Thesis (M. Eng.)(Chemical Engineering)--University of Pretoria, 2006. / Accompanied by a CD-ROM containing Matlab programs. Includes bibliographical references. Available on the Internet via the World Wide Web.

A third of adults in the UK admit to using controlled substances at least once hi their lives and the most commonly abused drug was found to be cannabis, followed by the opiates and ecognine derivatives. Forensic laboratories are continually trying to reduce the turnaround time for samples submitted for analysis, to less than the current time of four days. One of the main aims of this work was to reduce the time taken to prepare, extract and analyse hair for target analytes. A new method combining supercritical fluid extraction and solid phase micro-extraction (SFE/SPME) is introduced. This coupled procedure utilises the advantages of using supercritical carbon dioxide as an extraction solvent and collecting the extract on a selected SPME fibre. Together the combined techniques provide a method that is solvent-free and highly selective, whilst reducing sample preparation to a minimum. Digested hair samples are examined by SEM to find the best method. Alkali hydrolysis and enzyme digestion using proteinase K were found to be the most effective pre-extraction methods. Solid hair samples with the addition of a derivatization reagent (BSTFA) gave the best results using the coupled technique. After optimisation and validation, the extraction from both real and spiked samples resulted in recoveries between 60% to 80% for the target analytes A9 -tetrahydrocannabinol (A9- THC) , cannabinol (CBN) and cannabidiol (CBD). Other forensic applications such as the extraction of polycyclic aromatic hydrocarbons and pesticides from environmental and food samples and the examination of fire debris for the presence of accelerants are also carried out. PAH could easily be extracted from complex matrices to give recoveries of up to 97% for some analytes at the optimized conditions of 90°C at 4500 psi over a 10 minute dynamic extraction period. Pesticide extraction gave recoveries of 60 - 80% while the extraction of accelerants from fire debris clearly showed that accelerants such as diesel can be identified over the coincidental PAH and hydrocarbon peaks found in burnt debris. The coupling of SFE to SPME provides an exciting technique that has a wide range of applications and creates potential for a fully automated on-line system.

Thesis(MTech( Engineering))--Cape Peninsula University of Technology, 2012 / Platinum is a precious metal which may be processed under acidic conditions. Accordingly, the extraction of platinum from an acidic chloride media is of immense practical importance. In this study, the extraction of platinum was investigated in a Pt(IV)-HCl-Cyanex 921 matrix in order to establish the effect of temperature, extractant concentration, pH and the initial platinum concentration which had been used in the evaluated solvent extraction (SX) process. The extractant phase contained a mixture of Cyanex 921 and kerosene. In addition, the extraction mechanism of platinum, and the extracted species, are also described in the study, including the determination of the following: extraction ratio, extractant loading, distribution ratio, thermodynamic parameters, and the kinetic mechanism involved in the Pt(IV)-HCl-Cyanex 921 system used. Inductively coupled plasma emission spectroscopy (ICP-ES) was used to measure the platinum concentration in the aqueous phase with a mass balance being used to determine the concentration of platinum in the organic phase. Using a combination of the variables under investigation, the experiments which were evaluated indicated that it is possible to extract sufficient platinum chlorocomplex under the following conditions: pH of 1, Cyanex 921 concentration of 8% (v/v), temperature of 298 K and an initial platinum concentration of 55.22 mg/L. Under these conditions the maximum organic-phase loading of 253.9 mg/L was achieved as compared to the theoretical loading of 507.24 mg/L. The equilibrium loading of ~50% of the platinum chlorocomplex in the organic phase was achieved after 2400 seconds of reactor operation. In this case, a distribution ratio of 9.4 was achieved. This value was observed to be higher as compared to the other SX conditions evaluated in this study.

