In the rapidly changing scientific world, contributions of scientists and engineers are leading to major new solutions of significant medical problems. Biology and medicine are beginning to reduce the problems of disease to problems of molecular science, and are creating new opportunities for treating and curing disease. Such advances are coupled closely with advances in biomaterials and are leading to a variety of approaches for relieving suffering and prolonging life.Of particular interest is the central position that materials especially biopolymers, have taken in the development of novel treatments over the last 30 years. Biopolymers are used in many biomedical and pharmaceutical preparations, they play a central role in extracorporeal devices; from contact lenses to kidney dialyzers, are essential components of implants; from vascular grafts to cardiac pacemakers, and are the basis of controlled drug delivery technology; from hydrogels to micro and nanoparticles.In the last few years, novel synthetic techniques have been used to impart desirable chemical, physical, and biological properties to biomaterials. Materials have either been synthesized directly, so that desirable chain segments or functional groups are built into the material, or indirectly, by chemical modification of existing structures to add desirable segments or functional groups.Polymeric biomaterials can be produced by copolymerizations of conventional monomers to achieve nearly monodisperse polymers. It is possible to produce polymers containing specific hydrophilic or hydrophobic entities or biodegradable repeating units.One interesting strategy to develop multitalented biomaterials is the biosynthesis of polymers because these macromolecules have several advantages like: biological resorbability, hydrodegradability, absence of immunogenicity, and appropriately high molecular mass. The chemical derivatizability of these polymers allows the formation of several products with a wide range of properties.

One of the most dramatic events in any employee’s working career is to be dismissed and even more so if the employee regards the dismissal as unfair. The right not to be unfairly dismissed is considered one of the most basic workers’ rights in South Africa and is also contained in Convention C158 of the International Labour Organization (ILO). Section 23(1)(a) of the South African Constitution states that: “[e]veryone has the right to fair labour practices.” Labour legislation gives effect to this right in section 1(a) and 1 (b) of the LRA which states: “to give effect to and regulate the fundamental rights conferred by section 23 of the Constitution; to give effect to the obligations incurred by the Republic as a member state of the ILO.” Section 185(a) of the Labour Relations Act also states that: “[e]very employee has the right not to be unfairly dismissed.” Section 188(1)(a) – (b) expands on this protection against unfair dismissal by providing that a dismissal will be unfair: “if the employer fails to prove … that the dismissal was effected in accordance with a fair procedure”. The pre-dismissal procedures that must be followed by the employer have been codified to some extent in the Code of Good Practice: Dismissal, contained in Schedule 8 of the LRA. In terms of section 138(6) and section 203(3) of the LRA, commissioners who are required to determine if a dismissal was procedurally fair are compelled to take Schedule 8 into consideration. The main objectives of this thesis were to critically evaluate the content and application of those provisions of Schedule 8 that establish procedural requirements to disciplinary enquiries and to recommend possible changes to the Code of Good Practice: Dismissal. It is apparent that the procedural requirements for a disciplinary enquiry in terms of Schedule 8 are vastly different from those that still form the basis of most disciplinary codes and procedures implemented by employers after the Mahlangu v CIM Deltak judgment of the former Industrial Court in 1986. It is also clear that the principles of ILO Convention C158 are given effect in South Africa’s dismissal law. Procedural fairness in disciplinary enquiries does not lie in elaborate, complex and rigid court-like procedures but in flexibility and in adhering to the audi alteram partem principle. A disciplinary enquiry is not a court case and the workplace is not a court of law. The belief that South Africa’s dismissal law is rigid and inflexible is inaccurate. A comparative analysis of South African dismissal law with ILO Convention C158 and three other international jurisdictions clearly demonstrates that the dismissal regime in South Africa makes provision for flexibility. Employers, employees, trade unions, labour consultants and lawyers are all to blame for the formal court-like procedures that form the basis of most disciplinary enquiries in the workplace in South Africa today. The guidelines provided by Schedule 8 are in line with the ILO’s principles. Consequently disciplinary enquiries should be handled according to those principles. The disciplinary codes and procedures of employers should be amended to reflect the core principles of ILO Convention C158 and the five basic guidelines contained in Schedule 8. Furthermore disciplinary codes and procedures should not be used as an inflexible set of rules but as a guideline from which some deviation is permissible in certain circumstances. / Thesis (PhD)--University of Pretoria, 2010. / Human Resource Management / unrestricted

No description available.

Carbon dioxide levels have been steadily increasing over the past decades; as of 2019 (411 ppm), CO2 levels are at their highest in over 40 years (330 ppm in 1977); consequently, regulations in certain areas require the reduction of CO2 emissions to combat this trend. For effective carbon capture, we require a sorbent that has high adsorption capacity, stability, and recyclability; in addition, an efficient and economical way to release the captured gas is needed as well. Metal-organic frameworks (MOFs) possess a high surface area for adsorption, but releasing the stored gases requires additional energy input that limits the overall efficiency of carbon capture. Ag/UiO-66 provides a thermally stable complex with a high surface for adsorption of CO2 while the silver nanoparticles utilize light-induced local heating to act as a photoswitch for dynamic release of CO2; visible light in the 400 nm spectrum is used to liberate the captured CO2.

