Dissertationen zum Thema „Eutetic Solvents“

Le biogaz est une source d'énergie renouvelable produite naturellement par la digestion anaérobie de matières organiques. Il se compose principalement de méthane (CH4) et de dioxyde de carbone (CO2). Il contient également des traces de vapeur d'eau, de composés organiques volatils (COV) et de sulfure d'hydrogène. La valorisation du biogaz en biométhane nécessite l'élimination des contaminants présents dans le biogaz brut, en réduisant le niveau d'impuretés afin d'obtenir une teneur élevée en CH4, de l'ordre de 90 à 99 %. Les utilisations du biométhane sont les mêmes que celles du gaz naturel, mais il s'agit d'une source d'énergie non fossile et renouvelable à 100 %. De nombreuses technologies ont été testées et appliquées pour éliminer les impuretés du biogaz, telles que le lavage à l'eau, le lavage physique et chimique, la séparation par membrane, l'adsorption par variation de pression, les méthodes biologiques, etc. Les absorbants jouent un rôle important dans l'élimination des impuretés du biogaz. Il est donc impératif de mettre au point de nouveaux absorbants dotés d'une capacité d'absorption et d'une recyclabilité élevées. L'absorbant approprié doit également avoir une faible viscosité, une toxicité relativement faible, une faible pression de vapeur, un point d'ébullition élevé, une grande capacité d'absorption et un faible coût. Les solvants eutectiques profonds (DESs) sont un mélange de deux ou trois composés chimiques (généralement un composé accepteur d'hydrogène, HBA, et un composé donneur d'hydrogène, HBD), qui se combinent par le biais de liaisons hydrogène et dont le point de fusion est inférieur à celui de chacun de leurs composants purs. Ces solvants ont des propriétés physico-chimiques qui peuvent être ajustées en fonction de la nature des composés individuels et de leur ratio. L'objectif de cette thèse était d'évaluer des DES et des solvants verts conventionnels en tant qu'absorbants pour les COV/CO2. Nous avons évalué et comparé l'efficacité de différents DESs et absorbants conventionnels pour l'absorption de neuf COV et du CO2. Le coefficient de partage vapeur-liquide (K) des COV dans les solvants étudiés et la capacité d'absorption du CO2 dans les DES ont été déterminés à l'aide de la chromatographie en phase gazeuse couplée à l’espace de tête statique. L'effet du mélange de COV, de la température et de la teneur en eau a été évalué. Les capacités d'absorption des COV individuels, de leur mélange et du CO2/CH4 dans les DES et les solvants conventionnels ont également été évaluées à l'aide d'un dispositif dynamique simulant une colonne d'absorption industrielle. Les résultats statiques et dynamiques obtenus sont en bon accord. Les capacités d'absorption d’absorbants industriels ont également été évaluées à l'échelle industrielle en utilisant un échangeur développé par notre partenaire industriel (Terrao®)
Biogas is a renewable energy source produced naturally by the anaerobic digestion of organic matter. It consists mainly of methane (CH4) and carbon dioxide (CO2). It also contains traces of water vapour, volatile organic compounds (VOCs) and hydrogen sulphide. Biogas upgrading to biomethane requires the removal of contaminants in the raw biogas, reducing the level of impurities to achieve high CH4 content of about 90 to 99%. The uses of biomethane are the same as natural gas while being a 100% renewable and non-fossil energy source. Many technologies have been tested and applied to remove impurities from biogas, such as water scrubbing, physical and chemical scrubbing, membrane separation, pressure swing adsorption, biological methods, etc. Absorbents play an important role in removing impurities from biogas. Therefore, the development of novel absorbents with high absorption capacity and high recyclability is mandatory. The suitable absorbent should also have low viscosity, relatively low toxicity, low vapor pressure, high boiling point, high absorption capacity, and low cost. Deep eutectic solvents (DESs) are a mixture of two or three chemical compounds (usually a hydrogen acceptor compound, HBA and a compound hydrogen donor, HBD), which combine via hydrogen bonds that have a lower melting point than each of their pure components. These solvents have physico-chemical properties that can be tuned depending on the nature of the individual compounds and their ratio. The purpose of the thesis was to evaluate DESs and conventional green solvents as VOCs/CO2 absorbers for biogas upgrading. We evaluated and compared the efficiency of different DESs and conventional absorbents for the absorption of nine VOCs and CO2. The vapor–liquid partition coefficient (K) of the VOCs in the studied solvents and the absorption capacity of CO2 in DES were determined using static headspace-gas chromatography. The effect of VOC mixture, temperature water content was evaluated. The absorption capacities of individuals VOCs, their mixture and CO2/CH4 in DESs and conventional solvents were also evaluated using a dynamic set-up which simulated an industrial absorption column. Both static and dynamic results are in good agreement. Also, the absorption capacities of industrial absorbents were evaluated on an industrial scale using an exchanger developed by our industrial partner (Terrao®)

L’obiettivo di questi tre anni di Dottorato è stato lo studio e l’utilizzo nuovi solventi di reazione in grado di sostituire i solventi organici classici. In particolare sono stati studiati i Deep Eutectic Solvent (DES) e le miscele di Liquidi Ionici (IL). I DES sono stati utilizzati come solventi per lo studio di reazioni organiche, usate per la formazione di nuovi legami C-C. Nello specifico sono state studiate la reazione di Diels-Alder, e diverse reazioni di coupling C-C catalizzate da Pd. In seguito, i DES sono stati utilizzati per la formazione di nuovi gel supramolecolari, chiamati eutectogel. Questi gel sono stati formati usando come gelator amminoacidi naturali, consentendo quindi di ottenere gel interamente costituiti da composti non tossici. Questi materiali sono stati usati come fasi adsorbenti per la rimozione di coloranti cationici da soluzioni acquose. Infine, miscele di IL sono state utilizzate per la conversione di tre diversi carboidrati in 5-HMF, ottenendo rese soddisfacenti specialmente per la conversione del fruttosio.

A fundamental study of electropolishing of stainless steel and nickel based single crystal superalloy CMSX-4 in type III deep eutectic solvent based on choline chloride and hydrogen bond donor i.e. mixture of choline chloride with ethylene glycol in a 1:2 molar ratio was carried out and had been found to be competitive with the current concentrated mixture of inorganic acid electrolytes. Life cycle study was conducted to define the key process controlling factors like electrochemical stability, current efficiency, effect of history of electrolyte, recycling of ionic liquid and its reuse for electropolsihing. The electrochemical techniques like linear sweep anodizing curves, chronoamperometery and galvanostatic studies revealed that electropolishing in 1:2 ChCl:EG proceeded through the formation of viscous layer on the surface of the substrate similar to electropolishing in inorganic acid electrolytes. The optimization of electropolishing process was carried out using the experimental design strategies, Fractional Factorial Design (FFD) and found that electropolishing variables like addition of water, oxalic acid, electropolishing bath temperature, time and potential had positive impact on the surface finish. Surface texture measurements such as surface roughness and surface overlayer morphology of electropolished stainless steel and CMSX-4 was carried out using the microscopic techniques, atomic force microscopy (AFM), scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM) and digital holographic microscopy (DHM) and found to be the function of electropolishing time. Effect of electropolishing on corrosion behaviour of stainless steel was studied using the electrochemical techniques like open circuit potential measurements (OCP), potentiodynamic polarization curves and gravimeteric method showed improvement in the general or pitting corrosion of the workpiece. Nickel based superalloy was also successfully electropolished to remove the casting scales. The dissolution of two phases was found to be the function of electrochemical regime i.e. applied potential and current density.

Processing sulfur containing minerals is one of the biggest sources of acute anthropogenic pollution particularly in the form of acid mine drainage. Sulfur-based minerals are generally roasted to convert them to the oxide, producing SO2 or leached in acid producing H2S. This study attempts to show an innovative method for processing sulfide-based minerals using a deep eutectic solvent (DES), Ethaline, which is a mixture of choline chloride and ethylene glycol. It is shown that pyrite can be solubilised by both electrochemical oxidation and reduction in a DES. A novel method is demonstrated to investigate the redox properties of minerals using a paste made from the mineral powder in a DES. The first bulk electrochemical dissolution of pyrite is shown without the formation of H2S or SO2. The solubilised species are investigated using cyclic voltammetry UV-vis spectroscopy and EXAFS. In all cases for the iron minerals studied, it was found that the electrochemistry of the counter ion and not the metal, controlled the ease of dissolution. It is also shown that the soluble species, including elements such as arsenic, can be recovered electrochemically which could potentially decrease acid mine drainage. The electrochemical properties of other iron–sulfur and iron–arsenic minerals are also presented and compared to those of pyrite. The final part of this study uses different cell designs in an endeavour to optimise the space-time-yield of the electrochemically assisted digestion of jarosite. It was found that the electrochemical digestion of material was up to 20 faster than the chemical dissolution. It was, however found that formation of insoluble precipitates, particularly of lead and zinc sulfates affected the performance of the separator membranes and this could decrease the yield of digested metal. The presence of high concentrations of iron salts led to passivating films on the zinc surface during cementation.

En la presente memoria se describe el uso de líquidos eutécticos sostenibles (DESs en inglés) como medios de reacción, empleando diferentes catalizadores metálicos para llevar a cabo la síntesis de compuestos orgánicos de interés en química orgánica. En el Primer Capítulo se detalla el uso de un catalizador heterogéneo de cobre soportado sobre magnetita en el acoplamiento cruzado deshidrogenante de tetrahidroisoquinolinas en mezclas eutécticas. En el Segundo Capítulo se pormenoriza sobre la síntesis de un complejo tipo pinza de paladio y su empleo en la reacción de acoplamiento cruzado de Hiyama, tanto en mezclas eutécticas como en glicerol, como medios sostenibles de reacción. Asimismo, y con el fin de mejorar la compatibilidad de los catalizadores de paladio en estos líquidos eutécticos, se detalla el diseño y la síntesis de fosfinas catiónicas, las cuales han probado su efectividad como ligandos de paladio en reacciones típicas de acoplamiento cruzado (Suzuki, Heck y Sonogashira) en diferentes mezclas eutécticas. Finalmente, en el Tercer Capítulo se describen reacciones multicomponente de acoplamiento cruzado para la formación de enlaces C-S. Por un lado, se ha desarrollado una metodología para la inserción de SO2 catalizada por paladio a partir de ácidos borónicos y metabisulfito de sodio. Por otro lado, una variante de la metodología anterior permitió la síntesis de sulfonamidas sustituyendo los ácidos borónicos por compuestos de triarilbismuto y nitrocompuestos bajo catálsis de cobre. En este último caso, una nueva mezcla eutéctica ha sido descrita y caracterizada, tanto físco-química como biológicamente.

