Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 136-143). Also available on the Internet.

The effectiveness of a cyclodextrin (sugar-based) solution for enhancedsolubilization removal of multicomponent nonaqueous phase organic liquid (NAPL) contamination from an aquifer is tested in a pilot-scale field experiment. This effort is the first field test of this innovative technology, termed a "Complexing Sugar Flush" (CSF). The saturated zone within an enclosed cell was flushed with 8 pore volumes of 10wt% cyclodextrin solution. The cyclodextrin solution increased the aqueous concentrations of all the target contaminants to values from about 100 to more than 20,000 times the concentrations obtained during a water flush conducted immediately prior to the CSF. The degree of solubility enhancement was greater for the morehydrophobic contaminants. Conversely, the relative mass removal was greater for the less-hydrophobic compounds due to their generally higher apparent solubilities. The average reduction in NAPL mass for the target contaminants was about 41%. A relationship is developed to describe enhanced dissolution of a multiple-component NAPL, and is used to analyze the field data. The effluent concentrations for most of the target contaminants during the cyclodextrin flush were within a factor of two of the equilibrium values predicted using this theory. Deviations from ideal dissolution behavior were also observed. Finally, the cyclodextrin solution appeared to significantly enhance both the magnitude and the rate of NAPL dissolution compared to a water flush conducted prior to the cyclodextrin flush. These results contribute to a better understanding of the important physicochemical processes involved in using enhancedsolubilization agents for the remediation of multiple-component NAPLs.

Boltzmann's equation for binary chemical reactions has been solved by the modified moment method using the equivalent of the 13-moment approximations. It was found that the transport coefficients are nonlinear in the thermodynamic forces. This nonlinearity is at least quadratic. The rate coefficient also appears to be at least quadratic in fluxes. / The stability of the solutions of two coupled equations of change for the current under the influence of an electric field is examined. These equations are deduced from the structure of dissipative terms calculated in the modified moment method. Two steady state branches in current are found to bifurcate from the primary steady state branch as a critical field value E(,c) = 4.35 V/cm is crossed. The results are in good qualitative agreement with experiment. / The dynamical behaviour of the two coupled equations used above was also studied in order to establish the influence (if any) of the entropy production surface on the trajectory followed by the system. This aspect of the study proved to be difficult since the entropy production surface associated with the two equations used did not have sufficiently distinctive features. / In order to continue studies on the relationship between dynamical behaviour and the topography of the entropy production surface, the two basic equations used before were slightly modified, and new parameters were introduced. At the critical field value E(,c) = 1.48 V/cm, no secondary steady states bifurcated out of the unstable primary steady state as in the previous model. Rather, stable oscillations in current of more or less constant amplitude occurred. This may account for some of the current fluctuations observed in experiment. The entropy production surface associated with this pair of model equations consists of two intersecting locii of minima. It turns out that the trajectory follows these minimal regions for most of the orbit, crossing from one locus of minima to another either through the intersection near to the origin or by crossing a ridge of high entropy production. The average energy dissipated over this cycle turns out to be smaller than if the system had remained with the unstable steady state. / Out of the latter studies, the useful conjecture was made. Given the topography of the entropy production surface and the stability of the steady states, it is possible to qualitatively predict the dynamics of the system provided the entropy production surface has sufficiently distinctive features.

