Metodologia

Neste capítulo, serão apresentadas e fundamentadas as metodologias utilizadas no estudo da Orquestra Geração (OG). Adotando-se diferentes perspetivas teóricas, várias questões de investigação foram colocadas e diver- sas abordagens metodológicas foram sendo utilizadas, no sentido de se explorar o caso da OG – um caso complexo e multidimensional. Procurou-se, assim, compreender a realidade multifacetada deste projeto musical, social e pedagógico e aprofundar o conhecimento sobre os diversos intervenientes que o integram. Estes interagem continuamente uns com os outros, exprimindo e confrontando diferentes pontos de vista e partilhando experiências sociais e vivências musicais, cuja riqueza emocional converge para um objetivo comum: crescer, fazendo música em conjunto.info:eu-repo/semantics/publishedVersio

A simple approach for the determination and characterization of ternary phase diagrams of aqueous two-phase systems composed of water, poly(ethylene) glycol and sodium carbonate

In this work, an experimental protocol to determine liquid-liquid phase diagrams of aqueous two-phase systems (ATPS) in a chemical engineering course is described. Throughout this laboratory set of experiments, students will determine liquid-liquid ternary phase diagrams, comprising the solubility curves, tie-lines, tie-line lengths and critical points, for systems composed of poly(ethylene) glycol, sodium carbonate and water. Furthermore, students will apply the NRTL (Non-Random Two Liquid) model to fit the experimental tie-lines.publishe

Aqueous biphasic systems in the separation of food colorants

Aqueous biphasic systems (ABS) composed of polypropylene glycol and carbohydrates, two benign substances are proposed to separate two food colorants (E122 and E133). ABS are promising extractive platforms, particularly for biomolecules, due to their aqueous and mild nature (pH and temperature), reduced environmental impact and processing costs. Another major aspect considered, particularly useful in downstream processing, is the "tuning" ability for the extraction and purification of these systems by a proper choice of the ABS components. In this work, our intention is to show the concept of ABS as an alternative and volatile organic solvent-free tool to separate two different biomolecules in a simple way, so simple that teachers can effectively adopt it in their classes to explain the concept of bioseparation processes. Informative documents and general information about the preparation of binodal curves and their use in the partition of biomolecules is available in this work to be used by teachers in their classes. In this sense, the students use different carbohydrates to build ABS, then study the partition of two food color dyes (synthetic origin), thus evaluating their ability on the separation of both food colorants. Through these experiments, the students get acquainted with ABS, learn how to determine solubility curves and perform extraction procedures using colorant food additives, that can also be applied in the extraction of various (bio)molecules.publishe

Aqueous Biphasic Systems Composed of Ionic Liquids and Sodium Carbonate as Enhanced Routes for the Extraction of Tetracycline

Aqueous biphasic systems (ABS) using ionic liquids (ILs) offer an alternative approach for the extraction, recovery, and purification of biomolecules through their partitioning between two aqueous liquid phases. In this work, the ability of a wide range of ILs to form ABS with aqueous solutions of Na 2 CO 3 was evaluated. The ABS formed by IL 1 water 1 Na 2 CO 3 were determined at 25 C, and the respective solubility curves, tie-lines, and tie-line lengths are reported. The studied ILs share the common chloride anion, allowing the IL cation core, the cation isomerism, the presence of functionalized groups, and alkyl side chain length effects to be evaluated. An increase in the cation side alkyl chain length leads to a higher ability for liquid-liquid demixing whereas different positional isomers and the presence of an allyl group have no major influence in the phase diagrams behavior. Quaternary phosphoniumand ammonium-based fluids are more able to form an ABS when compared with imidazolium-, pyridinium-, pyrrolidinium-, and piperidium-based ILs. Moreover, the presence of an aromatic cation core has no major contribution to the formation of ABS when compared to the respective nonaromatic counterparts. Finally, to appraise on the systems applicability in downstream processing, selected systems were used for the partitioning of tetracyclines (neutral and salt forms) -a class of antibiotics produced by bacteria fermentation. Single-step extraction efficiencies for the IL-rich phase were always higher than 99% and confirm the great potential of ILs to be applied in the biotechnological field

Interacção de substâncias húmicas estuarinas com os iões hidrogénio, cobre(II) e chumbo(II)