Salt forms homogeneous solutions with water; most studies to date have assumed that deep eutectic solvents (DES) and water form similar homogeneous systems. Several studies have used quantum mechanical and molecular dynamic simulations to prove that this is indeed the case. Study of physical properties of ionic liquid-water/ systems have revealed some anomalous observations without considering the fact that there may be micro- or nano-heterogeneities with in these systems. The key aim of this project is to demonstrate the heterogeneity of DES-water mixtures by careful measurement of physical properties such as viscosity, conductivity, surface tension and density. The first stage of the study involved the investigation of the above physical properties for pure DESs and DESs mixed with different amounts water to investigate if these were homogeneous or heterogeneous in nature. Analysis of these data showed some characteristics of heterogeneity, the extent of which depends on the number of hydrogen bond donors in the pure DES. Dynamic light scattering was used to determine the extent of the heterogeneity in the three DESs under investigation, namely Ethaline, Glyceline and Reline. Pulsed Field Gradient NMR (PFG-NMR) and electrochemical techniques have been used to study diffusion coefficients in DES-water mixtures. The results of PFG-NMR showed that the behaviour of DES-water mixtures was non-Stokesian, hence DES-water mixtures have water-dominant and some ion-dominant domains. Electrochemical studies also showed the same trends due to the electroactive species partitioning between the different phases. It is thought that Reline-water mixtures are more heterogeneous than the corresponding Ethaline and Glyceline systems. Electroplating in DES-water mixtures has previously been shown to improve the quality of deposited films. The electrodeposition of copper from Ethaline was studied as a function of water content. It was found that water affected the speciation of copper in solution.

Mixtures of metal salts with complexing agents, such as urea, form liquids, which are known as deep eutectic solvents (DESs). This has previously been applied to metal salts such as ZnCl₂, AlCl₃ and CrCl₃.6H₂O. The aim of this thesis was to see if this model could be expanded to include alkali metal salts. Some of the hydrogen bond donors (HBDs) investigated were found to form liquid mixtures with a limited number of alkali metal salts, which showed melting temperatures below 25 °C. Utilising glycerol as a HBD exhibited the highest mutual solubility with the alkali metal salts of interest, therefore this study focussed on sodium salt:glycerol mixtures. Four sodium salts were chosen: NaBr, NaOAc, NaOAc.3H₂O or Na₂B₄O₇.10H₂O, which provided a range of fluidities and contained hydrates and anhydrous salts. The ionic conductivity and viscosity of these salts with glycerol were studied, and it was found that unlike previous studies of choline chloride with glycerol where the salt decreases the viscosity of glycerol, all of the sodium salts increased the viscosity of glycerol. This suggests that sodium salts have a structure making, kosmotropic effect, rather than structure breaking, chaotropic effect, on glycerol. This phenomenon is probably due to the high charge density of Na⁺, which coordinates to the glycerol. The ion transport properties and molecular dynamics of sodium salt:glycerol mixtures have been investigated at the microscopic level using nuclear magnetic resonance and electrochemical techniques. Self-diffusion coefficients of the components of the systems of interest were found to be 10⁻¹¹- 10⁻¹³ m² s⁻¹ range. T₁ relaxation times were investigated and all systems showed a transition from a diffusion-limited, slow molecular tumbling regime to a fast molecular, high mobility, tumbling regime. Poor solubility was experienced with a range of transition metal salt probes, which was attributed to complex ion speciation. It was concluded that the sodium salt:glycerol systems studied are not ideal for electrochemical applications. The ability of the salts to form viscous gels made them ideal plasticisers for starch. Starch DES mixtures were tested as a binder for medium density fibreboard (MDF). The properties of MDF samples were tested as a function of processing conditions and composition. Pilot scale production of plasticised starch MDF composites was successful, demonstrating the current industrial infrastructure can be utilised for large-scale production at a similar cost to MDF bound with urea formaldehyde resins.

Thin films of copper alloys are of interest for electronic applications. These are routinely produced by electrodeposition using aqueous solutions. The solvent strongly affects composition and morphology of the deposit which consequently affects the electrical and mechanical properties. The novelty of this thesis is that copper alloys are deposited from Deep Eutectic Solvents, DESs, which are forms of ionic liquids. The work shows that novel morphologies and compositions can be obtained using this approach. The electrodeposition of copper alloys is described from a solution of the metal salts in choline chloride based ionic liquids using urea and ethylene glycol as hydrogen bond donors. The thesis is split into three sections focussing on Cu alloys with Ag, Sn and P. These were chosen for their different phase behaviour. It is shown that the composition and morphology can be varied by altering the deposition potential and copper ion concentration of the plating bath. A variety of analytical techniques have been used to probe the deposition of these alloys. Although many of these are relatively standard for such studies this project uses an electrochemical quartz crystal microbalance (EQCM) for the first time to determine alloy composition in real time. From this data, the two systems Cu-Ag and Cu-Sn are shown to be close to 100% current efficiency, but the Cu-P does not fellow this trend. Analysis of the chronoamperometric transient behaviour during electrodeposition suggests that pure copper electrodeposition proceeds via three-dimensional instantaneous nucleation with diffusion-controlled growth. However, the deposition of most alloys does not fit either progressive or instantaneous nucleation models well. The alloy phases formed during deposition were analysed using X-ray diffraction and the surface morphologies and the compositions of the electrodeposited Cu alloys were analysed using SEM/EDAX. Thin films of Cu and Cu-P were electroformed onto Ti substrates and then peeled off. The mechanical properties of these films were tested and it was found that the incorporation of phosphorous was found to have a significant effect on the stress-strain curves. The final part of this study involved the dissolution of copper using cyclic voltammetry and EQCM and it was shown that diffusion of the chloride ligand to the electrode limits the rate of the anodic process.

Concentration gradients present in the solution during the redox chemistry of selected metals and conducting polymer (poly(3,4ethylenedioxythiophene) (PEDOT)) films redox cycled in Deep Eutectic Solvents (DES) were observed for the first time through the application of the Probe Beam Deflection (PBD) technique combined with the Electrochemical Quartz Crystal Microbalance (EQCM). Suitability of choline chloride (ChCl) based DES for applications as electrolytes in PEDOT based charge storage devices has also been investigated using EQCM. The combination of carefully optimized experimental parameters (temporally extended chronoamperometry and slow scan rate voltammetry) with modified design of the instrument (reduced probe’s distance of approach) allowed for in-situ observations of electrochemically induced concentration gradients in DES based systems. During the studies of electroactive polymer films, complete determination of mobile species transfers in PEDOT/Ethaline and PEDOT/Propaline systems has been achieved. The application of PBD-EQCM technique in studies of metal electrodeposition from DES allowed for monitoring metal speciation in dynamic and quantitative fashion. EQCM study of ChCl based DES indicated Ethaline as the most promising potential electrolyte for PEDOT based charge storage devices. Additionally, an unusual mass exchange process has been detected in PEDOT/Propaline and PEDOT/Acetaline processes. This work has shown a novel, affordable and non-invasive route for observation of electrode/electrolyte interface processes in DES. The experimental protocol developed can potentially be implemented in further studies of DES as well as Ionic Liquids.

Capítulo 1. Adiciones Michael asimétricas organocatalizadas en líquidos eutécticos. Siguiendo los principios de la “Química Verde” se desarrolló un sistema catalítico basado en disolventes eutécticos y organocatalizadores quirales derivados de 2-amino benzimidazol. Este nuevo sistema fue empleado para catalizar la adición enantioselectiva de compuestos de 1,3-dicarbonílicos a β-nitroestirenos. El procedimiento evita el uso de disolventes orgánicos volátiles tóxicos como medio reacción, proporcionando acceso a moléculas quirales altamente funcionalizadas de forma selectiva y eficiente. Además, la reacción puede realizarse a una escala de gramos y a su vez este sistema catalítico es fácilmente reciclable y reutilizable durante cuatro ciclos, lo que da lugar a un procedimiento limpio, económico, sencillo y escalable que cumple la mayoría de los criterios necesarios para ser un proceso medioambientalmente benigno y sostenible. Los estudios de RMN realizados a la mezcla organocatalizador-líquido eutéctico han confirmado el papel clave de los enlaces de hidrógeno entre el disolvente y el organocatalizador quiral, que permiten su recuperación y la reciclabilidad del sistema. Capítulo 2. α-Aminación electrofílica asimétrica organocatalizada en líquidos eutécticos. Empleando el sistema catalítico basado en el uso de catalizadores quirales de 2-benzoimidazol y líquidos eutécticos se realizó la α-aminación enantioselectiva de compuestos de 1,3-dicarbonílicos. Con este procedimiento, se evita el uso de compuestos orgánicos volátiles tóxicos como medios de reacción. Las moléculas quirales altamente funcionalizadas sintetizadas, que son importantes en la síntesis de productos naturales, se sintetizaron mediante un protocolo eficiente y estereoselectivo. Además, la reacción puede llevarse a cabo para la síntesis de un gramo de producto, siendo posible el reciclaje del sistema catalítico durante al menos cinco ciclos de reacción consecutivos. Este procedimiento representa un método barato, simple, limpio y escalable que cumple con la mayoría de los principios para ser considerado un proceso medioambientalmente benigno y sostenible. Capítulo 3. Líquidos eutécticos quirales. Diferentes mezclas eutécticas basadas en prolina fueron empleadas en la adición Michael asimétrica de cetonas sobre nitroalquenos. En vista de los resultados, y los estudios de 1H-RMN realizados, se confirmó una relación entre la conversión y selectividad del proceso con la constante asociación de los componentes de la mezcla eutéctica. Con estos datos un nuevo disolvente eutéctico quiral a base de bromuro de (S)-N,N,N,-trimetil-1-(pirrolidin-2-il)-metanamina y glicerol fue diseñado y sintetizado con éxito. Este sistema catalítico se mostró eficiente en la adición Michael de ciclohexanona a β-nitroestirenos, obteniendo selectividades moderadas en condiciones suaves. El sistema catalítico eutéctico fue recuperado fácilmente y reciclado hasta cinco veces en la adición de ciclohexanona a β-nitroestireno sin pérdida significativa de actividad catalítica.

