Дисертації з теми "Aqueous and non-aqueous systems"
Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: Aqueous and non-aqueous systems.
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 дисертацій для дослідження на тему "Aqueous and non-aqueous systems".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
Smylie, J. "Studies on the mechanism of template polymerisation in aqueous and non-aqueous systems." Thesis, University of Strathclyde, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372123.
Повний текст джерела
2
Jayaraman, Krithika M. "Mass transfer from non-aqueous phase liquids to the aqueous phase in groundwater systems." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-01122010-020214/.
Повний текст джерела
3
Banerjee, Ashis. "Rheological and thermodynamic investigation of some properties prevailing in aqueous and non-aqueous system." Thesis, University of North Bengal, 2009. http://hdl.handle.net/123456789/1357.
Повний текст джерела
4
Al-Dulaimi, Zaid. "Non-aqueous shale gas recovery system." Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/104172/.
Повний текст джерелаАнотація:
gh European energy demands, the difference in prices amongst Europe and ambitious gas producers, have produced a scenario of high competition in a region that suffers a lack of fossil resources still required for energy generation. Therefore, other sources are under the scope of various countries to mitigate these issues. Shale gas is one fuel that presents a scenario that would decrease European dependence on imported gas. Although shale gas production is unlikely to give the energy security desired to the whole Europe, it would make a difference for the communities that will adopt it. However, shale gas has acquired a bad reputation with the public, mainly because of its extraction methods. This bad reputation is attributed to hydraulic fracturing, technology well-known as fracking, and its risks associated towards air and water pollution. Therefore, companies, institutions and governments are looking for other alternative methods of extraction with more environmentally friendly processes. Producing extensive high-pressure pulse waves at the base of the wellbore by using detonation is a promising potential technique for shale gas extraction. A fundamental study of deflagration to detonation transition using recirculated shale gas formation with pure oxygen as an oxidiser has been studied to design a system with lower DDT distance and higher pressure waves. Three proposed cases of UK shale gas composition were studied. Chemical equilibrium software GASEQ and chemical kinetic software CHEMKIN-PRO were used to estimate the product parameters. Results showed that the effect produced by diluents, such as carbon dioxide, are eliminated by the use of higher hydrogen content carbon-to-hydrogen species for the three cases proposed. OpenFOAM CFD was used to calculate the deflagration to detonation transition parameters in stoichiometric hydrogen air mixtures to evaluate different obstacle geometries on the transition phenomenon to improve the detonation process. The shape and layout of obstacles were found to have a significant effect on flame acceleration, and subsequent detonation propagation. The interaction of transverse pressure waves generated at the obstructions governs the propagation mechanism. The transverse waves and its frequency appear to play a pivotal role in supporting the detonation wave. H iv It was found that rectangular shape obstacles reduce the reaction time, while triangular ones achieved detonation with the minimum run-up distance. On the other hand, semicircular shape obstacles generate the highest pressure in a detonation tube. The outcome from numerical calculations and CFD were the guide to construct an experimental rig of 21.2mm diameter and 1500mm length tube with different obstacle configurations to demonstrate the concept of pulse detonation for shale rock cracking. Experimental work has been performed to determine the potential of shale gas production in the Dullais Valley, South of Wales. It was found through several tests using BS standard volatile analyses, Transmission Electron Microscopy and pyrolysis RockEval evaluation that the potential of extraction in this region is fair, with similar concentrations of pyrite but with low energy content compared to those resources located in the Midlands and Yorkshire. However, the use of controlled pulse detonation could be the ideal technology for extraction in Wales, as low sulphur (S) content will produce lower unwanted emissions, with a process that can promote opening of pores and further gasification of oil based molecular, with a subsequent increase in shale gas production, topic that requires further research. Finally, a 2-dimensional simulation was performed using ANSYS Parameter Design Language (APDL) to investigate the effect of pressure pulse generated by the detonation tube on a pre-crack. Results showed that the layer close to the applied load will be displaced, which means that it will be smashed. The maximum Von Mises stresses were found to concentrate at the perforating hole corners, while the region immediately after the crack tip is susceptible to compression stresses. The Same behaviour was found for the stress intensity factor. According to that, it is believed that the cracks will propagate diagonally from the perforating hole base. Therefore, the current work has theoretically demonstrated the technology for shale gas recovery, with an optimised geometry consistent of internal obstacles, for a region with potential for shale gas exploitation.
5
Dakua, Vikas Kumar. "Physico-chemical studies on interactions between ion-solvent, ion-ion and solvent-solvent in aqueous and non-aqueous pure and mixed solvent systems." Thesis, University of North Bengal, 2008. http://hdl.handle.net/123456789/707.
Повний текст джерела
6
Das, Samir. "Investigation of solution behaviour and inclusion complexation of some noteworthy compounds with the manifestation of assorted interactions prevalent in aqueous and non-aqueous systems." Thesis, University of North Bengal, 2022. http://ir.nbu.ac.in/handle/123456789/4788.
Повний текст джерела
7
Escalante, García Ismailia Leilani. "Fundamental and Flow Battery Studies for Non-Aqueous Redox Systems." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1425046485.
Повний текст джерела
8
Theaker, Ian. "A structural and thermodynamic study of non-aqueous solvent/wax systems." Thesis, University of Hull, 1996. http://hydra.hull.ac.uk/resources/hull:4996.
Повний текст джерелаАнотація:
Non-aqueous wax/solvent systems of industrial relevance for the manufacture of paste polishes have been investigated. These mixtures have been modelled using a paraffin wax of Japanese origin (Nippon Seiro 140/145°F) in a solution of pure heptane to which dopant components are added.The stability of any resulting gel has been assessed via solubility studies and measurement of the solvent vapour pressure. A new technique for the measurement of vapour pressure in these systems has been developed. The operation of the apparatus has been made almost completely automatic by the use of modern control units.Complementary analytical techniques such as Differential Scanning Calorimetry and Nuclear Magnetic Resonance have been used to augment the data where appropriate and the structure of these pastes has been investigated with the use of Optical Microscopy.
9
Islam, Mojahedul. "The stability of foam, with special emphasis on non-aqueous systems." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/46269.
Повний текст джерела
10
Templeton, John Andrew. "Magnetite Oxidation in Aqueous Systems." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/43468.
Повний текст джерелаАнотація:
Magnetite, an iron oxide, is a possible candidate for in situ remediation of contaminated groundwater systems due to its oxidation/reduction potential for reduction of contaminants such as carbon tetrachloride. Little characterization and analysis has been done to describe the kinetics of magnetite transformation during oxidation. This work focuses on monitoring the concentrations of magnetite and one of its oxidation transformation products, maghemite, by the use of UV-Vis-NIR spectroscopy. As oxidation proceeded at a constant specific temperature, the concentration of magnetite decreases, which was indicated by a decrease in absorption in the NIR-region of the spectrum. As magnetite concentrations decreased, the concentration of maghemite increased, which was indicated by an increase in absorption in the UV-region. The temperature at which the suspensions of magnetite and maghemite were measured was of great importance for complete understanding of the magnetite transformation as seen by UV-Vis-NIR spectroscopy analysis. Higher measurement temperatures produced higher absorptivities of FeII-FeIII electron hopping transitions, while decreasing the absorptivity of FeIII-FeIII in the NIR and UV-regions respectively. Lower temperatures produced the opposite effects on the iron oxidesâ transitions. Higher temperature increased the rate of oxidation.Master of Science
11
Voigt, Mirko [Verfasser]. "Biodegradable non-aqueous in situ forming microparticle drug delivery systems / Mirko Voigt." Berlin : Freie Universität Berlin, 2011. http://d-nb.info/1026069688/34.
Повний текст джерела
12
Richter, Clemens [Verfasser]. "Investigation of Local and Non-Local Autoionization in Aqueous Systems / Clemens Richter." Berlin : Freie Universität Berlin, 2021. http://nbn-resolving.de/urn:nbn:de:kobv:188-refubium-31980-9.
Повний текст джерела
13
Horn, Ian Martin. "Structure and reactivity in aqueous systems." Thesis, University of Leicester, 1993. http://hdl.handle.net/2381/33736.
Повний текст джерелаАнотація:
Rate constants for chemical reactions in various aqueous systems have been measured and analysed. Oxidations of a number of organic dyes by the compound sodium perborate tetrahydrate have been extensively studied kinetically. These rate constants are compared to those for hydrogen peroxide and sodium percarbonate, for similar oxidations under the same conditions. A general review of peroxoanion chemistry is included, and a computer simulation of the perborate species in solution is presented. The theories of Debye and Huckel concerning kinetic salt effects are examined in the light of Desnoyer's theory of co-sphere interaction for ions in solution. The effects of added salt on the alkaline hydrolysis of the disodium salt of bromophenol blue are reported and analysed using Pitzer's equations for the activity coefficients of single ions in aqueous salt solutions. The Kirkwood-Buff theory of interactions in binary aqueous mixtures has been examined and extended according to the methods proposed by Ben-Naim. Calculated Kirkwood-Buff parameters are presented for ethanol + water, and t-butanol + water mixtures. Theory is described for the calculation of the so-called gk parameters for first- and second-order reactions. These parameters have been calculated for the alkaline hydrolysis of an iron(II) complex, and the spontaneous hydrolysis of 4-methoxypheny1-2, 2-dichloropropionate in t-butanol + water mixtures. The significance of the calculated parameters, in terms of the role of preferential solvation in the reaction mechanism, is discussed.
