THERMOCHEMICAL CONVERSION OF MARINE LITTER INTO FUELS AND CHEMICALSGian Claudio Paolo Faussone
, 2023, doktorska disertacija
Opis: Plastic waste is steadily polluting oceans and environments. Even when collected, it is still predominantly dumped or incinerated for energy recovery at the cost of CO2. However, no simple solution exists to deal with marine litter (ML). Overcoming limitations in collection, and in the environmentally, technically and economically acceptable use of the collected material, is of paramount importance. Chemical recycling can contribute to the transition towards a circular economy but the high variety and contamination of real waste remains the biggest challenge. In my research more than 100 kg of actual benthic ML from the North Adriatic Sea, including polyolefins packaging and polyamides fishing nets, were successfully processed “as-is” without pretreatment and converted into standardized marine gas oil (MGO) compliant with the ISO8217 via the pyrolysis and the distillation process; with 8 potential harmful emissions linked to the pyrolysis process monitored and curbed to safe levels. Approximately 45 wt% yield of raw pyrolysis oil (RPO) was obtained of which 50% (v/v) being MGO. RPO and its distillates were chemically characterized via GC-MS. For all samples, more than 30% of the detected compounds were identified. 2,4-dimethyl-1-heptene, a marker of PP pyrolysis, is the most represented peak in the chemical signature of all the marine litter samples, and it differentiates commercial and pyrolysis marine gasoil. Besides, I studied the detailed composition and the steam cracking performance of distilled pyrolysis oil fractions in the naphtha-range of ML and mixed municipal plastic waste (MPW) considered unsuitable for mechanical recycling. Advanced analytical techniques including comprehensive two-dimensional gas chromatography (GC × GC) coupled with various detectors and inductively coupled plasma – mass spectrometry (ICP-MS) was applied to characterize the feedstocks and to understand how their properties affect the steam cracking performance. Both waste-derived naphtha fractions were rich in olefins and aromatics (~70% in MPW naphtha and ~51% in ML naphtha) next to traces of nitrogen, oxygen, chlorine and metals. ICP-MS analyses showed that sodium, potassium, silicon and iron were the most crucial metals that should be removed in further upgrading steps. Steam cracking of the waste-derived naphtha fractions resulted in lower light olefin yields compared to fossil naphtha used as benchmark, due to secondary reactions of aromatics and olefins. Coke formation of ML naphtha was slightly increased compared to fossil naphtha (~50%), while that of MPW naphtha was more than ~180% higher. It was concluded that mild upgrading of the waste-derived naphtha fractions or dilution with fossil feedstocks is sufficient to provide feedstocks suitable for industrial steam cracking. Waste plastics oil (WPO) obtained from a relatively large-scale batch rotary kiln pyrolysis reactor was collected and stored for 60 months in dark at 10 °C, periodically thoroughly characterized and finally tested as the drop-in fuel in internal combustion engine. It was evaluated by investigation of combustion process and emission formation phenomena under a wide range of operating parameters. The results were compared with those obtained with diesel fuel at the same injection and gas path parameters to provide a comprehensive basis for further development of control strategies. Finally, the solid residue from the pyrolysis process was evaluated for material recovery or safe disposal, thus closing the mass balance of the whole process. Due to the great contamination of the original feedstock, stabilization of solid residue is required to attain not hazardous waste criteria, but once stabilized with Portland concrete, it could even be employed as construction material, therefore transforming a problem into an opportunity.
Ključne besede: marine litter, marine fuel, pyrolysis, circular economy, environmental impact, chemical recycling, steam-cracking, pyrolysis char
Objavljeno: 12.05.2023; Ogledov: 121; Prenosov: 4
Polno besedilo (14,33 MB)
Efficiency of the grid energy storage technology based on iron-chloride material cycleUroš Luin
, doktorska disertacija
Opis: Future high-capacity energy storage technologies are crucial for a highly renewable energy mix, and their mass deployment must rely on cheap and abundant materials, such as iron chloride. The iron chloride electrochemical cycle (ICEC), suitable for long-term grid energy storage using a redox potential change of Fe2+/Fe, involves the electrolysis of a highly concentrated aqueous FeCl2 solution yielding solid iron deposits. For the high overall energy efficiency of the cycle, it is crucial maximizing the energy efficiency of the electrolysis process. The thesis presents a study of the influence of electrolysis parameters on energy efficiency, performed in an industrial-type electrolyzer system. We studied the conductivity of the FeCl2 solution as a function of concentration and temperature and correlated it with the electrolysis energy efficiency as a function of current density. The contribution of the resistance polarization increases with the current density, causing a decrease in overall energy efficiency. The highest energy efficiency of 89 ±3 % was achieved using
2.5 mol dm-3 FeCl2 solution at 70 °C and a current density of 0.1 kA m-2.
