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Àrees temàtiques de la UPC::Enginyeria química

Optimization of membrane separation processes rely on the accurate determination of some parameters related to membrane structure, chemistry, morphology or transport mechanism. Therefore, membrane characterization is fundamental in membrane research and development. This thesis addresses two specific issues of membrane separation processes: the distribution of extent of concentration polarization (CP) over the membrane surface in test cells for pressure-driven membrane processes and the separate information of equilibrium (partitioning) and kinetic (diffusivity) properties of ion-exchange membranes for a better-understanding of ion-transport mechanisms. The implications of CP inhomogeneity for the interpretation of measurements of solute rejection were qualitatively illustrated using a simple model of locally-1D CP combined with a postulated probability distribution of unstirred-layer thickness over the membrane thickness. Disregarding the CP distribution under-estimates the CP of strongly positively-rejected solutes and over-estimates the CP for the negatively-rejected ones. This is especially important in nanofiltration where strong positive and pronounced negative rejections can occur simultaneously for solutes of different charges. Therefore, it is desirable to reduce the inhomogeneity of CP distribution to a minimum in membrane-testing devices. A novel test cell design was developed based on the classical configuration of rotating disk combined with the possibility of setting an operating pressure up to 20 bar. CFD simulations showed that CP was homogeneous over the major part of the membrane surface whereas there were some expectable deviations close to the membrane edge. The approach was also validated experimentally via studying the dependence of observed rejection on the rotation speed and demonstrating that intrinsic rejection was practically independent of it. Then, the cell utility was proved performing different ion rejection studies for several dominant salts (NaCl, MgCl2, Na2SO4 and MgSO4) plus trace ions (Na+, NH4+, Cl- and NO3-) and for electrolyte mixtures of NaCl and MgCl2. The solution-diffusion-electro-migration model was used to obtain ionic membrane permeances from the experimental data. Besides, experiments performed with a cross-flow test cell demonstrated that there was filtration along the membrane porous support even if the membrane is supported by an impermeable surface. This occurs in the peripheral parts of the membrane due to membrane sealing and contribute to CP inhomogeneity. Finally, a novel method based on non-stationary-diffusion of relatively small concentration differences was developed to determine salt diffusion and partitioning coefficients in addition to the ion perm-selectivity, which is the only parameter available from the conventional measurements of stationary membrane potential. An ion-exchange membrane supported by a relatively thick coarse-porous support (glass frit) is placed in a two-compartment stirred cell. The salt concentration in one compartment is kept stationary during the measurement whereas in the other compartment, the initial solution is rapidly replaced by a solution of different concentration. Thus, there is a time-dependent electrical response due to a progressive redistribution of applied concentration difference between the membrane and the porous support and the different ion perm-selectivities of those media. Experimental data was fitted to a mathematical model that describes transient transport phenomena including osmosis, which was found to contribute notably on the measurements. The osmotic permeability was determined in separate measurements. The rate of signal relaxation is primarily controlled by the diffusion permeability of the membrane but is also affected by the salt partitioning. The results were validated by comparison with the literature data and using conventional techniques. Systematic studies were also carried out under different conditions

Àrees temàtiques de la UPC::Enginyeria química

This thesis consists of a compendium of five works that illustrate the utilization of selected mathematical methods to solve specific chemical engineering problems. Hence, the thesis is intended to cover both, a review of fundamental mathematical procedures for the solution of models raised from chemical phenomena, and a demonstration of their effectiveness to obtain useful novel significant results. The opening paper explores diverse global optimization algorithms to adjust both kinetic constants and the binary interaction parameters (BIPs) for the Peng-Robinson equation of state to the experimental data. Those parameters are essential to determine the model raised from the supercritical transesterification of triolein with methanol to produce biodiesel, with CO2 as cosolvent, consisting of three reversible reaction in series. Here, a novel model merging the ordinary differential equations system raised from kinetic mechanism and the time-dependent thermodynamic state of the complex mixture is presented for diverse operating conditions. Among all results obtained, novel binary interaction coefficients for the intermediate reaction species (dioleins and monooleins) highlight. The second and fourth papers included in this thesis are aimed at the study of lanolin extraction from raw wool, using 5% ethanol in CO2. The former explores solid lanolin extraction under near-critical conditions by means of a mass-transfer model based on the shrinking-core concept, while the latter is addressed at the liquid lanolin supercritical extraction. Both models result in a partial differential equations (PDEs) system determined by the solubility of multiphasic lanolin, Henry-type partition coefficient and the lanolin mass transfer coefficient. Hence, in each paper the raised PDEs system is solved through a different method: in the second paper orthogonal collocation method is employed, while in the fourth paper finite differences method is used combined with the numerical integration of an expression previously obtained by means of the Laplace transform. Finally, an optimization procedure is used in order to fit the extraction parameters to the experimental data, achieving coherent results that agree well with those previously reported. Between the cases exposed, liquid lanolin extraction is significantly complex to model because of the diffusion phenomena that may occur inside the two lanolin fraction mixture added to the diffusion of solvent in the interphase. Therefore, in the third work a nonlinear autoregressive exogenous neural network model is designed to predict the outcoming extracted fraction of lanolin at diverse temperatures, pressures, solvent mass flow rates, wool packing densities and times. The problem with the scarce data available for training of the neural network is overcome by augmenting experimental data using an empirical Weibull function, which correctly predicts the lanolin breakthrough at the extractor exit. This hybrid Weibull - Neural Network algorithm results in a low prediction error and conform a powerful tool for optimizing operating conditions, proved by the fast convergence of genetic algorithm procedure. This thesis closes with Molecular Dynamics simulations for peptide-folding studies, followed by a Principal Component Analysis (PCA) and clustering analysis to understand the Free Energy Landscape of the peptide (FEL). Those methods are aimed at assessing the conformational profile of bombesin, a peptide with interest in drug design as a possible novel agonist and/or antagonist in the fight against cancer. Results suggest that the peptide adopts mainly helical structures at the C-terminus and, to a lesser extent, hairpin turn structures at the N-terminus. Those results agree with those available from NMR in a 2,2,2-trifluoroethanol/water (30% v/v), and point out a suitable a-helix conformation for binding where Trp8 and His12 interaction has a significant role.

