Microbial recovery of rare earth elements from metallic wastes and scrap

In this thesis the microbial recovery of the rare earth neodymium is being examined using biofilm of the bacterium Serratia sp. N14, which has been used previously for the removal of lanthanide elements from liquid solutions. The mechanism used is via the PhoN phosphatase enzyme of these cells, which releases phosphate from an organic feedstock and metal cations (M2+) existing in the solution precipitate on the bacterial cell as metal phosphate. Neodymium was announced in 2013 to be included in the five most critical rare earth elements (REEs) and among the recycling of REEs, this was less than 1%. Therefore, the need to recover neodymium from liquid metallic wastes and scrap leachates would be a crucial step to recycle such metals. The first aim of this project was to study the ageing properties of the PhoN of Serratia sp. N14 cells during one year of storage, with respect to total phosphate release (Pi) and neodymium recovery. A simple predictive mathematical model was produced for the evaluation of metal recovery over various months of storage. The second goal of this project, was to construct an outflow chamber onto existing equipment for a semi-continuous biofilm preparation as an alternative economic production of biofilm, since the normal ‘’in vessel’’ biofilm production, is not readily scalable. The activity of biofilm from this new method was compared with the biofilm produced in the normal chamber reactor after appropriate times of storage. The final aim was to establish the potential usefulness of the biofilm with respect to its tolerance to low pH values or to high salt concentrations (neutralized aqua regia), since the overall goal is to recover metals from solid scraps, which may have been leached in strong acid. The robustness of the metal accumulating biofilm is discussed with respect to this envisaged application

Role of fibrillation on Poisson's ratio of expanded polytetrafluoroethylene (PTFE)

The polytetrafluoroethylene (PTFE) paste extrusion was studied to elucidate the role of structure formation (fibrillation) on the Poisson’s ratio of final products such as stents and other implants. In particular two types of PTFE have been studied in capillary extrusion using dies having different reduction ratios (RR) and die entrance angles. The extrudates collected at different processing conditions, were tested in uniaxial extension to assess their mechanical properties. The tensile modulus, yield stress and ultimate tensile strength of the obtained extrudates were found to be increasing functions of reduction ratio, although the opposite effect was found for the ultimate elongational strain. Moreover, a PTFE paste was extruded using a capillary rheometer at various temperatures through cylindrical dies of different reduction ratios (1-D structure samples). Uniaxial tensile experiments were performed on the collected extrudates using the SER at different temperatures and Hencky strain rates. A nonlinear viscoelastic model (Matsuoka) was used to model the transient tensile results. An empirical model was also developed to predict the tensile ultimate strength as a function of processing conditions such as temperature and die reduction ratio, as well as, the testing operating conditions i.e., temperature and Hencky strain rate. PTFE flat profiles were extruded using slit dies, which promoted orientation of fibrils in two directions (2-D structure samples). Uniaxial tensile experiments were performed on the collected extrudates using the SER at different temperatures and Hencky strain rates to determine mechanical properties. Poisson’s ratio was determined using image analysis and the results were compared using data from the 1-D structure samples. Polarized Raman spectroscopy was used to gain additional information on the degree of fibril orientation at different locations along and across the width and length of the extrudates. Finally, a simple model was derived for the density change in tensile deformation by taking into the account the Poisson’s ratio and the strain recovery. Results of the Raman spectra and the strain recovery coefficient from density changes, were found to be in agreement with the fibril structure/morphology obtained from SEM micrographs.Applied Science, Faculty ofChemical and Biological Engineering, Department ofGraduat

Roman wall paintings in Greece: from the time of Augustus until the era of Constantine the Great