14
Wilkins, David M. "Nuclear quantum effects in aqueous systems." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:7ccdf595-d72e-49a7-a18c-346ba6bc2312.
Повний текст джерелаАнотація:
This thesis is concerned with the influence of nuclear quantum effects (NQEs) on the properties of aqueous systems. Although such systems have been studied ever since methods to account for NQEs within atomistic simulations were first developed, it has been shown in recent years that a full accounting for the flexibility of O-H bonds leads to a cancellation between intermolecular and intramolecular quantum effects, meaning that the total effect is often much smaller than was originally believed to be the case. Several examples of systems are studied in which NQEs give rise to a small, though detectable, effect. Path integral molecular dynamics simulations are used to explain the results of sum-frequency generation spectroscopy experiments that observe a small preference for hydrogen over deuterium atoms in the dangling O-H bonds at the surface of isotopically substituted liquid water. These simulations are able to give a free energy of isotope fractionation that agrees quite well with that obtained from experiments. The effect of quantum mechanics on dynamical properties is studied by using ring polymer molecular dynamics to look at two types of process: the exchange of water around monatomic, monovalent ions and the reorientation of hydrogen bonds in the pure liquid. In both cases, NQEs speed up the process by a small degree, but leave the mechanism of the process unchanged. This suggests that a classical treatment of these processes will give an excellent qualitative description, and will give a quantitatively reasonable result. The results of second-harmonic generation scattering experiments on aqueous solutions of ions are also considered: the ions are shown to give rise to long-ranged orientational correlations between solvent molecules. Replacement of light water with heavy water causes a significant change in the scattered signal intensity, a hallmark of NQEs. A preliminary, classical study is performed using both Debye-Hückel theory and molecular dynamics simulations to explain the microscopic origin of these effects.
15
Neves, Catarina Maia Seco Seiça. "Aqueous biphasic systems with ionic liquids." Master's thesis, Universidade de Aveiro, 2009. http://hdl.handle.net/10773/3092.
Повний текст джерелаАнотація:
Mestrado em Química Analítica e Controlo de QualidadeO objectivo principal deste trabalho é estudar o equilíbrio de fases de líquidos iónicos em sistemas aquosos bifásicos. Para isso foram estudadas as solubilidades mútuas entre água e líquidos iónicos hidrofóbicos, e foi criado um modelo que descreve esta propriedade. Além disso, foram realizados e estudados sistemas aquosos bifásicos com líquidos iónicos hidrofílicos e o sal inorgânico K3PO4. Os líquidos iónicos são sais compostos por iões grandes que não formam uma rede cristalina bem definida, e assim permanecem líquidos à temperatura ambiente ou perto desta. Estes compostos são solventes interessantes, em reacções orgânicas convencionais do tipo liquido-liquido e em processos de separação, devido às suas propriedades termofísicas, à sua grande capacidade de solvatação e à sua pressão de vapor desprezável. Em particular, o conhecimento de solubilidades mútuas com água é muito importante para a extracção de compostos orgânicos em meios aquosos, uma vez que são necessários líquidos iónicos com baixa solubilidade na água, e para tal o conhecimento das solubilidades mútuas é de elevada importância. Com este propósito, as solubilidades mútuas entre a água e os líquidos iónicos foram determinadas no intervalo de temperatura entre 288,15 K até 318,15 K e à pressão atmosférica. Os líquidos iónicos seleccionados permitiram o estudo da influência da estrutura do catião e do anião. De forma a complementar este estudo foi criado um modelo QSPR de forma a prever as solubilidades mútuas entre a água e os líquidos iónicos a 303,15 K. Os sistemas aquosos bifásicos com líquidos iónicos podem ser de especial interesse em aplicações de biotecnologia na separação e purificação de biomoléculas vitais. Assim, foi realizado um estudo sistemático envolvendo um grande número de líquidos iónicos baseados no catião imidazólio afim de se obter nova informação acerca da capacidade dos líquidos iónicos promoverem a formação de sistemas aquosos bifásicos e extraírem biomoléculas. Com este propósito, foi avaliada a influência da natureza do anião, bem como a estrutura do catião. Foram determinados diagramas de fase com líquidos iónicos, água e K3PO4, assim como as respectivas linhas de equilíbrio. Como complemento, os sistemas aqui estudados foram também caracterizados pelo seu potencial em extrair aminoácidos, para o qual o L-triptofano foi seleccionado como uma biomolécula modelo. ABSTRACT: The main goal of this work is to study the behavior of ionic liquids in aqueous biphasic systems. For that purpose it was studied the mutual solubilities of water and hydrophobic ionic liquids and created a model to describe that property. In addition, aqueous biphasic systems employing hydrophilic ionic liquids and an inorganic salt, K3PO4, were carried and analyzed. Ionic liquids are salts composed of large ions that cannot easily form an ordered crystal and thus remain liquid at or near room temperature. Their intrinsic thermophysical properties, their high solvating ability and their negligible vapour pressures make them interesting solvents in conventional organic liquid-phase reactions and in separation processes. In particular, the knowledge of their mutual solubilities with water is very important for the extraction of organic products from chemical reactions that proceed in aqueous media and in liquid-liquid extractions from aqueous phases since ionic liquids with low solubility in water are required, and therefore the knowledge of their mutual solubilities with water is highly important. With that aim, the mutual solubilities between water and hydrophobic ionic liquids were determined from temperatures ranging from 288.15 K to 318.15 K and at atmospheric pressure.The selected ILs allowed the study of the cation and anion structure influence. In order to complement this experimental approach, a QSPR model was built to predict mutual solubilities between water and ionic liquids at 303.15 K. Aqueous biphasic systems containing ionic liquids could be especially interesting in biotechnological applications for the separation and purification of vital biomolecules. Therefore, a systematic study involving a large number of imidazolium-based ILs was conducted to provide new information related to the ionic liquids ABS promoting capability and extraction ability. For that purpose, the influence of the anion nature as well as the cation structure composing the ionic liquids were evaluated. Phase diagrams of the aqueous biphasic systems formed by ionic liquids and K3PO4, and the respective tie-lines, were measured. In addition, the aqueous biphasic systems here investigated were also characterized according to their extractive potential of aminoacids, where Ltryptophan was selected as a model biomolecule.
16
Das, Bijan. "Physico - chemical investigations on the ion-solvent interactions of some Tetraalkylammonium and common ions in non-aqueous and mixed binary aqueous solvent systems." Thesis, University of North Bengal, 1992. http://hdl.handle.net/123456789/719.
Повний текст джерела
17
Phillips, Pamela June. "Microbial degradation of hydrocarbons in aqueous systems." Thesis, University of Surrey, 2003. http://epubs.surrey.ac.uk/842666/.
Повний текст джерелаАнотація:
There is a vast worldwide consumption of petroleum hydrocarbons and accidental release in to the environment is common. For example petroleum forecourt retail outlets have 'interceptors' to prevent release of hydrocarbons into the environment. The aim of this study was to investigate options for in-situ bioremediation of the hydrocarbon substrates within these 'interceptors' in a laboratory model. The initial studies on bioremediation were undertaken with diesel as the substrate. It was shown that the addition of nitrogen and phosphorus to the system increased hydrocarbon mineralisation by a factor of 16, resulting in increased carbon dioxide evolution. There was strong evidence indicating that nitrogen and phosphorus were the limiting factor for hydrocarbon metabolism in this aqueous system. Trichoderma harzianum and a soil bacterial isolate LFC D1 FI were assessed and shown to degrade hexadecane and pristane. The positive affect of adding a cosubstrate was evident in flask studies; the rates of degradation by LFC D1 FI and T. harzianum were approximately doubled and tripled respectively in the presence of glucose compared to treatments without glucose. Previous attention has focused on the ability of Phanerochaete chrysosporium to degrade polycyclic aromatic hydrocarbons; in this study the degradation of aliphatics was investigated. Spores from P. chrysosporium induced on the hydrocarbon substrate were found to be necessary to degrade hexadecane. Pseudomonas putida was unable to grow in liquid media containing hydrocarbons, however on solid media and in an aqueous environment containing acid-washed sand, degradation of hydrocarbons was evident, hi the presence of sand P. putida degraded both hexadecane and pristane by 70% of the initial concentration added; in the absence of sand no degradation in the aqueous system was seen. This suggests surface attachment plays an important role in hydrocarbon degradation by P. putida. The attachment and use of the sessile P. putida in aliphatic hydrocarbon degradation is discussed.
18
Hamilton, Robin. "Hydrolysis of silicone polymers in aqueous systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ64721.pdf.
Повний текст джерела
19
Cheluget, Eric Lang̀at. "Equilibrium in aqueous liquid-liquid salt systems." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39824.
Повний текст джерелаАнотація:
Experimental equilibrium phase diagrams, tie-lines and plait points were obtained for ternary systems consisting of water, sodium chloride and: 1-propanol at 298 K; n-dodecylammonium chloride at 303 K; poly(ethylene glycol) 8000 at 333 K; poly (propylene glycol)-425 at 278, 298 and 333 K; poly(propylene glycol)-725 at 278 and 298 K. For the 1-propanol and polymer systems, most of the salt was in the bottom phase while the nonionic solute was concentrated in the top phase. In the n-dodecylammonium chloride system the salt was evenly distributed between the phases while most of the surfactant was in the top phase. For the poly(propylene glycol) systems, the size of the region of two liquid phases increases with molecular weight and temperature.A modified form of the Flory-Huggins theory was developed for liquid-liquid equilibrium in binary aqueous systems of nonelectrolytes whose closed-loop phase diagrams contain both upper and lower consolute temperature points. The modification involved the assumption of an adjustable molecular size parameter $ chi sb{12}$. Calculations were performed for 15 aqueous binary systems. The models correlated the liquid-liquid equilibrium data accurately.
