions and red wine samples
Polymerisation of cyclodextrins and multiwalled carbon nanotubes for use in water purification
B.B. Mamb
Removal of geosmin and 2-methylisorboneol (2-MIB) in water from Zuikerbosch Treatment Plant (Rand Water) using â-cyclodextrin polyurethanes
Geosmin and 2-methylisorboneol (2-MIB) are major organic pollutants responsible for undesirable taste and odour in water. These compounds impact greatly on the aesthetic quality and general consumer acceptability of drinking water. The use of granular activated carbon (GAC) in the removal of geosmin and 2-MIB is generally ineffective since these compounds are present at very low concentrations (ngE.-1). Water treatment technologies that can remove geosmin and 2-MIB from water below human detection threshold (<10 ngE.-1) are highly sought by drinking water supplies, e.g. Rand Water. The removal of these odour-causing compounds from water samples using cyclodextrin- based nanoporous polyurethanes was investigated in our laboratory. Geosmin and 2-MIB were extracted from water samples by solid phase micro-extraction (SPME) and analysis was carried out using gas chromatography-mass spectrometry (GC-MS). Results from the analysis demonstrated that thesepolymers were highly effective in removing geosmin and 2-MIB