The thesis involves a study of the thermodynamics of ternary liquid mixtures involving carboxylic acids with nitriles, hydrocarbons including cycloalkanes, and water. Carboxylic acids are an important class of compounds with a great number of industrial uses and applications. In many parts ofthe world the separation of carboxylic acids (in particular acetic and propanoic acid) is an important and desirable task. In South Africa, these carboxylic acids together with many other oxygenates and hydrocarbons are produced by SASOL using the Fischer - Tropsch process. The separation of these acids from hydrocarbons and from water is a commercially lucrative consideration, and is the raison d' etre for this study. The work focussed on the use of nitriles in effecting separation by solvent extraction and not by the more common method of distillation. The nitrile compounds were chosen because of their high polarity. The carboxylic acids used in this study always refer to: acetic acid, propanoic acid, butanoic acid, 2-methylpropanoic acid, pentanoic acid and 3-methylbutanoic acid. The first part of the experimental programme is devoted to the determination of excess molar volumes of mixtures of (a carboxylic acid + nitrile compound), where the nitrile refers to acetonitrile, butanenitrile or benzonitrile, respectively. Densimetry was used to determine the excess molar volumes. The work was done in order to get some idea of the interactions involved between a carboxylic acid and a nitrile. The second part of the experimental study is concerned with the determination of excess molar enthalpies of mixtures of( a carboxylic acid + nitrile compound), where the nitrile refers to acetonitrile, butanenitrile or benzonitrile, respectively. The excess molar enthalpies were determined using flow microcalorimetry Again, this work was done in order to gain some insight into the interactions involved between a carboxylic acid and a nitrile. The third part of the experimental work consists ofternary liquid-liquid equilibria of mixtures of (acetonitrile + a carboxylic acid + heptane or cyclohexane), (benzonitrile + a carboxylic acid + water); and (butanenitrile + a carboxylic acid + water), at 298.15 K. The purpose was to investigate the use of nitriles as solvent extractors in separating carboxylic acids from hydrocarbons and also carboxylic acids from water. Ternary liquid-liquid equilibrium data are essential for the design and selection of solvents used in the liquid-liquid extraction process. The final section deals with the fitting of models of liquid mixtures to the experimental data collected in this work. The NRTL (Non-random, two liquid), UNIQUAC (Universal quasichemical), and FBT (Flory-Benson-Treszczanowicz) models were used. The modelling work served three purposes: • to summarise the experimental data • to test theories of liquid mixtures • prediction of related thermodynamic properties / Thesis (Ph.D.)-University of Natal,Durban, 2003.

No description available.

No description available.

Ionic liquids (ILs) are a novel class of ionic solvents, which are being used more and more often in chemical systems based on nanoparticles (NP) for several industrial and technological applications. However, at present we are unable to master the state of dispersion or aggregation of NP in these solvents, and the classic theories applied to colloidal stability, such as the DLVO, cannot be applied. In particular, the difficulty is found in the description of the electrostatic interactions in these ionic media. In this work, we try to better understand colloidal interactions in ILs through two systems that have been thoroughly characterized separately: magnetic maghemite nanoparticles, whose surface is well controlled in water, and the ionic liquid ethylammonium nitrate (EAN), known for its resemblance to water. These two systems are finally mixed together and studied at both the macroscopic and microscopic levels. We perform characterizations through several techniques: flame atomic absorption spectroscopy, optical microscopy under magnetic field, scattering methods (neutrons, X-rays and light), magneto-optic birefringence. We discover the importance of having a charged NP surface in order to obtain stable maghemite dispersions in EAN. In particular, the best colloidal stability is reached by adsorbing citrate molecules on the NP surface. We further investigate the effect of the NP's size and concentration, of the cationic counterion used to compensate the charge of citrate, of water content. Finally, we transfer our acquired knowledge to the realization of dispersions in biocompatible ILs.

Renewable energy sources such as biomass are becoming more and more important as alternative to fossil fuels. One of the most exciting new sources of biomass is microalgae. The Hartbeespoort Dam, located 37 km west of South Africa’s capital Pretoria, has one of the dense populations of microalgae in the world, and is one of the largest reservoirs of micro-algal biomass in South Africa. The dam has great potential for micro-algal biomass production and beneficiation due to its high nutrient loading, stable climatic conditions, size and close proximity to major urban and industrial centres. There are five major steps in the production of biodiesel from micro-algal biomass-derived oil: the first two steps involve the cultivation and harvesting of micro-algal biomass; which is followed by the extraction of oils from the micro-algal biomass; then the conversion of these oils via the chemical reaction transesterification into biodiesel; and the