Policarboxilats, Backbone, Cadenes laterals, Pes molecular, Empaquetament, Intensitat de color, Cuir, Biodegradabilitat, Respectuós amb el medi ambient, Agent de readobatge, and Àrees temàtiques de la UPC::Enginyeria química

The leather manufacturing process consists of a sequence of complex chemical reactions and mechanical processes that allow turning skin, a putrefiable by-product of alimentary industry, into leather, a stable high-value-added product with good hydrothermal resistance. During the last years, leather industry has evolved to an industry environmentally friendly thanks to the emergence of new chemicals and processes which have allowed the reduction of water and atmospheric emissions. One of these products has been conventional acrylic resins which are currently widely used as a retanning agents. However, they present a number of disadvantages in the final properties of the retanned leather. For this reason, in most cases, they are used together with different classic products constituted by formaldehyde, phenol, napthalene, etc. which have a certain degree of toxicity and possible carcinogenicity. The still use of certain chemicals with toxic constituents that could not be substituted for renewable or less polluting products, the obtention of reaction byproducts difficult to recycle or reuse during the diferent stages of the process and, the low properties of the leather retanned with convencional acrylic resins, it can conclude that there is still a large margin for improvement to reduce the environmental impact of the leather industry. In this doctoral thesis, modified acrylic resins known as polycarboxylates (PCEs) has been synthesized and studied as possible new environmentally friendly retanning agents instead of the conventional acrylic resins and classical products. PCEs synthesis has been done in two phases: free radical polymerization followed by Fischer esterification. Thus, branched polymers formed by acrylic backbone chains esterified with polyalcoholic side chains have been obtained. The characterization of these products has been carried out at the structural level through infrared spectroscopy (IR) and at molecular weight level through size exclusion chromatography (SEC). Both methods have allowed the identificaction of products of the same chemical nature but with differences in the molecular weight of the backbone chains and/or the side chains. The retanning tests have been carried out comparing their properties as retanning agents with a conventional linear acrylic resin of contrasted commercial use. The obtained leathers have been analyzed by physical and organoleptic assays. The results have shown that all PCE products render a high intensity of colour in the retanned leathers, one of the main drawbacks of the conventional acrylic resins. In addition, they have allowed to make a selection of the ideal PCE structure in relation to the application as a retanning agent. The validation of the obtained results has been done by scanning electron microscopy (SEM). To evaluate the environmental impact of the product, a biodegradability test has been performed. It has allowed to determine that PCE products have a higher degree of biodegradability compared to conventional acrylic resins. Consequently, as they are products with a high degree of biodegradability that don’t require the complementary use of classical toxic products, they can be considered as highly environmentally friendly products which can help to reduce the environmental impact of the leather industry life cycle. This project concludes that, in comparison to the conventional acrylic resins, PCEs are a real alternative of enhanced retanning agents more respectful with the environment.

Àrees temàtiques de la UPC::Enginyeria química

The cylinder in cross flow has been the subject of many numerical and experimental studies since it provides a deep insight of the physical phenomena occurring in a wide range of flow regimes. Despite a number of investigations at Reynolds number (Re = 3900), there has been a constant debate on the important aspects of the flow such as spanwise resolutions, lateral domain extent, convergence of turbulent statistics in the near wake, the so called U-V streamwise velocity profiles at x = 1D, where D is the cylinder diameter, and the critical Re for the onset of shear layer instability together with its characterization. In this thesis, an attempt has been made to address some of these issues and report new results through Direct numerical simulations (DNS) by employing spanwise domain extents i.e. Lz = 1.5D; 2D; 2.5D; pD at the moderate flow regime i.e. Re = 2000, where boundary layer is still laminar while the near wake has gone fully turbulent. Intermittent bursts of shear layer instability have been spotted at this Re indicating the signs of the incipient laminar to turbulent transition in the separating shear layer. It is further confirmed that the secondary instability develops in the regions between the opposite sign large scale spanwise vortices and features a phase lag of 135 degree. Pseudo-Floquet analysis gives a good prediction of fastest growing mode consistent with the reported numerical and experimental measurements. In the second part of the thesis, active flow control (AFC) past circular cylinder has been thoroughly investigated with the aid of parametric analysis at the same Re. We applied spanwise-dependent fluidic actuation, both steady and time-dependent, on the flow past a circular cylinder at Re = 2000. The actuation takes place in two configurations: in-phase blowing and suction from the slits located at ±90 degree (top and bottom) with respect to the upstream stagnation point for both steady and time periodic actuation, and blowing and suction from the top and bottom slits traveling oppositely with respect to each other in the spanwise direction. Optimal forcing amplitude and wavelength are obtained by sweeping across the parametric space. Spanwise-dependent time-independent forcing with wavelength ¿z = 2D has been found the optimal one in terms of drag reduction and attenuation in lift fluctuations. The time-dependent forcing with sinusoids travelling oppositely with respect to each other along the span produced significant reduction in drag force and lift fluctuations, however, the in-phase time periodic actuation with forcing frequency four times the natural vortex shedding frequency resulted in significant increased drag and lift fluctuation, signalling to a potential candidate for the energy harvesting applications. Finally, in the last part of the thesis, time-dependence of flow inside novel laminar-fluidic-oscillator has been analyzed using DNS. Again, pseudoFloquet stability analysis has been utilized to predict the fastest growing Fourier modes along the homogeneous direction. Supplementary three-dimensional numerical study has also been conducted for the suitable cases at various Re. It has been found that steady flow inside fluidic oscillator’s cavity bifurcates from steady state to time-periodic state through supercritical Hopf bifurcation. The secondary transition inside fluidic oscillator’s cavity occurs through the breaking of flow symmetry about the cavity axis by pitchfork supercritical bifurcation.