Introduction A method based on neutron activation is being developed to assist in resolving discrepancies between the expected yield and actual yield of radionuclides produced with the vertical-beam target station (VBTS) at iThemba LABS. The VBTS is routinely employed for multi-Ci batch productions of the radionuclide pairs 22Na/68Ga and 82Sr/68Ga using standardized natMg/natGa and natRb/natGa tandem targets, respectively [1]. The metal-clad target discs are bombarded with a primary beam of 66 MeV protons at an intensity of nominally 250 µA. The encapsulation materials are either Nb (for Mg and Ga) or stainless steel (for Rb) which serve to contain the molten target materials during bombardment and act as a barrier to the high-velocity cooling water which surrounds the targets in a 4π geometry. The natRb/natGa targets are typically bombarded according to a two-week cycle while natMg/natGa targets are bombarded on an ad-hoc basis, depending on a somewhat unpredictable 22Na demand. A too-large deviation between expected yield and actual yield has at times plagued this programme. These deviations can manifest both as an apparent loss or an apparent gain (relative to the expected yield) by up to about 15% in either direction. The resulting uncertainty of up to 30% (in the worst case) from one production batch to another can be costly and is unacceptable in a large-scale production regimen. This phenomenon is believed to be brought about by two types of problems: (1) Production losses, e.g. during the radio-chemical separation process or incomplete recovery of activated target material during the decapsulation step. (2) Incorrect values obtained for the accumulated proton charge. A problem of type (1) will always result in a loss of yield. A problem of type (2) can manifest as an apparent loss or gain. In an effort to get a handle on this second type of problem, neutron activation of suitable material samples, embedded in a target holder, is being investigated as an independent indicator of the total yield. For this purpose, samples of Co, Mn, Ni and Zn were activated during production runs and Co was found to be the most appropriate. Preliminary results will be presented after first discussing why the determination of the accumulated pro-ton charge is a problem with the VBTS. Materials and Methods The VBTS consists of a central region in which a target holder is located during bombardment as well as two half-cylindrical radiation shields which completely surround the target. The shields can be moved away from the central region on dedicated rails, e.g. when repairs or maintenance is required. FIGURE 1 shows the VBTS with the shields moved to the “open” position. As some components of the station are located below the vault floor, with the target position near floor level, it proved difficult to electrically isolate the VBTS as was done for the two horizontal-beam target stations at iThemba LABS [1]. The VBTS does not act as a Faraday cup like the other target stations. Instead, the beam current and accumulated charge is measured by means of a calibrated capacitive probe [1,2]. There appears to be a variation in the response of the capacitive probe, sensitive to the beam microstructure, in particular a dependence on the beam packet length. This problem is not yet fully resolved. FIGURE 2 (a) shows the beamstop of a VBTS target holder with several Co samples mounted on the outside as well as one each of Ni, Mn and Zn. The samples are small “tablets” with a 10 mm diameter and 1 mm thickness. The reactions of interest are 59Co(n,γ)60Co, 59Co(n,3n)57Co, nat-Ni(n,X)60Co, natNi(n,X)57Co, natZn(n,X)65Zn and 55Mn(n,2n)54Mn. The relevant half-lives are 60Co(5.271 a), 57Co(271.8 d), 65Zn(244.3 d) and 54Mn(312.2 d). The half-life should be long compared to the two-week cycle in order to reduce the dependence on the exact beam history, which is very fragmented over any production period. In this respect, 60Co is considered to be particularly attractive as its long half-life of more than 5 years leads to a negligible effect by the beam history. Note that the tandem targets, shown in FIGURE 2 (b), are mounted just upstream of the beamstop – in fact, the targets and beamstop form a single unit before being fitted into the target holder. At the end of bombardment, all samples were assayed for their characteristic γ-emissions using standard off-line γ-ray spectrometry with an HPGe detector connected to a Genie 2000 MCA. Calculations of the neutron fluence density in the central sample volume on the beamstop were also performed using the Monte Carlo radiation transport code MCNPX. For these calculations, the entire VBTS, a Rb/Ga target and the vault walls were included in the model. Results and Conclusion All samples activated significantly – copious amounts of 60Co were detected in the Co discs after a two-week run. The neutron fluence density for the case of a 250 µA, 66 MeV proton beam on a natRb/natGa tandem target is shown in FIGURE 3. The dominance of low-energy neutrons is evident, which is in part due to the large amount of paraffin-wax shielding material in close proximity to the target. While reactions such as the (n,2n) and (n,3n) would be sensitive to the more energetic part of the neutron spectrum, the (n,γ) capture reaction benefits from the large low-energy component. This explains the copious amounts of 60Co formed. It was therefore decided to only retain the central Co sample for subsequent bombardments, as shown in FIGURE 4. The first results are shown in TABLE 1. The accumulated charge as obtained from the capacitive probe (Q), the specific 60Co