The thesis "Roman wall paintings in Greece. From the time of Augustus until the era of Constantine the Great"presents for the first time in an overall scale the wall paintings of Roman imperial era that have come to light in the areas of modern Greek territory.The thesis focuses on the nature and function of the material in question, as well as on the construction technique and its iconography. Specifically, the present study examines for the first time the relationship of iconography with the decorated interiors, the frequency of wall paintings within a building as well as the relations of wall decorations with the types of buildings. Moreover it focuses on a number of other issues, such as whether and to what extent the material in question had any meaning for the ancient owners who ordered it, to what extent the agenda of projects was dictated by personal preferences, economic or social status, the current dominant artistic trends of the time, the existence of a single common art for mural decorations throughout the empire, as well as the detection and further developments of certain Italian styles in the provinces of Greece. Also it tries to decipher to what extent we are able today with the limited resources, sources and data that we have to understand this material. This study includes six chapters each of which determines the material in question in a different light. The first chapter is an introduction to Roman wall paintings in general, while the second examines the technique of wall decoration during the imperial period. The third chapter presents briefly the history of wall paintings in the Greek area until the late Hellenistic era. In this chapter, having as a starting point the early Greek times, an effort has been made to determine the nature and function of the mural decoration in the Greek world before the advent of the Romans, as well as the dominant artistic trends of wall decoration until the late Hellenistic era. The fourth chapter examines in general the wall decorations during the imperial period in the area of modern Greece, having as a basis, locations that present more frequently mural decorations. The fifth chapter deals with the iconography of the Roman wall paintings in Greece. Despite the fragmentary state of preservation of the material in question it can be detected the common iconographic trends between the Greek and Italian wall decoration, although it can not be expressed any definite conclusion as far as the prevalence of the new artistic trends in mural decorations is concerned. The last chapter examines through statistics and comparative conclusions the nature and the function of the material in question, as well as in what kind of buildings (private / public) and spaces (character and function of the rooms) the mural decoration is appeared

Environmental remediation through sequestration in surfactant micelles followed by sequestration in mesoporous materials

Many ubiquitous pollutants in aqueous systems (chlorinated hydrocarbons, phenols, etc.) can be removed quite efficiently by entrapment in surfactant micelles through the well-studied membrane-enhanced ultrafiltration process (MEUF). It is the common assumption that spherical micelles swell upon uptake of the pollutants. We show that uptake of specific pollutants (particularly phenols) results in a dramatic shape change of micelles from spherical to wormlike and vesicular structures. We have developed a facile follow-up method where the entrapped species in surfactant microstructures become encapsulated in mesoporous silicas. The pollutant is, therefore, highly concentrated with a volume reduction of several orders-in-magnitude and converted to solid materials for easy disposal. But, additionally, the process results in the generation of functional mesoporous materials. The fundamentals of such entrapment and encapsulation are studied through a combination of small angle neutron scattering, cryo-transmission electron microscopy and X-ray diffraction. There are remarkable modulations in micelle characteristics upon entrapment, with transitions from spherical micelles to wormlike micelles and, thence, to spherical vesicles and eventually to wormlike vesicles. These structures which are then used as templates for ceramic synthesis, create modifications in ceramic mesoporosity which are correlated to the characteristics of self-assembly

Environmental remediation through sequestration in surfactant micelles followed by sequestration in mesoporous materials

Many ubiquitous pollutants in aqueous systems (chlorinated hydrocarbons, phenols, etc.) can be removed quite efficiently by entrapment in surfactant micelles through the well-studied membrane-enhanced ultrafiltration process (MEUF). It is the common assumption that spherical micelles swell upon uptake of the pollutants. We show that uptake of specific pollutants (particularly phenols) results in a dramatic shape change of micelles from spherical to wormlike and vesicular structures. We have developed a facile follow-up method where the entrapped species in surfactant microstructures become encapsulated in mesoporous silicas. The pollutant is, therefore, highly concentrated with a volume reduction of several orders-in-magnitude and converted to solid materials for easy disposal. But, additionally, the process results in the generation of functional mesoporous materials. The fundamentals of such entrapment and encapsulation are studied through a combination of small angle neutron scattering, cryo-transmission electron microscopy and X-ray diffraction. There are remarkable modulations in micelle characteristics upon entrapment, with transitions from spherical micelles to wormlike micelles and, thence, to spherical vesicles and eventually to wormlike vesicles. These structures which are then used as templates for ceramic synthesis, create modifications in ceramic mesoporosity which are correlated to the characteristics of self-assembly