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New Polymeric Membranes for Organic Solvent NanofiltrationAburabie, Jamaliah 05 1900 (has links)
The focus of this dissertation was the development, synthesis and modification of
polymers for the preparation of membranes for organic solvent nanofiltration. High
chemical stability in a wide range of solvents was a key requirement. Membranes
prepared from synthesized polymers as well as from commercial polymers were designed
and chemically modified to reach OSN requirements.
A solvent stable thin-film composite (TFC) membrane is reported, which is fabricated on
crosslinked polythiosemicarbazide (PTSC) as substrate. The membranes exhibited high
fluxes towards solvents like THF, DMF and DMSO ranging around 20 L/m2 h at 5 bar
with a MWCO of around 1000 g/mol.
Ultrafiltration PTSC membranes were prepared by non-solvent induced phase separation
and crosslinked with GPTMS. The crosslinking reaction was responsible for the
formation of an inorganic-type-network that tuned the membrane pore size. The
crosslinked membranes acquired high solvent stability in DMSO, DMF and THF with a
MWCO above 1300 g/mol.
Reaction Induced Phase Separation (RIPS) was introduced as a new method for the
preparation of skinned asymmetric membranes. These membranes have two distinctive
layers with different morphologies both from the same polymer. The top dense layer is
composed of chemically crosslinked polymer chains while the bottom layer is a porous
structure formed by non-crosslinked polymer chains. Such membranes were tested for
vitamin B12 in solvents after either crosslinking the support or dissolving the support and
fixing the freestanding membrane on alumina.
Pebax® 1657 was utilized for the preparation of composite membranes by simple coating.
Porous PAN membranes were coated with Pebax® 1657 which was then crosslinked
using TDI. Crosslinked Pebax® membranes show high stability towards ethanol, propanol
and acetone. The membranes were also stable in DMF once crosslinked PAN supports
were used.
Sodium alginate polymer was investigated for the preparation of thin film composite
membranes. Composite membranes were prepared using PAN and crosslinked PAN
supports; these membranes were tested for methanol and DMF. Freestanding nanofilms
fixed on alumina were also tested for methanol and DMF as well as many other harsh
solvents. The alginate composite membranes showed excellent solvent stability and good
permeances and a MWCO of around 1300 g/mol.
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Conserved solvent networks in GPCR activationBlankenship, Elise 30 May 2016 (has links)
No description available.
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Cleaning of Printed Circuit Assemblies with Surface-Mounted ComponentsArzigian, J. S. 11 1900 (has links)
International Telemetering Conference Proceedings / October 30-November 02, 1989 / Town & Country Hotel & Convention Center, San Diego, California / The need for ever-increasing miniaturization of airborne instrumentation through the use of surface mounted components closely placed on printed circuit boards highlights problems with traditional board cleaning methods. The reliability of assemblies which have been cleaned with vapor degreasing and spray cleaning can be seriously compromised by residual contaminants leading to solder joint failure, board corrosion, and even electrical failure of the mounted parts. In addition, recent government actions to eliminate fully halogenated chlorofluorocarbons (CFC) and chlorinated hydrocarbons from the industrial environment require the development of new cleaning materials and techniques. This paper will discuss alternative cleaning materials and techniques and results that can be expected with them. Particular emphasis will be placed on problems related to surface-mounted parts. These new techniques may lead to improved circuit reliability and, at the same time, be less expensive and less environmentally hazardous than the traditional systems.
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SOLVENT EXTRACTION OF TERVALENT LANTHANIDES WITH N-BENZOYLPHENYLHYDROXYL AMINE.Fabara Ordoñez, Carlos Eduardo. January 1983 (has links)
No description available.
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Effect of solvents on the potential of ion-selective electrodes : A comparative studyAke, H. A. January 1979 (has links)
No description available.
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Neutron diffraction studies of solvent in crystals of vitamin Bâ†1â†2 coenzyme and of lysozymeBouquiere, John Philip January 1996 (has links)
No description available.