Chromium electrodeposition is important for the production of anti-wear and anti-corrosion coatings. It has been carried out for over 50 years in a multi-billion dollars industry using essentially the same technology based on chromic acid. The toxicity of the electrolyte makes the search for an alternative process an environmental imputative. In this study a variety of novel formulations of deep eutectic solvents are produced and tested to determine their efficacy for chromium deposition. The study concentrates on using urea as a complexing agent with a variety of trivalent chromium salts. In the first results chapter complexes of CrCl3·6H2O with urea are formed. It is shown that this system displays high conductivities, despite relatively high viscosities compared with the previously reported chromium based deep eutectic solvents. Thick, adherent, non-cracked black chromium could be deposited and produce relatively hard chromium coatings. EXAFS suggests that there are a variety of chromium species but they are probably cationic with a variety of oxygen donors as ligands. In the next section [Cr(en)3]3+ species was produced as the cationic species and this had a higher conductivity than any similar system previously described. Bright, adherent, hard chromium was obtained by electroreduction with constant speciation. A novel solvatochromic shift, that we are unaware of in the literature, demonstrates the charge transfer complex results in an unexpected colour change. In an endeavour the remove of Cl- from the formation chrome-alum (KCr(SO4)2·12H2O) was used as the metal salt. This produced unprecedented high conductivity for this type of medium with a low viscosity. It was proposed that unlike most ionic liquids mass transport is not limited by hole transport and instead it is proposed that these liquids function more like very concentrated electrolytes where ion paring becomes important. In the final result section a variety of additives are tested. Some are shown to have a significant effect on the morphology and hardness of the deposit. Ultimately bright metallic chromium films could be reproducibly produced with a hardness of 800±10 HV. This is the first process based on Cr(III) to be able to achieve these rigorous requirements and suggests the first real alternative to hexavalent chromium for hard chrome.

The physical properties, viscosity, conductivity, surface tension and density were measured for a series of alcohol based Deep Eutectic Solvents (DES) as a function of choline chloride (ChCl) concentration. The point at which the system becomes a saturated salt solution in the diol systems is at 20 mol% ChCl, because at higher concentrations the conductivity decreases despite the increase in number of charge carrying species. The addition of ChCl to glycerol results in a decrease in the viscosity of the system by interrupting the intermolecular hydrogen bonding of the glycerol molecules, whereas the addition of ChCl to the diols results in an increase in viscosity. The mono-alcohol phenol has been shown to form a DES in a ratio of 4:1 phenol: ChCl. Stable DES’s have also been formed using sugars, D-(-) fructose, D-glucose, xylitol and meso-erythritol. Determination of solvent-solute interactions is key to the understanding of solvent properties in liquids therefore the Kamlet-Taft parameters α, β, π* and ET (30) parameter were determined for a series of alcohol based DES using three solvatochromic dyes, 4-nitroaniline, N,N-dimethyl-4-nitroaniline and Reichardt’s dye ET (30). It is shown that they are similar to RNH3+X-, R2NH2+X- and imidazolium ionic liquids. The effect of ChCl on the Kamlet-Taft parameters is not uniform across the systems and is dependant upon the hydrogen bond donor. The solventless esterification of glycerol and lauric was carried out using ChCl with the intention of using its hydrogen bonding interaction with glycerol to behave a potential site inhibitor as to selectively form mono- or di-ester products. The work has shown that the addition of ChCl to the system, initially slows the rate of the mono-ester formation, but actually encourages the reaction to progress further towards the di-ester product, when compared to the pure glycerol system encouraging only mono-ester formation.

Ionic liquids have generated a large amount of interest as possible replacements for aqueous electrolytes in metal and alloy electrodeposition processes. A related class of fluid, the deep eutectic solvents, have recently been shown to have equally interesting electrochemical properties whilst also being more air and moisture stable and economical to produce. The electrodeposition of Zn from the deep eutectic solvents 1: 2 ChCl: ethylene glycol and 1: 2 ChCl: urea was investigated. A theory of relative chloride activities was developed and applied to effectively account for differences in the voltammetry, chronoamperometry and morphology of deposits obtained from the two solvents. Additionally the solute concentration was determined to have an effect on the physical properties of the solvent; moreover, this effect was seen to be solvent dependent. The first EXAFS study of metal speciation in deep eutectic solvents was used to elucidate the identity of the dissolved Zn species. A novel technique, the combined in-situ AFM-EQCM, has been designed and applied, in a time resolved manner, to the study of Zn electrodeposition from 1: 2 ChCl: ethylene glycol. It was shown that the organic additives ethylene diamine and ammonia could be used to modify the Zn deposit morphology. It has been proposed that the additives alter the Zn nucleation and growth mechanism through interaction with the free chloride ions in the electrochemical double layer. The effect of surfactants has also been described and sodium dodecyl sulphate found to be an effective levelling agent. The feasibility of Zn alloy deposition from choline chloride based deep eutectic solvents has been investigated. Zn-Cu and Zn-Co alloys were successfully deposited from deep eutectic solvents for the first time. In addition the electrochemical quartz crystal microbalance has been used in an original manner to monitor Zn-Sn co-deposit composition.

A fundamental study in to the correlation of nucleation mechanism with deposit morphology using silver salts as a well behaved system has been carried out in deep eutectic solvents i.e. mixtures of choline chloride (ChCl) with firstly ethylene glycol and secondly urea in a 1:2 molar ratio. The nucleation and growth kinetics of silver deposition were measured as a function of liquid type, deposition potential and silver salt type. The effect of different additives including surfactants (SDS and CTAB) and aqueous brightener (cresyl fast violet-CFV and crystal violet-CV) on nucleation was determined using electrochemical techniques such as cyclic voltammetery and chronoamperometery. Electrogravimetric studies were carried out using electrochemical quartz crystal microbalance (EQCM) to correlate the deposited mass of silver with findings from the electrochemical studies in both solvents. A qualitative evaluation of the nucleation and growth mechanism and quantitative estimation of the kinetic parameters of silver electrocrystallization process was carried out using the existing theoretical formalisms. A computer simulation was used to extract the nuclear number density, rate of nucleation, diffusion co-efficient and influence of the double layer charging by fitting the whole potentiostatic current transients using a ‘non-linear best fitting’ method. The analysis of the development of the surface by nucleation and growth of the silver deposition in real time was studied using the ex-situ AFM and in-situ DHM. The latter of these was the first demonstration of this technique for the study of nucleation and growth mechanism of metal deposition and the results showed good agreement with the ex-situ AFM findings.

Composite materials are important for their improved strength and wear resistance compared to pure materials. Metal composites have been electrodeposited from aqueous solutions although the instability of colloidal dispersions makes it difficult to obtain reproducible composite compositions. In this thesis metal composites are prepared using Deep Eutectic Solvents, DESs, which are a type of ionic liquid. The electro-deposition of copper and copper composites from DESs based on ethylene glycol and urea were investigated. The mass transport in both electrolytes was found to be diffusion controlled. The mechanism of copper nucleation is studied using chronoamperometry and it is shown that 3D progressive nucleation leads to bright nanostructure deposits. It was found that dispersed colloidal particles are stable over a prolonged period of time in DESs. This work uses an electrochemical quartz crystal microbalance (EQCM) to monitor both the current efficiency and the inclusion of inert particles into the copper co-deposits. The technique showed the majority of second phase was dragged onto the surface instead of sedimented. The effect of the addition of surfactants was also studied. DESs were also used in the electro-deposition of silver composites with alumina and silicon carbide. It was found that improved mechanical properties such as hardness and wear resistance could be obtained. The addition of LiF to the Type 3 deep eutectic solvents was also found to further improve the quality of the mechanical properties and led to smoother surfaces with lower friction coefficients. The final part of this study involved the deposition of nickel composites with the aim of producing coatings with hardness similar to chromium. The addition of organic additives as brighteners (ethylene diamine) leads to smooth and bright finishes. Two types of composites were added to the nickel electrolytes; SiC 1-3μm and Teflon μm. The surface morphology was found to change with particle size and type. The mechanical properties were studied and found to be affected by the type and the concentration of particulate incorporated in the nickel deposits.

5-Hydroxymethylfurfural (5HMF) can be produced from lignocellulosic biomass which is a non-toxic and biodegradable source. However, 5HMF is a useful feedstock for the production of Dimethylfuran (DMF), which a biofuel with characteristics similar to gasoline. In this study, a novel self-catalysed Deep Eutectic Solvent (DES) was formulated, which are ChCl-to-p-TSA (DES1), DEAC-to-p-TSA (DES2) and ChCl-to-adipic acid (DES3). The acid components perform a dual role as a hydrogen bond donor (HBD) and as a catalyst for the dehydration of fructose to 5HMF. The study was carried in a batch system at temperature (50–110 °C), reaction time (5–180 min), fructose-to- DES mass ratio (2.5–100 g/g) and DES mixing salt-to-acid ratio 0.5:1–2:1. The reaction kinetics and the effect of the novel DES composition on the dehydration reaction were also studied. It was found that fructose was readily dehydrated to 5HMF with yield of 78.3% at a temperature of 80 °C, reaction time of 60 min, DES molar mixing ratio of 1.5:1, and a feed ratio of 5. DES2 achieved a 5HMF yield of 84.8% at the same condition as DES1 except at a different molar mixing ratio of 0.5:1 (DEAC-to-p-TSA). Conversely, DES3 accomplished 100% fructose conversion and 5HMF yield and selectivity of 90.8% at a reaction temperature of 90 °C and at a reaction time of 120 min, using a DES molar mixing ratio of 1:1 and feed ratio (initial fructose) of 2.5. The reaction kinetics studied showed that DES1 and DES2 are approximately first order while DES3 1.8.

