Dissertations / Theses on the topic 'Filtration of liquid aerosols'

This thesis examines the particle capture, fibre wetting and droplet flow processes within wet filters collecting solid and liquid aerosols and within filters collecting only liquid aerosols. The processes involved in this type of filtration were examined through a series of experiments and models developed to describe the behaviour of fibre/liquid systems. This work can be summarized in 4 categories: (1) The bounce and immediate re-entrainment of liquid and solid monodisperse aerosols under a stable filtration regime (pre cake formation) by wet and dry fibrous filters. In this work it was found that the solid particles generally exhibited a lower fractional filtration efficiency than liquid particles (of the same size), although this difference decreased in the smaller size fractions. However, for the wet filtration regime (each fibre of the filter was coated by a film of water), no significant difference in filtration efficiency was detectable between solid and liquid aerosols. Either the bounce effect of the particles is inhibited by the liquid film, or the filtration conditions in the wet filter are so different that the aerosol properties are less significant with respect to capture. (2) A microscopic study of the effect of fibre orientation on the fibre wetting process and flow of liquid droplets along filter fibres when subjected to airflow and gravity forces was conducted. The flow of the liquid collected by the fibres was observed and measured using a specially developed micro-cell, detailed in the thesis. The experimental results were compared to a theoretical model developed to describe the flow of droplets on fibres. The theory and experimental results showed a good agreement. A sensitivity analysis of the model was performed which showed the droplet radius to be the most significant parameter. The model has the potential to improve filter self-cleaning and minimise water use. (3) An experimental study of the capture of solid and liquid (oil) aerosols on fibrous filters wetted with water. Variable quantities of liquid irrigation were used, and the possibility for subsequent fibre regeneration after clogging or drying was also studied. It was found that self-cleaning (removal of solid aerosols by water) occurred even under heavily dust-laden conditions, and post evaporation of water. With the collection of oil aerosols on fibres wetted with water, a predominance of the barrel shaped droplet on the fibre was observed, with oil droplets displacing water droplets (if the oil and fibre combination created a barrel shaped droplet), creating various compound droplets of oil and water not previously reported in literature. (4) An extensive experimental investigation of the wetting processes of fibre/liquid systems during air filtration (when drag and gravitational forces are acting) has shown many important features, including droplet extension, oscillatory motion, and detachment from fibres as airflow velocity increases. The droplet oscillation is believed to be induced by the onset of the transition from laminar to turbulent flow as droplet size increases. To model such oscillation it was necessary to create a new conceptual model to account for the forces both inducing and preventing such oscillation. The agreement between the model and experimental results is satisfactory for both the radial and transverse oscillations.

This thesis examines the particle capture, fibre wetting and droplet flow processes within wet filters collecting solid and liquid aerosols and within filters collecting only liquid aerosols. The processes involved in this type of filtration were examined through a series of experiments and models developed to describe the behaviour of fibre/liquid systems. This work can be summarized in 4 categories: (1) The bounce and immediate re-entrainment of liquid and solid monodisperse aerosols under a stable filtration regime (pre cake formation) by wet and dry fibrous filters. In this work it was found that the solid particles generally exhibited a lower fractional filtration efficiency than liquid particles (of the same size), although this difference decreased in the smaller size fractions. However, for the wet filtration regime (each fibre of the filter was coated by a film of water), no significant difference in filtration efficiency was detectable between solid and liquid aerosols. Either the bounce effect of the particles is inhibited by the liquid film, or the filtration conditions in the wet filter are so different that the aerosol properties are less significant with respect to capture. (2) A microscopic study of the effect of fibre orientation on the fibre wetting process and flow of liquid droplets along filter fibres when subjected to airflow and gravity forces was conducted. The flow of the liquid collected by the fibres was observed and measured using a specially developed micro-cell, detailed in the thesis. The experimental results were compared to a theoretical model developed to describe the flow of droplets on fibres. The theory and experimental results showed a good agreement. A sensitivity analysis of the model was performed which showed the droplet radius to be the most significant parameter. The model has the potential to improve filter self-cleaning and minimise water use. (3) An experimental study of the capture of solid and liquid (oil) aerosols on fibrous filters wetted with water. Variable quantities of liquid irrigation were used, and the possibility for subsequent fibre regeneration after clogging or drying was also studied. It was found that self-cleaning (removal of solid aerosols by water) occurred even under heavily dust-laden conditions, and post evaporation of water. With the collection of oil aerosols on fibres wetted with water, a predominance of the barrel shaped droplet on the fibre was observed, with oil droplets displacing water droplets (if the oil and fibre combination created a barrel shaped droplet), creating various compound droplets of oil and water not previously reported in literature. (4) An extensive experimental investigation of the wetting processes of fibre/liquid systems during air filtration (when drag and gravitational forces are acting) has shown many important features, including droplet extension, oscillatory motion, and detachment from fibres as airflow velocity increases. The droplet oscillation is believed to be induced by the onset of the transition from laminar to turbulent flow as droplet size increases. To model such oscillation it was necessary to create a new conceptual model to account for the forces both inducing and preventing such oscillation. The agreement between the model and experimental results is satisfactory for both the radial and transverse oscillations.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environmental Engineering
Faculty of Environmental Sciences
Full Text