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Ditopic reagents for the solvent extraction of platinum group metalsWilson, Andrew Matthew January 2014 (has links)
This work aims to develop solvent extractants to recover platinum and palladium from highly acidic chloride solutions bearing other platinum group metals (PGMs). In general, metal values can be recovered by solvent extraction through three different mechanisms: metal cation extraction (1); metalate anion extraction (2); or metal salt extraction (3). Mn- + n(LH)(org) ⇌ [M(L)n](org) + nH+ (1) MClx n- + nL(org) + nH+ ⇌ [MClx(LH)n](org) (2) MClx + nL(org) ⇌ [MClxLn](org) (3) The main objective of this thesis is to establish whether ditopic extractants can be developed which have chemical functionalities that allow both mechanisms (2) and (3) to operate, co-extracting Pt(IV) and Pd(II) as their chloridometalates in an outer sphere binding site (2) and allowing their separation by raising pH to transfer the more kinetically labile Pd(II) to an inner sphere binding site (3) and releasing H2PtCl6 to the aqueous strip solution. A review of the literature is presented in Chapter 1, noting current commercially available extractants and the processes in which they are, or have been, applied. Particular attention is paid to the mode of action of the reported extractants and whether they extract metal cations, anions or metal salts. This chapter also outlines the proposed solvent extraction circuit in which new reagents developed in this thesis would be incorporated and the methods applied during the screening of candidate extractants. Chapter 2 deals exclusively with the use of reagents with inner-sphere binding sites for the selective extraction of palladium over platinum. Work on a series of oxime reagents synthesised for palladium extraction as part of preliminary MSci research (Andrew M. Wilson, MSci Thesis, University of Edinburgh, 2011) is reviewed. Studies of the hydrolytic stability of oximes indicate that they are unsuitable for incorporation into ditopic reagents for use in a circuit with a highly acidic feed solution. Thioethers were studied as alternatives as they show high kinetic selectivity for palladium over platinum and are more stable under acidic conditions. The synthesis and extraction properties of model reagents (largely arylalkyl thioethers) are reported and compared with those of the commercially available di-n-hexylsulfide. Incorporation of a polar group such as an amide provides phase transfer catalysis, accelerating the rate of transport of Pd(II) into the organic phase, but reducing selectivity over Pt(IV). The identification of functionalities that operate as receptors for chloridometalates by forming outer-sphere assemblies is explored in Chapter 3. The synthesis of amine, amide and amino-amide extractants from acid chloride streams and the effects of variations of functional groups on the extraction of PtCl6 2− are described. Secondary amides were found to be stronger extractants than tertiary amides, and aliphatic amides also show better metalate extraction than aromatic amides. The interactions between protonated aminoamide reagents and PtCl6 2− werre analysed by X-ray crystallography, noting that C-H∙∙∙Cl interactions with the “soft” chloridometalate anion are more common than with the “hard” chloride ion which shows a preference for more conventional N-H∙∙∙Cl interactions. Chapter 4 combines the reagent types explored in Chapters 2 and 3, in ditopic extractants that have both inner- and outer sphere binding sites. The synthesis and characterisation of a series of thioether amide reagents are reported and the selective extraction of platinum and palladium over other PGMs are discussed. In-house screenings of aryl- and alkylthioetheramide extractants showed selective co-extraction of Pd(II) and Pt(IV), rejecting Ir(III). Pt(IV) can be selectively water-stripped followed by ammonia-stripping of Pd(II). Industrial screenings at Johnson Matthey Technology Centre further exemplified the selectivity of these extractants over Ru(III) and Rh(III), although third phases were formed when the reagents were used for recovery from highly concentrated metal-feed solutions. The mode of action of the ditopic extractants is discussed, based on DFT calculations, crystal structure determinations and NMR studies, which support the formation of outersphere metalate assemblies and inner-sphere palladium complexes. Chapter 5 describes new difunctional (inner + outer sphere complexation) extraction by a single chemical entity, in this case an unsaturated N-heterocycle (an azole). The synthesis and characterisation of a series of hydrophobic azoles are described. These have basicities which allow protonation when contacted with strongly acidic solutions (2), but can be deprotonated in contact with water to allow their neutral forms to form inner-sphere complexes with Pd(II). Triazole-based reagents show the selective co-extraction of Pt(IV) and Pd(II) and, as with the ditopic thioetheramide reagents reported in Chapter 4, allow the selective water stripping of Pt(IV) and subsequent ammonia stripping of Pd(II).