activity (A) at the end of bombardment (EOB), and their ratio (A/Q) are presented in the table, together with the deviation of individual ratios relative to their average for the case of the Mg/Ga tandem tar-gets only. Note that all samples were counted until the statistical uncertainties were negligible. Any systematic uncertainties are ignored at this stage as they are considered to remain the same from one batch production to another. For the sake of argument, the average value of the ratio is taken as the expected value. A positive deviation of the A/Q value is then indicative of a too-small value of the accumulated charge obtained from the capacitive probe, leading to a corresponding overproduction. Likewise, a negative value is indicative of a too-large value of the accumulated charge, leading to a corresponding underproduction. It is certainly true that the data in TABLE 1 are currently very limited. It is envisaged, however, that with time the growing database of values will assist in reducing the uncertainty in determining the accumulated charge and reduce the discrepancies between predicted and actual yields significantly. TABLE 1 illuminates the underlying problem satisfactorily. The four Mg/Ga tandem target bombardments, on identical targetry, were performed successively. The neutron activation correlates well the with actual yields, pointing directly to the current integration as the main source of error. The method already proves to be useful. An indication of an over or underprediction can be obtained prior to the target processing by recovering and measuring the Co disc. This in-formation can be used to make a decision concerning the present batch production and/or the subsequent one. One can either add beam to the present production target and/or in-crease/reduce the total beam on the subsequent production target to compensate for an expected overproduction or shortfall. In conclusion, we would like to stress that the capacitive probes show great promise and that better understanding and/or possibly some development of their signal processing algorithm may improve their ability to measure the accumulated charge to the desired accuracy. Segmented capacitive probes used at iThemba LABS and elsewhere for beam position measurement [1,3] are not affected by beam microstructure as only the ratios of the signal strengths on the different sectors are important. In this case, changes in response affect all sec-tors equally and the ratios are unaffected.

Tecnologies de transferència de calor de nova generació, amb menys consum d'energia per al benestar de la societat són necessàries. En aquest sentit, els líquids iònics (ILS) són en l'actualitat els fluids més investigats per la seva major estabilitat tèrmica i la naturalesa no volàtil que els fan més avantatjosos que els fluids convencionals. A més, la dispersió de nanopartícules metàl·liques en els fluids convencionals també estan sent investigats en els últims temps a causa de la seva major conductivitat tèrmica, millora en la fluïdesa reduint el cost de bombament, i absència de sedimentació de sal. Aquestes característiques fan fascinants als nanofluidos (NFs) com una bona alternativa a les solucions salines convencionals per a aplicacions de transferència de calor. En aquest treball, ILS basats en el catió imidazoli es van preparar amb anions com ara clorur, bromur, iodur i tetrafluroborate. Diverses propietats termofísiques com la conductivitat tèrmica, capacitat calorífica, densitat i viscositat d'aquests fluids van ser investigades en detall. Com que només hi ha molt pocs treballs publicats sobre NPs de metalls de transició en líquids iònics per a aplicacions de transferència de calor, aquesta tesi s'enfoca en el disseny de les ILS desitjats i en el desenvolupament de materials compostos de metalls de transició NPs amb els ILS iònics preparats. Per a aquest propòsit, es van utilitzar NPs de ruteni (Ru) i plata (Ag). Les propietats tèrmiques d'aquests líquids iònics es van millorar mitjançant la preparació in situ de compostos d'ILS amb nanopartícules de ruteni sense utilitzar agents tensioactius, a temperatura ambient. Per a la preparació dels ionanofluidos (INFs) amb plata, es van utilitzar nanoparículas amb morfologies variables, de 1D, 2D i 3D. Aquests ionanofluids redueixen la viscositat de líquids iònics de base juntament amb la millora en la seva conductivitat tèrmica. Des d'aquesta perspectiva, un catalitzador de carbó amb 5% de ruteni amb àcid de Bronsted IL [Hmim] [HSO4] com un co-catalitzador va ser desenvolupat per hidrogenólisis selectiva del bio-derivat d'àcid levulínic (LA) gamma-valerolactona (GVL) , el qual és un additiu de combustibles. / Tecnologías de transferencia de calor de nueva generación, con menos consumo de energía para el bienestar de la sociedad son necesarias. En este sentido, los líquidos iónicos (ILs) son en la actualidad los fluidos más investigados debido a su mayor estabilidad térmica y la naturaleza no volátil que los hacen más ventajosos que los fluidos convencionales. Además, la dispersión de nanopartículas metálicas en los fluidos convencionales también están siendo investigados en los últimos tiempos debido a su mayor conductividad térmica, mejora en la fluidez reduciendo el coste de bombeo, y ausencia de sedimentación de sal. Estas características hacen fascinantes a los nanofluidos (NFs) como una buena alternativa a las soluciones salinas convencionales para aplicaciones de transferencia de calor. En este trabajo, ILs basados en el catión imidazolio se prepararon con aniones tales como cloruro, bromuro, yoduro y tetrafluroborate. Varias