Orientador: Maria Helena Andrade Santana / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-12T13:59:09Z (GMT). No. of bitstreams: 1 Perez_AmandaGomesMarcelino_M.pdf: 7282541 bytes, checksum: 283cc7821ef608e1c94e849ed94b0def (MD5) Previous issue date: 2008 / Resumo: Este trabalho apresenta o desenvolvimento de nanopartículas de sericina para aplicação no tratamento cosmético dos cabelos. As nanopartículas foram obtidas a partir de soluções de sericina previamente extraídas de casulos ou fios de seda e formadas através de complexação eletrostática com goma guar. A superfície das nanopartículas foi modificada através da incorporação de agentes tensoativos catiônicos, com a finalidade de conferir-lhe densidade de carga positiva adequada para a adsorção aos fios de cabelo. O processo de produção envolveu as etapas de extração da sericina dos casulos ou fios de seda, reticulação, e modificação da superfície das nanopartículas. A extração foi realizada em autoclave ou a pressão atmosférica, utilizando água ou solução de carbonato de sódio como solventes. Durante a complexação foi estudada a influência da utilização de diferentes concentrações goma guar quaternizada, assim como a forma de adição desse agente, que foi feita em pó e em solução aquosa. A modificação na superfície das partículas foi feita com os tensoativos catiônicos cloreto de cetiltrimetil amônio (CTAC) e cloreto de behenyltrimetil amônio (BTAC), isoladamente e em mistura a diferentes proporções. A incorporação dos tensoativos catiônicos foi feita na presença dos eletrólitos resultantes da extração ou após separação das nanopartículas através de precipitação com etanol e posterior ressuspensão em água. Os efeitos foram analisados em termos de rendimento dos processos, tamanho das nanopartículas e potencial zeta. O poliquaternium 7, um derivado de amônia quaternária, foi adicionado à suspensão de nanopartículas como agente de viscosidade. Os resultados obtidos mostram a factibilidade da produção de nanopartículas de sericina com propriedades sensoriais promissoras para o condicionamento de cabelo danificado. O processo de produção é simples, escalonável e de fácil transferência para o setor industrial. / Abstract: This work presents the development of sericin nanoparticles applied to the cosmetic treatment of hair. The nanoparticles were obtained from sericin solutions, previously extracted from cocoons or silk yarn, and formed through electrostatic complexation with guar gum. The surface of the nanoparticles was modified through the incorporation of cationic surfactant agents, in order to obtain positive charge density, suitable for the adsorption on the hair surface. The production process involved the steps of sericin extraction from the cocoons or silk yarn, complexation and modification of the nanoparticles surface. The extraction was performed in autoclave and atmospheric pressure, using water or an aqueous solution of sodium carbonate as solvents. During the complexation was studied the effect of different concentrations of guar gum, as well as how to add this agent, which was made in powder and in an aqueous solution. The surface modification of particles was made with the cationic surfactant cetiltrimetil ammonium chloride (CTAC) and behenyltrimetil ammonium chloride (BTAC), alone and in combination with different proportions. The incorporation of cationic surfactant was made in the presence of electrolytes, resulting from the extraction, or after separation of the nanoparticles by precipitation with ethanol and resuspended in water later. The effects were analyzed in terms of efficiency of processes, nanoparticle size and zeta potential. The poliquaternium 7, a quaternary ammonium derivative, was added to the nanoparticles suspension as a viscosity agent. The results show the feasibility of output of sericin nanoparticles with promising sensory properties for the conditioning of damaged hair. The production process is simple, scalable and easy to transfer to the industrial sector. / Mestrado / Desenvolvimento de Processos Biotecnologicos / Mestre em Engenharia Química

M.Sc. / Sediment analysis, especially for trace metals, is important since aquatic sediments act as sinks for metals in the environment. Total element analysis yields insufficient information on the bioavailability and the geochemical fate of these metals. Sequential extraction procedures were developed to determine the partitioning of metals in sediment phases. The need for comparability of data produced world-wide led to the development of a sequential extraction procedure, which was proposed by the Community Bureau of Reference as a standard procedure (refered to as the BCR protocol). We contributed to the validation of the BCR procedure by using well-defined in-house model sediments. The results obtained for the model sediments showed that the BCR procedure could distinguish effectively between anthropogenically introduced metals and metals that form part of the mineral structure of the sediment components. The BCR procedure was applied to the sediments of the Vaal Dam and its contributing rivers. The amount of metals extracted in the first three steps of the sequential extraction procedure were low, indicating a very small contribution of anthropogenically introduced metals. It was therefore concluded that these sediments were relatively unpolluted compared to water systems in, for example, Europe.