The problem of filtration of liquid aerosols by both wettable and nonwettable filters has been extensively studied and the results of the theoretical calculations together with the experimental results are presented. More realistic models of filtration by both wettable and nonwettable filters have been developed and verified experimentally. A new instrument has been developed, and used in the experiments, for the measurement of the absolute concentration of aerosols in the gas stream. This instrument is based on the measurement of the initial vapour content of the gas stream simultaneously with the measurement of the vapour content after the total evaporation of aerosol. The concentration of the aerosol is calculated as the difference between these two values. The instrument was developed to provide fast and accurate measurements of aerosol concentration. The main advantages of the instrument are: high accuracy, simplicity of measurement, possibility of use for a wide range of substances, perfect suitability of operation for automatic monitoring technologies, etc. All rights for this instrument have been reserved and the fully automatic version will be available in the near future. It was found that the efficiency of filtration of aerosol on the wettable filter depends on the thickness of the liquid film on the fibre. This parameter was taken into account in the development of a theoretical model of filtration on wettable fibrous filters. The particle breakthrough problem has been solved by the optimisation of the aspect ratio (the ratio of the height by width) of the wettable filter. On this basis, industrial devices have been developed, patented, and implemented in industry. These devices provide a stable operating efficiency of higher than 99%. It was found experimentally that the efficiency of filtration of aerosol on the nonwettable filter depends on the diameter of the drop suspended on the filter, and on the area of the filter blocked by drops: this influences the velocity of filtration. All these parameters were taken into account in the development of a theoretical model of filtration on nonwettable fibrous filters. On the basis of this model, satisfactorily verified by the experiments, an industrial device has been developed. The harnessing of atomisers makes it possible to maintain the efficiency of filtration higher than 99%, even with a relatively high velocity of filtration of 2.7m/s. The new technology is tackling the problem of handling huge amounts of exhaust gases and this is particularly important for cramped installations when the space available for the air pollution control technology is quite limited. A highly efficient gas cleaning technology has been developed. This technology is based on combining two stages (wet scrubber and filter) of currently utilised air pollution control devices by submerging the fibrous filter into the liquid on the plate. The new device provides an effective division of the main gas stream into ultra-small bubbles which increase the contact area between the gas and liquid phases. It was estimated theoretically and verified experimentally that the efficiency of the proposed 'combined' technology, is 45% higher than the efficiency of the two stages technology. The technology has been patented and will be offered for industrial implementation in the near future.