Mineral oils are the most commonly used fraction of formulated lubricating oils except for some specialised applications where synthetic oils are employed. An alternative approach has been suggested using ionic liquids (ILs) due to their high viscosity index and high thermal stability. The aim of this study is to examine the use a different type of ionic liquids in the form of Deep Eutectic Solvents (DESs) as base lubricants as these have significantly improved environmental credentials. The first stage of the study involved the investigation of thermo-physical properties such as heat capacity, thermal stability, surface tension, viscosity index, melting point, conductivity and density to determine if the liquids are suitable fluids as lubricants. The data for a variety of imidazolium based ILs and standard mineral base oil were also determined and used for comparison sake. In addition the properties of DES mixtures with water were determined and self-diffusivity were measured using NMR spectroscopy. It was shown for the first time that aqueous DES mixtures are not homogeneous but instead they form bicontinuous micro-emulsions. This study has also been the first to quantify the corrosion rates of metals in DESs and ionic liquids. The corrosion of iron, aluminium and nickel was studied in four DESs and four ILs using both Tafel slope analysis and electrochemical impedance spectroscopy. The corrosion rate was found to change over time for some liquids and so the corrosion product films were characterised using Raman spectroscopy. The interfacial properties of DES and ILs are shown to be totally different from mineral base oil and the wettability in terms of contact angle and interfacial energies for various metals have been studied. The friction coefficient and wear volume were measured for DESs for dissimilar sliding couples. Finally, the change of both thermo-physical and mechanical properties due to the inclusion of two common surfactants sodium dodecylsulfate and cetyltrmethylammonium bromide are characterised in three DESs and shown to decrease the wear volume.

Mestrado em Biotecnologia Industrial e Ambiental
O gengibre é uma planta que tem atraído um interesse crescente tanto no sector alimentar como farmacêutico devido às suas propriedades medicinais. Como planta medicinal, é uma das mais antigas e populares do mundo. As suas propriedades terapêuticas advêm dos compostos bioativos presentes na sua composição, entre os mais importantes destacam-se os compostos fenólicos, nomeadamente o 6-shogaol e o 6-gingerol. Estes compostos despertam um grande interesse na comunidade científica devido ao seu poder antioxidante e anti-tumoral. Os processos convencionais de extração destes compostos requerem o uso de solventes orgânicos, no entanto, nos últimos anos tem-se intensificado a procura por solventes alternativos com maior capacidade de solvatação, eficientes e economicamente viáveis. Os solventes eutécticos profundos (DES) são uma classe de solventes novos, de baixo custo e de origem natural, baseados em percursores renováveis que apresentam baixa toxicidade, podendo ser catalogados como solventes amigos do ambiente. Neste contexto, o objetivo principal deste trabalho foca-se na obtenção de um extrato rico em compostos bioativos (nomeadamente 6-gingerol) a partir do gengibre utilizando DES como solventes de extração com possibilidade de recuperação do extrato e reciclagem dos DES, criando assim um processo sustentável. Para atingir este objetivo, foram estudadas as solubilidades de dois compostos fenólicos modelo, nomeadamente os ácidos siríngico e ferúlico em DES (puros e em solução aquosa), por forma a avaliar os DES mais promissores na solubilização dos compostos bioativos, assim como, as condições de extração. Entre as várias combinações entre doadores (ácidos orgânicos, polióis, açúcares e ureia) e aceitadores (ureia, cloreto de colina, betaína e prolina) de pontes de hidrogénio, o DES ácido propiónico:ureia foi o que apresentou melhores resultados. Com base nestes resultados e recorrendo a metodologias de superfície de resposta, foram avaliados e otimizados diversos parâmetros de extração do 6-gingerol usando soluções aquosas de DES. Simultaneamente, efetuaram-se extrações convencionais como controlo, seguido da identificação e quantificação do 6-gingerol presente nos extratos usando a cromatografia líquida de alta resolução (HPLC). A metodologia de extração do 6-gingerol a partir do gengibre usando os DES como solventes alternativos demonstrou ser mais seletiva, capaz de extrair mais 60 % de 6-gingerol quando comparado com os métodos de extração convencionais. Além disso, foi possível recuperar um extrato sólido rico a partir da solução de DES utilizando uma extração em fase sólida (SPE). Por fim, a caracterização dos extratos foi complementada com a análise da atividade antioxidante, usando o radical 2,2-difenil-1-picrilhidrazilo (DPPH). Os resultados indicam que os extratos obtidos a partir da metodologia proposta neste trabalho apresenta maior atividade antioxidante que os extratos obtidos com métodos de extração convencionais.
Ginger is a plant that has attracted the attention from both the food and pharmaceutical sectors due to its medicinal properties. As a medicinal plant, it is one of the oldest and most popular in the world. Its therapeutic properties arise from the bioactive compounds it contains, among which stand the phenolic compounds, and in particular 6-shogaol and 6- gingerol. These compounds aroused great interest in the scientific community due to its antioxidant and antitumoral properties. The conventional extraction methods of these compounds require the use of organic solvents, however, in recent years, there has been an intensified search for alternative solvents with higher solvation capacity, efficient and cheap. Deep-eutectic solvents (DES) are a new class of solvents, of low cost and natural origin, based on renewable precursors that have a low toxicity and can be categorized as environmentally friendly solvents. The goal of this work focuses on obtaining an extract rich in bioactive compounds (namely 6-gingerol) from ginger using DES as extraction solvents, and to evaluate the possibility of recycling of DES, thus creating a sustainable process. For that purpose the solubility of two phenolic model compounds, namely syringic and ferulic acids, were studied in DES (neat and in aqueous solution) in order to identify the most promising DES for the bioactive compound solubilisation, as well as the best extraction conditions. Between the several combinations amongst hydrogen bond donors (organic acids, polyols, sugars and urea) and hydrogen bond acceptors (urea, choline chloride, betaine and proline), propionic acid:urea revealed to have the best results. Based on these results and using the surface response methodology, several extraction parameters of ginger extraction using aqueous solutions of DES were optimized. Simultaneously, conventional extraction assays were carried for comparison, followed by the identification and quantification of 6- gingerol present in extracts by high pressure liquid chromatography (HPLC). Once optimized the different parameters of extraction it was possible to achieve an efficient methodology capable to enhance the 6- gingerol extraction in 60% when compared with the conventional extraction methodology. Besides, an extract was successfully recovered from the DES extract solution using solid-phase extraction (SPE). The extract characterization was complemented with the analysis of the antioxidant activity using 2,2-diphenyl-1-picrylhydrazil (DPPH). Results show that the extracts obtained with the methodology proposed in this work present a higher antioxidant activity than those obtained with conventional extraction techniques.

In metal electroplating processes, additives are normally added to the plating bath to improve the physical and mechanical properties of the coating such as brightness, roughness, thickness, hardness and resistance to corrosion. The effects of additives on the electrodeposition of metals from aqueous solution have been extensively investigated. However, very few studies have considered the effects of additives on the electrodeposition of metals from ionic liquids (deep eutectic solvents). This work has shown that ethylenediaminetetraacetic acid disodium salt dihydrate (EDTA), sodium iodide (NaI), boric acid (BA) and 5,5-dimethylhydantoin (DMH) as additives can be used to modify the Cu deposit morphology obtained from a 1:2 ChCl: ethylene glycol-based liquid (Ethaline 200) on a mild steel substrate. It was found that NaI significantly influenced the morphology of the Cu deposit, achieving a bright and thick Cu deposition. The effects of nicotinic acid (NA), boric acid (BA) and benzoquinone (BQ) on Zn deposit morphology from Ethaline 200 were also shown, and for the first time a bright zinc coating has been achieved on a copper substrate when NA was used. The feasibility of Zn-Ni alloy deposition from Ethaline 200-based deep eutectic solvents has been investigated in the absence and presence of boric acid and sodium bromide. It was found for the first time that a successful bright Zn-Ni alloy coating from Ethaline 200 can be produced in the presence of boric acid and NaBr as additives. Moreover, the effects of current density, temperature and concentration of Zn species on electrodeposition of Zn-Ni alloy from Ethaline 200 in the presence of both boric acid and NaBr have been studied. The last part of this work was to look at the effects of methyl nicotinate (MN) on the electrodeposition of Al from 1-ethyl-3-methylimidazolium chloride/AlCl3 and 1-butyl-3-methylimidazolium/AlCl3 as classical ionic liquids, and (1.5:1) AlCl3:acetamide, (1.5:1) AlCl3:N-methylacetamide and (1.5:1) AlCl3:N,N-dimethylacetamide as deep eutectic solvents. A mirror Al coating has been achieved on a copper substrate from both conventional ionic liquids as a result of using methyl nicotinate as an additive. MN has improved the morphology of Al deposited from (1.5:1) AlCl3:acetamide-based liquids and, furthermore, MN has been used to refine the grain size of the Al coating achieved from (1.5:1) AlCl3:N,N-dimethylacetamide as a deep eutectic solvent.