In terms of the energy input per Fe mass, this means 1.88 Wh g-1. The limiting energy input per mass of the Fe-deposit, calculated by extrapolating experimental results toward Eocell potential, was found to be 1.76 Wh g-1. For optimal long-duration electrolysis efficiency and performance, the optimal catholyte concentration range is
1-2 mol dm-3 FeCl2. We performed in situ X-ray absorption spectroscopy experimental studies to validate theoretical conclusions from literature related to the population and structure of Fe-species in the FeCl2 (aq) solution at different concentrations (1 - 4 mol dm-3) and temperatures (25 - 80 °C). This revealed that at low temperature and low FeCl2 concentration, the octahedral first coordination sphere around Fe is occupied by one Cl ion at a distance of 2.33 (±0.02) Å and five H2O at a distance of 2.095 (±0.005) Å. The structure of the ionic complex gradually changes with an increase in temperature and/or concentration. The apical H2O is substituted by a Cl ion to yield a neutral Fe[Cl2(H2O)4]0. The transition from the charged Fe[Cl(H2O)5]+ to the neutral Fe[Cl2(H2O)4]0 causes a significant drop in the solution conductivity, which well correlates with the existing state-of-the-art conductivity models. An additional steric impediment of the electrolytic cell is caused by the predominant neutral species present in the catholyte solution at high concentration. This correlates with poor electrolysis performance at a very high catholyte concentration (4 mol dm-3 FeCl2), especially at high current densities (> 1 kA m-2). The neutral Fe[Cl2(H2O)4]0 complex negatively affects the anion exchange membrane ion (Cl-) transfer and lowers the concentration of electroactive species (Fe[Cl(H2O)5]+) at the cathode surface. The kinetics of hydrogen evolution from the reaction between Fe powder and HCl acid was studied under the first-order reaction condition. The activation energy was determined to be 55.3 kJ mol-1.
Ključne besede: ICEC, Power-to-Solid, energy storage, hydrogen, ferrous chloride, electrolysis, Fe deposition, efficiency, XAS, structure and population, ionic species, ion association, conductivity
Objavljeno: 18.04.2023; Ogledov: 185; Prenosov: 12
Polno besedilo (4,34 MB)
Electronic and chemical surface properties of Bi2Se3 derived compoundsZipporah Rini Benher
, doktorska disertacija
Ključne besede: Bismuth selenide derived compounds, surface chemical and electronic properties, topological insulators, single crystals, phase separation, inorganic bulk heterostructures, ix
Bridgman method, X-ray powder diffraction, scanning electron microscopy, photoelectron spectroscopy
Objavljeno: 16.12.2022; Ogledov: 424; Prenosov: 6
Polno besedilo (9,56 MB)
Numerical simulations of nozzles with gas and liquid focusing for production of micro-jetsGrega Belšak
, 2022, doktorska disertacija
Ključne besede: numerical simulations, OpenFOAM, liquid sheets, micro-jets, multiphase flow, converging nozzles, double flow focusing nozzle, gas compressibility, vacuum conditions, atmospheric conditions, operational parameters, liquid properties, dissertations
Objavljeno: 07.12.2022; Ogledov: 524; Prenosov: 17
Polno besedilo (21,26 MB)
Van der Waals heterostructuresVadym Tkachuk
, doktorska disertacija
Ključne besede: Graphene, hexagonal boron nitride, PDI8-CN2, organic semiconductor, heterostructure, charge transport, electronic properties, 2D crystal, 2D crystal transfer, tunneling.