The problem of filtration of liquid aerosols by both wettable and nonwettable filters has been extensively studied and the results of the theoretical calculations together with the experimental results are presented. More realistic models of filtration by both wettable and nonwettable filters have been developed and verified experimentally. A new instrument has been developed, and used in the experiments, for the measurement of the absolute concentration of aerosols in the gas stream. This instrument is based on the measurement of the initial vapour content of the gas stream simultaneously with the measurement of the vapour content after the total evaporation of aerosol. The concentration of the aerosol is calculated as the difference between these two values. The instrument was developed to provide fast and accurate measurements of aerosol concentration. The main advantages of the instrument are: high accuracy, simplicity of measurement, possibility of use for a wide range of substances, perfect suitability of operation for automatic monitoring technologies, etc. All rights for this instrument have been reserved and the fully automatic version will be available in the near future. It was found that the efficiency of filtration of aerosol on the wettable filter depends on the thickness of the liquid film on the fibre. This parameter was taken into account in the development of a theoretical model of filtration on wettable fibrous filters. The particle breakthrough problem has been solved by the optimisation of the aspect ratio (the ratio of the height by width) of the wettable filter. On this basis, industrial devices have been developed, patented, and implemented in industry. These devices provide a stable operating efficiency of higher than 99%. It was found experimentally that the efficiency of filtration of aerosol on the nonwettable filter depends on the diameter of the drop suspended on the filter, and on the area of the filter blocked by drops: this influences the velocity of filtration. All these parameters were taken into account in the development of a theoretical model of filtration on nonwettable fibrous filters. On the basis of this model, satisfactorily verified by the experiments, an industrial device has been developed. The harnessing of atomisers makes it possible to maintain the efficiency of filtration higher than 99%, even with a relatively high velocity of filtration of 2.7m/s. The new technology is tackling the problem of handling huge amounts of exhaust gases and this is particularly important for cramped installations when the space available for the air pollution control technology is quite limited. A highly efficient gas cleaning technology has been developed. This technology is based on combining two stages (wet scrubber and filter) of currently utilised air pollution control devices by submerging the fibrous filter into the liquid on the plate. The new device provides an effective division of the main gas stream into ultra-small bubbles which increase the contact area between the gas and liquid phases. It was estimated theoretically and verified experimentally that the efficiency of the proposed 'combined' technology, is 45% higher than the efficiency of the two stages technology. The technology has been patented and will be offered for industrial implementation in the near future.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environmental Engineering
Faculty of Environmental Sciences
Full Text

Fibrous filter materials are commonly adopted in a variety of industrial and domestic processes to remove fine particles. Filter performance may be assessed by two parameters: the proportion of particles passing through the media (penetration), and the resistance to gas flow through the filter (pressure drop). Another parameter, the filter lifetime, may be important where economical factors are key.

This work has examined the physico-chemical properties of coalescing filters on a micro-scale, considering them as either a capillary system or a fibre-droplet system. This work has developed a validated theoretical model for droplet-fibe forces in both phillic and phobic systems and a computational fluid dynamics solver for droplet-fibre systems. This work will significantly improve the design and optimisation of coalescing filter systems.

Cette étude s’inscrit dans le cadre de l’amélioration des connaissances liées à l’évaporation d’aérosols liquides semi-volatils collectés sur des filtres à fibres. Le phénomène d’évaporation d’aérosols collectés sur médias fibreux induit des problèmes de sécurité avec notamment une surexposition des salariés aux vapeurs, à l’aval des systèmes généraux de filtration de l’air. De plus, lors des contrôles des concentrations atmosphériques des aérosols, l’évaporation induit une sous-estimation de la phase particulaire de l’aérosol prélevé qui est problématique en termes de prévention de l’exposition. L’objectif de ces travaux a donc été de produire de nombreux résultats expérimentaux afin, d’une part, de compléter les rares présents dans la littérature et, d’autre part, d’améliorer les modèles théoriques développés précédemment. Deux approches expérimentales ont été menées afin d’identifier le processus d’évaporation d’un aérosol collecté. La première, nommée approche globale, permet de suivre l’évaporation de l’aérosol par la quantification des vapeurs à l’aval du filtre, au cours du temps. La seconde, nommée approche microscopique, étudie l’évaporation de gouttes collectées sur les fibres d’une fibre à l’échelle microscopique. Les deux approches réalisées lors de ces travaux s’accordent sur le fait que l’évaporation d’un aérosol liquide semi-volatil ne peut être modélisée par les modèles proposés par la littérature. Des hypothèses ont été avancées afin d’expliquer la divergence de cinétique d’évaporation entre la théorie et les expérimentations
This study falls within the scope of improving knowledge concerning evaporation of semi-volatile liquid aerosols collected on fibrous filters. Under these conditions, the aerosol evaporation phenomenon causes problems of safety, in particular over-exposure of employees to vapours downstream of general air filtering systems. Furthermore, when controlling aerosol atmospheric concentrations, evaporation results in under-estimation of the sampled aerosol particle phase and this is clearly problematic in exposure prevention terms. The aim of this work was therefore to record a large number of experimental data, both to make up for their scarcity in the literature and to improve previously developed theoretical models. Two experimental approaches were implemented to identify the evaporation process for a collected aerosol. The first, termed the global approach, allowed us to monitor aerosol evaporation by measuring vapour quantity downstream of the filter with respect to time. The second, microscopic, approach considers evaporation of droplets collected on the filter fibres on a microscopic scale. The two approaches implemented during this research lead to agreement on the fact that evaporation of a liquid semi-volatile aerosol cannot be satisfactorily represented by the theoretical models proposed in the literature. Hypotheses are advanced to explain the divergence in evaporation kinetics between theoretical and experimental work