propiedades termofísicas como la conductividad térmica, capacidad calorífica, densidad y viscosidad de estos fluidos fueron investigadas en detalle. Como sólo hay muy pocos trabajos publicados sobre NPs de metales de transición en líquidos iónicos para aplicaciones de transferencia de calor, esta tesis se enfoca en el diseño de las ILs deseados y en el desarrollo de materiales compuestos de metales de transición NPs con los ILs iónicos preparados. Para este propósito, se utilizaron NPs de rutenio (Ru) y plata (Ag). Las propiedades térmicas de estos líquidos iónicos se mejoraron mediante la preparación in situ de compuestos de ILs con nanopartículas de rutenio sin utilizar agentes tensioactivos, a temperatura ambiente. Para la preparación de los ionanofluidos (INFs) con plata, se utilizaron nanoparículas con morfologías variables, de 1D, 2D y 3D. Estos ionanofluids reducen la viscosidad de líquidos iónicos de base junto con la mejora en su conductividad térmica. Desde esta perspectiva, un catalizador de carbon con 5% de rutenio con ácido de Bronsted IL [Hmim] [HSO4] como un co-catalizador fue desarrollado para hidrogenólisis selectiva del bio-derivado de ácido levulínico (LA) gamma-valerolactona (GVL), el cual es un aditivo de combustibles. / New generation heat transfer technologies with less energy consumption and improved economy are needed for welfare of the society. In this regard, ionic liquids (ILs) are most investigated fluids due to their higher thermal stability and non-volatile nature which make them more advantageous than the conventional fluids. In addition, dispersion of metal nanoparticles in conventional fluids are also being investigated in recent times due to their higher thermal conductivity, easy flow, which reduce pumping cost as well as no salt sedimentation. These fascinating features make NFs as a good alternative to the conventional salt solutions for heat transfer applications. In this work, imidazolium cation based ILs were prepared with variation in anions such as chloride, bromide, iodide and tetrafluroborate. Several thermophysical properties as thermal conductivity, heat capacity, density and viscosity of these fluids were investigated in detail. As there are only a very few reports available on transition metal NPs in ILs for heat transfer applications, this thesis work is focused on first designing the desired ILs and then developing composites of transition metal NPs with the prepared ionic ILs. For this purpose, NPs of ruthenium (Ru) and silver (Ag) were used. Thermal properties of these ILs were improved by in-situ preparation of composites of ILs with ruthenium nanoparticles without using capping agents or surfactants at room temperature. For preparing Ag containing ionanofluids (INFs), readily available NPs of Ag with variable morphologies, of 1D, 2 D and 3 D were used. These ionanofluids reduced the viscosity of base ILs along with the enhancement in their thermal conductivity. From this perspective, Carbon supported 5% ruthenium catalyst with Bronsted acidic IL [Hmim][HSO4] as a co-catalyst was developed for selective hydrogenolysis of bio-derived levulinic acid (LA) gamma-valerolactone (GVL) which is fuel additive.

L’aprofitament de biomassa per produir biocombustibles i bioproductes a partir de fonts renovables està despertant un gran interès en els últims anys motivat per la oportunitat de convertir un residu en una font primària d’energia fàcilment accessible a escala local i regional. Catalunya és una regió amb una gran massa forestal i que genera molts residus agrícoles. L’aprofitament d’aquesta biomassa permet la millora del sector agro-forestal, la preservació i conservació del paisatge tradicional, reduir el risc d’incendis i incrementa la diversificació energètica reduint la dependència dels combustibles fòssils i mitigant els efectes del escalfament global. En aquest context, l’objectiu principal d’aquesta tesi és la valorització de residus de biomassa agro-forestal com a biocombustibles d’alta densitat energètica mitjançant processos de torrefacció i piròlisis per tal d’avançar cap a un model energètic més sostenible. En primer lloc, s’avaluà la valorització dels residus de biomassa agrària com a pellets torrefactes mitjançant un procés de torrefacció participant en una prova pilot desenvolupada en una zona rural per tal de demostrar la viabilitat tècnica i econòmica d’implementar aquest procés com a una estratègia local d’aprofitament d’aquest residu, en el que es coneix com economia circular i bioeconomia. En primer lloc, es caracteritzà la biomassa original i els productes de torrefacció. Els pellets torrefactes obtinguts tenen característiques dins estàndards europeus del pellets comercialitzables. El líquid de torrefacció és un producte aquós amb alts continguts d’àcid acètic i furfural, sent un potencial pesticida biodegradable o un protector de fusta. A més a més, es demostrà la viabilitat econòmica d’implementar una planta mòbil de torrefacció en un zona rural. El bio-oil és un producte líquid procedent de la piròlisi rapida de la biomassa amb un gran potencial com a combustible líquid i plataforma química per a la obtenció de bio-productes, sent així una potencial matèria prima en una biorefineria. Actualment, el bio-oil és un biocombustible pobre degut a la seva corrosivitat, alta viscositat, alt contingut en oxigen i la seva inestabilitat tèrmica i química. Per aquest motiu, es requereixen processos de millora d’aquest producte, encara que aquest redueixen la seva viabilitat econòmica. En aquest context, dos processos de millora del bio-oil han estat estudiats utilitzant processos