Àrees temàtiques de la UPC::Enginyeria química

Rare Earth Elements (REEs) are known as the remarkable components in many technologies that are driving the modern world. They are widely used in chemical engineering, permanent magnets, fluorescent lighting, sensors, cell phones, lasers, electronics, rechargeable batteries, etc., because of their unique physicochemical properties. In order to supply the required amounts of these elements and fulfil their increasing demands, it is necessary to recovery this elements from secondary sources. Despite many efforts that have been done on recycling REEs, only less than 1% of REEs is recycled which can be due to the numerous challenges, such as collection of different final products and separation of REEs from other contaminants/metals. Among the different techniques used for separation and purification of REEs from aqueous solution, biosorption has received great attention in recent decades. In this sense, biopolymers have been vastly utilized for the treatment of solutions containing metals. Alginate and chitosan are two kinds of biopolymers that have been utilized by many researchers due to being environmentally-friendly and effective. The purpose of this work was to study the adsorption of Nd+3, Tb+3, and Dy+3 ions from aqueous solutions by using new magnetic nanocomposites based on calcium alginate (CA) and carboxymethyl chitosan (CMC) biopolymers, a novel synthetic biodegradable polyamide named poly(pyrimidine-thiophene-amide) (P(PTA)), and magnetic nanoparticles (Ni0.2Zn0.2Fe2.6O4). The synthesis of the P(PTA) was performed in two steps. Firstly, a diamine-phenol monomer (TMAPD) was synthesized. Secondly, the polymer was obtained by polycondensation of TMAPD in 1,3-dipropyl imidazolium bromide ionic liquid as a solvent to avoid the use of the toxic triphenyl phosphite/N-methylpyrolidone/pyridine/LiCl that is required in the conventional direct polycondensation. The magnetic nanoparticles (Ni0.2Zn0.2Fe2.6O4) were synthesized by hydrothermal technique. The magnetic nanocomposites named CA/CMC/Ni0.2Zn0.2Fe2.6O4, CA/P(PTA)/Ni0.2Zn0.2Fe2.6O4, CMC/P(PTA)/Ni0.2Zn0.2Fe2.6O4 were synthesized by gelation method, and P(PTA)/Ni0.2Zn0.2Fe2.6O4 was synthesized by hydrothermal method. Different techniques were used to analyze the synthesized materials. XRD was used to confirm the formation of the Ni0.2Zn0.2Fe2.6O4 and determine the size of the particles. The P(PTA) synthesis was confirmed by NMR analysis. The morphologies of the Ni0.2Zn0.2Fe2.6O4 and magnetic nanocomposites was investigated by FE-SEM technique. TGA was used for determining the thermal stability of the P(PTA) and magnetic nanocomposites. EDX was used for elemental analysis of the Ni0.2Zn0.2Fe2.6O4, P(PTA), and magnetic nanocomposites. VSM analysis was applied to determine the magnetic properties of the Ni0.2Zn0.2Fe2.6O4 and the magnetic nanocomposites. To determine the functional groups of all products, FT-IR analysis was applied. Finally, the adsorption of the REEs was investigated in single and ternary batches, and column experiments. For the batch experiments, the effects of main parameters such as pH, contact time, adsorbent dosage, initial concentration, ionic strength, and temperature on the adsorption of the REEs were investigated in details. In addition, DeltaG', DeltaH', DeltaS' as thermodynamic parameters were determined. In ternary system, response surface methodology based on central composite design (RSM-CCD) was used for the ternary system to predict the adsorption efficiency of the REEs and the interactions among different parameters. The kinetic and isotherm models were applied to fit the experimental data of the REEs adsorption in batch system. Besides, the obtained data from column system were fitted by the models.

Àrees temàtiques de la UPC::Enginyeria química

Economic growth at any expense is no longer an option. Awareness of the growing human footprint is crucial to face the problems that the impoverishment of ecosystems is causing and will cause in the future. One of the key challenges to address it is moving toward approaches to manage resources in a more sustainable way. In this light, circular economy stands as a promising strategy to improve the lifetime of resources by closing material and energy loops. The Process Systems Engineering (PSE) community has been developing methods and tools for increasing efficiency in process systems since the late 1980s. These methods and tools allow the development of more sustainable products, processes, and supply chains. However, applying these tools to circular economy requires special considerations when evaluating the introduction of waste-to-resource technologies. This Thesis aims at providing a set of models and tools to support in the decision-making process of closing material cycles in process systems through the implementation of waste-to-resource technologies from the circular economy perspective. The first part provides an overview of approaches to sustainability, presents the optimization challenges that circular economy and industrial symbiosis pose to PSE, and introduces the methodological and industrial scope of the Thesis. Part two aims at assessing the environmental and economic reward that may be attained through the application of circular economy principles in the chemical industry. With this purpose, a systematic procedure based on Life Cycle Assessment (LCA), economic performance and Technology Readiness Level (TRL) is proposed to characterize technologies and facilitate the comparison of traditional and novel technologies. The third part describes groundwork tasks for optimization models. A methodology is presented for the systematic generation of a list of potential waste-to-resource technologies based on an ontological framework to structure the information. In addition, this part also presents a targeting approach developed to include waste transformation and resource outsourcing, so a new dimension of potential destinations for waste are explored for the extension of material recovery. Finally, part four includes the development of decision-making models at the strategic and tactical hierarchical levels. At the network level, a framework is presented for the screening of waste-to-resource technologies in the design of process networks. The most promising processing network for waste recovery is identified by selecting the most favorable waste transformation processes among a list of potential alternatives. After the network selection, an optimization model is built for the detailed synthesis of individual processes selected in the resulting network. The developed methodologies have been validated and illustrated through their application to a case study under different viewpoints in the process industry, in particular to the chemical recycling of plastic waste. Despite the low Technology Readiness Level of some chemical recycling technologies, the results of this Thesis reveal pyrolysis as a promising technology to close the loop in the polymer sector. Overall, all these positive outcomes prove the advantages of developing tools to systematically integrate waste-to-resource processes into the life cycle of materials. The adaptation to this change of perspective of the well-established methods developed by the PSE community offers a wide range of opportunities to foster circular economy and industrial symbiosis. This Thesis aims to be a step forward towards a future with more economically efficient and environmentally friendly life cycles of materials.

Àrees temàtiques de la UPC::Enginyeria química

Nowadays mining and hydrometallurgical industries generate a considerable amount of acidic liquid wastes (ALWs), which are characterised by a low pH and the presence of metals (e.g. Fe, Cu, Zn and Rare Earth Elements (REEs) among others) and non-metals (e.g. As, Se). These effluents are usually treated by the addition of lime to neutralise the acidity and to remove the metals as hydroxides and hydroxyl-sulphates, and the non-metals as calcium-based electrolytes and the resultant effluent is discharged into the natural water bodies. However, the high cost associated with this treatment makes necessary to explore other more sustainable alternatives. Nowadays, the European Union (EU) is promoting circular schemes to valorise effluents for the recovery of valuable elements. Additionally, it is worthy of mention initiatives such as the Critical Raw Material List, which promotes the recovery of valuable compounds from secondary resources. Therefore, ALWs from mining, hydrometallurgical and metallurgical industries can be a source of acid and metal recovery. Among the alternatives to the established neutralisation by lime addition, membrane technologies are being studied. In this thesis, two membrane technologies such as nanofiltration (NF) and diffusion dialysis (DD) will be used for the valorisation of ALWs.Acid Mine Drainage (AMD), which is a by-product of the mining industry, was the first model system treated with NF for acid recovery and concentrating the metals in solution. AMDs are characterised by a pH<3 and the presence of metals (Al, Fe, Cu and Zn, among others). REEs, which are identified as Critical Raw Materials by the EU, can be found as minor components. Different membranes, including acid-resistant, were tested under different feed composition to evaluate their influence in the membrane performance. NF membranes were able to treat AMD, especially those based on an active layer made of polyamide, with high metal rejections (>98%) and favouring the acid transport. Nevertheless, their low stability in acid media makes these membranes susceptible to use at long- term operation. Changes in the chemical and physical structure of the active layer were evaluated by using FSEM-EDAX, FTIR and XPS. Solution speciation was found to have a significant impact on membrane rejection. Moreover, a numerical approach based on the Solution-Electro-Diffusion model (SEDM) coupled with reactive transport, was developed to characterise the transport of species through membrane permeances. Furthermore, the prediction capability of the developed model was studied and tested to determine its potential application for process design.Besides, an ALW from a metallurgical industry composed by a mixture of H2SO4 and HCl (0.3