Cette étude concerne la filtration par un filtre à fibres d'un gaz contaminé soit par des particules solides submicroniques soit par un aérosol liquide submicronique. Après une synthèse de l'ensemble des travaux réalisés antérieurement, nous nous intéressons dans un premier temps à caractériser les différents filtres (très haute efficacité et moyenne efficacité) mis à notre disposition. Les résultats expérimentaux relatifs à la filtration de particules solides nous ont permis de détailler le processus de colmatage et de décrire en particulier l'évolution de la perte de charge, de l'efficacité, du profil de pénétration de l'aérosol au sein du medium. Des observations au microscope montrent que dans une première étape du colmatage, des dendrites sont formées sur les fibres dans la profondeur du filtre et que dans une seconde étape un gâteau se construit sur la surface du filtre. L’originalité de la partie expérimentale réside dans la caractérisation du gâteau et la détermination du point de transition entre les deux phases de la filtration. Un nouveau modèle théorique a été développé et permet de rendre compte de l'ensemble des résultats expérimentaux. La filtration d'un aérosol liquide a été décrite et a mis en évidence l'existence d'une masse seuil pour laquelle on observe une brutale augmentation de la perte de charge du filtre, correspondant à la présence d'un film liquide forme sur la surface du filtre. L’influence de certains paramètres opératoires a été étudiée ainsi que la nature de l'aérosol, en particulier la tension superficielle du liquide. Enfin, diverses approches ont permis de décrire théoriquement les phénomènes observés et d'ouvrir différentes perspectives de modélisation plus fines.

The photochemistry of liquid aerosols has been investigated with the aim of using the physical properties of liquid aerosols to enhance the reactivity of photochemical and photocatalytic systems. The properties of aerosols that enhance reactivity are summarised under four headings: the optics of micro droplets, diffusion into small particles, surface and interfacial reactivity, and capillarity effects. A range of systems have been developed for the photochemistry of liquid aerosols. A number of photocatalytic systems have been studied and a significant enhancement in the photolysis of molybdenum hexacarbonyl has been observed, relative to the liquid phase. A computational study of the light intensity distribution inside liquid aerosols droplets in photochemical and photocatalytic systems has been carried out. Large enhancements of the internal field intensity relative to the incident field have been observed. It is proposed that the internal intensity distributions are the source of the increased rate of molybdenum hexacarbonyl photolysis. A model has been proposed for gas-liquid transfer, based on the capillary wave motion of the liquid surface.