Objavljeno: 24.10.2022; Ogledov: 521; Prenosov: 19
Polno besedilo (38,13 MB)
Structure optimisation of biopigment prodigiosin from Serratia marcescens ATCC 27117 and antimicrobial and anticancer properties of novel halogenated derivativesJelena Lazić
, 2022, doktorska disertacija
Opis: Prodigiosins (PGs) are a class of bacterial secondary metabolites with remarkable biological activities and colour. In this study, optimised fermentative production of prodigiosin (PG) using waste processed meat as a substrate has been achieved to levels of 83.1 ± 3.0 mg/L from a commercially available Serratia marcescens ATCC 27117 strain within 12 h. Methods were established for the reliable PG extraction from both the bacterial cell pellet and the culture supernatant, while gravitation column chromatography was used to obtain pure bacterial PG.
The structure of the isolated PG was optimised by environmentally acceptable oxidative bromination reactions, obtaining mono- and dibrominated derivatives (PG-Br and PG-Br2). Chemical structures were confirmed by structural characterisation using nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS), showing that PG-Br is a mixture of two monobrominated isomers in approximately equal ratios, while PG-Br2 was afforded as a pure derivative.
PG and its brominated derivatives (Br-derivatives) showed anticancer potential with half-maximal inhibitory concentration (IC50) values ranging from 0.62 to 17.00 μg/mL on four tested cancer cell lines (A549 lung, A375 skin, MDA-MB-231 breast, HCT116 colon) and an induction of early apoptosis, but low selectivity against healthy cell lines (MRC-5 lung fibroblasts and HaCaT skin keratinocytes). All three PG, PG-Br and PG-Br2 compounds did not affect roundworms (Caenorhabditis elegans) at concentrations up to 50 μg/mL. However, an improved toxicity profile of Br-derivatives in comparison to the parent PG was observed in vivo using zebrafish (Danio rerio) model system, when 10 μg/mL applied at 6 h post fertilisation caused death rate of 100, 30 and 0% by PG, PG-Br and PG-Br2, respectively, which is a significant finding for further structural optimisations of bacterial PGs.
Ključne besede: prodigiosin, Serratia marcescens, meat waste, halogenation, novel derivatives, anticancer activity, apoptosis, zebrafish embryotoxicity
Objavljeno: 21.10.2022; Ogledov: 575; Prenosov: 27
Polno besedilo (3,39 MB)
NONDESTRUCTIVE THERMAL, OPTICAL, CHEMICAL AND STRUCTURAL CHARACTERIZATION OF ADVANCED MATERIALS BY OPTOTHERMAL TECHNIQUESHanna Budasheva
, doktorska disertacija
Opis: Advanced materials are promising ones in application in fields where it is necessary to decrease energy consumption and ensure better performance at a lower cost. They are materials, which have enhanced properties compared to conventional materials in the field of their applications.1 The huge group of them contributes significantly to every aspect of our lives. Among them, chosen for the present study, are resins for passive sampling of iron species in natural water and sediments, anticorrosive coatings, and multilayered polysaccharide aerogels for medical applications.
The composition and structure of each material determine its chemical, mechanical and physical properties, consequently their performance.2 The ability to use advanced materials in areas where their impact will be significant is largely dependent on the ability to precisely determine their characteristics to identify their properties that are either unique or has a better value. Therefore, the development of new methods or improvement of already known ones will make a great contribution to the development of the fields of application of the selected materials.
The present study is focused on the examination of the chosen materials by determining their optical, chemical, thermal and structural properties for applying them further in the desired applications. To provide the needed characterization, optothermal techniques such as optothermal beam deflection spectrometry (BDS) and thermal lens spectrometry (TLS) are developed and applied.
This dissertation is composed of the following chapters: introduction, theoretical background, optothermal techniques, research goal, part I (gels for passive sampling of iron species in natural water and sediments), part II (anticorrosive coatings), part II (polysaccharide aerogels), references. The core of this dissertation is presented in chapters 5 to 7. Each of the chapters separately covers the information about a selected group of advanced materials, including the sections describing sample preparation, developing the required characterization method, results, and conclusion. The connection link of these chapters is the study of the diffusion process of iron into different types of binding gels in passive samplers; external composites through the anticorrosive layers; drugs into the surrounding during the drug delivery process.
