Thesis (MTech (Chemical Engineering))--Cape Technikon, Cape Town, 2002 / The activation of green '"'Smartie"" coke (a mixture of medium temperature pitch and waxy oil coke) was investigated in a laboratory scale fluidised bed (FB) and a rotary kiln as function of (1) heat treatment temperature (HIT) and (2) heat treatment time (HTt). Activation in the FB was more effective (in terms of surface area development) and the product obtained from this type of reactor had a larger percentage of mesopores than the products from the rotary kiln. It was possible to produce a product with an iodine number equal to 745 mg iodine per gram carbon. The study revealed that it is possible to tune the pore structure of "Smartie" coke derived activated carbons by changing the activation device and systematically changing the activation conditions. It was possible to obtain products ranging from a predominantly microporous structure to products with a predominantly mesoporous structure. Unfortunately, in comparison to commercially available activated carbons, the total surface areas were still too low and it will be necessary to perform further investigations focused on increasing the total surface areas. The gold adsorption tests performed on the activated carbon compared well to those of activated carbon currently in use in the gold industry.

Thesis (Masters Degree (Chemical Engineering)) - Cape Technikon, Cape Town, 1996 / With the increasing awareness ofpreserving the environment, the need for other lixiviants in leaching processes has escalated. The investigation for lixiviants, especially for gold, has entailed mostly the halogen group. From halogens, iodine forms the most stable gold complex. The aim ofthis study was to investigate the adsorption characteristics of gold-iodide onto a coconut shell based activated carbon. In the first part of this study, the factors influencing the adsorption kinetics and equilibrium were investigated. Mixing experiments and interruption tests indicated clearly that the principal adsorption mechanism is by first order film diffusion. When the initial gold concentration was changed, the adsorption kinetics and equilibrium decrease viith an increase in gold concentration. This is due to the shielding effect by the adsorbed gold as it is partly reduced on the carbon surface. The concentration of iodide increased the adsorption kinetics and equilibrium. The increase in concentration of iodine leads to an increase in concentration ofthe principal oxidising agent, tri-iodide, thereby decreasing the adsorption parameters as the gold gets redissolved from the carbon surface. Furthermore, iodine and trio-iodide adsorbs competitively, thereby decreasing the rate ofadsorption ofthe gold complex. This is further iterated by experiments where the carbon was pre-treated v.ith a iodine/iodide solution. In acidic solutions, none, or a minimal amount ofthe gold is red11ced on the carbon surface, adsorption is only in the complex form, while in a alkaline solution, the gold is partly adsorbed and partly reduced. In the second section, the adsorption is approached from a basic electrochemical perspective. Here, depending on the pH ofthe solution, it is shown that the potential ofthe solution dictates the species of iodine and gold-iodide complex in solution, it affects the adsorption characteristics ofthe activated carbon.

Thesis (Masters Degree(Chemical Engineering))--Cape Peninsula University of Technology, 2008 / ABSTRACT Carbon-in-pulp (CIP) technology is firmly entrenched in the mining sector due to numerous advances in the last few decades. CIP technology recovers complexed gold in solution from slurry streams by contacting the pulp with carbon and separating the two by screening. The carbon-in-leach (CIL) process, where the pulp contains free cyanide, is closely related to CIP. Both these processes, especially CIL, are complex and are governed by a number of interacting unit processes. The overall process efficiency is dependant on a large number of variables, making the process difficult to optimize. This study uses simple adsorption and leaching rate equations in order to predict dynamic CIL/CIP plant performance under varying operating conditions. This will assist plant metallurgists to achieve optimum efficiency, highlight plant sensitivity to certain variables and will ultimately result in proactive process control. Various assumptions were made in order to keep the modeling considerations as simple and realistic as possible. The process was assumed to have linear kinetic and equilibrium operation. The process was simulated using Simulink in Matlab. Variables are solved on a time step basis by Matlab’s built in optimization algorithms. Simulation results illustrated that the use of simple leaching and adsorption rate expressions are effective for investigating dynamic plant behavior under changing operating conditions.