Liquid-liquid equilibrium in aqueous biphasic salt systems was modelled using an expression for the excess Gibbs energy of the solution. The expression is based on modified forms of the Mean Spherical Approximation, the Bromley equation, and the Flory-Huggins theory. The model requires 3 and 5 adjustable parameters for tenary and quaternary systems, respectively. The model accurately correlated vapor- and liquid-liquid equilibrium data for 8 ternary and 3 quaternary aqueous biphasic salt systems.
20
Fee, Monica. "Evaluation of chitosan stability in aqueous systems." Thesis, University of Nottingham, 2006. http://eprints.nottingham.ac.uk/14334/.
Повний текст джерелаАнотація:
This study considers the molecular weight, conformation, stability and nanoparticle formation of the polysaccharide chitosan in relation to its pharmaceutical applications in the drug delivery. Chitosan has bioadhesive and absorption enhancing properties that augment its use in the delivery of therapeutic proteins and peptides across mucosal membranes. The molecular weights of a range of chitosans, with degree of acetylation (DA) ranging form 7 to 30%, were studied using the hydrodynamic techniques of SEC-MALLS (size exclusion chromatography coupled with multi-angle laser light scattering) and analytical ultracentrifugation. It was found that there was reasonable agreement between the two techniques with molecular weights obtained ranging between 42000 and 200000 kDa. These results indicated that the use of SEC-MALLS as a measure of degradation during storage studies would be valid and this technique would be more convenient due to the much shorter time required for each sample. Conformational studies indicated that in 0.2M acetate buffer, pH 4.3, the chitosan samples studied appeared to have an extended conformation which is in agreement with studies performed by other researchers (e.g. Anthonsen, M. W., K. M. Vårum and O. Smidsrød (1993) Carbohydrate Polymers 11: 193-201 and Dyer, A. M., M. Hinchcliffe, P. Watts, J. Castile, I. Jabbal-Gill, R. Nankervis, A. Smith and L. Illum (2002) Pharmaceutical Research 19(7): 998-1008), non-withstanding complications in interpretation through possible solvent draining effects (Berth, G., Colfen, H., Dautzenberg H (2002) Prog. Coil. Int. Sci. 119, 50-57). Degradation studies were performed using viscosity measurements and SECMALLS to measure molecular weight. The effect of solution parameters such as pH and ionic strength were examined as well as structural parameters, e.g. molecular weight and DA. Degradation was found to increase as the pH of the solution decreased indicating that acid hydrolysis was occurring. The range of ionic strength studied (0.1 - 0.3M) did not have any significant effect on degradation rate. For the samples studied, molecular weight appeared to have little effect on degradation, however, the more deacetylated the polysaccharide, the slower the rate of degradation due to increased charged residues along the chain. Finally chitosan nanoparticles were then prepared using ionotropic gelation with tripolyphosphate pentasodium. This technique produced nanoparticles in the size range 320 - 380 run with an insulin loading capacity of 30-50%. Insulin-loaded nanoparticles were prepared and resuspended in acetate buffer at various pHs. The molecular weight and insulin loading was tested at 2-week intervals and results indicated that chitosan degradation was reduced by 30% compared to a control chitosan solution, and the total amount of insulin incorporated remained constant over the storage period.
21
Briggs, Barbara. "Kinetics in aqueous and microhetero-geneous systems." Thesis, University of Leicester, 1985. http://hdl.handle.net/2381/34028.
Повний текст джерелаАнотація:
Rate constants for chemical reactions in various aqueous and micro- heterogeneous systems have been measured and analysed. A large part of the thesis is concerned with interpreting kinetic trends in two water-in-oil microemulsions. Kinetic data for inorganic reactions involving low-spin iron (II) di-imine oorplexes and for reactions involving the organic substrates, 2,4-dinitrochlorobenzene, crystal violet and malachite green in microemulsions have been collected and used to identify different structural zones in these solvent systems. The kinetic data are interpreted in terms of a model in which reaction occurs at an interfuse. Reactions involving cis-bis(pyridine)tetracarbonylmolybdenum (0) in oil- in-water, water-in-oil microemulsions and organic solvent mixtures have been studied. Aquation reactions of iron (II) hexadentate Schiff base have been used to identify microheterogeneous phases in water-rich '2-butoxyethanol + water' mixtures. Solvent effects on initial and transition states are discussed for reactions of iron (II) glyoxal bis-N methylamine with hydroxide ions in 'methanol + water' mixtures and reactions of iron(II) 1,10-phenan- throline with hydroxide ions in 'isopropanol + water' mixtures. Transfer chemical potentials for single ions, in 'acetone + water' mixtures, have been estimated, using solubility data for salts in conjunction with the assumption that transfer chemical potentials for tetraphenylboronate and tetraphenylarsonium ions are equal. Effects of added salt on the neutral hydrolysis of phenyldichloro- acetate in aqueous solutions are examined in terms of solvent cosphere interactions between ions. The temperature dependence of rate constants for reactions of iron (II) 4-methyl, 1,10-phenanthroline have been examined. The results are discussed in terms of isobaric, isothermal and isochoric activation parameters. The meaning of the term 'isochoric' is clarified in this context.
22
Goh, Sher Leen. "Removal of organic contaminants from aqueous systems." Thesis, University of Strathclyde, 2015. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24743.
Повний текст джерелаАнотація:
This research investigates the removal of aromatic organic contaminants (nitrobenzene (NB), aniline (AN), paracetamol (PCT) and hydroquinone (HQ)) from aqueous systems. For NB, this study focusses on removal via both iron reduction and adsorption, while removal of the other three compounds is focussed purely on adsorption. The results demonstrate NB degradation using iron powder produces AN, with the rate decreasing under basic conditions, due to corrosive effects; it is established that the iron surface is essential to the degradation process. Initial NB concentration influences degradation, and pseudo-first order kinetics are observed for all systems studied. For the adsorption studies on all four species, non-functionalised Macronet MN200, acidic functionalised hyper-cross-linked polymeric resins MN500 and S957, and Granular Activated Carbon (GAC) were tested as sorbents. The results show the kinetics of adsorption, for all contaminants, follow pseudo-second order models with rates controlled by particle diffusion. For adsorption of NB, PCT and HQ, the equilibrium uptake capacities increase with decreasing acidic functionalisation of the sorbent surface; while the opposite trend was obtained for AN removal. The adsorption rate decreased as sorbent acidic capacity increased, for all sorbents, due to the inherent surface chemistry and smaller surface area of the acidic functionalised sorbents used. For equilibria study, the Freundlich equation fits the data most appropriately and adsorption of all contaminants onto the selected sorbents is a physical process. Adsorption of NB, AN, and PCT onto the studied sorbents is favourable, while it is moderately favourable for HQ. Leaching tendencies showed < 40% of all contaminants were leached from the sorbents with the higher leaching rates for the macroporous sorbents. Overall, the results obtained suggest polymeric resins as viable candidates for the removal of targeted aromatic substances from aqueous systems.
23
Duncan, Laura Kristin. "Characterization of C60 Nanoparticles in Aqueous Systems." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/32439.
Повний текст джерелаАнотація:
The discovery that negatively charged aggregates of C60 fullerene are stable in aqueous environments has elicited concerns regarding the potential environmental and health effects of these aggregates. Although many previous studies have used aggregates synthesized using intermediate organic solvents, this work primarily employed an aggregate production method that more closely emulates the fate of C60 upon accidental release into the environment â extended mixing in water. The aggregates formed via this method (aqu/nC60) differ from those produced using the more common solvent exchange methods. The aqu/nC60 aggregates are heterogeneous in size (20 nm and larger) and shape (angular to round), negatively charged, and crystalline in structure â exhibiting a face centered cubic (fcc) system. Solution characteristics such as aqu/nC60 aggregate size and concentration were found to be dependant upon preparation variables such as stirring time, initial C60 concentration, and initial particle size.
Additional experiments indicate that aggregate charge, structure, and stability are highly dependant upon the identity of co-solutes (NaCl, CaCl2, sodium citrate) and their concentrations. Citrate concentrations greater than 0.5 mM resulted in the formation of very small (< 20 nm) spherical aqu/nC60 particles. At moderate citrate concentrations (~ 1 mM) a more negative surface charge was observed, which may be an indication of increased nC60 stability. In contrast, high concentrations of monovalent and divalent electrolytes result in aggregation and sedimentation of nC60 out of solution. Our research describes the effect that solution composition has on aggregate formation and stability, and suggests that C60 fate and transport will be a function of solution composition.Master of Science
24
Huang, Tien-Lu. "Oscillating Aqueous Gels as Drug Delivery Systems." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366066532.
Повний текст джерела
25
Zappia, Michael Joseph. "Electrochemical phase diagrams for aqueous redox systems." Case Western Reserve University School of Graduate Studies / OhioLINK, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=case1054840226.
