Thesis (M.S.)--University of Wisconsin--Madison, 1967. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Gerald E. Speitel, Jr. Vita. Includes bibliographical references.

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.

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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Thesis (M.Sc.(Chemical Engineering))--University of the Witwatersrand, Faculty of Engineering, 1987. / Experimental work showed that the adsorption of the aurocyanide ion by activated carbon is under film diffusion control until the carbon reaches 70 per cent of its equilibrium loading capacity. A rate expression based on the classical film diffusion rate expression is suggested and the model for the batch test developed. The proposed model is shown to simulate batch adsorption tests at different ratios of carbon mass to solution volume. The mass transfer coefficient was linked to the carbon particle size and agitation rato by the use of dimensionless numbers. Correlations are suggested for fixed beds, fluidized beds and rolling bottles. It was determined experimentally that, at equivalent Reynolds numbers, the fixed bed provides the optimum system for mass transfer.

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2002. / Includes bibliographical references (leaves 185-202). Also available in electronic version. Access restricted to campus users.

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