last step is the separation and purification of the produced biodiesel. The first two steps are the most inefficient and costly steps in the whole biomass-to-liquids (BTL) value chain. Cultivation costs may contribute between 20–40% of the total cost of micro-algal BTL production (Comprehensive Oilgae Report, 2010), while harvesting costs may contribute between 20–30% of the total cost of BTL production (Verma et al., 2010). Any process that could optimize these two steps would bring a biomass-to-liquids process closer to successful commercialization. The aim of this work was to study the cultivation and harvesting of micro-algal biomass from the Hartbeespoort Dam for the production of biodiesel. In order to do this a literature study was done and screening experiments were performed to determine the technical and economical feasibility of cultivation and harvesting methods in the context of a new integrated biomass-to-liquids biodiesel process, whose feasibility was also studied. The literature study revealed that the cyanobacterium Microcystis aeruginosa is the dominant micro-organism species in the Hartbeespoort Dam. The study also revealed factors that promote the growth of this species for possible incorporation into existing and new cultivation methods. These factors include stable climatic conditions, with high water temperatures around 25oC for optimal Microcystis growth; high nutrient loadings, with high phosphorus (e.g. PO43-) and nitrogen concentrations (e.g. NO3-); stagnant hydrodynamic conditions, with low wind velocities and enclosed bays, which promote the proliferation of Microcystis populations; and substrates like sediment, rocks and debris which provide safe protective environments for Microcystis inoculums. The seven screening studies consisted of three cultivation experiments, three harvesting experiments and one experiment to determine the combustion properties of micro-algal biomass. The three cultivation experiments were conducted in three consecutively scaled-up laboratory systems, which consisted of one, five and 135-litre bioreactors. The highest productivity achieved was over a period of six weeks in the 5-litre Erlenmeyer bioreactors with 0.0862 g/L/d at an average bioreactor day-time temperature of 26.0oC and an aeration rate of 1.5 L/min. The three cultivation experiments revealed that closed-cultivation systems would not be feasible as the highest biomass concentrations achieved under laboratory conditions were too low. Open-cultivation systems are only feasible if the infrastructure already exists, like in the case of the Hartbeespoort Dam. It is recommended that designers of new micro-algal BTL biodiesel processes first try to capitalize on existing cultivation infrastructure, like dams, by connecting their processes to them. This will reduce the capital and operating costs of a BTL process significantly. Three harvesting experiments studied the technical feasibility and determined design parameters for three promising, unconventional harvesting methods. The first experiment studied the separation of Hartbeespoort Dam micro-algal biomass from its aqueous phase, due to its natural buoyancy. Results obtained suggest that an optimum residence time of 3.5 hours in separation vessels would be sufficient to concentrate micro-algal biomass from 1.5 to 3% TSS. The second experiment studied the aerial harvesting yield of drying micro-algal biomass (3% TSS) on a patch of building sand in the sun for 24 hours. An average aerial harvesting yield of 157.6 g/m2/d of dry weight micro-algal biomass from the Hartbeespoort Dam was achieved. The third experiment studied the gravity settling harvesting yield of cultivated Hartbeespoort Dam-sourced microalgae as it settles to the bottom of the bioreactor after air agitation is suspended. Over 90% of the micro-algal biomass settled to the bottom quarter of the bioreactor after one day. Cultivated micro-algal biomass sourced from the Hartbeespoort Dam, can easily be harvested by allowing it to settle with gravity when aeration is stopped. Results showed that gravity settling equipment, with residence times of 24 hours, should be sufficient to accumulate over 90% of cultivated micro-algal biomass in the bottom quarter of a separation vessel. Using this method for primary separation could reduce the total cost of harvesting equipment dramatically, with minimal energy input. All three harvesting methods, which utilize the natural buoyancy of Hartbeespoort Dam microalgae, gravity settling, and a combination of sand filtration and solar drying, to concentrate, dewater and dry the micro-algal biomass, were found to be feasible and were incorporated into new integrated BTL biodiesel process. The harvesting processes were incorporated and designed to deliver the most micro-algal biomass feedstock, with the least amount of equipment and energy use. All the available renewable power sources from the Hartbeespoort Dam system, which included wind, hydro, solar and biomass power, were utilized and optimized to deliver minimum power loss, and increase power output. Wind power is utilized indirectly, as prevailing south-easterly winds concentrate micro-algal biomass feedstock against the dam wall of the Hartbeespoort Dam. The hydraulic head of 583 kPa of the 59.4 meter high dam wall is utilized to filter and transport biomass to the new integrated BTL facility, which is located down-stream of the dam. Solar power is used to dry the microalgae, which in turn is combusted in a furnace to release its 18,715 kW of biochemical power, which is used for heating in