As amostras de carvão ativo de bagaço de cana-de-açúcar foram preparadas em temperaturas de carbonização de 500, 600 e 700 ºC, com tempos de ativação de 60 e 120 minutos e concentração de agente ativante (ZnC12) 30 e 60% em relação ao bagaço seco original. Foi utilizado como padrão, para verificação de eficiência, um carvão ativo alemão (Riedel). Estas amostras foram caracterizadas pelas seguintes análises: rendimento; teor e umidade; teor de cinzas; pH; teor de substâncias solúveis em água. Foi também estudado o desempenho destas amostras no descoramento de água de lavagem de cana-de-açúcar, utilizando 1% e 1,5% em peso de carvão ativo. Amostras preparadas a 500 ºC, 60 minutos e concentração de agente ativamente 0%, 30% e 60% em relação ao peso de bagaço seco original foram utilizadas no tratamento de água de lavagem de cana-de açúcar visando a diminuição do potencial poluidor, essas mesmas amostras foram utilizadas para determinação de poder de adsorção, equação e isoterma de Freundlich. Os resultados mostraram ser viável, em escala de laboratório a obtenção de carvão ativo de bagaço de cana-de-açúcar, para utilização no tratamento de água de lavagem de cana-de-açúcar visando diminuir o seu potencial poluidor. / Samples of activated carbon from cane-thrash were prepared in carbonization temperatures of 500, 600 and 700 ºC; activation times of 60 and 120 minutes, and concentrations of activating agent (ZnC12) 30 and 60% in relation to the original dry bagasse. A German activated carbon, was used a standard (Riedel). The samples were characterized by the following analysis: yield, proportion (5) of humidity, proportion of ashes; pH; proportion of solubles in water substances. It was also studied the performance in discolouring sugar-cane washing water using 1% and 1,5% in weight of activated carbon. Samples prepared in 500 ºC, 60 minutes and activating agent concentration of 0%, 30% and 60% in relation to the weight of the original dry bagasse were used in the treatment of sugar-cane washing water the purpose of reducing the polluter potential. They were used to determine the adsorption power, equation and Freundlish isotherm. The results showed it is possible to obtain active carbon from cane-thrash in laboratory scale, to be used in the treatment of sugar-cane washing water with the purpose of reducing its polluter potential.

Rapeseed protein isolate from pH 10 NaOH extraction was analyzed by gas chromatography (isothiocyanates) and UV absorption (goitrin) (Youngs and Wetter, 1967) and found to contain glucosinolates at levels equivalent to 0.75 mg 3-butenyl isothiocyanate, 0.57 mg 4-pentenyl isothiocyanate, and 0.51 mg oxazolidinethione (goitrin) per g isolate. A two-stage process was developed to decrease the levels of these toxins. Isolate slurry was incubated at pH 7.2 with crude myrosinase extracted from white mustard seed (to convert glucosinolates to isothiocyanates and goitrin), adjusted to pH 10, and passed through a granular activated carbon column. Subsequent analysis revealed only 0.006 mg 4- pentenyl isothiocyanate per g isolate. Goitrin was not detectable. Infrared analysis confirmed that the column was also partially effective in nitrile removal. To eliminate the need for myrosinase purification, the process was modified to include ground white mustard seed addition directly to rapeseed meal slurry. After incubation, the protein was extracted, purified by isoelectric precipitation, re-dissolved, and treated by the activated carbon column. This modification was included in the "recommended detoxification procedure". Subsequent experiments on protein extracts prepared and carbon treated at pH's from 3 to 12, inclusive, revealed that all treatments in the range of pH 3 to 10 were at least 93% effective in isothiocyanate removal. A lower efficiency was observed above pH 10. Storage tests (24 hours) on aglycone containing protein solutions showed increased loss of isothiocyanates with increasing pH from 5 to 10. This could be due to their interaction with protein (Bjorkman, 1973). The column completely removed chromatographically purified glucosinolates from aqueous solution. However, the results could not be duplicated for solutions containing rapeseed protein. Glucosinolate content was determined by trimethylsilation and gas chromatography (modified method of Underhill and Kirkland, 1971). / Land and Food Systems, Faculty of / Graduate

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As part of an Environmental Protection Agency grant to reduce the trihalomethane concentration in the Melbourne, Florida drinking water, a granular activated carbon (GAC) plant was operated for approximately 1 year. Four GAC pilot plant systems were operated in parallel each treating a different influent. Raw water, coagulated, settled and filtered water, filtered water with ozone pretreatment, and filtered water with chlorine dioxide pretreatment were pumped through the individual systems. Influent and effluent concentrations of various pollutants were monitored regularly throughout the study. The raw water GAC system showed rapid breakthrough for color, total organic carbon (TOC) and trihalomethanes (THM's). It was concluded that GAC treatment of raw water was inefficient and would require enormous quantities of GAC. The three coagulated, settled, and filtered water systems showed little variation in the removal of color, TOC and THMFP. For this reason, ozone and chlorine dioxide would not be useful in increasing the removal of pollutants from the Melbourne water. The most attractive use of GAC was evident with the coagulated, settled, and filtered water. At no time during the study did the effluent concentrations approach the influent concentrations of the three major pollutants. In addition, the predicted capacity of the GAC based on batch studies was exceeded significantly. It appears biological growth was present within the activated carbon and is aiding the GAC with pollutant removal. With biological activation, carbon usage rates could be significantly reduced, thus making the GAC alternative economically feasible.