Повний текст джерела
26
Vaz, Tatiana Sofia Marçalo. "Extraction of antioxidants with aqueous biphasic systems." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/13303.
Повний текст джерелаАнотація:
Mestrado em Bioquímica - Bioquímica ClínicaNowadays, antioxidants present a great relevance in a variety of applications used by the pharmaceutical and the cosmetic industries. The antioxidants are able to inhibit or to retard the oxidation of other compounds, and mainly the oxidation caused by free radicals, and that is the reason of their importance in the industry and their incorporation into a variety of products. For the utilization of antioxidants in effective quantities, it is necessary to either chemically synthesize them, what is expensive and may causes problems due to their non-natural origin, or to extract them from their natural sources (biomass). Conventional methods for the extraction of antioxidants and the following purification are normally expensive and time-consuming. Therefore, other extraction methods, like the liquid-liquid extraction using aqueous biphasic systems (ABS), have been studied. In this work, the use of ABS based on ionic liquids (ILs) and polymers is proposed as an alternative for the conventional systems that are mostly composed of polymers and inorganic salts. The use of ILs allows the tuning of the properties of the extraction systems by variation of their ions and so to increase the extraction efficiencies. In this work, it is shown, for the first time, that poly(vinyl pyrrolidone) (PVP) and poly(vinyl alcohol) (PVA) of different molecular weights form ABS with phosphonium-based and imidazolium-based ILs. The respective phase diagrams were determined at 25 °C to define the minimum concentrations that are necessary for the formation of two aqueous phases. Finally, the ability of these systems as liquid-liquid extraction systems was evaluated. To this end, the partition coefficients and extraction efficiencies of several antioxidants (gallic acid, vanillin, vanillic acid and syringic acid) using the studied systems were determined. Extraction efficiencies ranging from 75% to 95 % were obtained for the different systems, thus demonstrating their capability for extracting purposes. In general, the most efficient system for the extraction of antioxidants was that composed of the IL 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([C4mim][CF3SO3]) and the PVA of 9,000-10,000 g.mol-1 (PVA9) for the extraction of all the studied antioxidants.
Atualmente os antioxidantes apresentam uma relevância elevada numa vasta gama de aplicações utilizadas pela indústria farmacêutica e de cosmética. Os antioxidantes são capazes de inibir ou de retardar a oxidação de outros compostos, principalmente a oxidação causada por radicais livres, e daí o seu destaque na indústria e da sua incorporação nos produtos mais variados. No entanto, para a utilização de antioxidantes em quantidades eficazes, é necessário sintetizá-los quimicamente, o que é dispendioso e pode acarretar problemas devido à sua origem não natural, ou extraí-los das suas fontes naturais (biomassa). Os métodos convencionais para a extração e posterior purificação de antioxidantes são normalmente dispendiosos e morosos. Neste sentido, têm vindo a ser estudados outros métodos de extração, e mais recentemente, a extração líquido-líquido recorrendo a sistemas aquosos bifásicos (SAB). Neste trabalho propõe-se a utilização de SAB constituídos por líquidos iónicos (LIs) e polímeros como alternativa aos sistemas convencionais maioritariamente formados por polímeros e sais inorgânicos. A utilização de LIs permite afinar as propriedades dos sistemas extrativos por variação dos iões que os compõem, e portanto, aumentar as eficiências de extração. Neste trabalho foi demostrada, pela primeira vez, a formação de SAB constituídos por polivinilpirrolidona (PVP) e álcool polivinílico (PVA) de várias massas moleculares e LIs das famílias dos fosfónios e dos imidazólios. Os respetivos diagramas de fase foram determinados a 25 ºC de modo a inferir sobre as concentrações mínimas necessárias para a formação de duas fases aquosas. Por fim, estes sistemas foram avaliados quanto à sua capacidade como sistemas de extração do tipo líquido-líquido. Para tal, determinaram-se os coeficientes de partição e as eficiências de extração para vários antioxidantes (ácido gálico, vanilina, ácido vanílico e ácido siríngico) utilizando os diversos sistemas estudados. Obtiveram-se eficiências de extração que variaram entre 75 % e 95 %, o que demonstra a viabilidade destes sistemas na extração de antioxidantes. De um modo geral, o sistema mais eficiente para extrair antioxidantes é composto pelo LI 1-butil-3-metilimidazólio trifluorometanosulfonato ([C4mim][CF3SO3]) juntamente com o PVA de 9.000-10.000 g.mol-1 (PVA9) para todos antioxidantes estudados.
27
Hotrum, Natalie Elizabeth. "Interactions between kappa-carrageenan and beta-lactoglobulin in gelling and non-gelling aqueous systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ43172.pdf.
Повний текст джерела
28
Law, Karianne Mia. "Controls on trace element partitioning in carbonate systems." Thesis, University of Bristol, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300560.
Повний текст джерела
29
Bridgeman, Catherine H. "Computational studies of layered materials and aqueous systems." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388760.
Повний текст джерела
30
Xu, Rong. "Equilibrium studies of aqueous surfactant systems containing additives." Thesis, University of Salford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395703.
Повний текст джерела
31
Junker, Beth H. (Beth Helene). "Monitoring and assessment of aqueous/perfluorocarbon fermentation systems." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14333.
Повний текст джерела
32
Louros, Cláudia Leonor Santos. "Extraction of biomolecules with aqueous two phases systems." Master's thesis, Universidade de Aveiro, 2009. http://hdl.handle.net/10773/3113.
Повний текст джерелаАнотація:
Mestrado em Materiais Derivados de Recursos RenováveisOs líquidos iónicos (LIs) representam uma nova classe de solventes iónicos com pressões de vapor desprezáveis o que os torna potenciais substitutos para compostos orgânicos voláteis que são actualmente utilizados. Para além disso, a combinação selectiva do catião e do anião permite afinar as suas propriedades termofísicas e a sua capacidade de solvatação/extracção. Os sistemas aquosos bifásicos (SAB) são considerados uma alternativa rentável e eficaz para a extracção, recuperação e purificação de diversas biomoléculas. Neste trabalho, traçaram-se os diagramas de fases de sistemas compostos por líquido iónico + sal inorgânico + água e líquido iónico + hidratos de carbono + água, à temperatura de 298 K e pressão atmosférica. Para além do interesse em SAB baseados em LI e sais inorgânicos, a aplicação de hidratos de carbono para substituir os sais inorgânicos em sistemas de elevada carga iónica aparenta ser uma abordagem mais benéfica. Os dois tipos de SAB estudados foram avaliados no que respeita à sua capacidade para extracção de biomoléculas. As biomoléculas seleccionadas comportam aminoácidos, corante alimentares e alcalóides. Os SAB compostos por LIs demonstraram ser uma potencial abordagem para a extracção de biomoléculas em processos biotecnológicos. ABSTRACT: Ionic liquids (ILs) represent a new class of ionic solvents that exhibit negligible vapour pressures and that further makes them potential substitutes for the volatile organic compounds currently employed. Moreover, the selection of both the cation and anion and, therefore, the possibility of fine-tunning their thermophysical properties and solvation/extraction performance, is an extremely important feature. Aqueous biphasic systems (ATPS) are considered attractive alternatives for the extraction, recovery and purification of several biomolecules. In this work, phase diagrams composed by ionic liquid + inorganic salt + water, at 298 K and atmospheric pressure, were determined. Besides the interest on IL-based ATPS with inorganic salts, the application of carbohydrates to substitute those highly charged systems seems to be a more benign approach. Both type of ATPS were evaluated trough their extraction capability for biomolecules. The selected biomolecules include amino acids, food colourings and alkaloids. ILs-based ATPS have shown to be a prospective extraction media for biomolecules in biotechnological processes.
33
Almeida, Ana Mafalda Rodrigues. "Purification of antibodies using aqueous two-phase systems." Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/11789.
Повний текст джерелаАнотація:
Mestrado em Bioquímica - Métodos BiomolecularesCom o aparecimento de microrganismos resistentes a antibióticos, de doenças que não respondem a terapias comuns recorrendo a fármacos e de indivíduos que são incapazes de responder ao método de vacinação tradicional, hoje em dia, é de grande preocupação para a sociedade humana, o desenvolvimento de anticorpos específicos com aplicação em imunoterapia passiva. Apesar de os anticorpos de mamíferos serem mais específicos, os anticorpos obtidos a partir de gema de ovo de galinhas imunizadas, imunoglobulina Y (IgY), são uma alternativa possível onde a quantidade de anticorpos obtida é maior e recorrendo ainda a métodos não invasivos. Esta grande quantidade disponível de anticorpos permite explorar um novo tipo de biofármacos menos dispendiosos que os convencionais. No entanto, o custo da produção de IgY com elevado grau de pureza continua a ser mais elevado do que o de outras terapias convencionais devido à falta de uma técnica de purificação eficiente. Assim, neste trabalho, estudaram-se três tipos de sistemas aquosos bifásicos (SAB) constituídos, nomeadamente, por polímeros e Na2SO4, por polímeros, Na2SO4 e líquidos iónicos (LIs) como adjuvantes, e por Na2SO4 e LIs, como uma técnica de extração e purificação alternativa para o IgY a partir da gema de ovo. De acordo com os resultados obtidos pode-se constatar que a purificação do IgY não foi conseguida num único passo de extração (sendo a β-livetina o maior contaminante encontrado). No entanto, e dos resultados conseguidos, mostrou-se que os SAB utilizando LIs como adjuvantes permitem uma extração seletiva da β-livetina para uma das fases e será possível purificar a imunoglobulina ao aplicar extrações sucessivas. De entre os vários SAB avaliados, os que permitiram melhores resultados em termos de extração seletiva e posterior purificação do IgY são constituídos por polietilenoglicol (PEG) com uma baixa massa molecular e por LIs com o anião dicianamida.