Àrees temàtiques de la UPC::Enginyeria química

Accidental releases of flammable hydrocarbons in chemical process industries can trigger severe hazards: explosions, fires, and dispersion of toxic vapour clouds. Explosions and toxic releases may injure people within large damage radius; however, fires are the most common accidental events that may lead to catastrophic consequences in terms of life and property losses. Within this framework, the prediction of the related-fire effects may significantly contribute to identify measures needed to eliminate or mitigate the consequences of accidents in processing environments. Semi-empirical methods can provide rapid estimations of the flame-geometry descriptors as well as estimations of the heat flux received at a given distance from the fire origin. Based on that information, active protection systems and inherent safer design measures (i.e. safety distances between equipment) can be determined to prevent major fire accidents. Nevertheless, these are based on empirical and statistical data, and do not cover the overall characteristics of the fire behaviour. Computational Fluid Dynamics (CFD) modelling can provide more detailed insights of the related fire effects considering additional complexity, such as different geometries and alternative boundary conditions, and representing different fire sizes: from small to large scale fires. Nevertheless, CFD requires detailed input data, expert knowledge on the phenomenon simulated and on the physical models implemented, and demands high computational resources. The use of CFD modelling for technological risk analysis is still incipient, so detailed validation exercises are needed before their use in real applications. This thesis is mainly aimed at assessing the predictive capabilities of different CFD codes (FDS, FLACS-Fire and FireFOAM) when predicting the hazardous effects of hydrocarbon pool fires and jet fires. Specifically, large-scale pool fires of diesel and gasoline (from 1.5 to 6 m-diameter), vertical sonic jet fires of propane (from 0.09 to 0.34 kg/s with orifice diameters of from 10 to 25.5 mm), vertical subsonic jet fires of methane in normal- and sub- atmospheric pressures (from 0.6 to 1 bar with an orifice diameter of 3 mm), and vertical and horizontal subsonic jet fires of propane (from 0.007 to 0.11 kg/s with orifice diameters of from 12.75 to 43.1 mm-diameter) have been modelled in different CFD codes. Prescribing burning rates provide accurate predictions of the pool fire effects with maximum cell sizes of 0.2 m. On the other hand, the cell sizes of sonic and subsonic jet fires should be determined by considering a fire characteristic diameter of 16 and 12, respectively. A minimum number of 400 solid angles is recommended to obtain accurate estimations of the thermal flux. Based on the numerous computational simulations performed, Best Practice Guidelines (BPG) are developed to determine a code as ‘valid’ or not, and to provide guidance on the most suitable modelling settings when performing CFD simulations of accidental hydrocarbon fires. The BPG usefulness is proved through a case study of an oil storage farm located in the Port of Barcelona. Large over-estimations of the heat flux values are found with semi-empirical correlations and thus, the safety measures required would be very conservative and costly. Therefore, CFD modelling is recommended method to perform detailed FHA in chemical and process industries.

Àrees temàtiques de la UPC::Enginyeria química

Nowadays, rare earth elements (REEs) have gained importance due to their indispensable and critical use in many high-tech industries like hybrid cars, fluorescent lamps, flat screen televisions, mobile phones, disc drives and wind turbines. Since these metals are needed to supply the required functionality in advanced technologies development and the lack of alternative materials, the REEs recovery from urban mining seems to be promising. Moreover, being the ores mines and their strip mining to REEs production placed in a few specific countries such as China, United States and Australia, the stable supply of such metals is becoming a concern. The absence of economical and operational primary deposits in other territories is making many countries consider the REEs recycling from pre-consumer scrap, industrial residues and end-of­ life products. However, about only 12.5% of e-waste is currently being recycled for all metals due to technological problems, inefficient collection and a lack of incentives and pilot-scale feasible testing to be industrially implemented. In this thesis, different routes to recover and separate these elements from end-of-life products like NdFeB magnets and fluorescent lamps have been developed considering the relevance of these applications in the REEs field and the feasibility of the complete industrial implementation. Regarding NdFeB magnet, it was demonstrated that Nd, the most REE representative component found in magnet wastes, was separated from an Nd/Tb/Dy mixture by using solvent extraction process and intensified processes like liquid membranes in flat sheet configuration. To avoid the inter-step pH conditioning in a continuous industrial process when cationic extractants are used, an ionic liquid such as Primene 81R.Cyanex 572 was proposed in an industrial counter-current extraction process. The results disclosed that two stages were required to separate Nd from the mixture with a purity of 99.7% removing =99% of the initial Tb and Dy. Although both cationic extractants, Cyanex 272 and Cyanex 572, were able to separate the Nd, the transport through the liquid membrane using the former is about 35% slower than using Cyanex 572. Hence, to obtain similar results to those got with Cyanex 572, the membrane area or the working time should be increased when Cyanex 272 is used. REEs from fluorescent lamp wastes were recovered and selectively separated with purities =99.9% by using a process that can be industrially implemented and combines acidic leaching treatments, liquid membranes and cross-flow solvent extraction process. Two successive acidic leachings were needed: (L1) to remove the Ca avoiding its precipitation in following stages of the process and (L2) to recover the REEs present in the waste. Unfortunately, a REEs amount, mainly Y and Eu, was also dragged in the liquid fraction from L1 and these REEs were recovered using Cyanex 923 as carrier by a hollow fibre renewal liquid membrane module. Furthermore, a transport modelling was developed to foresee the permeability coefficient values for Y and Eu depending on the organic solution viscosity and the membrane characteristic parameters. A mathematical modelling was developed using D2EHPA to predict the Y/Eu/Ce mixture extraction behaviour to investigate the optimal separation conditions of the REEs found in the leachate coming from the L2. Once the REEs behaviour was studied in the extraction modelling, the recovery and separation of the REEs were experimentally achieved obtaining purities =99% by four stages cross-flow solvent extraction process using two ionic liquids, Primene 81R.02EHPA and Primene 81R.Cyanex 572. In this sense, REEs recycling processes of both wastes promote potential circular economy based on solutions where a waste is turned into a resource.

Rare earth elements, Critical status, Urban mining, Hydrometallurgical routes, Solvent extraction, Mathematical modelling, Supported liquid membranes, Leaching process, Ionic liquids, and Àrees temàtiques de la UPC::Enginyeria química

The rare earth elements (REEs) are essential ingredients for the development of modern industry and the transition to a more sustainable economy model. The unique physicochemical features of these elements, such as their magnetism and optical properties, are greatly expanding their application. They have become key elements for the manufacture of many ordinary consumer goods like hybrid cars, fluorescent lamps or electronic devices like mobile phones or tablets. The growing popularity of the rare earth elements derivatives is leading to an increase in the global demand and the price of these elements. Unfortunately, the current availability of these resources is limited due to three main factors: their heterogeneous geological location, their low concentration in the ores, and the environmental issues related with their mining. All these disadvantages concerning the supply of the rare earth elements have led to the study of new techniques to obtain them, such as the recycling of end-of-life products. Recycling of REEs arises as a new secondary source of supply of REEs, especially in Europe where large amounts of technological waste are generated every year. Currently, the recycling of rare earth elements represents less than 1% of the global supply. Nevertheless, some studies in the literature assume that by 2050 the recovery rate of REEs will be 90% for wind turbines, 70% for electrical vehicles and 40% for the rest of derivative products. The research presented in this thesis relies on experimental investigation of new hydrometallurgical routes, the majority of them involving the use of ionic liquids, which could eventually be applied for the recovery of rare earth elements from end-of-life products. Matemathical modelling of the reported extraction systems has been carried out in order to provide a computational instrument that can be easily tailored for prediction of other collecting processes requiring minor adjustments.