amb un consum energètic assumible aprofitant la temperatura de sortida del bio-oil durant el procés de producció i el temps d’emmagatzematge. En primer lloc, es caracteritzà el bio-oil i s’avaluà un mètode de quantificació i identificació de la composició química del bio-oil mitjançant l’anàlisi per GC-MS per tal d’aconseguir una millor caracterització d’aquest producte així com la monitorització dels canvis químics que puguin tenir lloc durant els processos de millora. Posteriorment, s’avaluà un procés catalític de millora del bio-oil utilitzant bentonites i zeolites a 60 ºC. Aquest procés mostrà una reducció de l’acidesa del bio-oil encara que no degut a la catàlisi de reaccions sinó al caràcter bàsic d'aquests materials a aquesta temperatura. Finalment, nous processos d’hidrogenació del bio-oil a temperatura ambient aprofitant l’alta reactivitat de l’hidrogen naixent han estat avaluats per tal de reduir el contingut d’oxigen d’aquest i augmentar el seu poder calorífic. L’hidrogen naixent ha estat produït in situ via l’oxidació d’un metall utilitzant el bio-oil com a medi àcid i via l’electròlisi de l’aigua continguda en el bio-oil, resultant el primer mètode més simple i efectiu. Així, el procés d’hidrogenació via oxidació del zinc s’ha realitzat a diferents condicions experimentals mostrant uns resultats molt esperançadors ja que s'observen diferències significatives entre el bio-oil d'abans i de després del procés de millora. Per concloure, Aquest treball mostra el potencial, present i futur, de valoritzar residus agro-forestals mitjançant processos termoquímics com a biocombustible i bioproductes. / Biomass use to produce biofuels and bio-products from a renewable source is raising a high interest in recent years motivated by the opportunity of converting biomass residues into a primary energy source easily available at local and regional scale. Catalonia is a region with large forest area and generates large amounts of agro-forestry residues. Their use might improve the agro-forestry sector by the preservation and restoration of traditional landscapes, reduce forest fire risk and increase energy diversification reducing fossil fuels dependency and mitigating the global warning effects. In this direction, the main aim of this thesis is to add-value to agro-forestry biomass residues as enhanced biofuels by means of torrefaction and pyrolysis biomass conversion processes in order to move towards a more sustainable energy model. A study of adding value to agricultural waste biomass as torrefied pellets by means of torrefaction process is performed participating in a pilot scale test carried out in a rural region to demonstrate the technic-economic viability implementing of this process as a local strategy to make use of this residue moving towards a circular and bioeconomy. Firstly, raw and torrefied products are characterised. The obtained torrefied pellets characteristics are within the European law standards of pellets demonstrating they are marketable products. Torrefaction liquid is an aqueous product with high contents of acetic acid and furfural making it a potential biodegradable pesticide or wood preservative. Moreover, the economic viability of implementing this mobile torrefaction plant in a rural region is proved being highly dependent on the scenario considered. Bio-oil is a liquid product produced by fast pyrolysis process of biomass with a great potential as liquid biofuel product and chemical platform to obtain bio-products, being a potential feedstock from a biorefinery scenarios. Currently, bio-oil is a low value biofuel due to its corrosiveness, high viscosity, high oxygen content and its thermal and chemical instability. Because of that, its upgrading is required to obtain an enhanced product, even though bio-oil upgrading processes reduce the economic viability of bio-oil as a marketable product. In this context, two novel bio-oil upgrading processes are explored to obtain an enhanced bio-oil using reduced energy and resources cost upgrading process in comparison to conventional. Firstly, bio-oil characterisation is performed, as well as it is assessed and reached a reliable quantitative analysis of bio-oil chemical compounds by means of GC-MS to achieve a further characterization of this product and to permit a proper monitoring of bio-oil properties changes during the upgrading processes. Then, it is tested a catalytic upgrading process using bentonite and zeolite HZSM-5 at 60 ºC to avoid the necessity of a bio-oil external heating due to bio-oil coming out of the fast pyrolysis at this temperature. Results show an acidity reduction of treated bio-oil, although a reduced catalytic reaction is observed due to the quick deactivation of these catalysts at this temperature. Finally, novel hydrogenation procedures to hydrogenate bio-oil at ambient temperature in order to reduce its oxygen content and increase its calorific value using the high reactivity of nascent hydrogen are explored. Nascent hydrogen is generated via metal oxidation using bio-oil as acidic medium and via water electrolysis contained in bio-oi resulting nascent hydrogen via zinc metal oxidation the simplest and more effective process relative to the other tested ones. An extended study of this hydrogenation process is assessed at different experimental conditions showing the potentially of this cheap and simple novel hydrogenation process. In conclusion, this research shows the current and future potential of adding value to agro-forestry waste biomass by means of thermochemical processes as biofuels and bioproducts to move towards a bioeconomy strategy.