Filtration is the most widely utilised air quality control technique used in a Heating, Ventilating and Air Conditioning (HVAC) duct systems in an indoor environment. Biological particles may be deposited onto, and re-aerosolized from, the filter surface, however, a range of variables such as types of microorganisms, filter characteristics, humidity, temperature and others factors can contribute to re-aerosolization. In this study, new methods are investigated to remove or inactivate the microorganism in the simulated HVAC system and controlled environment by adding various technologies to the current filtration systems. Two new technologies were tested; the first, emitting ions in the testing chamber, and the second, coating tea tree oil (TTO) onto the fibrous filter surface, in order to determine the most efficient and cost effective method for airborne biological particle control. Two commercial low-efficiency HVAC filters were tested in this investigation using a number of monodisperse polystyrene latex (PSL) spheres with diameters 0.5, 0.8, 1.0, and 1.5 μm. An influence of air ionization on the filtration process was investigated by running of an ionizer that was placed at a range of distances apart from the filter (5, 15, 25, and 45cm). The results of this investigation show that the current theoretical model underestimates the efficiencies of the particle deposition onto the filter fibres. However, this could be explained by the fact that some incoming particles are repelled from the filter, due to repelling electrostatic forces caused by unipolar ions captured by the filter. This investigation concluded that emitted air ions enhance the filtration efficiency, but found that the efficiency depends upon the filter type and the distance from the ion emitter to the filter surfaces. This investigation has provided strong evidence that ionization enhances the filtration efficiency, and that there are significant enhancements when the ion emitter is operated at 5 cm upstream of the filter. The results of this study illustrate that the continuous emission of negative ions in the vicinity of a low-efficiency HVAC filter significantly enhances its performance of removal airborne biological particles including bacteria, fungal spores and virus in the ambient air environment. Finally, bacteria (B. subtilis, E. coli and P. fluorescens) and fungal spores (Rhizopus stolonifer and A. niger) were examined by coating the filter fibres with biologically active TTO and biologically neutral light mineral oil (MO). It was found experimentally that pre-coating of the filter fibres with TTO and then using this filter for bioaerosols control, resulted in rapid inactivation of captured microorganisms and minimising a number of viable particles possibly blown off from the filter by the air. It was shown that 90 percent of the robust B. subtilis bacterial strain was inactivated during 30 minutes of the technology operation. Furthermore, the inactivation efficiency of some more sensitive bacterial aerosols of E. coli and P. fluorescens were found to be above 99 percent for the same time interval of 30 minutes. Fungal strains were found to be more robust with only 52-54 percent inactivation achieved over 60 minutes experimental run.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
Full Text

Surgical masks are intended to be used to prevent transmission of disease from a health care worker to a patient. Often times, they are relied upon by health care workers for their own protection. In light of recent developments regarding preparation for health care worker response to global infectious diseases such as H1N1 Influenza, health care workers may experience a false sense of security when wearing surgical masks. The goal of this study was to evaluate the filtration efficiency of a double strap tie-on surgical mask. The manufacturer asserts a >95% efficiency with a 0.1 um challenge aerosol under FDA testing procedures. The NIOSH Title 42 CFR Part 84 certification criteria call for testing at a rate of 85 lpm representing a human moderate to heavy work load breathing rate. Three sizes of monodispersed aerosols (polystyrene latex beads: 0.5 um, 1.0 um, 2.0 um) were used. The specific aims were to measure the collection efficiencies of this mask for the various particle sizes. Two tests were performed. In the first, masks were affixed to a dummy head and the edges of the mask were not sealed. In the second, the edges of the masks were sealed to the head using silicone sealant, so all penetration was through the filtering material of the mask. Differences in upstream and downstream particle concentrations were measured. Thus, penetration by leakage around the mask and through the filtering material was measured. The experimental set up involved passing the aerosol from the nebulizer through a diffusion dryer and Kr-85 charge equilibrator ensuring a dry charge neutralized aerosol cloud for detection by a LASAIR particle counter. The analysis revealed that the filtration efficiency for 0.5 um particles ranged from 3% to 43% for the unsealed masks and 42% to 51% for the sealed. For 1.0 um particles, the efficiency was 58% to 75% for unsealed and 71% to 84% for sealed masks. For 2.0 um, the efficiency was 58% to 79% for unsealed masks and 69% to 85% for the sealed masks. The data were statistically significant and indicated that surgical masks were associated with very low filtration efficiency. This suggests that they may be inadequate against airborne viruses and bacteria.