The solubility of silver chloride was measured in solutions from 1 x 10^-5M. to 1 x 10^-1M. in chloride ion concentration. Ag^110 was used as a radiotracer to measure the solubility. Evidence for the formation of molecular silver chloride and silver dichloride complex anions was found. A least squares analysis of the experimental data was used to calculate the solubility product constant and the formation constants for the molecular species and the complex ions. The solubility product constant was determined to be 1.74 x 10^-10. The formation constant of the molecular species and the complex ion were calculated to be 1.84 x 10^3 and 1.53 x 10^5 respectively. The agreement of the solubility product constant with that determined by potentiometric measurements was very good. The formation constant of molecular silver chloride was investigated further by extraction with an organic solvent. Nitrobenzene was used as the solvent and the distribution coefficient for the molecular silver chloride in nitrobenzene and aqueous solutions was determined to be 0.32. Evidence was found for the extraction of the molecular species and not the silver ions. However, at high chloride concentrations HAgCl_2 appears to be extracted. By the use of the distribution coefficient, and the concentration of silver in the organic phase, the formation constant of the molecular species was determined to be 1.5 ± .5 x 10^3.

No description available.

No description available.

Thesis (PhDEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Separation processes are an integral part of chemical engineering. The purity of a chemical product is among the principal factors influencing its value. Therefore, any method that can increase the purity of a product or decrease the cost of purification will have a direct effect on the profitability of the entire plant. An important class of separation processes is the solvent-based separations. This includes processes like extractive distillation, liquid-liquid extraction and chromatographic separation. Heterogeneous azeotropic distillation is closely related to these processes. The most important variable in the design of a solvent-based separation process is the choice of solvent. A genetic algorithm for the computer-aided molecular design of solvents for extractive distillation had been previously developed by the author. This algorithm was improved and expanded to include liquid-liquid extraction, heterogeneous azeotropic distillation, gas-liquid chromatography and liquid-liquid (partition) chromatography. At the same time the efficiency of the algorithm was improved, resulting in a speed increase of up to 500% in certain cases. An automatic parameter tuning algorithm was also implemented to ensure maximum efficiency of the underlying genetic algorithm. In order to find suitable entrainers for heterogeneous azeotropic distillation a method is required to locate any ternary heterogeneous azeotropes present in a system. A number of methods proposed in the literature were evaluated and found to be computationally inefficient. Two new methods were therefore developed for ternary systems. A methodology for applying these methods to quaternary and higher systems was also proposed. Two algorithms to design blended solvents were also developed. Blended solvents allow the use of simpler and thus cheaper solvents by spreading the active functional groups over several molecular