Tesis con contenido restringido por transferencia tecnológica / El potente desarrollo experimentado por los paises a nivel mundial durante el siglo pasado, ha generado una fuerte competencia por los recursos naturales que ha hecho insostenible el uso actual del suelo. A nivel europeo se pretende aliviar estas tensiones reintroduciendo en el proceso productivo los residuos susceptibles de ser valorizados, aplicando políticas que tienden a buscar un equilibrio entre prevenir la contaminación actual y recuperar la pasada, y están basadas en los principios de cautela, acción preventiva y corrección de los atentados al medio ambiente, así como en el principio “quien contamina paga”. La problemática en suelos contaminados por metales pesados en la Región de Murcia es extensa y en determinadas ocasiones elevada, llegando a alcanzar valores muy por encima de los valores de fondo que se encuentran en estas zonas. Entre dichos emplazamientos se encuentran los sedimentos de la bahía de Portmán, que constituyen un grave problema por su magnitud y su fuerte impacto ambiental. Autorizada confidencialidad por la Comisión General de Doctorado. Los objetivos que se pretenden alcanzar con éste trabajo son, estudiar el efecto que los suelos contaminados de la bahía de Portman, procedentes de residuos minerometalúrgicos, pueden provocar sobre las infraestructuras de hormigón con las que se encuentren en contacto y Autorizada confidencialidad por la Comisión General de Doctorado. Para ello se diseñaron dos experiencias. En una primera, Autorizada confidencialidad por la Comisión General de Doctorado. En la segunda se recrearon cuatro posibles escenarios de contacto de las infraestructuras de hormigón y los sedimentos contaminados, en ambiente marino, con condiciones reductoras y oxidantes y períodos de humedad/sequedad, analizando posteriormente características macroscópicas, microscópicas y mecánicas de las probetas. Autorizada confidencialidad por la Comisión General de Doctorado. Aunque durante el tiempo que duró el estudio las características mecánicas de las probetas no se han visto alteradas, son evidentes los efectos negativos que los escenarios planteados, todos en condiciones estáticas, producen en el hormigón, alguno de ellos incluso con desagregación física en función de las condiciones redox. / The strong growth experienced by countries worldwide over the past century, has generated strong competition for natural resources that have become unsustainable with the current land use. At a European level they are trying to avoid these stresses introduced into the production process of waste that can be valorized, applying policies that tend to find a balance between preventing the current pollution and recovering the past and are based on the principles of precaution, preventative action and correction of environmental damage, as well as on the principle "the polluter pays". The problem in soils contaminated by heavy metals in the region of Murcia is extensive and in some cases higher, reaching values well above background levels found in these areas. Among these sites are the sediments of the bay of Portman, which are a serious problem because of its magnitude and its strong environmental impact. Authorized confidentiality by the General Doctoral Committee. The objectives that are trying to be achieved with this work is to study the effect of the contaminated soils of the bay of Portman, from mining waste, that can provoke in the concrete infrastructure with which they are in contact and Authorized confidentiality by the General Doctoral Committee. To achive these objectives there were two experiments designed. Authorized confidentiality by the General Doctoral Committee. In the second there were four possible scenarios contact infrastructures and contaminated concrete in the marine environment, with reducing and oxidizing conditions and periods of wet / dry sediments, then analyzing macroscopic, microscopic and mechanical properties of the concrete specimens . Authorized confidentiality by the General Doctoral Committee. Although during the period of study the mechanical properties of the concrete specimens have not been affected, the negative effects are evident that the proposed scenarios, under all static conditions, occur in the concrete, some of them even physical crumbling depending on the redox conditions.

S'ha estudiat la degradació fotoquímica de compostos tòxics (toxines i pesticides) en aigua i sucs de fruita, utilitzant radiació UV-visible, en que una làmpada de vapor de mercuri de mitja pressió, que emet entre 250 i 700 nm, es la font d'emissió. Les cinètiques de fotodegradació dels compostos tòxics depenen de la seua concentració en el medi reaccionat. en el cas de micotoxines (patulina i ocratoxina A), s'ha obtingut que la degradació fotoquímica segueix una cinètica de primer ordre. Per als pesticides, la fotodegradació de benomil també es pot descriure amb una cinètica de primer ordre, mentre que el tiabendazol segueix cinètiques d'ordre zero i pseudo primer ordre. Per a les micotoxines i tiabendazol s'ha estudiat la compensació cinètica i termodinàmica, havent obtingut que per la patulina i tiabendazol en el procés global de fotodegradació el control és entròpic, però per a l'ocratoxina A el control és entàlpic. / Se ha estudiado la degradación fotoquímica de compuestos tóxicos (toxinas y plaguicidas) en agua y zumos de fruta, utilizando radiación UV-visible, siendo la fuente una lámpara de vapor de mercurio de media presión que emite entre 250 y 700 nm. Las cinéticas de fotodegradación de los compuestos tóxicos dependen de su concentración en el medio reaccionante. En el caso de micotoxinas (patulina y ocratoxina A), se ha obtenido que la degradación fotoquímica sigue cinéticas de primer orden. Para plaguicidas, la fotodegradación de benomilo también se puede describir mediante cinéticas de primer orden; sin embargo, el tiabendazol sigue cinéticas de orden cero o pseudo primer orden. Para las micotoxinas y tiabendazol se ha estudiado la compensación cinética y termodinámica, habiendo obtenido que para patulina y tiabendazol en el proceso global de fotodegradación el control es entrópico; pero para la ocratoxina A el control ha resultado ser entálpico. / In this thesis, a study of removing various toxic compounds (toxins and pesticides) present in fruit juices and water by applying a treatment with UV radiation is shown. The radiation source is a mid-pressure mercury lamp, emitting on the 250-700 nm wavelength range. Photodegradation kinetics of toxic compounds depends on its concentration in the reaction medium. For mycotoxins (patulin and ochratoxin A), it has been obtained that the photochemical degradation follows first order kinetics. For pesticides like benomyl, the photodegradation can be described by first-order kinetics; however, thiabendazole follows zero order or pseudo first order kinetics. For mycotoxins and thiabendazole the kinetics and thermodynamics compensation has been studied, having obtained that patulin and thiabendazole photodegradation control is entropic for all processes; but for ochratoxin A control has been enthalpic.