With the emergence of antibiotic-resistant microorganisms, diseases that are unresponsive to drug therapy, and the appearance of individuals that are unable to respond to conventional vaccines, the development of antigenspecific antibodies for use in passive immunotherapy is, nowadays, a major concern in human society. Despite the most focused mammal antibodies, antibodies obtained from egg yolk of immunized hens, immunoglobulin Y (IgY), are an alternative option that can be obtained in higher titres by non-stressful and non-invasive methods. This large amount of available antibodies opens the door for a new kind of cheaper biopharmaceuticals. Nevertheless, the production cost of high-quality and/or high-purity IgY still remains higher than other drug therapies due to the lack of an efficient purification method. Therefore, in this work, three types of aqueous two-phase systems (ATPS) were studied constituted by polymers and Na2SO4, polymers, Na2SO4 and ionic liquids (ILs) as adjuvants and by Na2SO4 and ILs, as an alternative technique for the selective extraction, and thus purification, of IgY from egg yolk. According to the obtained results, the complete purification of IgY was not achieved in a single step procedure (with β-livetin being the major contaminant found). However, the results obtained reveal that ATPS using ILs as adjuvants allow the selective extraction of β-livetin for one phase and it is possible to purify the immunoglobulin if successive extractions are applied. Amongst the various ATPS evaluated, the improved results on the selective extraction and subsequent purification of IgY were obtained with ATPS consisting of polyethylene glycol (PEG) of low molecular mass and ILs with the anion dicyanamide.
34
Ferreira, Ana Maria da Conceição. "Separation of dyes with reversible aqueous biphasic systems." Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/12572.
Повний текст джерелаАнотація:
Mestrado em Engenharia QuímicaThe main objective of this work conveys on the study of reversible aqueous two-phase systems (ATPS), constituted by ionic liquids (ILs), and their potential application for the selective separation of dyes mainly used in the textile industry. The textile manufacturing is one of the main industries which discharges a heavy load of chemicals, especially large contents of dyes during the dying process through wastewaters, which results in severe environmental and economic concerns. In this context, this work focuses on the applicability of reversible ATPS, as well as on the development of more benign systems than those studied hitherto, as an alternative technique for the removal of dyes from wastewaters. Additionally, special attention was also given to the understanding of the molecular mechanisms which rule the partitioning of dyes between the coexisting phases of ATPS. IL-based ATPS display a widespread applicability in the extraction, concentration and purification of a large range of compounds, including dyes. Thus, this work started with investigations on the extraction of a set of dyes (chloranilic acid, indigo blue and sudan III) using more conventional ATPS composed of ILs and an organic/inorganic salt. At this stage, the influences of the IL chemical structure, the salting-out ability of the salt employed and the consequent pH of the aqueous medium were evaluated by the dyes extraction efficiencies. The results obtained reveal that a proper selection of the IL and salt can lead to the complete extraction of the three dyes studied for the IL-rich phase in a single-step procedure. After demonstrating the high capacity of ATPS formed by ILs to extract dyes from aqueous phases, it was studied the applicability of pH-triggered reversible ATPS in the selective separation of organic and inorganic dyes (sudan III and pigment blue 27). The reversibility of this type of ATPS was achieved by the manipulation of the speciation of the organic salt used. The results obtained confirm the reversibility behaviour of ATPS by a pH-driven phenomenon, at least for three times, as well as their selective separation capability with both dyes being extracted for opposite phases. Finally, and after demonstrating the existence of reversible pH-triggered ATPS, mixtures of a polymer and cholinium-based ILs combined with anions derived from carboxylic acids were investigated, foreseeing the search of more benign and biocompatible systems. The reversibility of these systems was achieved with the speciation of the IL anion as a function of the pH. These systems were finally evaluated in what concerns their performance for the extraction and selective separation of dyes (sudan III, pigment blue 27 and pigment 29), and the study revealed that IL-polymer systems are capable of selectively extract organic and inorganic dyes for opposite phases.
O principal objetivo do presente trabalho recai no estudo de sistemas aquosos bifásicos (SAB) reversíveis, constituídos por líquidos iónicos (LIs), bem como na sua potencial aplicação para a separação seletiva de corantes utilizados maioritariamente pela indústria têxtil. Esta é uma das principais indústrias que liberta uma grande quantidade de produtos químicos, destacando-se a descarga de elevadas quantidades de corantes através dos respetivos efluentes aquosos, o que é motivo de elevada preocupação tanto a nível ambiental como económico. Este trabalho centra-se no estudo da aplicabilidade de SAB reversíveis, através de variações de pH do meio aquoso, assim como na procura de SAB constituídos por LIs mais benignos que os estudados até ao momento, como uma técnica alternativa para a remoção de corantes de efluentes aquosos. Adicionalmente, também se deu um especial destaque à interpretação dos mecanismos que regem a partição de corantes entre as duas fases neste tipo de sistemas. Os SAB constituídos por LIs apresentam uma grande aplicabilidade na extração e purificação de uma vasta gama de compostos, incluindo corantes. Assim, iniciou-se o presente trabalho com a extração de um conjunto de corantes (ácido cloroanílico, azul indigo, sudão III) utilizando SAB mais convencionais e constituídos por LIs e um sal orgânico/inorgânico. Nesta etapa avaliou-se o efeito da estrutura química do LI sobre a capacidade de extração, assim como o efeito do sal e consequente pH do meio. Os resultados obtidos revelaram que uma seleção adequada do LI e do sal pode conduzir à extração completa dos três corantes estudados e num único passo operacional. Após demonstrar a elevada capacidade de SAB constituídos por LIs para extrair corantes de fases aquosas, estudou-se a aplicabilidade de SAB reversíveis, por variações de pH, na separação seletiva de corantes orgânicos e inorgânicos (sudão III e pigmento azul 27). A reversibilidade deste tipo de SAB foi conseguida com a manipulação da especiação do sal orgânico utilizado. Os resultados obtidos confirmaram a reversibilidade dos SAB, pelo menos até três vezes, por variação do pH, assim como uma capacidade de extração seletiva de cada um dos corantes para fases opostas. Por fim, e após confirmada a existência de SAB reversíveis, estudaram-se misturas de um polímero e LIs da família das colinas com aniões derivados de ácidos carboxílicos com o intuito de encontrar sistemas mais benignos e biocompatíveis. A variação do pH e reversibilidade neste tipo de sistemas foi conseguida com a especiação do anião do LI. Estes sistemas foram finalmente avaliados no que respeita à sua capacidade de extração e separação seletiva de corantes (sudão III, pigmento azul 27 e pigmento 29), e o estudo revelou que os sistemas LI-polímero conduzem a uma extração seletiva entre os corantes orgânicos e os pigmentos inorgânicos.
35
Castro, Leonor Sofia Oliveira. "Antibodies purification using aqueous micellar two-phase systems." Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/21187.
Повний текст джерелаАнотація:
Mestrado BiotecnologiaNos últimos anos, terapias à base de anticorpos mono e policlonais têm atraído muita atenção por parte da indústria farmacêutica levando a um aumento da investigação neste campo. A imunoglobulina G (IgG), um dos anticorpos já aprovados pela Food and Drug Administration (FDA) é uma das imunoglobulinas mais abundantes nos mamíferos, cuja obtenção requer o uso de técnicas invasivas. Como alternativa, e devido às semelhanças estruturais com a IgG, surge o uso da imunoglobulina Y (IgY) que se encontra presente na gema de ovo de galinha. Além disso, as quantidades de IgY presente na gema do ovo são bastante altas (100-150 mg/ovo) quando comparadas com a quantidade de IgG no soro (200mg/40mL de sangue). Contudo, o isolamento da IgY a partir da gema de ovo é bastante dispendioso e moroso, uma vez que requer o uso de processos com várias etapas. Tendo em conta estas desvantagens torna-se indispensável o desenvolvimento de um método mais económico e mais biocompatível. Os sistemas micelares de duas fases aquosas, um tipo específico de sistemas de duas fases aquosas que recorrem ao uso de surfactantes, surge como alternativa para a extração, purificação e/ou concentração de (bio)moléculas. Adicionalmente, o uso de líquidos iónicos (LIs) como co-surfactantes pode modificar as propriedades do surfactante e dessa forma conduzir a mudanças na extração das (bio)moléculas. Neste sentido, o objetivo deste trabalho é o desenvolvimento de um novo método para a extração, purificação e concentração da IgY através do uso de sistemas micelares de duas fases aquosas convencionais e mistos com LIs pertencentes à família dos imidazólios e fosfónios a atuar como co-surfactantes. Para tal, foram otimizados parâmetros como a concentração de surfactante e da fração de proteínas solúveis em água, a ausência e presença de (LIs) bem como o efeito da sua concentração e estrutura química. Após toda a otimização, os melhores resultados foram obtidos com o sistema convencional e sistema misto com [C16mim]Cl, onde se obtiveram purificações de 51.2 % e 64.5% e rendimentos de 100% e 74.7%respetivamente.