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The chemistry of the alkali-induced solubilisation of coalShoko, Lay. January 2005 (has links)
Thesis (M.Sc.)(Chemistry)--University of Pretoria, 2005. / Abstract in English. Includes bibliography. Available on the Internet via the World Wide Web.
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Copper solvent extraction by ultrasound-assisted emulsification / Extraction liquide-liquide du cuivre en émulsions formées à l'aide d'ultrasonsDuhayon, Christophe C. 25 March 2010 (has links)
The goal of this research is to improve an extractive metallurgy process based
on solvent extraction. This process should fit the exploitation of small local
copper-rich deposits. In these conditions, the plant has to be as compact as
possible in order to be easily transported from one location to a subsequent
one. Improved extraction kinetics could ensure a high throughput of the
plant despite its compactness. In addition, the extraction reagent should
not be damaging for the environnement. On this basis, we propose to use
ultrasound-assisted solvent extraction. The main idea is to increase the
extraction kinetics by forming an emulsion in place of a dispersion thanks to
the intense cavitation produced by ultrasound. The benefit of this method
is to improve the copper extraction kinetics by increasing the interfacial
surface area and decreasing the width of the diffusion layer. We studied the
implementation of an highly branched decanoic acid (known as Versatic-
10®acid) as a copper extraction reagent dispersed in kerosene.
Emulsification is monitored through the Sauter diameter of the organic
phase droplets in aqueous phase. This diameter is measured during pulsed
and continuous ultrasound irradiation via a static light scattering technique.
The phenomenon of emulsification of our system by ultrasound is effective,
and the emulsification process carried out in the pulsed ultrasound mode is
at least as efficient as the emulsification obtained under continuous mode.
No improvement of emulsification is observed beyond a threshold time of
the ultrasound impulse. This may be attributed to a competition between
disruption and coalescence. The use of mechanical stirring combined with
pulsed ultrasound allows to control the droplet size distribution.
In presence of ultrasound, the extraction kinetics of Versatic-10 acid is
multiplied by a factor ten, and therefore reached a value similar to the kinetics
observed without ultrasound with an industrial extractant such as
LIX-860I®(Cognis). Extraction kinetics measurements are carried out by
monitoring the copper ion concentration in the aqueous phase with an electrochemical
cell.
We conclude that ultrasound-assisted emulsification can be implemented
under certain conditions. Emulsification is a first step, and the following
destabilization step has to be studied. The device using ultrasound-assisted
emulsification should be followed by an efficient settling-coalescing device. A
possible solution would be to promote emulsion destabilization by increasing
the ionic strength with an addition of MgSO4, a salt that is not extracted
by the extraction reagent in the considered range of pH.
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Long-Term Performance of Enhanced Anaerobic Bioremediation and the Occurrence of Sustained Treatment at Chlorinated Solvent SitesBurcham, Mike 16 September 2013 (has links)
The objective of this research was to evaluate the long-term performance of enhanced anaerobic bioremediation (EAB) at chlorinated solvent sites and the occurrence of sustained treatment following EAB. A database of groundwater concentration versus time records was compiled for 25 sites with at least three years of post-treatment data. The median post-treatment monitoring period for these sites was 5.2 years, with a maximum of 11.7 years. Long-term performance was evaluated based on concentration changes from before treatment to the final year of post-treatment monitoring. Results indicate that the median concentration reduction for all 25 sites was approximately 80%, just under 1 order of magnitude. Sustained treatment, where concentrations remain suppressed after ceasing active treatment, was evaluated using a lines-of-evidence approach including analysis of rebound, statistical concentration trends after treatment, and decay rates from before and after treatment. Results indicate that sustained treatment is occurring at a majority of the sites.
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