the power-intensive extraction unit of the processing facility. Most of the processes in literature that cover the production of biodiesel from micro-algal biomass are not thermodynamically viable, because they consume more power than what they produce. The new process sets a benchmark for other related ones with regards to its net power efficiency. The new process is thermodynamically efficient, exporting 20 times more power than it imports, with a net power output of 5,483 kilowatts. The design of a new integrated BTL process consisted of screening the most suitable methods for harvesting micro-algal biomass from the Hartbeespoort Dam and combining the obtained design parameters from these harvesting experiments with current knowledge on extraction of oils from microalgae and production of biodiesel from these oils into an overall conceptual process. Three promising, unconventional harvesting methods from Brink and Marx (2011), a micro-algal oil extraction process from Barnard (2009), and a process from Miao and Wu (2005) to produce biodiesel through the acid-catalyzed transesterification of micro-algal oil, were combined into an integrated BTL process. The new integrated biomass-to-liquids (BTL) process was developed to produce 2.6 million litres of biodiesel per year from harvested micro-algal biomass from the Hartbeespoort Dam. This is enough to supply 51,817 medium-sized automobiles per year or 142 automobiles per day of environmentally friendly fuel. The new BTL facility consists of three sections: a cultivation section where microalgae grow in the 20 km2 Hartbeespoort Dam to a concentration of 160 g/m2 during the six warmest months of the year; a harvesting section where excess water is removed from the micro-algal biomass; a reaction section where fatty acid oils are extracted from the microalgae and converted to biodiesel, and dry biomass rests are combusted to supply heat for the extraction and biodiesel units of the reaction section. The cultivation section consist of the existing Hartbeespoort Dam, which make up the cultivation unit; the harvesting section is divided into a collection unit (dam wall part of the Hartbeespoort Dam), a concentration unit, a filtration unit, and a drying unit; the reaction section consists of an oil extraction unit, a combustion unit, and a biodiesel unit. At a capital cost of R71.62 million (R1.11/L) (±30%), the new proposed BTL facility will turn 933,525 tons of raw biomass (1.5% TSS) into 2,590,856 litres of high quality biodiesel per year, at an annual operating cost of R11.09 million (R4.28/L at 0% producer inflation), to generate R25.91 million (R10.00/L) per year of revenue. At the current diesel price of R10.00/L, the new integrated BTL process is economically feasible with net present values (NPV) of R368 million (R5.68/L) and R29.30 million (R0.45/L) at discount rates of 0% and 10%, respectively. The break-even biodiesel prices are R5.34/L and R7.92/L, for a zero NPV at 0% and 10% discount rates, respectively. The cultivation of micro-algal biomass from the Hartbeespoort Dam is only economical if the growth is allowed to occur naturally in the dam without any additional cultivation equipment. The cultivation of micro-algal biomass in either an open or a closed-cultivation system will not be feasible as the high cost of cultivation will negate the value of biodiesel derived from the cultivated biomass. The utilization of the three promising harvesting methods described in this work is one of the main drivers for making this process economically feasible. At a capital cost of R13.49 million (R37.77/ton of dry weight micro-algal biomass) and a operating cost of R2.00 million per year (R210.63/ton of dry weight micro-algal biomass) for harvesting micro-algal biomass from the Hartbeespoort Dam, harvesting costs account for only 19% and 18% of the overall capital and operating costs of the new process, respectively. This is less than harvesting costs for other comparative processes world-wide, which contribute between 20 and 30% of the overall cost of biomass-to-liquids production. At current fuel prices, the cultivation of micro-algal biomass from and next to the Hartbeespoort Dam is not economical, but the unconventional harvesting methods presented in this thesis are feasible, if incorporated into the new integrated biomass-to-liquids biodiesel process set out in this work. / Thesis (Ph.D. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2011.

Renewable energy sources such as biomass are becoming more and more important as alternative to fossil fuels. One of the most exciting new sources of biomass is microalgae. The Hartbeespoort Dam, located 37 km west of South Africa’s capital Pretoria, has one of the dense populations of microalgae in the world, and is one of the largest reservoirs of micro-algal biomass in South Africa. The dam has great potential for micro-algal biomass production and beneficiation due to its high nutrient loading, stable climatic conditions, size and close proximity to major urban and industrial centres. There are five major steps in the production of biodiesel from micro-algal biomass-derived oil: the first two steps involve the cultivation and harvesting of micro-algal biomass; which is followed by the extraction of oils from the micro-algal biomass; then the conversion of these oils via the chemical reaction transesterification into biodiesel; and the last step is the separation and purification of the produced biodiesel. The first two steps are the most inefficient and costly steps in the whole biomass-to-liquids (BTL) value