Controlled-release formulations for pesticide applications act as depot systems that continuously release the active ingredients into the environment over a speci ed period, usually from months to years. However, some applications require fast-dissolving drug delivery. The interest of this research is in fast-release of water-insoluble pesticides into aquatic environments. This study considered the use of dextrin starch and urea eutectics as fast release, solid dosage carrier forms that contain an active ingredient. The chosen active for this study is an acaricide called amitraz (N-methylbis-(2,4-xylyliminomethyl)- methylamine). The focus is on matrix-based dosage forms such as tablets, granules or bres that either disintegrate or dissolve to release a water-insoluble active. These types of dosage forms can be fabricated using processes such as lyophilisation, spray drying, solvent casting, hot melt extrusion, compression moulding, wet granulation, compaction and electrospinning. A simple melt-casting procedure has been discussed in the present work. Dextrin is a water-soluble form of partially hydrolysed starch and is a promising candidate matrix material for dissolving solid dosage forms. The molecular weight of the dextrin was analysed with MALDI-TOF methods and rheological relations. Glycerolplasticized thermoplastic dextrin-based nanocomposites were prepared with a twin-screw extrusion-compounding process. The nano llers included a layered double hydroxide (LDH), cellulose nano bres (CNF) and stearic acid. The time-dependent retrogradation of the compounds was monitored by X-ray di raction (XRD) and dynamic mechanical thermal analysis (DMA). XRD showed that the inclusion of stearic acid in the formulations led to the formation of an amylose-lipid complex and a stable crystallinity during ageing. Dissolution rates in water for samples containing dextrin starch, were characterised using an iodine indicator and UV-visible spectroscopy. High pressure di erential scanning calorimetry (HPDSC) indicated that the addition of stearic acid led to the formation of amylose-lipid complexes (ALC's). An additive system containing stearic acid and CNF was deemed suitable for compounding with amitraz. Compounding at temperatures above the melting point of the latter led, on dissolution in water, to the release of much ner particles of the acaricide, which was con rmed with particle size analysis (PSA). The addition of the acaricide caused an apparent increase in the dissolution rate of the thermoplastic dextrin. Two eutectic urea systems were considered for casting with amitraz. A eutectic system of urea and acetamide was found to display a melting point of 44 C at a 37 wt.% urea composition. The other system consisting of urea and 1,3-dimethylurea displayed a eutectic point at 32 wt.% urea composition which melted at 59 C. Di erential scanning calorimetry (DSC), however, con rmed a melting point depression due to a high moisture content caused by the compounds high hygroscopicity. The endotherm of the sample containing no excess moisture showed a melting point of 70 C. The 1,3-dimethylurea system was deemed suitable for casting with amitraz. XRD of the eutectic composition indicated a small amount of co-crystallisation. The samples were cast as disks of various diameters while keeping the height of the disks constant. The creation of the cast disks showed automatic generation of a nely dispersed form of the active through the process of melting the deep eutectic solvent, the dissolution of the active and its phase separation on cooling and solidi cation of the eutectic. This implies that ne grinding of the actives might not be necessary. Eutectic casts containing 20 wt.% amitraz dissolved at a slower rate than casts not containing the hydrophobic active ingredient. The advantageous features of these casts were exempli ed using the acaricide incorporated into the urea & 1,3-dimethylurea eutectic. This work provides two safe, biodegradable and water soluble materials for use as a matrix to contain active ingredients. One material, the eutectic organic salt casts, can be produced at low temperatures (<100 C) and can be directly cast into storage containers. The complete dissolution of the cast compounded with a hydrophilic active is rapid (4-6 min). The second material, a thermoplastic dextrin, was melt compounded in an extruder at temperatures not exceeding 120 C. This compound containing 20 wt.% of the active dissolved over a 12 hour period. Dextrin, known to be widely used as an adhesive, will aid in the adhesion of the active ingredient to the surface where it must be used.
Dissertation (MEng (Chemical Engineering))--University of Pretoria, 2019.
PAMSA
Department of Science and Innovation under Grant DST/CON 0004/2019
Chemical Engineering
MEng (Chemical Engineering)
Unrestricted

Ionic liquids and deep eutectic solvents are areas of great interest to non-aqueous reaction systems. They can be fine-tuned for an array of properties and are often less harmful than other, organic, solvents. This research focused specifically on self-assembly in ionic liquids and deep eutectic solvents with an eye to understand self-assembly processes. Not only does this work offer industrial applications, for isolated reaction systems and batteries, it also provides an interesting insight into the possibility of non-aqueous life-forms. If compartmentalisation can occur without water, then perhaps so too can the other requirements of life. Ionic liquid nanostructure significantly affected phospholipid self-assembly with more nanostructure resulting in more curved micellar phases, rather than the lamellar phases observed in water and less structured ILs. This held true for both zwitterionic lipids and ionic surfactants, demonstrated by microscopy, small angle neutron and x-ray scattering. Phospholipids formed swellable lamellar phases in all fourteen of the deep eutectic solvents tested. Examination of lipid transition temperatures by polarising optical microscopy demonstrated that the components of the solvent could influence lipid behaviour and stability, solvents with long alkyl components acted as cosurfactants. Tethered lipid membranes and electrical impedance spectroscopy demonstrated that membranes could exist, and form, in a pure IL environment (ethanolammonium formate). This is the first time such a technique has been used to study membranes in an IL and offers unparalleled opportunities for further research. Furthermore, this technique was used to demonstrate the continued function of a membrane transporter, valinomycin, in ethanolammonium formate. Valinomycin continued to transport potassium with an extremely high selectivity over sodium. These results show that compartmentalisation, and even protein function, can continue even in the absence of water.

Abstract: Selection and refinement of a method for copper corrosion removal were undertaken in an environmentally friendly way by using deep eutectic solvents (DES) integrated in a cellulose-based membrane. DES is a potential “green” solvent based on natural compounds. In this thesis, a DES composed of choline chloride and ascorbic acid in a 2:1 ratio, was prepared and used for copper corrosion cleaning. The DES was diluted with water and the DES to water ratio was optimized in terms of efficiency, time consumption, and selectivity of cleaning. It was found that DES solutions, having a concentration higher than 70 wt.% were suitable for dissolving copper corrosion products. Meanwhile, they exhibited a supressed dissolution ability of CaCO3 which is a common compound in many of the supporting structures used for copper artefacts. These solutions were then used for swelling cellulose membranes, and the swelling capacity was monitored for a week. The swollen membrane was put on an electrochemically corroded copper sheet for 24 hours. By removing the membrane, the green malachite layer was successfully removed from the copper sheet while preserving a reddish-brown cuprite layer. This was confirmed by performing X-ray diffraction analysis before and after cleaning the copper sample. For heritage objects, the defacing copper corrosion products of Cu (II) need to be removed apart from protective layer of cuprite. We concluded that the cellulose membranes containing DES solutions are promising materials for this purpose.

Tin electrodeposits produced from aqueous electrolytes are frequently used within the electronics industry due to their high solderability and corrosion protection. One limitation to using these deposits is their spontaneous formation of long conductive filament whiskers. These whiskers grow post-electrodeposition and increase the risk of unwanted electrical shorts within electronic devices. In this thesis, tin electrodeposits produced from a proprietary bright acid Tinmac electrolyte, currently used in industry, were studied. Electrodeposits were produced using a range of current densities with and without agitation and were characterised with respect to crystallographic orientation, topography and surface finish. Moreover, the intermetallic compound (IMC) growth produced at the copper substrate-tin coating interface was assessed over a period of time as its growth is considered to be a significant driving force behind whisker formation. In addition, a technique for the electrochemical anodic oxidation of tin electrodeposits on copper substrates was developed. This technique was used throughout this project for the study of IMC growth from tin electrodeposits as it was able to effectively remove the tin whilst leaving the IMCs and substrate unaffected. Ionic liquids exhibit promising electrochemical characteristics for electrodeposition but are still not widely utilised in industry. Their ability to deposit tin coatings has been studied in the present investigation. Trials concentrated on process optimisation to produce uniform electrodeposits by varying current density, SnCl2.2H2O concentration, and electrolyte composition. These deposits were then characterised and compared to tin coatings of similar thickness produced from Tinmac with respect to topography, surface finish, crystallographic orientation, IMC growth, and whisker propensity. Electrodeposits produced from the ionic liquid electrolyte exhibited a different crystallographic texture, topography, and IMC growth compared to those produced from Tinmac. Moreover, the deposit produced from the ionic liquid featured increased whisker growth compared to those produced from Tinmac, but in a wider context, far less growth than conventional tin electrodeposits in the literature. In addition, by exploiting other electrochemical characteristics of ionic liquids, such as their large potential window, future work may be able to produce novel tin or tin alloy electrodeposits which may further reduce the whisker propensity of deposits produced in this investigation.

The galvanic deposition of metals has wide ranging applications in many industries. One example is the printed circuit board industry, where galvanic coatings are used as both a catalyst for the activation of the surface of a substrate and protective coating to prevent the oxidation of the surface. Deep Eutectic Solvents (DESs) have received growing interest in the area of metal processing, due to the unique solvation properties and ability to dissolve metal salts, without the need for addition of acids or bases. The DESs have been widely applied in electrochemical processes, where electrochemistry can be performed without the need for addition of an electrolyte. In this work, the speciation of the group 10 and 11 metals has been characterised using UV – Vis spectroscopy. The electrochemistry of the group 10 and 11 elements has been characterised using cyclic and linear sweep voltammetry and related to the speciation of the metal centres. Further characterisation of the electrochemistry was performed using an electrochemical quartz crystal microbalance, allowing for the rate and current efficiency of the electrochemical reaction to be measured. Galvanically deposited coating of group 10 and 11 metals, were produced on a standardised copper substrate. The morphology of the coatings was characterised by atomic force (AFM) and scanning electron microscopy (SEM) and the composition by energy dispersive X – ray (EDX) and X – ray photoelectron spectroscopy (XPS). The mechanism by which the galvanic coatings are formed was probed. The reaction mechanism was predicted from the formal electrode potential of the metal redox couples. The predicted mechanisms were experimentally investigated using quartz crystal microbalance experiments. The quartz crystal microbalance also allowed for the determination of the rate of the galvanic reactions.