In the past few years, therapies based on mono- and polyclonal antibodies have attracted attention from pharmaceutical industries leading to a drastic research increment in this field. Immunoglobulin G (IgG), one of the antibodies already approved by Food and Drug Administration (FDA), is the most abundant mammalian immunoglobulin, whose acquisition requires the use of invasive techniques. As an alternative to the use of mammalian antibodies, Immunoglobulin Y (IgY) from hens’ egg yolk emerges due to its structural similarity to IgG. Furthermore, the IgY amount present in egg’s yolk can be quite high (100-150 mg/egg) when compared with the IgG amount in the blood serum (200 mg/40 mL of blood). However, IgY isolation from the egg’s yolk is quite expensive and time consuming, since it requires multistep processes. Taking these disadvantages into account, the development of a cheaper and more biocompatible technique for IgY extraction and purification becomes mandatory. Aqueous micellar two-phase systems (AMTPS) are a special type of aqueous two-phase systems that comprise micellar solutions of surfactants for (bio)molecules extraction, purification and/or concentration. Additionally, the use of ionic liquids (ILs) as co-surfactants can modify the surfactant properties, leading to changes in the phase separation as well as in the (bio)molecules fractionation. In this sense, this work aims at the development of a new extraction, purification and concentration technique for IgY from egg’s yolk using both conventional and mixed AMTPS with tensioactive ILs belonging to two distinct families, namely imidazolium and phosphonium, acting as co-surfactants. Thus, parameters like the surfactant and the water-soluble proteins fraction (WSPF) concentration, the presence/absence of IL as well as the effect of its concentration and structural features were optimized. After the optimization procedure, the best results were obtained with the conventional system and mixed AMTPS with [C16mim]Cl, were a purification of 51.2 % and 64.5 % and yields of 100% and 74.7%, respectively, were obtained.
36
Calixto, João Paulo Duarte. "Concentration of tumor biomarkers using aqueous biphasic systems." Master's thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/15353.
Повний текст джерелаАнотація:
Mestrado em Bioquímica - Bioquímica ClínicaAccording to the World Health Organization, around 8.2 million people die each year with cancer. Most patients do not perform routine diagnoses and the symptoms, in most situations, occur when the patient is already at an advanced stage of the disease, consequently resulting in a high cancer mortality. Currently, prostate cancer is the second leading cause of death among males worldwide. In Portugal, this is the most diagnosed type of cancer and the third that causes more deaths. Taking into account that there is no cure for advanced stages of prostate cancer, the main strategy comprises an early diagnosis to increase the successful rate of the treatment. The prostate specific antigen (PSA) is an important biomarker of prostate cancer that can be detected in biological fluids, including blood, urine and semen. However, the commercial kits available are addressed for blood samples and the commonly used analytical methods for their detection and quantification requires specialized staff, specific equipment and extensive sample processing, resulting in an expensive process. Thus, the aim of this MSc thesis consisted on the development of a simple, efficient and less expensive method for the extraction and concentration of PSA from urine samples using aqueous biphasic systems (ABS) composed of ionic liquids. Initially, the phase diagrams of a set of aqueous biphasic systems composed of an organic salt and ionic liquids were determined. Then, their ability to extract PSA was ascertained. The obtained results reveal that in the tested systems the prostate specific antigen is completely extracted to the ionic-liquid-rich phase in a single step. Subsequently, the applicability of the investigated ABS for the concentration of PSA was addressed, either from aqueous solutions or urine samples. The low concentration of this biomarker in urine (clinically significant below 150 ng/mL) usually hinders its detection by conventional analytical techniques. The obtained results showed that it is possible to extract and concentrate PSA, up to 250 times in a single-step, so that it can be identified and quantified using less expensive techniques.
De acordo com dados disponibilizados pela Organização Mundial de Saúde, cerca de 8,2 milhões de pessoas morrem anualmente com cancro. A elevada taxa de mortalidade associada ao cancro resulta da maioria dos pacientes não efetuar exames de rotina e porque a manifestação dos sintomas, na maioria dos casos, acontece quando o paciente já se encontra numa fase avançada da doença. Atualmente, o cancro da próstata representa a segunda maior causa de morte entre indivíduos do sexo masculino em todo o mundo. Tendo em conta que não existe cura para casos avançados de cancro da próstata, a estratégia passa por um diagnóstico precoce que permita aumentar a taxa de sucesso dos tratamentos. O antigénio prostático específico (PSA) é um biomarcador importante do cancro da próstata que pode ser detetado em fluidos biológicos, nomeadamente sangue, urina e sémen. No entanto, os kits comerciais disponíveis utilizam amostras de sangue e os métodos analíticos normalmente utilizados na sua deteção e quantificação requerem pessoal especializado, equipamento específico e um processamento extensivo das amostras, resultando em processos com um elevado custo associado. Assim, o objetivo deste mestrado passou por desenvolver um método simples, eficiente e menos dispendioso para a extração e concentração de PSA a partir de amostras de urina utilizando sistemas aquosos bifásicos (SAB) constituídos por líquidos iónicos. Numa fase inicial, determinaram-se os diagramas de fases de um conjunto de sistemas aquosos bifásicos constituídos por um sal orgânico e por líquidos iónicos. Em seguida, avaliou-se a capacidade dos mesmos para a extração do PSA. Os resultados obtidos demonstram que, nos sistemas em estudo, o antigénio prostático específico é totalmente extraído para a fase rica em líquido iónico num único passo. Por fim, averiguou-se a aplicabilidade dos SAB estudados para a concentração do PSA a partir de soluções aquosas e de urina. A baixa concentração deste biomarcador na urina (clinicamente significativo abaixo de 150 ng/mL) dificulta a sua deteção através de técnicas analíticas convencionais. Os resultados obtidos demonstraram que é possível extrair e concentrar PSA até 250 vezes, numa única etapa, sendo este detetável através de técnicas menos dispendiosas.
37
Simms, Ryan W. "Living/controlled Polymerization Conducted in Aqueous Based Systems." Thesis, Kingston, Ont. : [s.n.], 2007. http://hdl.handle.net/1974/700.
Повний текст джерела
38
Levine, Mark Louis. "Electrophoresis of solutes in aqueous two-phase systems." Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/186087.
Повний текст джерелаАнотація:
Electrophoresis of solutes was studied in aqueous two-phase systems, concentrating on the special behavior in the interfacial region. Moving boundary electrophoresis was examined in a free fluid U-tube apparatus. Zone electrophoresis was investigated in two-phase systems which were gelled by the addition of acrylamide, which was subsequently polymerized. The size and nature (concentration or dilution) of polarizations which were found to occur was found to depend on the magnitude of the equilibrium partition coefficient of the solute in the two-phase system, as well as the direction of migration across the interface. These polarizations are in addition to those commonly known to occur near regions where electrophoretic flux changes radically, such as near interfaces. They can be a direct result of the requirement for equilibrium across the interface, as demonstrated by our experiments. Models were constructed to numerically simulate this behavior, which accounted for unsteady state electrophoresis and diffusion of multiple proteins or other amphoteric solutes. Two cases were explored, one requiring instantaneous solute equilibration across the interface, the other allowing for a resistance to mass transfer here. All models demonstrated a characteristic noted in experimental studies, concentration at interfaces when electrophoresis is from equilibrium preferred phase towards non-preferred phase. Furthermore, the equilibrium model correctly predicted the complex relationship between partition coefficient, direction of migration, and moving boundary or zone electrophoresis, which causes differences in the polarizations observed in these various systems. The simulation could also quantitatively estimate the width of the polarized region to within an order of magnitude, in comparison with experimental results, while hampered by a lack of mobility data for solutes in solutions containing polymers.
39
Ling, Tiong Tze. "Improving Simulations of Aqueous Systems through Experimental Bias." Thesis, Curtin University, 2020. http://hdl.handle.net/20.500.11937/81286.
Повний текст джерелаАнотація:
In order to enhance the ab initio molecular dynamics treatment of aqueous systems, the Boltzmann inversion directed simulation method was developed that derives a corrective bias to the system pairwise potential using experimental data. The bias acts as an empirical correction that enables routine-level simulation of density functional theory water to achieve comparable liquid structure to experiment at ambient temperature without significantly increasing computational cost.
40
Ross, Alistair Chassels. "Enzyme inactivation at the aqueous/organic interface." Thesis, University of Strathclyde, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366528.
Повний текст джерела
41
Silva, Milene Alexandra Cirne da. "Detection of non-steroidal anti-inflammatory drugs in aqueous effluents using ionic liquids." Master's thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/15495.
Повний текст джерелаАнотація:
Mestrado em Biotecnologia - Biotecnologia Industrial e AmbientalSignificant improvements in human health have been achieved through the increased consumption of pharmaceutical drugs. However, most of these active pharmaceutical ingredients (APIs) are excreted by mammals (in a metabolized or unchanged form) into the environment. The presence of residual amounts of these contaminants was already confirmed in aqueous streams since treatment processes either wastewater treatment plants (WWTPs) or sewage treatment plants (STPs) are not specifically designed for this type of pollutants. Although they are present in aqueous effluents, they are usually at very low concentrations, most of the times below the detection limits of analytical equipment used for their quantification, hindering their accurate monitoring. Therefore, the development of a pre-concentration technique in order to accurately quantify and monitor these components in aqueous streams is of major relevance. This work addresses the use of liquid-liquid equilibria, applying ionic liquids (ILs), for the extraction and concentration of non-steroidal anti-inflammatory drugs (NSAIDs) from aqueous effluents. Particularly, aqueous biphasic systems (ABSs) composed of ILs and potassium citrate were investigated in the extraction and concentration of naproxen, diclofenac and ketoprofen from aqueous media. Both the extraction efficiency and concentration factor achievable by these systems was determined and evaluated. Within the best conditions, extraction efficiencies of 99.4% and concentration factors up to 13 times were obtained.