chain. Cultivation costs may contribute between 20–40% of the total cost of micro-algal BTL production (Comprehensive Oilgae Report, 2010), while harvesting costs may contribute between 20–30% of the total cost of BTL production (Verma et al., 2010). Any process that could optimize these two steps would bring a biomass-to-liquids process closer to successful commercialization. The aim of this work was to study the cultivation and harvesting of micro-algal biomass from the Hartbeespoort Dam for the production of biodiesel. In order to do this a literature study was done and screening experiments were performed to determine the technical and economical feasibility of cultivation and harvesting methods in the context of a new integrated biomass-to-liquids biodiesel process, whose feasibility was also studied. The literature study revealed that the cyanobacterium Microcystis aeruginosa is the dominant micro-organism species in the Hartbeespoort Dam. The study also revealed factors that promote the growth of this species for possible incorporation into existing and new cultivation methods. These factors include stable climatic conditions, with high water temperatures around 25oC for optimal Microcystis growth; high nutrient loadings, with high phosphorus (e.g. PO43-) and nitrogen concentrations (e.g. NO3-); stagnant hydrodynamic conditions, with low wind velocities and enclosed bays, which promote the proliferation of Microcystis populations; and substrates like sediment, rocks and debris which provide safe protective environments for Microcystis inoculums. The seven screening studies consisted of three cultivation experiments, three harvesting experiments and one experiment to determine the combustion properties of micro-algal biomass. The three cultivation experiments were conducted in three consecutively scaled-up laboratory systems, which consisted of one, five and 135-litre bioreactors. The highest productivity achieved was over a period of six weeks in the 5-litre Erlenmeyer bioreactors with 0.0862 g/L/d at an average bioreactor day-time temperature of 26.0oC and an aeration rate of 1.5 L/min. The three cultivation experiments revealed that closed-cultivation systems would not be feasible as the highest biomass concentrations achieved under laboratory conditions were too low. Open-cultivation systems are only feasible if the infrastructure already exists, like in the case of the Hartbeespoort Dam. It is recommended that designers of new micro-algal BTL biodiesel processes first try to capitalize on existing cultivation infrastructure, like dams, by connecting their processes to them. This will reduce the capital and operating costs of a BTL process significantly. Three harvesting experiments studied the technical feasibility and determined design parameters for three promising, unconventional harvesting methods. The first experiment studied the separation of Hartbeespoort Dam micro-algal biomass from its aqueous phase, due to its natural buoyancy. Results obtained suggest that an optimum residence time of 3.5 hours in separation vessels would be sufficient to concentrate micro-algal biomass from 1.5 to 3% TSS. The second experiment studied the aerial harvesting yield of drying micro-algal biomass (3% TSS) on a patch of building sand in the sun for 24 hours. An average aerial harvesting yield of 157.6 g/m2/d of dry weight micro-algal biomass from the Hartbeespoort Dam was achieved. The third experiment studied the gravity settling harvesting yield of cultivated Hartbeespoort Dam-sourced microalgae as it settles to the bottom of the bioreactor after air agitation is suspended. Over 90% of the micro-algal biomass settled to the bottom quarter of the bioreactor after one day. Cultivated micro-algal biomass sourced from the Hartbeespoort Dam, can easily be harvested by allowing it to settle with gravity when aeration is stopped. Results showed that gravity settling equipment, with residence times of 24 hours, should be sufficient to accumulate over 90% of cultivated micro-algal biomass in the bottom quarter of a separation vessel. Using this method for primary separation could reduce the total cost of harvesting equipment dramatically, with minimal energy input. All three harvesting methods, which utilize the natural buoyancy of Hartbeespoort Dam microalgae, gravity settling, and a combination of sand filtration and solar drying, to concentrate, dewater and dry the micro-algal biomass, were found to be feasible and were incorporated into new integrated BTL biodiesel process. The harvesting processes were incorporated and designed to deliver the most micro-algal biomass feedstock, with the least amount of equipment and energy use. All the available renewable power sources from the Hartbeespoort Dam system, which included wind, hydro, solar and biomass power, were utilized and optimized to deliver minimum power loss, and increase power output. Wind power is utilized indirectly, as prevailing south-easterly winds concentrate micro-algal biomass feedstock against the dam wall of the Hartbeespoort Dam. The hydraulic head of 583 kPa of the 59.4 meter high dam wall is utilized to filter and transport biomass to the new integrated BTL facility, which is located down-stream of the dam. Solar power is used to dry the microalgae, which in turn is combusted in a furnace to release its 18,715 kW of biochemical power, which is used for heating in the power-intensive extraction unit of the processing facility. Most of the processes in literature that cover the production of biodiesel from micro-algal biomass are not