Àrees temàtiques de la UPC::Enginyeria química

The worldwide poultry industry generates a large amount of wastes which, accordingly to the current law, are mostly discarded. These wastes include chicken feathers, keratin structures which 109.056.179 ton were generated in 2017 around the world. Taking into account this massive production and also their chemical and physical properties, keratin fibers that come from chicken feathers (CFs) are regarded as a potentially interesting material for its valorization in various areas. This option would make CFs an ecologic alternative (implying circular economy and biodegradability) to products that are already sold nowadays. Due to the increasing demand of sustainable plastic products, the use of CFs as a reinforcement of composite materials with low density polyethylene (LDPE) and polypropylene (PP) matrixes is regarded. Specifically, this work is focused on the fabrication process optimization, enhancing the compatibility between the matrix and the reinforcement. In order to achieve this objective, two strategies are followed: first, by the chemical modification of the chicken feathers by either acetylation or silanization and, secondly, by the addition of adhesion promoters like maleated polyethylene (MAPE) and maleated polypropylene (MAPP). The tests on the physical properties of the composites show that the addition of 20 % of CFs to the thermoplastic matrix decreases the tensile strength associated to a weak interfacial adhesion as it was demonstrated by scanning electron microscopy. However, when the MAPE/MAPP is added to the mixture, a significant increase in the tensile strength was noticed. On the contrary, acetylation and silane treatments did not result in any practical improvement of the properties of the biocomposites. On the other hand, nonwoven fabrics using CFs are made for acoustic insulation purposes. It is demonstrated that it is possible to fabricate a material with 50 % CFs and 50 % wool (W), with similar acoustic properties to those of a conventional insulation material such as stone wool (SW), even behaving better for frequencies below 2200 Hz. Life cycle assessment (LCA) studies show that the environmental impacts decrease when the amount of CFs increases in those nonwoven materials containing CFs and W, except for abiotic depletion and eutrophication impact categories. However, SW only present worse environmental performance than the CFs based nonwoven fabrics for few impact categories due to the negative contribution caused by the impacts associated to the W processing. Finally, the sorption of Cu2+ using CFs is studied and the results were compared with those obtained for commercial bentonite (BNT). The study of sorption kinetics at pH 4 show that, for low concentrations of Cu2+ (0,2 mM), sorption is greater and faster for CFs (94 %) rather than for BNT (67 %). Nevertheless, at higher metal concentrations (6 mM), BNT show a higher sorption capacity (87 %) than CFs (15 %). Similar results are obtained using CFs in real industrial wastewater. The material characterization by means of infrared spectroscopy and thermogravimetry techniques, before and after its use, shows that there are no significant changes in the structure of the sorbent, which would allow their reuse.

Àrees temàtiques de la UPC::Enginyeria química

This thesis focuses on the preparation of nanomaterials made of proteins and polymers. Even though the technology has advanced in the last decades to design new devices at the atomic scale, researchers are still inspired by what Nature has produced and optimized for millions of years. Following this concept, this work uses proteins forming water-filled channels, called porins, which regulate the flow of ions and biomolecules in cellular life. Two proteins were studied: Omp2a and VDAC36. The first part of the dissertation is the thermomechanical properties study of the latest hybrid membrane developed by the IMEM group: an thin nanoperforated poly(lactic acid) (PLA) film with the Omp2a porin immobilized onto the surface . For this purpose, a new equipment based on the microcantilever technology was used. The SCAnning LAser analyzer (SCALA) characterizes the coated cantilevers which allows the following of the cantilever bending induced by the compression/expansion of the sample coating (i.e. proteins or polymers). In this study, the intermolecular reorganization of Omp2a aggregates was evidenced as well as the protein secondary structure stability against temperature. The same method was employed to study the impact of nanofeatures (perforations and drugs domains) on films of PLA. They affected the glass transition and the cold crystallization temperatures. The changes were dependent on the size and abundance of the nanofeatures, which can modulate the properties of future materials. Moreover, this work established a protocol for the study of biomolecules and polymers attached to microcantilevers, allowing an accurate study of the thermomechanical properties using very low amounts of sample. The second part of the thesis is the development of new hybrid nanomaterials composed of VDAC36, PLA and poly(3,4-ethylenedioxythiophene) (PEDOT). An efficient protocol was established for the production of VDAC36 and its subsequent refolding was achieved. The beta-barrel nature of the protein was revealed and its tendency to form oligomers was demonstrated. Finally, the size of the protein inner channel could be determined. The VDAC36 was added to the polymer material made of three alternating layers of PLA and PEDOT. The electrical properties of the material were modified by the addition of the protein: the overall resistance was reduced and the supercapacitive behaviour was enhanced. The description of the electrical equivalent circuit also revealed that the protein induced the diffusion of ions. To improve the material, the number of layers was increased and the conducting polymer was modified by incorporating a monomer bearing a dodecyl chain. The modifications were proved useful as the protein content and the electrical properties increased. Finally, the new hybrid material could provide an adaptive electrical response according to the concentration of biomolecules.