As melhorias significativas alcançadas nas condições de vida dos seres humanos têm sido acompanhadas por um aumento no consumo de compostos farmacêuticos. No entanto, a maioria destes ingredientes farmacêuticos ativos (IFA) acabam por ser excretados pelos mamíferos (numa forma inalterada ou metabolizados) para o ambiente. A presença de quantidades residuais destes contaminantes já foi confirmada em correntes aquosas de abastecimento, uma vez que os processos de tratamento em estações de tratamento de águas residuais (ETARs) e estações de tratamento de esgoto (ETEs) não são projetados especificamente para este tipo de poluentes. Estes poluentes estão presentes em baixas concentrações nos efluentes aquosos (entre μg.L-1 e ng.L-1) e, por vezes, próximo dos limites de deteção do equipamento analítico utilizado dificultando a sua monitorização. Consequentemente, o desenvolvimento de uma técnica de pré-concentração assume uma enorme relevância a fim de quantificar com precisão e exatidão estes poluentes em correntes aquosas. Este trabalho aborda a utilização de equilibrio líquidolíquido, utilizando líquidos iónicos (LIs) como solventes, para a extração e concentração de fármacos anti-inflamatórios não esteroides (AINEs) a partir de correntes aquosas. Particularmente, foram estudados sistemas aquosos bifásicos (SAB) compostos por LIs e citrato de potássio na extração e concentração de naproxeno, diclofenaco e cetoprofeno. Avaliou-se quer a eficiência de extração quer o fator de concentração alcançado com este tipo de sistemas. Nas melhores condições estudadas, a eficiência de extração e o fator de concentração alcançados são de 99,4% e 13 vezes, respetivamente.
42
Ukeje, Michael Anayo. "Effect of particle size distribution on the rheology of dispersed systems." Thesis, Imperial College London, 2000. http://hdl.handle.net/10044/1/7492.
Повний текст джерела
43
Feng, Ling, and Ling Feng. "Advanced oxidation processes for the removal of residual non-steroidal anti-inflammatory pharmaceuticals from aqueous systems." Phd thesis, Université Paris-Est, 2013. http://tel.archives-ouvertes.fr/tel-00952080.
Повний текст джерелаАнотація:
The thesis mainly focused on the implementation of advanced oxidation processes for the elimination of three non-steroidal anti-inflammatory drugs-ketoprofen, naproxen and piroxicam in waters. The three compounds are among the most used medicines, whose presence in waters poses a potential ecotoxicological risk. Due to the low pharmaceuticals removal efficiency of traditional wastwater treatement plants, worldwide concerns and calls are raised for efficient and eco-friendly technologies. Advanced oxidation processes, such as ozonation-biofiltration, electro-Fenton and anodic oxidation processes, which attracted a growing interest over the last two decades, could achieve almost complete destruction of the pollutants studied. Firstly, removal of selected pharmaceuticals from tap water was investigated by electrochemical advanced oxidation processes "electro-Fenton" and "anodic oxidation" with Pt or boron-doped diamond anode and carbon felt cathode at lab-scale. Removal rates and minieralization current efficencies under different operatioanl conditions were analysed. Meanwhile, intermediates produced during the mineralization were also identified, which helps to propose plausible oxidation pathway of each compound in presence of *OH. Finally, the evolution of the global toxicity of treated solutions was monitored using Microtox method, based on the fluorescence inhibition of Vibrio fischeri bacteria. In the second part, the three nonsteroidal anti-inflammatory molecules added in organics-free or surface water were treated under varying ozone treatment regimes with the quite well established technology ozone/biofiltration. A bench-scale biological film was employed to determine the biodegradability of chemical intermediates formed in ozonized surface water. Identification of intermediates formed during the processes and bacterial toxicity monitoring were conducted to assess the pharmaceuticals degradation pathway and potential biological effects, respectively
44
Feng, Ling. "Advanced oxidation processes for the removal of residual non-steroidal anti-inflammatory pharmaceuticals from aqueous systems." Thesis, Paris Est, 2013. http://www.theses.fr/2013PEST1109/document.
Повний текст джерелаАнотація:
La thèse a porté principalement sur la mise en œuvre de procédés d'oxydation avancée permettant l'élimination de trois anti-inflammatoires non stéroïdiens, le kétoprofène, le naproxène et le piroxicam dans l'eau. Ces trois composés sont parmi les médicaments les plus utilisés, dont la présence dans les eaux naturelles présente potentiellement un risque toxicologique. En raison de la faible efficacité d'élimination des produits pharmaceutiques par les stations traditionnels de traitement des eaux usées, les scientifiques se sont mis à la recherche de technologies de traitements efficaces et respectueuses de l'environnement. Les procédés d'oxydation avancée, comme l'ozonation-biofiltration, l'électro-Fenton et l'oxydation anodique peuvent permettre d'atteindre la destruction presque complète des polluants étudiés et de ce fait ils ont suscité un intérêt grandissant au cours des deux dernières décennies. Tout d'abord, ce travail s'intéresse à l'élimination de certains produits pharmaceutiques dans des solutions synthétiques préparées dans l'eau de robinet à l'aide des procédés électro-Fenton et oxydation anodique dans une cellule électrochimique équipée d'une anode de platine ou de diamant dopé au bore et d'une cathode de feutre de carbone. Cette étude a été menée à l'échelle du laboratoire. Les vitesses d'élimination des molécules pharmaceutiques ainsi que le degré de minéralisation des solutions étudiées ont été déterminées sous différentes conditions opératoires. Pendant ce temps, les sous-produits de l'oxidation générés au cours de la minéralisation ont également été identifiés, ce qui nous a permis de proposer les voies d'oxydation possible pour chaque composé pharmaceutique en présence du radical hydroxyl •OH. Enfin, l'évolution de la toxicité au cours des traitements a été suivie en utilisant la méthode Microtox, basée sur l'inhibition de la fluorescence des bactéries Vibrio fischeri. Dans la deuxième partie de ce travail de thèse, les trois anti-inflammatoires non stéroïdiens ont été ajoutés dans une eau déminéralisée ou dans une eau de surface. Ces eaux ont été traitées à l'aide de différentes doses d'ozone; puis le traitement à l'ozone à été combiné à un traitement biologique par biofiltration. Un biofilm biologique déposé à la surface d'un filtre de charbon actif a été utilisé pour déterminer la biodégradabilité des sous-produits d'oxydation formés dans les eaux de surface ozonée. L'identification des intermédiaires formés lors des processus de traitement et des contrôles de toxicité bactérienne ont été menées pour évaluer la voie de dégradation des produits pharmaceutiques et des effets biologiques potentiels, respectivementThe thesis mainly focused on the implementation of advanced oxidation processes for the elimination of three non-steroidal anti-inflammatory drugs-ketoprofen, naproxen and piroxicam in waters. The three compounds are among the most used medicines, whose presence in waters poses a potential ecotoxicological risk. Due to the low pharmaceuticals removal efficiency of traditional wastwater treatement plants, worldwide concerns and calls are raised for efficient and eco-friendly technologies. Advanced oxidation processes, such as ozonation-biofiltration, electro-Fenton and anodic oxidation processes, which attracted a growing interest over the last two decades, could achieve almost complete destruction of the pollutants studied. Firstly, removal of selected pharmaceuticals from tap water was investigated by electrochemical advanced oxidation processes “electro-Fenton” and “anodic oxidation” with Pt or boron-doped diamond anode and carbon felt cathode at lab-scale. Removal rates and minieralization current efficencies under different operatioanl conditions were analysed. Meanwhile, intermediates produced during the mineralization were also identified, which helps to propose plausible oxidation pathway of each compound in presence of •OH. Finally, the evolution of the global toxicity of treated solutions was monitored using Microtox method, based on the fluorescence inhibition of Vibrio fischeri bacteria. In the second part, the three nonsteroidal anti-inflammatory molecules added in organics-free or surface water were treated under varying ozone treatment regimes with the quite well established technology ozone/biofiltration. A bench-scale biological film was employed to determine the biodegradability of chemical intermediates formed in ozonized surface water. Identification of intermediates formed during the processes and bacterial toxicity monitoring were conducted to assess the pharmaceuticals degradation pathway and potential biological effects, respectively
45
Tahat, Amani Naser. "Computer simulation of an excess proton in aqueous systems." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/396325.
Повний текст джерелаАнотація:
This thesis aims at studying the microscopic physical-chemical properties of an excess proton in aqueous systems. From bulk water environments to narrow hydrophobic channels constructed with a double-layered graphene slab, the local proton structure has been computed and analyzed together with a variety of dynamical properties, including proton diffusion, transfer rates and spectroscopic vibrational bands. All these properties have deep relationship with the most relevant structures associated with the proton: the hydronium ion (H3O)+, the Zundel dimer (H5O2)+, and the Eigen complex (H9O4)+. The influence of temperature and confinement has been systematically evaluated in a wide variety of thermodynamic conditions, ranging from low temperature amorphous ices to high temperature sub-critical states.