Doutoramento em QuímicaNeste trabalho foi estudado o comportamento ácido-base de substâncias húmicas de águas estuarinas, bem como a sua interacção com iões de metais vestigiários, nomeadamente os iões cobre(l1) e chumbo(ll). As substâncias húmicas foram extraídas e isoladas da água de um estuário, por adsorção a resina XAD-8, segundo o método adoptado pela Intemational Humic Substances Society (IHSS). Os ácidos fúlvicos e os ácidos húmicos obtidos foram posteriormente fraccionados segundo a carga, por eluição com solventes de pH crescente, após a adsorção na resina X4D-8. As substâncias húmicas recolhidas foram caracterizadas por análise elementar e espectroscopias de infravemelho e de ressonância magnética nuclear de "C. A composição das substâncias obtidas é típica das amostras estuarinas, verificando-se, como é usual, uma maior aromaticidade dos ácidos húmicos relativamente aos ácidos fúlvicos. O fraccionamento segundo a carga separa as fracções obtidas essencialmente no que respeita ao teor em grupos carboxílicos, verificando-se que este diminui com o pH do solvente utilizado na eluição. O grau de aromaticidade, pelo contrário, aumenta com o pH da eluição. A quantificação e a caracterização dos grupos funcionais, muito heterogéneos, das substâncias húmicas foi efectuada através de titulações com base, seguidas potenciometricamente. A determinação da concentração hidrogeniónica é o passo decisivo nos estudos de protonação e foi efectuada com o máximo rigor. Nesse sentido, foi proposto e utilizado um método de calibração inovador, em que os parâmetros da resposta do eléctrodo são retirados da própria titulação das substâncias húmicas. Os parâmetros de protonação, nomeadamente as concentrações e afinidades hidrogeniónicas, foram estimados utilizando modelos de distribuição discreta e de distribuição contínua para as afinidades, tendo-se concluído que a heterogeneidade das substâncias húmicas pode ser modelada satisfatoriamente dos dois modos, desde que seja utilizado um número suficientemente elevado de parâmetros. (etc.)The aim of this work was to study the proton and metal ion interactions with estuanne humic matter. The humic substances were isolated from an estuanne water by adsorption onto an XAD-8 resin, accordingly to the procedure proposed by the Intemational Humic Substances Society. The fulvic and humic acids thus obtained were further fraccionated on a charge base, by desorption from XAD-8 resin with solvents of sequencially higher pH values. The substances were characterized by elemental analysis, IR and %-NMR spectroscopies, and were found to be typical of estuanne humic matter. The carboxylic content was higher for fulvic than for hurnic acids, and for the aromaticity the reverse was true. The charge fraccionation separated the substances mainly for their carboxylic content, which varied inversely with the pH of extraction. The acid-base behaviour of the substances was studied by potentiometnc titrations. A new method of electrode calibration was developed to determine the proton conmtration, that withdraws the electrode parameters directly from the humic substances titrations. The method proved to be both consistent and reliable. Base titrations were periormed at three electrolyte concentrations, as well as electrolyte titrations at constant pH. The dissociation of the functional groups is enhanced when raising ionic strength values, and their heterogeneity is diminished. The electrostatic effect was modelled using both a Donnan rnodel and a thermodynamic double layer model. After correcting the base titrations data for this efíect, an intrinsic distnbution for proton affinities was obtained. The estimated parameten for the rnolecular size show that the humic molecules radius is about twice the fulvic one. Hysteresis was observed for proton binding to the humic substances, probabiy due to confomational changes of the particles, since revenibility of hysteresis was dependent on ionic strength. . The binding of copper to the hurnic and fulvic acids was studied by potentiornetric titrations using a copper ion selective electrode. The binding of the fulvic acids was the sarne for pH values 4, 6 and 8, but for the hurnic acids it was higher for the highest pH. The affinity of copper(l1) was slightly stronger for phenolic than for carboxylic groups. The cornplexation of lead with the humic substances was studied by voltarnrnetric techniques. The experiments were perfomed at high ligandlrnetal ion ratios as usually found in the aquatic environrnent, and so a sensitive technique such as anodic stripping voltamrnetry was used to determine the complexing pararneters. The binding of lead to the hurnic substances was mainly due to carboxylic goups, and was stronger for the lowest ionic stregth. The influente of secondary phenomena, such adsorption and surface electrode concentrations, was studied and proved to affect voltamrnetric determinations. The conforrnation of hurnic substances particles in solution was found to be dependent on the procedure followed for the solution preparation

Development of back-extraction and recyclability routes for ionic-liquid-based aqueous two-phase systems

In the last decade, aqueous two-phase systems (ATPS) composed of ionic liquids (ILs) and inorganic salts have been largely explored as novel extractive platforms. The use of ILs as phase-forming components in ATPS has led to outstanding extraction performances compared to more traditional approaches. Nevertheless, despite those exceptional achievements, IL regeneration, recycling and reuse lagged behind and still remain a challenging task towards the development of greener cost-effective processes. Aiming at overcoming these shortcomings, the phase diagrams of novel ATPS composed of imidazolium-based ILs and Na2CO3 or Na2SO4 were determined and their extraction efficiencies for a model antioxidant - gallic acid - were evaluated. The most promising IL-based ATPS were then used in sequential two-step cycles (product extraction/IL recovery) so as to evaluate the efficacy on the IL recyclability and reusability. Extraction efficiency values ranging between 73% and 99% were obtained in four sequential partitioning experiments involving gallic acid while allowing the regeneration of 94-95% of the IL and further reutilization. Moreover, to support the vast applicability of the back-extraction routes and the recyclability concept proposed here, the most prominent systems were further tested with two additional antioxidants, namely syringic and vanillic acids. In both examples, the extraction efficiencies were higher than 97%. The remarkable results obtained in this work support the establishment of IL-based ATPS as a sound basis of greener cost-effective strategies with a substantial reduction in the environmental footprint and economical issues

Enhanced tunability afforded by aqueous biphasic systems formed by fluorinated ionic liquids and carbohydrates

This work unveils the formation of novel aqueous biphasic systems (ABS) formed by perfluoroalkylsulfonate-based ionic liquids (ILs) and a large number of carbohydrates (monosaccharides, disaccharides and polyols) aiming at establishing more benign alternatives to the salts commonly used. The respective ternary phase diagrams were determined at 298 K. The aptitude of the carbohydrates to induce phase separation closely follows their hydration capability, while the length of the IL cation/anion fluorinated chain also plays a crucial role. Finally, these systems were investigated as liquid-liquid extraction strategies for four food dyes. Single-step extraction efficiencies for the carbohydrate-rich phase up to 94% were obtained. Remarkably and contrarily to the most investigated IL-salt ABS, most dyes preferentially migrate for the most hydrophilic and biocompatible carbohydrate-rich phase - an outstanding advantage when envisaging the products recovery and further use. On the other hand, more hydrophobic dyes preferentially partition to the IL-rich phase, disclosing therefore these novel systems as highly amenable to be tuned by the proper choice of the phase-forming components