Carbonized organic precursors such as wood, shells and some plant seeds are very porous. They are nanostructured and tend to be hard, but have pure mechanical properties as a result of their porosities. An attempt was made to carbonize an organic precursor to produce a bulk material with much less porosity for possible use in structural applications such as reinforcement in metal and polymer matrices. A bulk nanocarbon (BNC) material was synthesized using high energy ball milling and the carbonization of corn cob. Corn cob was mechanically milled for up to 20 hours by applying high energy ball milling to produce the milled powder. The milled powder was cold-compacted and carbonized at up to 1500°C to fabricate the BNC material. The material revealed both micro and nano-porosities; the porosities decreased with carbonizing temperature and hold time. Micropores were mostly closed for samples carbonized above 1300oC, whereas they formed interconnected network at lower carbonization temperatures. BNC has a young's modulus of 120 GPa, about ten times that of extruded graphite. / Master of Science / Wood, shells, and plant seeds are examples of organic precursors. When organic precursors are carbonized, they can become very porous, nanostructured, and hard, but deliver pure mechanical properties because of their porosities. A selected organic precursor was carbonized, in an attempt, to produce a bulk material with much less porosity for possible use in structural applications such as reinforcement in metal and polymer matrices. A bulk nanocarbon (BNC) material was made using high energy ball milling and the carbonization of corn cob (the selected organic precursor). This bulk material revealed both micro and nano-porosities, and a young's modulus of 120 GPa, about ten times that of extruded graphite.

Wound repair is a complex series of events that begins immediately after wounding, and can continue for a number of months to years. Various physiological and mechanical factors may impair the healing response, resulting in a chronic wound, characterised by a sustained inflammatory response. One of the main cells involved in both the inflammatory phase and proliferation phase of wound healing is the macrophage. There are thought to be different activation states which allow the macrophage to be involved in the two different phases of wound healing, namely the classically activated macrophage and the alternatively activated macrophage. Changes in the number of classically activated/alternatively activated macrophages in the wound is likely to have an effect on wound healing. Therefore a more thorough understanding of macrophage activation states during wound healing would broaden the understanding of the role of this cell in this process. The overall aim of this project was to investigate whether diabetic bone marrow progenitor cells or macrophages respond to activation stimuli differently in comparison to wild type cells. The hypothesis of this thesis is that diabetic macrophages will not respond to appropriate stimuli and thus alternative and classical macrophages will not behave 'appropriately', resulting in impaired healing. The results of this thesis indicate that impaired wound healing in the diabetic environment may be due to both the diabetic wound environment itself and intrinsic differences in diabetic macrophages. This work indicates that signals from the wound environment activates and influences macrophages, as these cells do not express activation markers until they enter the wound environment. However, the culture system devised in this study indicates that even before activation with signals they would receive in the wound environment, diabetic cells are more pro-inflammatory and have impaired migration. In addition, these macrophages respond differently to activation supporting the hypothesis that the macrophages are intrinsically different and that diabetic cells do not behave 'appropriately' which could contribute to impaired wound healing.

In this work, the stability of acid-modified activated carbons is assessed in the typical biomass conversion reaction environment of 200 °C, 17 bar water. Activated carbons were modified with a variety of common liquid and gas phase methods and characterized. Acid-modified carbon catalysts were exposed to hot liquid water for 24 h and further characterized to determine the effect of this exposure on their surface chemistry. It was found that the liquid phase acidifying agents of H₂SO₄ and HNO₃ are most effective at adding acidic functionalities to the carbon. Exposure to hot liquid water was found to significantly decrease the carboxylic and sulphonic acid site concentrations on the carbons and slightly increased lactonic group concentrations. Kinetic studies indicate that these surface chemical changes occur within the first 4 h exposure to this environment, and that increased exposure temperature results in more efficient acid site removal. XPS measurements show that H₂SO₄ modification imparts partially stable sulfonic acid groups on the carbon surface while HNO₃ modification imparts nitro groups which are unstable at exposure temperatures above 150 °C. The second part of this work focuses on the application of these acid-modified activated carbon catalysts as well as a variety of mixed metal oxide catalysts to the hydrolysis of the model biomass compound cellobiose. Catalyst screening reactions indicate that amorphous silica alumina catalysts are stable and selective but only slightly active whereas silica niobia catalysts are highly active but less selective and stable. Modified activated carbon catalysts were found to have moderate activity and selectivity. An investigation into the mechanism of silica niobia deactivation was performed and apparent activation energies were found for cellobiose hydrolysis over a variety of mixed metal oxide catalysts. Finally, a novel activated carbon synthesis mechanism was developed based on knowledge of surface site stability. This carbon catalyst was found to be highly active, selective, and stable for cellobiose hydrolysis but further characterization is required to fully understand its effectiveness as a catalyst.