thermodynamically viable, because they consume more power than what they produce. The new process sets a benchmark for other related ones with regards to its net power efficiency. The new process is thermodynamically efficient, exporting 20 times more power than it imports, with a net power output of 5,483 kilowatts. The design of a new integrated BTL process consisted of screening the most suitable methods for harvesting micro-algal biomass from the Hartbeespoort Dam and combining the obtained design parameters from these harvesting experiments with current knowledge on extraction of oils from microalgae and production of biodiesel from these oils into an overall conceptual process. Three promising, unconventional harvesting methods from Brink and Marx (2011), a micro-algal oil extraction process from Barnard (2009), and a process from Miao and Wu (2005) to produce biodiesel through the acid-catalyzed transesterification of micro-algal oil, were combined into an integrated BTL process. The new integrated biomass-to-liquids (BTL) process was developed to produce 2.6 million litres of biodiesel per year from harvested micro-algal biomass from the Hartbeespoort Dam. This is enough to supply 51,817 medium-sized automobiles per year or 142 automobiles per day of environmentally friendly fuel. The new BTL facility consists of three sections: a cultivation section where microalgae grow in the 20 km2 Hartbeespoort Dam to a concentration of 160 g/m2 during the six warmest months of the year; a harvesting section where excess water is removed from the micro-algal biomass; a reaction section where fatty acid oils are extracted from the microalgae and converted to biodiesel, and dry biomass rests are combusted to supply heat for the extraction and biodiesel units of the reaction section. The cultivation section consist of the existing Hartbeespoort Dam, which make up the cultivation unit; the harvesting section is divided into a collection unit (dam wall part of the Hartbeespoort Dam), a concentration unit, a filtration unit, and a drying unit; the reaction section consists of an oil extraction unit, a combustion unit, and a biodiesel unit. At a capital cost of R71.62 million (R1.11/L) (±30%), the new proposed BTL facility will turn 933,525 tons of raw biomass (1.5% TSS) into 2,590,856 litres of high quality biodiesel per year, at an annual operating cost of R11.09 million (R4.28/L at 0% producer inflation), to generate R25.91 million (R10.00/L) per year of revenue. At the current diesel price of R10.00/L, the new integrated BTL process is economically feasible with net present values (NPV) of R368 million (R5.68/L) and R29.30 million (R0.45/L) at discount rates of 0% and 10%, respectively. The break-even biodiesel prices are R5.34/L and R7.92/L, for a zero NPV at 0% and 10% discount rates, respectively. The cultivation of micro-algal biomass from the Hartbeespoort Dam is only economical if the growth is allowed to occur naturally in the dam without any additional cultivation equipment. The cultivation of micro-algal biomass in either an open or a closed-cultivation system will not be feasible as the high cost of cultivation will negate the value of biodiesel derived from the cultivated biomass. The utilization of the three promising harvesting methods described in this work is one of the main drivers for making this process economically feasible. At a capital cost of R13.49 million (R37.77/ton of dry weight micro-algal biomass) and a operating cost of R2.00 million per year (R210.63/ton of dry weight micro-algal biomass) for harvesting micro-algal biomass from the Hartbeespoort Dam, harvesting costs account for only 19% and 18% of the overall capital and operating costs of the new process, respectively. This is less than harvesting costs for other comparative processes world-wide, which contribute between 20 and 30% of the overall cost of biomass-to-liquids production. At current fuel prices, the cultivation of micro-algal biomass from and next to the Hartbeespoort Dam is not economical, but the unconventional harvesting methods presented in this thesis are feasible, if incorporated into the new integrated biomass-to-liquids biodiesel process set out in this work. / Thesis (Ph.D. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2011.

A multidisciplinary approach has been applied to the development of sustainable technologies for three industrially relevant projects. Reversible ionic liquids are novel carbon dioxide capture solvents. These non-aqueous silylamines efficiently capture carbon dioxide through chemical and physical absorption and release carbon dioxide with minimal addition of heat. The development of these capture agents aims to eliminate the need for a co-solvent, while minimizing energy loss and achieving solvent recyclability. Also presented is the use of carbon dioxide for amine protection during chemical syntheses. Amine protection is widely used in almost all sectors of chemical and pharmaceutical industries. The use of carbon dioxide as a reversible protecting group reduces solvent waste during protection and deprotection and improves the atom economy of existing processes. Sustainable chemistry has also been applied to the use of reversible ionic liquids as switchable surfactants for nanoparticle synthesis. The reversible ionic liquid system offers two significant advantages toward a more efficient synthesis and deposition of nanoparticles in that an additional surfactant is not required, and due to the reversible nature of the ionic liquids, a facile and waste-reduced deposition method exists.