In Part I, the BDS method for the study was chosen, it was optimized, and a detailed protocol was developed for the determination of iron in passive sampler gels. The iron residues in the initial solutions were checked by a suitably tuned TLS method. The developed technique was applied to get the iron species distribution in the gel samples deposited in the sediments in the Vrtojbica River. The method was applied to the gels applied on ice from Antarctica in order to obtain the iron species distribution on its surface as well. The obtained results were validated using the TLS, UV-Vis and ICP-MS methods. The chapter contains the analysis of the Fe diffusion depth into the resin sampler, which is presented for the first time. The information is obtained by using the mathematical model and applying it to the obtained practical results by frequency scanning of the gels. The crucial information about the thermal properties of their layers containing Fe-ions from the fitting procedure was extracted. On the basis of these results, information about the diffusion depth of Fe inside the gels was obtained, which has not been previously described in the literature.
In Part II, the porosity in the anticorrosion coatings on the basis of their thermal parameters was determined. For the first time, the opened porosity was extracted from the total one. The analysis of Si/Zr-based hybrid sol-gel coatings has shown that the addition of cerium salts into the sol-gel matrix produces changes in its physical, chemical and corrosion properties. And it was found that the sample with the biggest amount of incorporated zirconium and loaded with cerium has the lowest values of porosity and, hence, the best barrier properties of the coating. The obtained thermal parameters of the Si/Zr-based hybrid sol-gel coatings by BDS were validated by the use of the photothermal radiometry method. On the other hand, the analysis of siloxane methacrylate coating has shown that the sol-gel hybrid methodology offers an important route for modification of thermal properties by a combination of inorganic to organic contents where the former than as an integral part of the coating network affects the thermal properties without the need for introducing fillers or nanoparticles.
In Part III, the multilayered structure of the samples, containing hyaluronic acid, amoxicillin and fucoidan layers deposited on stainless support has been analyzed by the use of the BDS technique. The thermal parameters of each layer were determined, as well as their thickness. The results revealed the diffusion between neighboring layers and followed changes in the properties of the whole sample, which is reflected in its thermal properties. Such data for multilayered materials, which potentially can be used for drug delivery systems, are presented for the first time.
Presented results indicated the ability of the BDS system for the chemical characterisation of the solid materials, the detection of their thermal parameters; investigation of total, opened and closed porosity; determining the thickness of layers in multilayered structures. The TLS method served as the validating one for the purpose of getting comprehensive information in liquid samples about their chemical composition. In summary, this dissertation explores alternative ways to apply optothermal methods to various areas of advanced materials to characterize them in order to improve their initial properties.
Ključne besede: optothermal beam deflection spectrometry, thermal lens spectrometry, diffusive gradients in thin films, iron species, anticorrosive layers, porosity, polysaccharide aerogels, multilayered structures
Objavljeno: 29.08.2022; Ogledov: 728; Prenosov: 43
Polno besedilo (5,46 MB)
Synthesis and application of transition metal phosphide nanomaterials as electrocatalysts for water splitting and chemical transformationsTakwa Chouki
, 2022, doktorska disertacija
Opis: In this thesis, we will focus on the solvothermal synthesis of iron phosphides (FeP, Fe2P) using triphenylphosphine (TPP) as an inexpensive and stable phosphorus source. The obtained iron phosphides were applied as electrocatalysts in hydrogen evolution reaction (HER), oxygen evolution reaction (OER), Rhodamine B (RhB) degradation, Escherichia coli (E. coli) inactivation,
nitrates reduction reaction (NO3RR) to ammonia (NH3), and as counter electrodes in dye-sensitized solar cells (DSSCs). Detailed characterizations of catalysts were carried out to investigate the correlations between the material structure and catalytic activity.
The first part of the thesis gives an introduction to the topic which cover overview of literature about the use of transition metal phosphide as efficient electrocatalysts in water splitting studies, NO3RR to NH3 and DSSCs.
The second part is a description of the experimental methods.
The third part discusses the solvothermal synthesis of FeP and Fe2P catalysts using TPP precursor. The phase conversion of iron phosphides at elevated temperatures under reductive atmosphere was reported. Structural characterizations of the obtained materials were achieved using multiple techniques. The electrocatalytic activities of heat-treated iron phosphide films for HER were studied in acidic environment.