Àrees temàtiques de la UPC::Enginyeria química

The origin of building blocks of life and how life thrived on Earth remains a topic of high interest for researchers of the Origin of Life. In this thesis, we deal with concepts, perspectives and implications of the system termed hydroxyolite, a combination of outstanding biopolymers (nucleic acids such as DNA and RNA) and an exceptional mineral (hydroxyapatite). First we study, based on Revilla et al. (2013) and Bertran et al. (2014), how hydroxyapatite forms crystals able to encapsulate DNA or RNA when nucleic acids are used as a nucleating template. Later, in Bertran et al., (2016), we reported the mechanism of how the encapsulated nucleic acid is released to the surroundings when environmental conditions change, for instance becoming more acidic. As a consequence, we postulated that DNA existing in cells can be encapsulated and protected by hydroxyapatite against environmental attacks (i.e. poisonous gases, gamma radiation or enzymatic degradation) until they change, making feasible the reintroduction of nucleic acids in the mainstream of life. We hypothesized about the implications of such a system in the early history of life when mass extinction events occurred on Earth (Turon et al., 2015). Moreover, we extended the hydroxyolite concept, borrowed from the materials chemistry, to other disciplines such as paleontology, biology, biotechnology and medicine by considering hydroxyolites as equivalents to non-viral vectors that can introduce and release DNA into a cell (transfection). Such nucleic acid triggers the expression of foreign proteins if released in the cytosol or might be recombined with cell genome when DNA is released in the target cell nucleus. In the second part of the thesis, we studied the hydroxyolite system from a complementary perspective. We speculate about the consequences of being hydroxyapatite the first actor and not the nucleic acid. We propose that hydroxyapatite might act as an inorganic mold if considered as a catalytic substrate that facilitates the synthesis of simple organic molecules as the building blocks of life. Thus, we identified a prebiotic scenario, a volcanic eruption under lightning, where a phenomenon known as dirty storm usually occurs under certain conditions. Hydroxyapatite is known in nature to be part of igneous rocks and volcanic ash in small but significant concentrations. We replicated in the laboratory such extreme conditions by developing a thermally and electrically stimulated polarization. A process performed at 1000 ºC and under a difference of potential of 300 kV·m-1, to obtain permanently polarized hydroxyapatite (Turon et al., 2016; PCT/EP2017/069437) that turned out to be an enhanced catalyst compared to hydroxyapatite able to fix nitrogen and carbon from a gas mixture of N2, CO2 and CH4 (Rivas et al., 2018). The catalyst, under UV light, converts them into amino acids (Glycine and D/L-Alanine) and small organic molecules by means of a new inorganic photosynthetic process. In this work, we develop an integrative prebiotic model that describes how simple molecules might be synthesized from mildly reducing atmospheres by combining previous models such as volcanos as giant reactors, minerals as catalysts and photochemical reactions in the atmosphere under prebiotic sun light. All of them under the framework of a prebiotic inorganic photosynthesis, a process that might be considered the corner stone of the rise of the building blocks of life.

Àrees temàtiques de la UPC::Enginyeria química

Development of new drug molecule is expensive and time consuming. Improving safety efficacy ratio of “old” drugs has been attempted using different methods such as individualizing drug therapy, dose titration, and therapeutic drug monitoring. Delivering drug at controlled rate, slow delivery, targeted delivery are other very attractive methods and have been pursued vigorously. Now a new class of bioceramics based on calcium phosphate (CaP) salts is on the verge of being widely applied in the clinic. Among various types of CaP, hydroxyapatite (HAp) have attracted more attention in biomedical fields due to its exceptional features such as biocompatibility, bioactivity, osteoconductivity and osteoinductivity. Its "chemical similarity" with the mineralized phase of biologic bone makes it unique. HAp as an excellent carrier of osteoinductive growth factors and osteogenic cell populations. HAp can incorporate the drug molecules either physically or chemically so that the drug retains intact until it reaches to the target site. It could also gradually degrade and then deliver the drug in a controlled manner over time. So therefore, this bioceramic is an excellent candidate for targeted drug delivery regardless of its density. Careful selection of reaction conditions, reagent concentrations and adsorption agents often provides a degree of size and shape control in nanoparticles dissolution, and a considerable amount of recent research has been devoted to developing such methods. Delivery of drug carriers to the target cells can be only a part of the whole story of successful drug targeting. Some drug carriers may have to gain access to and get inside the cytoplasm of a target cell in order to release the drug at the optimum rate for the pharmacological effectiveness. In that sense, intracellular targeting is an important systemic targeting. On the other hand, in some pathologies, especially in cancer, cell defends itself actively by using molecular ‘pumps’ in cell membrane that actively expel drugs form the interior -multidrug resistance (MDR)- and therefore their impairment is likely to have a significant therapeutic benefit. Thus, understanding mechanism of intracellular localization is critical in developing some drug delivery systems. This release is strongly influenced by resistances to mass transfer, intracrystalline diffusion and adsorpted species. The main goal of this Thesis is to design an effective MDR reversing nanoparticulate drug delivery system consists of a HAp polymeric matrix from which the drug is released intracellularly.

Àrees temàtiques de la UPC::Enginyeria química

In this work two research topics are presented: investigation of carbonation reactions of high – calcium waste materials and CO2 storage in coal. Firstly, sorption capacity of CO2 and CH4 of hard coal and associated sorption-induced expansion of the material was measured. This investigation was maintained in isothermal and non-isothermal conditions. Experiments were done on purpose-design apparatus allowing simultaneous measurement of sorption kinetics and sorption-induced swelling/contraction of coal. Chosen coal sample had higher sorption capacity for CO2 when compare to capacity for CH4.. Next to CO2 storage, the topic of CO2 utilization has been investigated. Carbonation of European high-calcium fly ashes is assessed. The experiments have been done on different fly ashes with content of 5-36% CaO. Complementary, characterization and analysis of fly ash samples has been performed. Acceleration of carbonation has been explored. Experiments has been done in temperature range between 25 and 290°C, 1-12 bar of CO2, CO2 + H2O and simulated flue gas over reaction times between 2 and 72 hours. Major conclusions of this work is that increasing the temperature and pressure strongly enhances the process of carbonation. Also, addition of water vapor substantially accelerates the process and increase its kinetics. This thesis reports that maintaining the carbonation process without steam addition leads to effective carbonation conversion. Chemical fixation of CO2 molecules with solid material of fly ash with high content of CaO to produce calcium carbonate is possible. The highest sequestration capacity achieved is 117.7 g CO2/kg fly ash and highest carbonation efficiency obtained is 48%. The microstructural analysis of fly ash samples showed the evolution of the cenosphere surface according to the carbonation experiments conditions. Different shapes and sizes of calcium carbonate has been detected after carbonation experiments. The compositional constraints of fly ashes that control reaction with CO2 has been described. It was found that not the bulk content of CaO is the factor controlling the carbonation reaction, but the content of free lime. Impact on carbonation of two pressure flow systems was assessed: batch and continuous flow, with and without addition of steam. Using he batch treatment with addition of steam gave the highest carbonation efficiency. Another set of carbonation experiments which has been done was with using simulated flue gas (84% N2, 15% CO2, 1 % H2O) instead of pure CO2 stream, in conditions: 160°C, 6 bar of gas and 2 hours of reaction time. It was concluded that using flue gas instead of pure stream of carbon dioxide lowers the carbonation rate of about 9%. Final part of this research was to determine the change of free lime content in fly ash samples before and after carbonation. Carbonation reactions lead to substantial decrease of free lime contents in fly ashes. In most cases, the amount of free lime in fly ash after carbonation was compatible with the current EU legislations regarding fly ash incorporation to cement as admixture.