backbones. It was observed in a number of cases that the blended solvents performed better than their individual components. This was attributed to synergistic interactions between these components. Experimental evidence for this effect was also found. The algorithm was applied to a number of industrially important separation problems, including the extremely difficult final purification process of alpha olefins. In each case solvents were found that are predicted to perform substantially better than those that are currently used in industry. A number of these predictions were tested by experiment and found to hold true. / AFRIKAANSE OPSOMMING: Skeidingsprosesse is 'n integrale deel van chemiese ingenieurswese. Die suiwerheid van 'n chemiese produk is een van die hoof faktore wat die waarde daarvan bepaal. Derhalwe sal enige metode wat die suiwerheid van 'n produk kan verbeter, of die koste van die suiwering daarvan kan verlaag, 'n direkte effek op die winsgewendheid van die hele aanleg hê. 'n Belangrike groep skeidingsprosesse is die oplosmiddel-gebaseerde skeidings. Dit sluit prosesse soos ekstraktiewe distillasie, vloeistofvloeistof ekstraksie en chromatografiese skeidings in. Heterogene azeotrope distillasie is nou verwant aan hierdie prosesse. Die belangrikste veranderlike in die ontwerp van so 'n oplosmiddel-gebaseerde proses is die keuse van oplosmiddel. 'n Genetiese algoritme vir die rekenaargesteunde molekulêe ontwerp van oplosmiddels vir ekstraktiewe distillasie is voorheen ontwikkel deur die skrywer. Hierdie algoritme is verbeter en uitgebrei om vloeistofvloeistofekstraksie, heterogene azeotrope distillasie, gas-vloeistof chromatografie en vloeistof-vloeistof (verdelings) chromatografie in te sluit. Ter selfde tyd is die doeltreffendheid van die algoritme verbeter, wat 'n verbetering in spoed van tot 500% in sekere gevalle tot gevolg gehad het. 'n Algoritme om die parameters van die onderliggende genetiese algoritme outomaties te verfyn is ook geïm plementeer om die optimale werksverrigting van die algoritme te verseker. Om gepaste saamsleepmiddels vir heterogene azeotrope distillasie te vind, word 'n metode benodig om enige ternêre heterogene azeotrope aanwesig in 'n stelsel op te spoor. 'n Aantal sulke metodes wat in die literatuur voorgestel is, is geëvaluEer en daar is gevind dat hierdie metodes ondoeltreffend is. Twee nuwe metodes is derhalwe ontwikkel vir ternêre stelsels. 'n Metodiek om hierdie metodes op kwaternêre en hoër stelsels toe te pas, is ook voorgestel. Twee algoritmes vir die ontwerp van gemengde oplosmiddels is ook ontwikkel. Gemengde oplosmiddels laat die gebruik van eenvoudiger en dus goedkoper oplosmiddels toe, deur die aktiewe funksionele groepe oor 'n aantal molekulêe strukture te versprei. Daar is 'n aantal gevalle waargeneem waar die mengsel beter skeiding bewerkstellig het as die individuele oplosmiddels waaruit dit bestaan. Dit is toegeskryf aan 'n sinergistiese wisselwerking tussen die komponente van die mengsel. Eksperimentele getuienis vir hierdie effek is ook ingewin. Die algoritme is toegepas op 'n aantal belangrike skeidingsprobleme vanuit die bedryf, insluitende die uiters moeilike finale suiwering van alfa olefiene. In elke geval is oplosmiddels gevind wat volgens voorspelling aansienlike beter skeidings sal bewerkstellig as dié wat tans in die bedryf gebruik word. 'n Aantal van hierdie voorspellings is eksperimenteel getoets en korrek bewys.

Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Liquid-liquid extraction is a branch of solvent extraction that employs addition of an immiscible solvent, as a separating agent, to a liquid feed. Various types of equipment can be used, however if the process requires more than three stages, typically an extraction column, operated in a countercurrent manner would be employed. In order to scale-up and design a commercial extraction column, it is necessary to quantify the extraction system hydrodynamics and mass transfer characteristics. The principal objectives of countercurrently operated extraction columns concern the mass transfer rate and permissible throughput. The performance of a countercurrent extraction column can be adversely affected by axial mixing, which disturbs countercurrent plug flow. Various methods have been devised whereby it is possible to evaluate the performance of a column extraction and scale it up to ensure that the commercial operation achieves the same separation achieved on a pilot scale. Classical axial dispersion models allow quantification of axial mixing and mass transfer rates. Two Backflow models were derived to describe the performance of a Vibrating Plate Extraction (VPE) Column, one for steady state and one for unsteady state operation. The steady state model consisted of a series of simultaneous equations, which were solved using the Excel solver function. The unsteady state model consisted of 54 ordinary differential equations, which were solved stagewise using a fourth order Runge Kutta procedure. The steady state model was based on a dissociation extraction process, whereby meta-cresol (mcresol) was separated from para-hydroxy-benzaldehyde (PHB). The process used the differing de-protonation constants of the two components and the fact that the solubility of the ionic species of each was low in the organic solvent. The extraction system was quantified using a combination of acid-base and extraction theory. Experimentally determined concentration profiles, measured along the length of the column, were force fitted to the model, thereby allowing determination of the model parameters. The mass transfer coefficients ranged between 0.0098 and 0.189 Imin, and it was found that backmixing of the dispersed phase was negligible, while that of the continuous phase was low (varying between 0 and 0.3). The unsteady state model, used to describe the dynamic response of a VPE, was based on a system whereby tert-butyl hydroquinone (TBHQ) was recovered from a purge stream. Conductivity measurements of the raffinate were used to determine the residence time distribution in the column, and hence allowed determination of the extent of axial mixing. It was preferable that the column be operated with minimum settler volumes, otherwise buffering in the settlers occurred, thereby masking axial mixing effects. This method did not facilitate accurate determination of backmixing, at least two other conductivity measurements in the column needed to be measured. / AFRIKAANSE OPSOMMING: Vloeistof-vloeistofekstraksie is 'n vertakking van oplosmiddelekstraksie wat gebruik maak van die toevoeging van 'n onmengbare oplosmiddel as 'n skeidingagent tot die vloeistofvoer. Verskeie tipes apparaat kan gebruik word, maar as die proses meer as drie stadia vereis, sal 'n ekstraksiekolom, in teenstroom bedryf, tipies gebruik word. Om dit moontlik te maak om 'n kommersiele ekstraksiekolom te skalleer en te bedryf, moet die ekstraksiesisteem se hidrodinamika en massa-oordragkarakteristieke gekwantifiseer word. Die hoof doelwitte van ekstraksiekolomme wat teenstroom bedryf word, gaan om die massa-oordrag en toelaatbare deurset. Die skeidingsdoeltreffendheid van 'n teenstroom ekstraksiekolom kan nadelig beinvloed word deur aksiale vermenging, wat teenstroom propvloei versteur. Verskeie metodes is voorgestel wat dit moontlik maak om die doeltreffendheid van 'n ekstraksiekolom te evalueer en te verseker dat dieselfde skeiding verkry word vir 'n kornmersiele aanleg as vir 'n loodsaanleg. Klassieke aksiale dispersiemodelle laat kwantitatiewe berekening van aksiale vermenging en massa-oordragtempos toe. Twee terugvloeimodelle is afgelei om die werksverrigting van 'n Vibrerende Plaat Ekstraksiekolom (VPE) te beskryf. Die gestadidge toestand model bestaan uit 'n stelsel gelyktydige vergelykings wat opgelos is d.m.v. Excel. Die ongestadige toestand model bestaan uit 54 gewone differensiaalvergelykings, wat stapsgewys opgelos is d.m.v. die vierde orde Runge-Kutta metode. Die gestadigde teostand model is gebaseer op 'n dissosiasie ekstraksieproses, waardeur m-kresol geskei is van p-hidroksiebensaldehied (PHB). Die proses maak gebruik van die verskillende protoneringskonstantes van die twee verbindings en die feit dat die oplosbaarheid van beide die ioniese spesies laag is in die organiese oplosmiddel. Die ekstraksiestelsel is gekwantifiseer deur gebruik te maak van 'n kombinasie van suur-basis- en ekstraksieteorie. Die model is gepas op eksperimenteel bepaalde konsentrasieprofiele, gemeet langs die lengte van die kolom. Die massa-oordragkoeffisiente het waardes aangeneem tussen 0.0098 en 0.189 Imin en daar is gevind dat die terugvermenging van die verspreide fase weglaatbaar was, terwyl die van die kontinue fase laag was (tussen 0 en 0.3). Die ongestadige toestand model wat gebruik is om die dinamiese respons van die VPE te beskryf, is gebaseer op 'n stelsel waar tert-butielhidrokinoon (TBHQ) herwin is vanuit 'n bloeistroom. Geleidingsmetings van die raffinaat is gebruik om die residensietydverspreiding in die kolom te bepaaI en het derhalwe toegelaat dat die mate van aksiale vermenging bepaaI kon word. Die kolom moet by voorkeur met minimale skeiervolumes bedryf word, anders is daar 'n buffereffek in die skeiers, wat die aksiale vermenging verskuiI. Hierdie metode Iaat nie die akkurate bepaling van terugvermenging toe nie en minstens twee ander geleidingsmetings in die kolom was benodig.