Les mescles de baix punt de fusió o mescles eutèctiques denominades DES per les sigles en anglès (Deep Eutectic Solvents), són bàsicament preparades a partir de compostos acceptors de ponts de hidrogen, els anomenats HBA, (en general una sal d'amoni quaternària), i donadors de ponts d'hidrogen (HBD) com són alcohols, àcids, amines i carbohidrats; que formen sistemes que contenen una àmplia varietat d'espècies catiòniques i / o aniòniques regides per interaccions de pont d'hidrogen que presenten una baixa energia d'enllaç, causant dels baixos punts de fusió que aquestes presenten. Aquesta és una de les característiques importants a l'hora d'emprar els diferents tipus de DES, pel que fa a el tipus de reacció i / o procés sintètic; per exemple, aquests dissolvents eutèctics han estat àmpliament utilitzats i estudiats en processos d'extracció de biomassa, síntesi de polímers, catàlisi, electroquímica, síntesi de nano partícules, entre d'altres. En el present treball, es presenta la preparació de nous solvents eutèctics de base biològica a partir de glicerol (Gly), el qual va ser obtingut mitjançant la hidròlisi de greixos animals no comestibles i després emprat per sintetitzar l'alcohol 3- cloro-1,2-propanodiol, que és el precursor del compost racèmic: clorur de rac-2,3-dihidroxipropiltrietilamonio: [Et3N+CH2CH(OH)CH2OH]Cl- (DPTAC). Dit compost es va sintetitzar emprant el 3- cloro-1,2-propanodiol, trietilamina i metanol. El compost (DPTAC), que inicialment va ser obtingut en forma de barreja racèmica, va ser transformat en un compost enantiomèricament enriquit mitjançant un procés d'acetilació quimioenzimàtica i d'acetilació directa emprant acetat d’isopropilè, per tal de separar la mescla racèmica. De la mateixa manera, es va obtenir el clorur de S - (-) 2,3-dihidroxipropiltrietilamoni, partint de l'alcohol precursor òpticament pur (2a). Totes aquestes sals van ser acetilades directament amb anhídrid acètic. Tots ells van ser emprats com HBA per preparar diferents mescles eutèctiques (DES). Així, es van emprar tres compostos de base biològica: glicerol (Gly), àcid làctic (LA) i urea com HBD per formar cadascuna de les mescles. Finalment, l'etilenglicol (7) va ser també utilitzat per formar un DES concret. És important destacar que el disseny d'aquests dissolvents es va dur a terme utilitzant l'estratègia de "disseny modular" en què cada DES conté un HBA de diferent naturalesa i propietats. Inicialment, es presenta l'estudi de les propietats físiques (viscositat, densitat, relació estequiomètrica, entre d'altres) de cada DES. Posteriorment, s'estudia la seva funció com a dissolvents en diferents processos químics. Els DES preparats van ser utilitzats com a dissolvents en el procés de fraccionament i extracció de material ligno-cel·lulòsic en diferents mostres de biomassa de fusta dura, com són la sansa, i la poda de branques (de tipus llenyós) d'arbres fruiters. Els resultats van mostrar que es pot extreure lignina tipus Klasson i es recuperen fraccions riques en holocel·lulosa utilitzant cada un dels DES. Els DES preparats van ser també utilitzats per estudiar la seva influència sobre la formació dels adductes endo:exo, en reaccions típiques de ciclació [4π + 2π] tipus Diels-Alder, entre el ciclopentadiè i acrilat d'etil o acrilat de butil. D'altra banda, amb base en els requeriments del procés, van ser seleccionats els DES adequats per ser utilitzats com a mitjans de reacció en la reacció d'obtenció d'alcohols quirals secundaris mitjançant la reducció de cetones pro-quirals en presència de NaBH4. La riquesa enantiomèrica dels alcohols produïts es va estudiar emprant un reactiu de derivatització quiral (reactiu de Mosher). D'aquesta manera es va estudiar la configuració absoluta de l'alcohol: 1-feniletanol (12) (obtingut com a producte de la reacció anterior). A més, van ser realitzats assajos preliminars per valorar la possibilitat de reciclar els DES obtinguts. Per a això, els DES inicials, preparats entre el compost racèmic (DPTAC) amb els quatre compostos HBD van ser fraccionats, fent ús d'una resina de bescanvi catiònic fort, per tal de comprovar que la facilitat amb què aquests són separables; a més de ser reusables i reciclables. Condicions que ha de complir un solvent perquè pugui ser considerat dins de la categoria "Green Solvents"; tenint en compte que els materials de partida per a la formació de les mescles eutèctiques gairebé són íntegrament compostos de base biològica. Tots els compostos precursors i els DES preparats van ser caracteritzades per FT-IR i tècniques d'espectroscòpia de 1H i 13C RMN; el compost racèmic va ser analitzat mitjançant espectrometria de masses; la proporció entre els adductes formats en les reaccions de Diels-Alder, va ser estudiada utilitzant cromatografia de gasos GC-FID (230 ° C i 270 ° C). L'activitat òptica i l'angle de rotació específica van ser mesurats en els compostos enantiomèricament enriquits i òpticament purs. Finalment, la separació de cada DES, realitzada mitjançant columnes de bescanvi catiònic, va ser seguida per FT-IR i 1H RMN.
Las mezclas de bajo punto de fusión o mezclas eutécticas denominadas DES por sus siglas en inglés (Deep Eutectic Solvents), son básicamente mezclas preparadas a partir de compuestos aceptores de puentes de hidrógeno llamados HBA, (generalmente sales de amonio cuaternarias) y donantes de puentes de hidrógeno de diferente naturaleza (HBD), por ejemplo, alcoholes, ácidos, aminas y carbohidratos; que forman sistemas que contienen una amplia variedad de especies catiónicas y/o aniónicas regidas por interacciones, principalmente de puentes de hidrógeno, que presentan una baja energía de enlace que causan los bajos puntos de fusión que estas presentan. Precisamente, esta es una de las características importantes a la hora de emplear los diferentes tipos de DES, dependiendo del tipo de reacción y/o proceso sintético. Por ejemplo, estos disolventes eutécticos han sido ampliamente utilizados y estudiados en procesos de extracción de biomasa, síntesis de polímeros, catálisis, electroquímica, síntesis de nanopartículas, entre otros. En el presente trabajo se presenta la preparación de diferentes novedosos disolventes eutécticos de base biológica, a partir de glicerol (Gly). Este glicerol fue obtenido mediante la hidrólisis y trans-esterificación de grasas animales no comestibles, y luego empleado para sintetizar el alcohol 3-cloro-1,2-propanodiol, que es el precursor del compuesto racémico de interés: el cloruro de rac-2,3-dihidroxipropiltrietilamonio: [Et3N+CH2CH(OH)CH2OH]Cl-, [C9H22N+O2]Cl- o (DPTAC). Dicho compuesto se sintetizó empleando el cloroalcohol obtenido, trietilamina y metanol. El compuesto (DPTAC) que inicialmente fue obtenido en forma de mezcla racémica, fue transformado en un compuesto enantiomericamente enriquecido mediante un proceso de acetilación quimioenzimática y de acetilación directa empleando acetato de isopropileno, con el fin enriquecer enantiomericamente este compuesto racémico. Además, se obtuvo el cloruro de S-(-)-2,3-dihidroxipropiltrietilamonio (S)-(-)-(DPTAC), partiendo del alcohol precursor ópticamente puro. Estas sales fueron acetiladas directamente con anhídrido acético y empleadas como componente HBA, en presencia de tres compuestos de base biológica: glicerol (Gly), ácido láctico (LA) y urea que actuaron como compuesto HBD en la formación de cada una de las mezclas eutécticas (DES). Además, el etilenglicol (EG) fue también utilizado para formar otro DES concreto. Es importante tener en cuenta que, el diseño de estos disolventes se realizó empleando la estrategia de “diseño modular” para que cada DES contenga un HBA de naturaleza y propiedades diferentes. En este trabajo es presentado el estudio de las propiedades físicas (viscosidad, densidad, relación estequiométrica, entre otras) de cada DES. Posteriormente, se estudió su empleo como disolventes en diferentes procesos químicos; donde, los DES preparados fueron utilizados como disolventes en el proceso de fraccionamiento y extracción de material ligno-celulósico en diferentes muestras de biomasa de madera dura como son: el orujo de oliva, y la poda de ramas (de tipo leñoso) de árboles frutales. Los resultados mostraron la obtención de lignina tipo Klasson y de fracciones ricas en holocelulosa utilizando cada uno de los DES. Asimismo, los DES preparados fueron utilizados para estudiar su influencia sobre la formación de los aductos endo:exo, en reacciones típicas de ciclación [4π+2π] tipo Diels-Alder, entre el ciclopentadieno con acrilato de etilo y acrilato de butilo. Por otra parte, con base en los requerimientos del proceso, fueron seleccionados los DES adecuados para ser utilizados como medios de reacción, en la obtención de alcoholes quirales secundarios mediante la reducción de cetonas pro-quirales en presencia de NaBH4. La riqueza enantiomérica de los alcoholes producidos se estudió empleando un reactivo de derivatización quiral (reactivo de Mosher). De esta manera se estudió la configuración absoluta del alcohol: 1-feniletanol (12) (obtenido como producto de la reacción anterior).
Low melting mixtures or Deep eutectic mixtures called DES (Deep Eutectic Solvents) are prepared from hydrogen bond acceptors called HBA, (usually a quaternary ammonium salt), and different hydrogen bond donors (HBD) for example alcohols, acid amines, and carbohydrates; form systems that contain a wide variety of cationic and/or anionic species governed by hydrogen bonding interactions that present low binding energy, causing their low melting points. This is one of the important characteristics when using the different types of DES, in terms of the type of reaction and/or synthetic process; for example, these eutectic solvents have been widely used and studied in biomass extraction processes, polymer synthesis, catalysis, electrochemistry, nanoparticle synthesis, among others. This work presents the preparation of several novel bio-based eutectic solvents from glycerol (Gly), which was obtained by hydrolysis and trans-esterification of inedible animal fats and then used to synthesize alcohol 3-chloro-1,2-propanediol, which is the precursor of the racemic compound: rac-2,3-dihydroxypropyltriethylammonium chloride: [Et3N+CH2CH(OH)CH2OH]Cl- (DPTAC). This compound was synthesized using the mentioned chloro-alcohol, triethylamine, and methanol. Compound (DPTAC) that was initially obtained as a racemic mixture, was transformed into an enantiomerically enriched compound employing chemoenzymatic acetylation and direct acetylation process using isopropylene acetate to separate the racemic mixture. Similarly, S-(-)-2,3-dihydroxypropyltriethylammonium chloride was obtained starting from the optically pure precursor alcohol. All these salts were acetylated directly with acetic anhydride. All of them were used as HBA to prepare different eutectic mixtures (DES). Thus, three bio-based compounds were used: glycerol (Gly), lactic acid (LA), and urea as HBD to form each of the mixtures. Finally, ethylene glycol (7) was also used to form a specific DES. It is important to note that the design of these solvents was carried out using the strategy of "modular design" in which each DES contains an HBA of different nature and properties. Initially, the study of the physical properties (viscosity, density, stoichiometric ratio, among others) of each DES is presented. Subsequently, their use as solvents in different chemical processes is also studied, the DES prepared were used as solvents in the process of fractionation and extraction of lignocellulosic material in different samples of hardwood biomass, such as olive pomace, and pruning of branches (woody type) of fruit trees. Results showed the obtaining of Klasson-type lignin and fractions rich in holocellulose using each of the DES. DES prepared were used to study their influence on the formation of endo: exo adducts, in a typical [4π + 2π] Diels-Alder type cyclization reactions, between cyclopentadiene with ethyl acrylate and butyl acrylate. On the other hand, based on the process requirements, suitable DES were selected to be used as reaction media to obtain chiral secondary alcohols by reducing pro-chiral ketones in the presence of NaBH4. The enantiomeric richness of the alcohols produced was studied using a chiral derivatization reagent (Mosher's reagent). In this way, the absolute configuration of the alcohol was studied: 1-phenylethanol (12) (obtained as a product of the previous reaction). In addition, preliminary tests were carried out to assess the possibility of recycling the DES obtained. For this reason, the initial DES prepared between the racemic compound (DPTAC) with the four HBD compounds were fractionated using a strong cation exchange resin to verify the ease with which they are separable; besides, being reusable and recyclable. Conditions that a solvent must meet to be considered within the “Green Solvents” category. Taking into account that the starting materials for the formation of eutectic mixtures are almost entirely bio-based compounds. All the precursor compounds and DES prepared were characterized by FT-IR and 1H and 13C NMR spectroscopy techniques; the racemic compound was analyzed by mass spectrometry; the proportion between the adducts formed in the Diels – Alder reactions was studied using GC-FID gas chromatography (230 ° C and 270 ° C); Optical activity and specific angle of rotation were measured on enantiomerically enriched and optically pure compounds. Finally, the separation of each DES, carried out using cation exchange columns and followed by FT-IR and 1H RMN.