The fourth part discusses the use of Fe2P nanoparticles (NPs) for OER.
The fifth part outlines the use of Fe2P precatalyst in water treatment studies. Using a thin film of Fe2P precatalyst, RhB degradation and E. coli inactivation in the presence of in-situ generated reactive chlorine species were reported. Characterization of Fe2P electrocatalysts before and after the test was carried out using different techniques.
The sixth part shows for the first time the use of FeP and Fe2P as a noble metal-free electrocatalysts for NO3RR to NH3. In this chapter we will emphasize the nitrate reaction pathways, which are highly complex and poorly understood.
The seventh part demonstrates the use of FeP and Fe2P catalysts as robust and efficient counter electrodes in DSSCs.
Ključne besede: solvothermal synthesis, iron phosphides, electrocatalysis, HER, OER, RhB degradation, E. coli inactivation, NO3RR to NH3, DSSCs, dissertations
Objavljeno: 29.08.2022; Ogledov: 717; Prenosov: 67
Polno besedilo (6,35 MB)
Gradivo ima več datotek! Več...
Exploration of yeast biodiversity potential for development of alternative biofungicides in viticultureRowland Adesida
, 2022, doktorska disertacija
Opis: Botrytis cinerea Pers., the fungal plant pathogen and the causal agent of gray mould diseases in grapevine, is vastly responsible for substantial economic losses in table and wine grapes production worldwide by negatively affecting plant growth and causing the
reduction of grape and wine quality. The conventional approach for pathogen control has been up to date based on synthetic fungicides with good effectiveness against pathogens but a negative impact on the environment. The growing level of harmful residues in the environment and some also detected in wines have led the European
Union and many winemakers to limit the application of synthetic fungicides to earlier season. However, with a high risk of disease also late in the season, the need for other solutions is clear. Consequently, more and more research is focused on finding potential alternatives in the form of effective biological control agents. Although there are several reports of yeast’s biocontrol activity, they are up to date still poorly commercialized for such purposes. As
the yeasts represent an important part of the grape microflora, competing with other microorganisms (including pathogens) for nutrients and space, we decided to examine the potential of autochthonous yeasts as "green" alternatives in fighting against
phytopathogens such as B. cinerea in viticulture. With this aim, we tested the biocontrol activity of 119 different indigenous yeasts belonging to 30 different species of 17 genera against filamentous fungus B. cinerea, the causal agent of grey mould or botrytis
bunch rot in grape. The yeasts were screened for putative multidimensional modes of action such as antifungal volatiles (VOC), in vitro inhibition of fungal mycelial growth, competition for nutrients, hydrolytic enzyme activities, and yeast tolerance to fungicides like copper, iprodione and cyprodinil/fludioxonil combination. With a qualitative detection of the hydrolysis activity by using screening methods based on solid medium with chitin or βD-glucosides as substrates, we found that many tested yeasts were capable of producing lytic enzymes with the ability to degrade the cell wall of phytopathogenic fungi and are potentially also able to produce VOCs via hydrolysis of grape glycosides as a result of β-glucosidase presence. Furthermore, we observed the capability of tested yeast to inhibit fungal mycelia growth on plate and assimilation of a wide variety of carbon sources; however, no siderophore producers were detected. In general, the yeasts under observation were tolerant to the tested fungicides. Their fungicide resistance can indeed be regarded as a beneficial trait for potential biofungicide agent (PBA) candidates due to open possibilities of applications and combinations within low input pest management strategies in the vineyard. Finally, a field experiment in Pinot noir and Pinot gris vineyards was designed to study different combinations of optimized canopy microclimate manipulation (CMM) techniques and potential biocontrol agent (PBA) application. In experimental
conditions, the ability of PBA’s to maintain appropriate population density for disease prevention was observed. In addition, the grape and wine quality parameters were analysed to observe the possible impact of implemented biocontrol yeast on final products.