Àrees temàtiques de la UPC::Enginyeria química

Chronic wounds became burdensome problem of worldwide healthcare systems, along with the increased elderly population, which is the most vulnerable risk group, predisposed to their development. Chronic wounds represent a “silent epidemic” that affect a large fraction of the population and are often regarded as a comorbid condition. Statistical surveys indicated that 1-2 % of the population in developed countries will suffer from chronic wounds during their lifetime. Contemporary clinical treatment involves a combination of techniques and procedures aiming at eradication of wound chronicity and switching the biochemical entities to normal wound healing. In this regard, wound dressings have been affirmed and widely accepted as integral part of wound healing therapies. Wound care, by using dressings dates from ancient times, when for instance ancient egyptians applied and arranged bandages. Nowadays, the market is dominated by dressings, which only function besides a simple physical barrier is to balance the wound moisture by either absorbing excess exudates or providing moisture environment. However, the multifactorial nature of chronic wounds often renders this single-factor directed therapy as low or non-effective, aggravating the patient outcome. Thus, the demands for expanding the treatment options to more effective therapy brought about the development of bioactive dressings. These dressings should not only protect the wound and control the wound moisture, but also interact with various adverse wound constituents, modulating their bio-activities in favor of healing. Materials with inherent wound healing features are highly desireable and more attention to such materials among the research communities has lead to the design of wound dressings with improved characteristics. However, amongst the myriad novel dressings synthesized, there is still lack of universal dressing with a panel of features able to address most of the devastating chronic wound constituents. The lack of such on-market dressing, lead to huge economical burden of the healthcare systems, holding significant part of their budgets. Development of universal multifunctional dressing, appropriate for management of many types of chronic wounds will boost the health systems to minimize the costs and improve the quality of patient’s life. This thesis develops multifunctional biopolymer-based hydrogel materials as a bioactive platform with appropriate exploitation characteristics for treatment of chronic wound. To this end, hydrogels were developed by using environmentally benign approach, based on enzymatic reactions. Intrinsically bioactive biopolymer chitosan which served as a matrix, was modified with thiol groups and further in situ enzymatically crosslinked with two different natural polyphenols. The incorporated in the biopolymer matrix polyphenols, exhibited dual role on the hydrogel performance by providing: 1) structural integrity by crosslinking the biopolymer chains; 2) bioactive features, through interaction with major chronic wound factors. The multifunctionality of the obtained materials in the treatment of chronic wounds was evaluated by in-vitro and ex-vivo experiments with chronic wound exudates. The hydrogels exhibited beneficial for wound healing properties, such as inhibitory activity against deleterious wound enzymes and antioxidant activity, and antibacterial activity coupled with biocompatibility to human skin cells.

Peptides, Synthetic polymers, ω-pentadecalactone, Globalide, Aminoended initiator, Amino acid, Hybrid copolymers, Doxorubicin, Transfection, and Àrees temàtiques de la UPC::Enginyeria química

Naturally produced peptides or proteins can be regarded as highly refined polymers. When synthetic polymers are married to proteins or peptides, the resulting bioconjugates can synergistically combine the properties of the individual components and overcome their separate limitations. This Thesis is focused on the study of hybrid copolymers based on polypeptides and polymacrolactones. Block and graft copolymers have been synthesized by making use of the ring opening polymerization method (ROP) mainly and extensively characterized including both their chemical structure and their structure in the solid state. The self-assembly properties of the new copolymers have been preliminary examined regarding their potential application as nanocarriers for pharmaceutical compounds. This Thesis initially reports the ROP of w-pentadecalactone (PDL) using different amino-ended initiators and assisted by either organic or enzymatic catalysts. This method was then extended for the ROP of PDL using bisamino-ended poly(ethylene glycol) (PEG) for the preparation of poly(w-pentadecalactone)-b-poly(ethylene glycol)-b-poly(wpentadecalactone) [PPDLx-PEG-PPDLx] triblock copolymers. These amphiphilic ABA-type copolymers were able to selfassemble in water to form nanoparticles with diameters between 100 and 200 nm. Hybrid copolymers of poly(ester-peptide) or poly(ether-ester-peptide) type exhibiting different architectures (e.g. diblock, triblock, graft or triblock/grafted) respectively, were then synthesized using as building blocks: poly(w-pentadecalactone), poly(globalide) (PGl), PEG as well as polypeptides derived from the L-glutamic acid (Glu), L-lysine (Lys), L-alanine (Ala) and L-phenylalanine (Phe) a-amino acids. The hybrid copolymers were synthesized through several stages depending on the desired architecture. The first stage in the preparation of these copolymers was the synthesis of macroinitiators from PDL or PGl containing either an amino group at the end of the chain or multiple amine groups along their polymeric chain. In the second stage, such macroinitiators were used to trigger the polymerization of the a-amino acid N-carboxyanhyrides (NCA) with the COOH group of L-glutamic acid and NH2 of L-lysine duly protected as g-benzyl-L-glutamate (BLG) and eNcarbobenzoxy-L-lysine (ZLL) respectively. Some copolymers containing BLG or ZLL units were treated with acids to render copolymers bearing the amino acids residues with their COOH or NH2 functionalities in the free form. All of the synthesized copolymers were fully characterized through GPC and NMR spectroscopy. The thermal properties were studied by TGA and DSC techniques. The conformation adopted by the peptide-based copolymers in the solid-state was assessed by FTIR, and their crystalline structure was examined by X-ray diffraction using synchrotron radiation in most cases. The conformation in aqueous solution of water-soluble copolymers containing Glu or Lys residues in the free form was explored by circular dichroism. The self-assembly behavior in aqueous medium of all the amphiphilic copolymers was investigated with the purpose of obtaining nanoparticles with the appropriated diameters required for their application as biomedical nanocarriers. The nanoparticles were duly characterized by light scattering and SEM and TEM microscopies. Block and graft copolymers were able to load doxorubicin and release it under pH control. Copolymers containing L-lysine were shown to be able of condensing DNA. The potential of these copolymers as DDS of anticancer drugs and vectors for transfection have been evidenced.

Àrees temàtiques de la UPC::Enginyeria química

In 1931, the first research work related to microencapsulation was published, in which a microcapsule formation technology using gelatine as a wall material was described by a process called "coacervation". The interest in this technology is based on the possibility of avoiding the degradation of the physicochemical and biological properties of substances exposed to conditions that are harmful by means of packing it under a polymeric wall, that can be of different thicknesses or characteristics, thus allowing to control the release of the microencapsulated substance. In this thesis the manufacture of microcapsules of aromas by complex coacervation using gelatin and gum arabic as wall material is proposed. The process is based on 5 stages: Dissolution of gelatin and gum in the aqueous phase, microemulsion of the aroma in the aqueous phase in presence or absence of a surfactant, coacervation of the gelatin and gum, gelation of the coacervate forming the wall of the capsule and the crosslinking of the wall material by a crosslinking agent. Initially, the research will focus on the development of a complex coacervation microencapsulation protocol that encapsulates much of the aroma of the system, obtaining relatively spherical microcapsules. The microemulsion stage has the greatest influence on the final efficiency of the encapsulation and, therefore, this is the stage that has focused most interest in recent years. The interfacial phenomena linked to this process determine the particle size, the stability of the emulsion and the interaction of the components of the system at the oil-water interface, in this case, gelatin, gum and the possible surfactants present. This is why a part of the present thesis will focus on the study of the influence of different surfactants (SMA, SDS and Kolliphor®) on the morphology of the microcapsules and the efficiency of encapsulation. The last part will focus on the study of the crosslinking process. Typically, microcapsules formed by complex coacervation using gelatin and gum arabic as wall materials have been cross-linked with glutaraldehyde or formaldehyde, substances with high toxicity. That is why recent studies have attempted to replace these aldehydes with the enzyme transglutaminase. To confirm whether transglutaminase is an option comparable to glutaraldehyde or formaldehyde, a study of the kinetics of cross-linking of the microcapsule wall will be carried out, obtaining the equations that regulate this process depending on the type of cross-linking agent studied.