Here we describe the fabrication and testing of novel cells using a conducting polymer membrane, Zn metal anode and a deep eutectic solvent electrolyte. Several different polyaniline-modified electrodes have been formed in various deep eutectic solvents (DESs) and aqueous media using cyclic voltammetry, and subsequently characterised using the electrochemical quartz crystal microbalance (EQCM). The morphologies of the obtained polymers have also been characterised using scanning electron microscopy (SEM), atomic force microscopy (AFM) and 3D optical microscopy. The more compact and dense polyaniline (PANI) films were achieved in DESs, while the films produced from aqueous media exhibited open structures of increased porosities. EQCM showed that the motion of mobile species between films and electrolyte during redox cycling, via the related change in mass, is different in DESs compared to aqueous media; a contributory factor is the higher viscosity and ionic nature of the latter. The electrochemical stabilities and capacitances of these polymers were studied after incorporation of graphite (GR) particles or metal oxides. Graphite particles improved the power and energy densities, as well as the stability of polymers, compared with their ‘pure’ counterparts. The capacity retention of the ternary nanocomposites (PANI/MoO2/GR electrode grown from Oxaline) was 87 %, whereas the lowest retention was found for pure PANI was 13 % after 300 charge–discharge cycles. The PANI composite has been successfully used as a cathode, with Zn metal as anode, in wet batteries (aqueous salt/DES electrolyte). The battery suffered from a low coulombic efficiency of only 51 % in DES at room temperature, whereas at 50oC the efficiency was 97 %. At 50oC and a current density of 0.0625 mA cm-2, the battery showed an energy density of 104 Wh kg-1 at a power density of 75 W kg-1, and a capacity of 344 mA hg-1 for discharge at 0.09 mC cm-2.This suggests the polymer/graphite systems would be more suitable for a power source and battery applications than those using only the pure polymer.

In this work we discuss the mechanism of action of this technique and demonstrate its efficacy as a means to synthesise single-phase strontium niobates of controlled stoichiometry. Also, the interaction between an ionic liquid, 1-ethyl-3-methylimidazolium acetate (emim)OAc, and biopolymers. It was demonstrated how they are intimately involved in the control of shape, size and crystallinity of a strontium niobate, and the direct involvement of the oxygen content of the resultant crystal composition in the synthesis of YBa2Cu3O7−δ (YBCO) superconductor. An extensive mechanistic study of the synthesis of the high temperature superconductor YBa2Cu3O7−δ using different ionic liquids and deep eutectic solvents, as well as mono-molecular chelating agents is also presented. Key experimental factors required for the synthesis of a metal oxide were recognised, focussing on the identification of precursory phases and elements that will augment or disrupt the synthesis, thereby assuring finer control over the desired crystal composition. Furthermore, it is presented for the first time the use of a deep eutectic solvent (DES), namely betaine:D-(+)-glucose which is capable of solubilize insoluble-in-water metal salts, like barium nitrate, and produce after calcination, high yields (>90 %) of Bi2Sr2CaCu2O8+x (BSCCO or Bi-2212) superconductor. Moreover, the stability of the DES is studied along several days to comprehend how the evolution of the DES is directly involved in the synthesis of the metal oxide. Lastly, the synthesis of a new sodium strontium niobate crystal composition is reported, Na0.1Sr0.9NbO3, via a choline chloride-based DES by forming, during the calcination process, high temperature-stable crystal compositions which, eventually will re-combine to form and entirely new crystal composition. Additionally, as a comparative analysis the synthesis is also studied via (emim)OAc.

Content: The application of split leather is an important issue in leather industry as most of them was not properly treated and wasted. In this study the application of choline chloride (ChCl), urea (U) and corresponding deep eutectic solvents (DES) on the modification of thermal stability and mechanical strength of mink split leather was investigated. TGA and DSC results indicated DES treatment enhanced thermal stability of split leather, and ChCl treatment reduced the stability. While, U treatment provided a kinetic inhibition during the thermal-decomposition. In terms of the mechanical strength, both ChCl and U treatment reduced burst intensity and extended height. While, after DES treatment the burst intensity and extended height increased significantly. In terms of the dosage, 7% DES provided best performance. Results mentioned above illustrated that DES formed by simply mixing ChCl and U provided strong interaction with fiber, enhanced the crosslinks. A hypothesis of [Ch(Urea)]+[Cl(Urea)]- type structure was proposed, as it enabled DES forming strong hydrogen bonds with functional groups on leather fiber, enhancing the crosslinks and therefore improving the thermal stability and mechanical strength. The DES treatment on leather fibers improved their overall performance and thereby broaden their applications. Take-Away: 1. DES obtained by mixing ChCl and urea presented very different effect in leather treatment, as the thermal stability and physical strength of leather improved significantly after the DES treatment. 2. A hypothesis of [Ch(Urea)]+[Cl(Urea)]- type structure was proposed, illustrating a formation of strong hydrogen bonds between DES and functional groups on leather fiber. This enhances the crosslinks and therefore improves the thermal and mechanical strength of leather.

Les solvants eutectiques profonds (DES) sont récemment apparus comme une nouvelle classe de solvants verts présentant un potentiel élevé pour remplacer les solvants organiques usuels. Bien que découverts récemment, les DES ont fait l'objet de nombreuses recherches au cours des dernières années en raison de leurs propriétés intéressantes. Cependant, il reste encore beaucoup à découvrir étant donné le nombre quasiment illimité de DES potentiels et de leur polyvalence. Notre étude vise à examiner l'effet des DES sur les liposomes, adoptés comme modèles membranaires, et sur les membranes cellulaires. Elle a également cherché à évaluer la capacité de solubilisation des DES envers des composés bioactifs volatils. Ainsi, une sélection de DES ainsi que de nouveaux solvants ont été tout d'abord préparés et caractérisés. Des mesures de densité, de viscosité et de polarité ont été effectuées et ont montrées que les propriétés des DES pouvaient être ajustées en fonction de leur composition. L'organisation des phospholipides et des liposomes au sein des DES a ensuite été étudiée à l'aide de microscopies optique et à force atomique. Les phospholipides s'auto-assemblent en vésicules dans les DES à base de chlorure de choline tandis que les liposomes se convertissent en bicouches lipidiques avant leur reconstitution en vésicules. De plus, des études de cytotoxicité et des examens morphologiques ont été combinés afin d'évaluer l'impact de quelques DES sur MDA-MB-231, une lignée cellulaire de cancer du sein humain. Les résultats ont montrés que l'effet dépendait fortement de la composition du DES. D'autre part, la capacité de solubilisation des DES envers des composés bioactifs volatils a été testée par chromatographie en phase gazeuse couplée à un espace de tête. L'influence de la présence d'eau et de certains systèmes d'encapsulation tels que les liposomes et les cyclodextrines sur la capacité de solubilisation des DES ont été analysés. Enfin, la libération du trans-anéthole à partir des DES a été suivie par extraction multiple de l'espace de tête. Les DES ont été capables de mieux solubiliser les composés bioactifs volatils et de contrôler leur libération par rapport à l'eau. Dans l'ensemble, ces travaux mettent en évidence l'utilisation potentielle des systèmes à base de DES comme véhicules de solubilisation de composés bioactifs
Deep eutectic solvents (DES) recently emerged as a novel class of green solvents with a high potential to replace common organic solvents. Despite their novelty, DES were extensively explored in the past years owing to their remarkably interesting properties. Yet, a lot remains to be uncovered given the limitless number of possible DES and their versatility. The current sudy aimed to examine the effect of DES on liposomes, adopted as model membranes, and on cell membranes. It also sought to evaluate the solubilizing ability of DES toward bbioactive volatile compounds. Therefore, a group of selected DES along with new solvents were first prepared and characterized. Density, viscosity and polarity measurements were mainly carried out and showed that DES' properties can be tuned depending on their composition. The organization of phospholipids and liposomes within the DES was then investigated using optical- and atomical force microscopies. Phospholipids self-assembled into vesicles in choline chloride-based DES while liposomes converted to lipid bilayers before their reconstitution into vesicles. Moreover, cytotoxicity studies and morphological examinations were combined to evaluate the impact of some DES on MDA-MB-231, a human breast cancer cell line. Results showed that the effect is highly dependent on the DES' composition. On the other hand, the solubilizing ability of the DES toward bioactive volatile compounds was tested using static headspace-gas chromatography. The influence of the presence of water and some encapsulation systems such as liposomes and cyclodextrins on the overall DES' solubilization efficiency was further analyzed. At last, the release of trans-anethole from the DES was monitored via multiple headspace extraction. DES were able to greatly solubilize the bioactive volatile compounds and to control their release when compared with water. Altogether, this work highlights the potential use of the DES-based systems as solubilization vehicles for bioactive compounds

This thesis describes the work of my Ph.D studies in Industrial Engineering during past three years. It regards preparation of copper-tin alloys from green solvents for decorative purposes. Actual industrial process involves cyanide based complex bath in order to produce white bronze layers and they often contain lead as brightener and whitener. The aim of the thesis is to develop a more environmental friendly process for white bronze electrodeposition. Two different electrolytes were considered as eligible candidates: one involves a simple organic acid aqueous solution as bulk electrolyte, and the other one is a new deep eutectic solvent bath. The investigation of electrodeposition using methanesulfonic acid as complexing agent considered a commercial bath and its optimization in order to be used in the decorative industry. The focus of the study was on the optimization of deposition parameters and verification of bath and deposit stability which was very important from industrial point of view. Obvious improvements on deposits quality and bath stability can be realized by replacement on anode material and utilization of pulse current. Contrary to that, research on electrodeposition from deep eutectic system was quite new and few relevant studies can be referred especially in the field of alloys. As a result, this work started from deposition of single metal for better understanding of behaviors of mixtures between choline chloride and ethylene glycol or urea. Successful deposition of copper-tin alloys can be carried out under warmed conditions and variation on film composition can be controlled by changing concentrations of metallic salts in the bath. Pulse current acted as an effective tool to refine microstructure of deposits in a similar way as in aqueous solvents. Since no brightener was added, reduced luster was observed here and working mechanism of additives was found to be rather different from that in conventional baths. In summary, operation parameters including temperature, salt concentration, anode material and supporting electrolytes influence the resultant properties of deposits in great extent. Deposit quality from both solvents can be improved by using pulse current with proper frequency.