The biocontrol yeast Pichia guilliermondii ZIM 624 was selected and applied in experimental vineyards based on yeast testing results. We were able to detect and confirm PBA yeast’s suitable density on grapes until harvest. In the case of early defoliation for both varieties lower grape compactness was observed together with lower yield/ plant, regardless of PBA yeast/ no yeast application. Among grape basic quality parameters, the optimized techniques showed a positive effect on sugar content. Still, unexpectedly, in the treatments with biocontrol yeasts some trends toward higher
acidity were noticed in Pinot gris.
Ključne besede: sustainable viticulture, Botrytis cinerea, gray mould, yeasts, biocontrol, canopy microclimate manipulation, grapevine metabolite, dissertations
Objavljeno: 07.07.2022; Ogledov: 858; Prenosov: 107
Polno besedilo (4,17 MB)
Gradivo ima več datotek! Več...
CO2 dynamics and dissolutional processes in the karst vadose zoneLovel Kukuljan
, 2022, doktorska disertacija
Opis: The dynamics and distribution of carbon dioxide (CO2) in karst systems are crucial for understanding fundamental karst processes, namely precipitation and dissolution, which drive karst development both at the surface and underground. The study of CO2 transport provides valuable insights into the role of karst systems in the global carbon cycle and the impact on present climate, but also into the growth of speleothems, which are one of the most reliable terrestrial archives for palaeoclimate reconstruction. Due to the complexity of karst systems, long-term monitoring and high-resolution analyses of cave air and water geochemistry are essential to better understand the controlling factors that affect these processes and their outcomes. In the framework of this dissertation, cave climate and water hydrochemistry monitoring was established in a side-passages of the renowned Postojna Cave in Slovenia during 2017–2021. In the Pisani Passage, high CO2 concentrations, large temporal variations and a heterogeneous distribution of CO2, as well as extreme dissolution features, have already been detected in previous studies. The aim of the present study was to investigate these observations in depth and to find the reasons for their occurrence. This led to creating of a conceptual model for CO2 transport in karst systems that would be valid not only in this case but in karst areas worldwide.
The first focus of the study is dedicated to understanding the spatio-temporal dynamics of the partial pressure of CO2 (pCO2) in the Pisani Passage, which is mainly transported by advection (i.e., cave ventilation). Continuous measurements of airflow velocity, air temperature and pCO2 showed (1) that airflow through the karst massif is driven by both the action of the chimney effect and external winds, and (2) that the relationship between the direction of airflow, the configuration of airflow pathways and the connection to the outside explains the observed variations in pCO2. Due to the particular configuration of the airflow pathways, the terminal chamber of Pisani Passage accumulates high levels of CO2 (>10,000 ppm) and forms high vertical gradients of up to 1000 ppm/m. The pCO2 is low and uniform during updraft when outside air flows into the cave chamber through open, unobstructed passages (i.e., high-flow, low-pCO2 pathways). When the airflow reverses direction to downdraft, the chamber is fed by low-flow, high-pCO2 pathways that enter the cave passage through a CO2-rich fracture network embedded in a vadose zone. The spatial distribution of inlets and outlets results in minimal mixing between the low and high pCO2 pathways, leading to high and persistent pCO2 gradients.
In addition to the chimney effect driving the seasonal ventilation of the cave, the specific signs of a secondary wind-driven effect were also found; which is the second focus of this study. Wind flow over irregular topography leads to near-surface air pressure variations, and thus, pressure differences between cave entrances at different locations. Pressure differences depend on wind speed and direction and their relationship to surface topography and the location of cave entrances. Winds can act in the same or opposite direction as the chimney effect, either enhancing, diminishing or even reversing the direction of density-driven airflows. In the case of Postojna Cave, north and northeast winds enhance the downdraft and limit updraft, while the opposite is true for south winds, which enhance the updraft and limit downdraft. To investigate the importance of wind-driven flow, a computational fluid dynamics model was used to calculate the wind pressure field over Postojna Cave and the pressure differences between selected points for different configurations of wind speed and direction. These values were compared with those obtained from airflow measurements in the cave and from simple theoretical considerations. Despite the simplicity of the approach and the complexity of the ca
Ključne besede: cave climate, cave ventilation, carbon dioxide, dripwater geochemistry, speleothem corrosion, Postojna Cave, Slovenia
Objavljeno: 22.06.2022; Ogledov: 839; Prenosov: 51
Polno besedilo (8,45 MB)