L’aplicació industrial de biofiltres percoladors per la dessulfuració de corrents de biogàs en condicions aeròbies requereix del desenvolupament i aplicació d’estratègies de control per poder aconseguir una operació robusta, estable i fiable davant de condicions de carga de H2S variables. El control d’aquest tipus de reactors es difícil ja que la seva controlabilitat depèn de diversos paràmetres com el transport O2, l’activitat biològica,l’ estructura de la bio-pel·lícula i la variabilitat de la carga entre altres. Degut a això, abans de la implementació experimental de les estratègies de control, el sistema ha de ser profundament estudiat per poder de caracteritzar les diferents variables que comprenen un llaç de control. En aquesta tesi, no només s’ha dut a terme un estudi experimental per poder entendre el funcionament dels biofiltres percoladors per a la dessulfuració aeròbia de corrents de biogàs, sinó que també s’ha inclòs un estudi utilitzant un model amb el objectiu d’avaluar les diferents estratègies abans de la seva implementació experimental. L’estudi abiòtic sobre el tipus de configuració del flux gas-líquid realitzat prèviament a la posada en marxa del biofiltre percolador, va indicar que la configuració en paral·lel es la mes adequada per a millorar el transport gas-líquid d’oxigen, el qual va ser avaluat mitjançant la taxa estàndard de transport d’oxigen. A més a més, es va demostrar que la regulació de la velocitat de percolació era una variable més efectiva per tal de obtenir taxes de transferència d’oxigen mes altes si es comparava amb la regulació del cabal d’aeració. Aquest resultat va ser posteriorment confirmat durant els experiments biòtics, on l’efecte del rendiment del biofiltre percolador davant la regulació de la velocitat de percolació i del cabal d’aeració va ser quantificat. La regulació de la velocitat de percolació va demostrar tenir una major influència en els principals paràmetres de rendiment tal com l’eficiència d’eliminació, la capacitat d’eliminació i principalment sobre la selectivitat de sulfat, indicant ser una variable adequada per la millora del transport de O2 en el llit empacat. Posteriorment la tritimetria va ser avaluada com a possible variable mesurada, amb el fi de poder relacionar l’activitat biològica i els canvis operacionals amb la producció de protons i la taxa de producció de protons generat per la reacció biòlogica. La titrimetria va ser aplicada a tant a un procés en continu, com en un procés discontinu, indicant que la producció de protons es una variable més adequada per a la monitorització del procés que per l’aplicació en un llaç de control. Abans de la implementació experimental de les estratègies de control, un model dinàmic incloent els diferents processos fisicoquímics i biològics que formen part de la eliminació de altes carregues de H2S en corrents de biogàs mitjançant biofiltres percoladors va ser desenvolupat, i satisfactòriament calibrat i validat. Aquest model va permetre l’avaluació de la influencia de diferents paràmetres sobre les principals variables operacionals mitjançant un anàlisi de sensibilitat, així com dels límits de controlabilitat, les capacitats màximes i conèixer el valor afegit de les estratègies de control en la dessulfuració de biogàs en biofiltres percoladors en condiciones aeròbies. Finalment, control retro-alimentat i anticipatiu basat en la regulació de la velocitat de percolació va ser experimentalment avaluat. Aquestes estratègies van ser dissenyades a partir de informació obtinguda durant la caracterització de les variables manipulades i amb el anàlisi realitzat amb el model. Les estratègies de control basades en la regulació de la velocitat de percolació van demostrar ser una eina efectiva per la millora del rendiment dels biofiltres percoladors en condicions aeròbies degut a una considerable millora del transport gas-líquid d’oxigen, sense la necessitat de diluir el corrent de biogàs. / La aplicación industrial de biofiltros percoladores para la desulfuración de biogás en condiciones aerobias requiere del desarrollo y aplicación de estrategias de control con el fin de poder conseguir una operación robusta, estable y fiable en condiciones de carga variable de H2S. El control de este tipo de reactores biológicos es difícil ya que su controlabilidad depende de parámetros como el transporte de O2, actividad biológica, estructura de la biopelícula, y la variabilidad de la carga entre otros. Por ello, antes de realizar la implementación de las estrategias de control, el sistema debe de ser profundamente estudiado para caracterizar las diferentes variables que comprenden un lazo de control. En esta tesis, no solo trabajo experimentación en diferentes condiciones de operación ha sido realizado para entender la desulfuración de biogás en biofiltros percoladores en condiciones aeróbicas, sino que también un estudio utilizando un modelo también ha sido incluido con el fin de poder evaluar las diferentes estrategias antes de su implementación experimental. El estudio abiótico sobre el tipo de patrón de flujo gas-liquido realizado previo a la puesta en marcha del biofiltro percolador, indico que el patrón en paralelo era la configuración más adecuada para mejorar el transporte gas-liquido de O2, el cual fue evaluado utilizando la tasa de estándar de transferencia de oxígeno. Además, se demostró que la regulación de la velocidad de percolación era la variable más efectiva para poder obtener mayores tasas de transferencia de oxígeno si se comparaba con la regulación del caudal de aireación. Este resultado luego fue confirmado en los experimentos bióticos, donde