Classical molecular dynamics simulations have been used to model dynamics of the systems, whereas a multi-scale empirical valence bond method has been applied to model the specific quantum nature of the proton. Within this approach, a variety of diabatic bond states is defined and a semi-classical Hamiltonian is constructed. The linear combination of all diabatic states involves a different quantum weight for each state, so that proton characteristics have contributions from high to low values of each coefficient, implicitly accounting for the delocalization of the proton.
We have observed that a lone proton in unconstrained water produces important changes in the local water structure, especially at low temperatures. Below 273 K, the mobility of the proton gets significantly reduced, compared to ambient conditions, although it can still be transferred along the whole range explored. The activation energy barriers show a clear Arrhenius-like dependence and range of the order 1 kJ/mol.
When the system is confined inside a hydrophobic channel, the microscopic behavior of the lone proton is seriously affected: as the distance between graphene plates is reduced below 1.5 nm, the local structure of the proton shows a clear enhancement and indicates a tendency of lone quantum charge to move closer to the interfaces. At the shortest interplate distances (0.9 and 0.7 nm), the system becomes nearly planar, and two-dimensional water sheets formed by one to two layers have been observed. In such cases, both Zundel and Eigen structures are still seen (indicated by a signature 2500 1/cm frequency band), with a tendency of mixed Zundel-Eigen moieties to disappear and to be replaced by single hydronium species.
The combined effect of hydrophobic plates and temperature changes has been evaluated at densities between 0.02 and 0.07 1/Å^3. As a general trend, a competition between the two effects has been observed. So, as it was indicated above, confinement has strong influence on the local structure of the proton, whereas changes in temperature mainly affect proton's dynamics. Both proton transfer and proton diffusion are activated processes with energies up to 10 kJ/mol, depending of the particular thermodynamic state of the system.Aquesta tesi té com a objectiu l'estudi de les propietats microscòpiques fisicoquímiques d’un protó en excés en medi aquós. S’ha estudiat des d’aigua no confinada en condicions ambientals fins a sistemes formats per mostres d’un protó aquós tancat en canals hidrofòbics construïts amb una doble capa de grafè. L'estructura local del protó s'ha calculat i analitzat juntament amb una varietat de propietats dinàmiques, incloent la difusió del protó, els ritmes de transferència i les bandes vibracionals espectroscòpiques. Totes aquestes propietats tenen una profunda relació amb les estructures més rellevants associats amb el protó: l’ió hidroni (H3O)+, el dímer de Zundel (H5O2)+ i el complex d’Eigen (H9O4)+. La influència de la temperatura i el confinament s'han avaluat sistemàticament en una ampla varietat de condicions termodinàmiques, que van des de gel amorf a baixa temperatura fins a estats sub-crítics d'alta temperatura. S’han fet servir simulacions clàssiques de dinàmica molecular per tal de modelitzar la dinàmica microscòpica dels sistemes, mentre que mitjanant el mètode d'enllaç empíric de valència a multi-escala s'ha caracteritzat la naturalesa quàntica específica del protó. Dins d'aquest enfocament, s’ha definit una varietat d'estats diabàtics d’enllaç i s’ha construït un hamiltonià semi-clàssic. La combinació lineal de tots els estats diabàtics implica un pes quàntic diferent per a cada estat, de manera que les característiques de cada protó tenen contribucions numèriques diverses pels valors de cada coeficient, representant de manera implícita la deslocalització del protó. Hem observat que un protó sol en l'aigua sense restriccions de confinament produeix canvis importants en l'estructura local de l'aigua, especialment a baixes temperatures. Per sota de 273 K, la mobilitat del protó es redueix significativament en comparació a les condicions ambientals, tot i que la càrrega encara pot ser transferida en tota la gamma de sistemes explorats. Les barreres d'energia d'activació mostren una clara dependència de tipus Arrhenius en un el rang d’energies de l'ordre d'1 kJ/mol. Quan el sistema està confinat dins d'un canal hidrofòbic, el comportament microscòpic del protó solitari es veu seriosament afectat: quan la distància entre les plaques de grafè es redueix per sota de 1.5 nm, l'estructura local del protó mostra un increment clar en la localització i indica una tendència de del protó a acostar-se a les interfícies. En les distàncies entre plaques més curtes (0.9 i 0.7 nm), el sistema es torna gairebé pla de manera que es formen làmines d'aigua quasi-bi-dimensionals, amb una o dues capes de molècules. En aquests casos, les estructures d’Eigen i Zundel encara es veuen (com indica una banda de freqüència de 2500 1/cm), però amb una tendència dels complexos mixtos Zundel-Eigen a desaparèixer i ser reemplaçats per espècies individuals tipus ió hidroni. L'efecte combinat de les plaques hidrofòbiques i els canvis de temperatura s'ha avaluat en densitats entre 0.02 i 0.07 1/Å^3. Com a tendència general, s'ha observat una competència entre els dos efectes. Així, com s’ha indicat anteriorment, el confinament té una forta influència sobre l'estructura local del protó, mentre que els canvis de temperatura afecten principalment a la seva dinàmica. Tant la transferència de protons com la seva difusió de protons són processos activats amb energies que poden arribar fins als 10 kJ/mol, en funció de l'estat termodinàmic particular del sistema.
46
Bourton, Emma Catherine. "Countercurrent chromatography of proteins using aqueous two-phase systems." Thesis, Brunel University, 2008. http://bura.brunel.ac.uk/handle/2438/6271.
Повний текст джерелаАнотація:
The biotechnology industry requires high - capacity protein manufacturing processes that retain protein functionality. Large - scale countercurrent J- type centrifuges have been developed by the Brunel Institute for Bioengineering that successfully purify small organic molecules using aqueous - organic phase systems. Aqueous two - phase systems (ATPS) have been used historically to purify bio-molecules whilst retaining their biological function. This thesis focuses on extending CCC to the separation of proteins, using a model ATPS of PEG-1000 and potassium dihydrogen phosphate to separate a mixture of lysozyme and myoglobin. Initial studies were on the behaviour of this phase system in aJ- type CCC centrifuge fitted with a multilayer column; the variable parameters examined were centrifuge rotational speed, mobile phase flow rate and direction, and type of mobile phase. A set of optimum conditions were identified that gave good retention and stability of the phases in the column. These conditions were applied to separate a mixture of the proteins lysozyme and myoglobin in the same centrifuge. However, the proteins did not elute as predicted from their equilibrium distribution ratios. It appears that the wave - like mixing and settling behaviour of the phases in the centrifuge was insufficient for the proteins to achieve equilibrium partitioning. A centrifugal partition chromatography (CPC) centrifuge was introduced to the study. This provided full protein separation, credited to the cascade phase mixing created by this design of centrifuge. The experimental parameters were used in an experiment on a pilot - scale CPC instrument. The CPC study was extended to the isolation of a target protein (phosphomannose isomerase) from a fermentation supernatant. CPC gave partial purification of the protein with retention of enzyme activity. This thesis demonstrates the importance of phase mixing in CCC, which has led to a new column design by BIB with the potential of industrial - scale protein purifications.
47
Hong, Tao. "Fundamental study on tin recovery in acidic aqueous systems." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54952.
Повний текст джерелаАнотація:
Tin is widely used in solder, tin plating and tin alloys. The current recovery rate of tin metal is low and insufficient with just over 300,000 tonnes annually. The grade of tin concentrates in traditional smelting methods needs to be at least 60%. Otherwise, iron, the chief impurity in tin concentrates can form tin-iron alloys and result in inefficient recovery of tin. Therefore, a hydrometallurgical technology to treat lower grade tin concentrates is proposed to solve the problem and close the demand gap for tin. The electrochemical reduction of chromium(III) solutions was conducted with a graphite felt cathode in acidic aqueous systems (chloride, sulfate and MSA). The parameters of acid concentration, current density, graphite felt thickness, graphite felt surface condition and graphite felt usage frequency were investigated. It was found that acid concentration has a significant influence on chromium(III) reduction in the sulfate and MSA system, while slight effect in the chloride system. In addition, the lifetime of the graphite felt in the sulfate and MSA system was shorter than that in the chloride system. These electrochemical differences may result from the pathway difference in electron transfer between the electrode and the chromium(III) ions. In general, chromium(III) ions in the chloride system showed the best electrochemical reduction activity. The chromium(II) ions synthesized from electrochemical reduction of chromium(III) ions were then used to effect the reduction of SnO₂ powder. The effect of temperature on the recovery test in the chloride, sulfate and MSA system was investigated. It was found that under the conditions of this thesis, the predominant recovery product of SnO₂ is Sn metal, rather than Sn(II). Generally, the recovery kinetics and total conversion were low in the sulfate and MSA system; however, the chloride system showed significantly better recovery results. This may be attributed to the catalysis effect of the chloride ions on the recovery process.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
48
Khan, Ikhtiar. "Solubility relationships of organic acids in aqueous atmospheric systems." Thesis, University of East Anglia, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357177.
Повний текст джерела
49
Kadhim, Hussain S. A. "Bioremediation of chlorophenolics from aqueous systems using Coriolus versicolor." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299611.
Повний текст джерела
50
Turner, Richard John. "The rheology and structure of aqueous gelatin-silica systems." Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274624.
Повний текст джерела