Àrees temàtiques de la UPC::Enginyeria química

Hydrogen is one of the most promising solutions for the energy future, since its combustion only produces water vapour, so it does not pollute. In addition, it can be obtained from abundant and renewable substances. Fuel cells in vehicles can use hydrogen directly and it has multiple applications in the industry. Today, hydrogen is primarily produced by steam reforming of natural gas. However, this process of production does not reduce emissions of greenhouse gases and requires high temperatures and pressures, which implies a high-energy supply. In addition, it does not use a non-renewable energy source to produce it. In contrast, photocatalytic production of H2 can be carried out at environmental conditions and using directly the Sun and renewable substances such as ethanol. In this research work, different catalysts have been prepared using different synthetic methods for the photocatalytic production of hydrogen from ethanol-water mixtures. Chapter 1 presents the most relevant aspects related to the experimental work carried out in this doctoral thesis. In addition, the background and objectives are included. Chapter 2 describes the preparation of TiO2 lyogels decorated with preformed gold nanoparticles and their photocatalytic behaviour in the production of hydrogen. Two different series were prepared. Initially, TiO2 lyogels were calcined at different temperatures before depositing the preformed gold nanoparticles and then a different group of lyogels was calcined after depositing the nanoparticles. The characterization results showed differences in the composition of crystalline phases present in the materials. After performing the photocatalytic tests, they revealed a strong dependence on the crystalline phase of the catalyst with its photocatalytic activity. In Chapter 3, the influence of the morphology of catalysts decorated with pre-formed Au-Cu nanoparticles on the photocatalytic production of hydrogen is studied. The synthetic methods used to produce nanostructures with defined morphology are often very complicated or difficult to reproduce. Here, a microstructure prepared by a simple synthetic method is explored and compared to other materials with morphology that have already been clearly established in the literature, in addition to the commercial catalyst TiO2-P25. The photocatalytic results showed that this microstructure achieved the highest photocatalytic activity of all the morphologies tested and was equivalent to that of the commercial catalyst TiO2-P25. In Chapter 4, the effect of depositing isolated platinum atoms on the surface of TiO2 with defined morphology in the photocatalytic production of hydrogen is studied. They have been compared with the commercial catalysts TiO2-P90 and P25 and with the catalysts decorated with AuCu nanoparticles. The effect of two types of thermal treatments, calcination and reduction, is studied. Besides, the effect of the reduction temperature and the stability of the reduced catalyst was also studied. The results showed a high photocatalytic activity compared to the samples with Au. The reduced catalysts showed a higher photocatalytic activity than the calcined ones but they were less stable.

Àrees temàtiques de la UPC::Enginyeria química

In this thesis, different theoretical approaches designed to study a wide interval of length- and/or time-scales have been used to examine the microscopic properties of chemical systems with varying degrees of complexity and size. Firstly, the conformational preferences and optical properties of a tripeptide derived from the RGD sequence, the unit of a cell adhesive activity domain in adherent proteins, have been analyzed. Calculations on this peptide, which contains an exotic amino acid bearing a 3,4-ethylenedioxythiophene (EDOT) ring as side group, have been performed using DFT and time depending DFT methods. Results indicate that the bioactive characteristics of the RGD sequence become unstable in presence of the new residue because of both the steric hindrance caused by the EDOT side group and the repulsive interactions between the oxygen atoms belonging to the backbone amide groups and the EDOT side group. This information has been used to propose some chemical changes oriented to improve the bioadhesive properties. The interaction of a cell penetrating tetrapeptide, RPAR, adsorbed onto a gold substrate and the deposition of a pre-assembled peptide-polymer conjugate, cyc[(L-Gln-D-Ala-L-Lys-D-Ala)2] coupled with two poly(n-butyl acrylate) blocks, onto a mica substrate have been examined through molecular dynamics (MD). Results indicate that RPAR binds both the (100) and (111) gold surface facets. The conformation of the adsorbed peptide differs considerably from the bioactive conformation. However, the new conformations are not stabilized by strong intramolecular interactions. Accordingly, gold nanoparticles can be considered as suitable vehicles for the transport and targeted delivery of this CendR peptide. For the pre-assembled peptide-polymer conjugate, a theoretical approach that simulates the selective and progressive desolvation of the nanotube-like assembly has been used, demonstrating that the solvent presence during deposition is the main responsible for the unexplained conformational preferences of the acrylate blocks. When the proportion of solvent drops, the loss of many attractive solute-solvent interactions induces a meaningful increase in the number of torsions. MD has been also used to understand the impact of the solvation medium and the action of a detergent in the structure of a representative outer membrane protein (OMP). Calculations show the destabilization of the protein in water, while in presence of detergent molecules in solution or the bilayer induce a partial and complete protective effect, respectively. Combining stochastic algorithms and MD simulations the atomistic details of polymer coatings deposited over metal surfaces have been modeled to reproduce the experimentally observed topographic features of poly(3,4-ethylenedioxythiophene), PEDOT, deposited onto stainless steel. Results have provided an excellent model system to test the developed modeling strategy. Multi-phasic simulations have been conducted to explain the influence of protein···polymer interactions in the antimicrobial biocapacitors activity of lysozyme (LYZ)-containing PEDOT electrodes through atomistic MD calculations. Two models have been investigated: i) a biphasic system in which the protein was adsorbed onto the surface of PEDOT, PEDOT/LYZ; and ii) a biocomposite in which the LYZ was homogeneously distributed inside the PEDOT matrix, P(EDOT-LYZ). MD simulations have been performed in absence and presence of electric fields, the latter mimicking the one originated by the voltage cell difference in biocapacitors. In PEDOT/LYZ electrodes, the loss of biological activity has been attributed to the anisotropy of the PEDOT···LYZ electrostatic interactions. In contrast, anisotropic effects are minimized in P(EDOT-LYZ), conserving activity. The bactericidal activity of PEDOT/LYZ and P(EDOT-LYZ) biocapacitors is independent of the electric field applied or supplied during charge-discharge processes.