This thesis describes the work of my Ph.D studies in Industrial Engineering during past three years. It regards preparation of copper-tin alloys from green solvents for decorative purposes. Actual industrial process involves cyanide based complex bath in order to produce white bronze layers and they often contain lead as brightener and whitener. The aim of the thesis is to develop a more environmental friendly process for white bronze electrodeposition. Two different electrolytes were considered as eligible candidates: one involves a simple organic acid aqueous solution as bulk electrolyte, and the other one is a new deep eutectic solvent bath. The investigation of electrodeposition using methanesulfonic acid as complexing agent considered a commercial bath and its optimization in order to be used in the decorative industry. The focus of the study was on the optimization of deposition parameters and verification of bath and deposit stability which was very important from industrial point of view. Obvious improvements on deposits quality and bath stability can be realized by replacement on anode material and utilization of pulse current. Contrary to that, research on electrodeposition from deep eutectic system was quite new and few relevant studies can be referred especially in the field of alloys. As a result, this work started from deposition of single metal for better understanding of behaviors of mixtures between choline chloride and ethylene glycol or urea. Successful deposition of copper-tin alloys can be carried out under warmed conditions and variation on film composition can be controlled by changing concentrations of metallic salts in the bath. Pulse current acted as an effective tool to refine microstructure of deposits in a similar way as in aqueous solvents. Since no brightener was added, reduced luster was observed here and working mechanism of additives was found to be rather different from that in conventional baths. In summary, operation parameters including temperature, salt concentration, anode material and supporting electrolytes influence the resultant properties of deposits in great extent. Deposit quality from both solvents can be improved by using pulse current with proper frequency.

The control of interfacial microstructural stability is of utmost importance to the reliability of liquid solder interconnects in high temperature electronic assemblies. This is primarily due to excessive intermetallic compounds (IMCs) that can form and continuously grow during high temperature operation, which practically renders conventional barrier metallisations inadequate. In this study, electrically conducting, NbOx containing Ni coatings were developed using electrodeposition. Their suitability as a solder diffusion barrier layer was assessed in terms of the electrical conductivity and barrier property. The present work explores a novel electrochemical route to produce Ni-NbOx composite coatings of good uniformity, compactness and purity, from non-aqueous glycol-based electrolytes consisting of NiCl2 and NbCl5 as metal precursors. The effects of cathodic current density and NaBH4 concentrations on the surface morphology, composition and thickness of the coatings were examined. A combined study of Scanning Transmission Electron Microscopy (STEM) and Electrochemical Quartz Crystal Microbalance (EQCM) was conducted to understand the fundamental aspects of this novel electrodeposition process. The composite coatings generally exhibited good electrical conductivity. The reaction behaviour between a liquid 52In-48Sn solder and Ni-NbOx, with Nb contents up to 6 at.%, were studied at 200°C. The results indicate that, Ni-NbOx with sufficient layer thickness and higher Nb content, offered longer service lifetime. Nb enrichment was generally observed at or close to the reaction front after high temperature storage, which suggests evident effectiveness of the enhanced diffusion barrier characteristics.

Com este estudo pretende-se verificar, por simulação, detalhes estruturais e propriedades de sistemas ternários formados por Deep Eutectic Solvents (DES) e água, gerando hidro-géis e prever a extensão de extração de clorofenóis da água, em um sistema bifásico DES/Água. Os DESs estudados são obtidos pela mistura na proporção 1:4 de dodecanoato de sódio com o ácido octanóico, ou ácido nonanóico, ou ácido decanóico, a 40 ºC. Os resultados obtidos mostraram que ocorre transferência de massa do poluente da fase aquosa para a fase rica em DES, no caso do sistema bifásico, com poluentes localizados próximos à interface. Os outros sistemas mostraram a formação de domínios aquosos entre as redes tridimensionais formadas pelo DES, característica de hidrogel. Uma proposta de organização estrutural do DES e do gel foi feita baseada em análises das funções de distribuição radial (RDF) calculadas. Concluiu-se que DES tem potencial de utilização em extração de poluentes hidrofóbicos; Modeling and simulation of systems involving Deep Eutectic Solvents and water - structure, properties and extraction of pollutants ABSTRACT: The present study’s goals are to clarify through molecular dinamics simulation, structural details and properties of ternary systems formed by DES and water, generating hydrogel, and to predict the extraction extension of chlorophenols from water, in a two-phase DES/water system. The DESs are obtained by mixing 1:4 sodium dodecanoate with oc-tanoic acid, or nonanoic acid, or decanoic acid. The temperature was maintained at 40 ° C in all simulations. The obtained results showed that the mass transfer of the pollutant from the aqueous phase to the DES rich phase, in the two-phase system. The other systems have shown the for-mation of aqueous domains present between the three-dimensional networks formed by DES, characterizing hydrogel. A proposal of DES’s conformation was made based in the RDF analyses. It was concluded that DES has the potential to be used in the extraction of hydrophobic pollutants.

Electronically conducting polymers based on functionalised thiophenes and pyrroles have continued to stimulate academic interest as well as starting to be employed in practical applications and uses. This thesis describes studies of the electronic properties of mixed thiophene-pyrrole polymers (based on custom synthesised mixed monomer precursors) and polymers electrodeposited from commercially available monomers, pyrrole and 3,4-ethylenedioxythiophene, in respect to energy storage applications including batteries and ion selective membranes. In such applications the movement of ion and solvent through the polymer film during oxidation and reduction cycles is critical to application and function, e.g. charging rate, metal ion permeability or adhesion stability. Recently the unexpected behaviour of polypyrrole in choline chloride based ionic liquids has been described. These liquids are especially attractive because of their unique solubility profiles, high stability, low volatility and low toxicity. This thesis describes the electrochemical characterisation, DC capacitance behaviour and ion/solvent transport properties of conducting polymers using a range of electrochemical methodologies in combination with acoustic impedance electrochemical quartz crystal microbalance techniques (EQCM) and X-Ray Photo-electron Spectroscopy (XPS). The behaviour of several mixed thiophene-pyrrole films, polypyrrole and poly 3,4-ethylenedioxythiophene in different electrolyte media; deep eutectic solvents (DESs), conventional organic solvents and aqueous media are contrasted in this thesis. PEDOT and one of the mixed thiophene-pyrrole polymers (poly 2-(thiophene-2-yl)-1H pyrrole) gave the highest DC capacitances of the polymers investigated, with high values observed in both choline chloride based (Type III) and zinc based (Type IV) DESs. The ion dynamics of the polymers p-doping in the DESs, observed to fit gravimetric data recorded, was able to show a marked difference in the ion transfers between DES types and a conventional organic solvent, acetonitrile. Both polymers in acetonitrile and the zinc based DES (ZnCl2 / EG) satisfied the electro-neutrality condition through dominance of anion transfers. Whereas, polymers in the choline chloride based DES (Ethaline) satisfied the electro-neutrality condition through dominance of choline cation transfers (in the opposite direction to anion transfers). This research involved work towards the development of a new class of rechargeable batteries based on a Zinc-Polymer system incorporating a novel, inexpensive, environmentally sustainable solvent. This work is necessitated by the problems associated with petrol and diesel powered vehicles and the limitations of batteries available for electric vehicles.

Following the concept of sustainable development, Green Chemistry is actively seeking for new solvents to replace conventional ones that present inherent toxicity, flammability and hazardous environmental fate. In this contest, Natural Deep Eutectic Solvents (NaDES) have recently emerged as new generation solvents; NaDES are eutectic mixtures of naturally occurring hydrogen bond donors (HBD, e.g choline chloride) and hydrogen bond acceptors (HBA, e.g. sugars, organic acids, amino acids) that display peculiar solubilization behaviour. In the present study, the possibility of use NaDES as eco-compatible bioactive formulations to deliver high value compounds in agricultural field was evaluated. The investigated NaDES were composed by betaine and choline chloride as HBA, and various HBD with different reactivity: acid (citric acid, lactic acid, malic acid), basic (urea) and neutral (glycerol and ethylene glycol). NaDES formulations were produced by extraction of highly-valuable macromolecules from algae biomasses (Arthrospira platensis and Phaeodactylum tricornutum) and grape by-products (grape pomace and grape seeds). Since NaDES ecotoxicological profile is poorly known, the toxicity of NaDES was investigated on soil animals (Eisenia andrei) and plants (Lepidium sativum, Avena sativa, Ocimum basilicum and Lactuca sativa) and their biodegradability were assessed. Results revealed NaDES high extraction efficiency and promising ability as antioxidants and inhibitors of the enzyme urease. NaDES formulations did not seem to produce promoting effects on plants and exhibited different toxicological profiles based on the tested organisms and the solvent composition. Overall, NaDES containing acids and urea as HBD showed a significant toxicity on the tested organisms.