el efecto en el rendimiento del biofiltro percolador de la regulación de la velocidad de percolación y del caudal de aireación fue cuantificado. La regulación de la velocidad de percolación demostró tener una mayor influencia en los principales parámetros de rendimiento tales como la eficiencia de eliminación, la capacidad de eliminación y principalmente sobre la selectividad de sulfato, indicando ser una variable manipulada adecuada para poder mejorar el transporte de O2 en el lecho empacado. Posteriormente la titrimetría fue evaluada como posible variable medida, con el fin de relacionar la actividad biológica y los cambios operacionales mediante la producción de protones y la tasa de producción de protones. La titrimetría fue aplicada tanto a un proceso continuo como un proceso discontinuo, indicando que la producción de protones era una variable adecuada más adecuada para la monitorización de procesos que para el control de procesos. Antes de la implementación experimental de las estrategias de control, un modelo dinámico incluyendo los procesos físico-químicos y biológicos envueltos en la eliminación de altas cargas de H2S en corrientes de biogás mediante biofiltros percoladores fue desarrollado, y satisfactoriamente calibrado y validado. Este modelo permitió evaluar la influencia de diferentes parámetros sobre los principales parámetros operacionales a través de un análisis de sensibilidad, así como determinar los límites de controlabilidad, las capacidades máximas y conocer el valor añadido que tienen las estrategias de control en la desulfuración de biogás mediantes biofiltros percoladores en condiciones aerobias. Finalmente, control retroalimentado y control anticipativo basado en la regulación de la velocidad de percolación fueron experimentalmente evaluados. Dichas estrategias de control fueron diseñadas en base a la información obtenida durante la caracterización de las variables manipuladas y mediante el análisis realizado con el modelo. Las estrategias de control basadas en la regulación de la velocidad de percolación demostraron ser una herramienta efectiva para mejorar el rendimiento de los biofiltros percoladores debido a una mejora en el transporte de oxígeno, sin la necesidad de diluir la corriente de biogás. / Industrial application of biotrickling filters (BTF) for biogas desulfurization under aerobic conditions requires the development and application of control strategies in order to achieve a robust, stable and reliable operation under variable hydrogen sulfide (H2S) loading rates (LR) conditions. Controlling this type of biological reactors is highly difficult since their controllability depends on several parameters such as O2 transfer, biological activity, biofilm structure, and LR variability among others. Therefore, before the implementation of control strategies, these systems must be deeply studied to characterize the different variables involved in control loops. In this thesis, not only experimental work under different operational conditions has been performed to understand biogas desulfurization under aerobic conditions in BTFs, but a model-based study has been also included in order to test and evaluate different control strategies before its experimental implementation. The abiotic study of gas-liquid flow pattern performed before BTF start-up, indicated that co-current flow pattern was the most suitable configuration in order to improve the O2 mass transport from the gas to the liquid phase, which was evaluated through the standard oxygen transfer rate (SOTR). Moreover, it was demonstrated that trickling liquid velocity (TLV) regulation provided higher SOTR values when compared to air flowrate (AFR) regulation. This result was later confirmed in biotic tests, where the effect in BTF performance of TLV and AFR regulation was quantified. TLV showed a high influence over the main performance parameters such as removal efficiency (RE), elimination capacity (EC) and principally over sulfate selectivity, indicating that TLV is a suitable variable to manipulate in order to improve O2 transport in the packed bed. Afterwards titrimetry was evaluated as possible measured variable, in order to relate biological activity and operational changes through proton production (HP) and proton production rate (HPR). Titrimetry was applied for a continuous process as well in a discontinuous process, indicating that HP was a suitable indicator to use in processes monitoring, in order to provide further information of the process state rather for control purposes. Before implementing control strategies, a dynamic model describing physical-chemical and biological processes for the removal of high loads of H2S from biogas streams in BTFs was developed and successfully calibrated and validated allowing a proper description of different operational scenarios. This model was used to evaluate the influence of different parameters over the main process variables through a sensitivity analysis, and mainly to determine the control limits, capabilities and added value of different feedback control strategies applied to biogas desulfurization in aerobic BTFs. Finally, feedback and feedforward control strategies based on TLV regulation were experimentally evaluated in a desulfurizing BTF under aerobic conditions. Control strategies were designed based in knowledge obtained in the characterization manipulated variables and with the model-based analysis. Application of control strategies based in TLV regulation showed to be a suitable tool in order to improve BTF performance through O2 transport improvement, without increasing biogas dilution.