Fluid flow and filtration phenomena associated with filtration of liquid aluminum using reticulated ceramic filters were systematically investigated. It was found that fluid flow through this type of filter could be described by Darcy's Law up to a Reynolds number of 8, and the permeability of this type of filter ranged from about $9 times10 sp{-3}$ to $4 times10 sp{-2} rm mm sp2$.
Parameters affecting filtration processes during the initial period were identified, some of which could be quantified numerically using a 2-D computational domain. According to these numerical analyses, the clean filter coefficient for this type of filter was linearly dependent on the dimensionless Stokes velocity of the suspended particles, had a $-$0.96 power dependence on the Peclet number, a $-$6.93 power dependence on the effective porosity of the filter, and exhibited only a weak dependence on the Reynolds number, in the Darcy velocity regime.
The dynamic behaviour of this type of filter was analyzed theoretically and simulated numerically using newly proposed correlations relating the filter coefficient and the pressure drop to the amount of particles captured within the filter (the specific deposit), and a model describing the morphology of captured particles. The simulated results showed that the filtration efficiency and the pressure drop increased with inlet particle concentration and filtration time; these increases were however, insignificant when the inlet particle concentration was less than 1 ppm for filtration periods of two hours, however, when the inlet concentration (initial and continued) reached 10 ppm, the change became appreciable.
Experimental data, obtained from liquid aluminum filtration tests conducted by the author in both laboratory and industrial settings, compared favourably with the numerical results.

Les performances de filtration des filtres de CTA vis-à-vis de particules et d’aérosols microbiens (AM) ont été étudiées ainsi quel’influence des conditions opératoires sur le comportement de microorganismes collectés sur les filtres. A l’échelle du laboratoire, une mini CTA ayant deux étages de filtration en série a été développée et validée pour l’étude de filtres prototypes ayant des géométries industrielles. Trois types de filtres de différentes efficacités ont été considérés : G4, F7 et F9 selon la norme EN 779. Deux configurations de filtres ont été étudiées : 1) G4 plan plissé/F7 à poches et 2) F7/F9 à poches. Les filtres ont été colmatés séquentiellement par des particules d’alumine, qui assurent une fraction minérale, puis du riz microniséqui apporte le champignon Penicillium chrysogenum et assure une fraction organique agissant comme substrat pour les microorganismes. Enfin, un AM composé d’endospores de Bacillus subtilis et de spores d’Aspergillus niger a été nébulisé pour la contamination des filtres. Après colmatage, des périodes de marche/arrêt de la ventilation de différentes durées (10 j ou 6 semaines) ont été simulées. Lors des reprises de la ventilation, des comptages de particules et d’AM en avaldes filtres ont été effectués. Les principaux résultats sont : (i) les filtres placés en 2ème étage présentent un colmatage plus faible que ceux du 1er étage de filtration, (ii) survie de B. subtilis, croissance de P. chrysogenum et décroissance d’A. niger sur les filtres quelle que soit la période d’arrêt de ventilation étudiée, et (iii) lors des reprises de ventilation, il n’a pas été observé de relargage d’AM pour la fraction échantillonnée.D’autre part, deux CTA à pleine échelle ont été étudiées pendant 6 mois. Une CTA ayant deux étages de filtration avec une configuration G4 plan plissé/F7 à poches, traite l’air extérieur et le souffle vers des locaux desservis. L’autre CTA correspond à l’extraction de l’air vicié d’un local pour le rejeter vers l’extérieur. La perte de charge des filtres, l’humidité relative, et la température de l’air ont été suivies en continu. L’efficacité des filtres vis-à-vis des particules et des aérosols microbiens a été mesurée une fois par mois. Une méthodologie originale de suivi mensuel de la concentration des microorganismescollectés sur les filtres a été mise en oeuvre. Les principaux résultats sont : (i) faible évolution de la perte de charge du filtre placé en 2ème étage, (ii) efficacité des filtres G4 comparable à celle des filtres G4 prototypes, (iii) efficacité du filtre F7 plus faible que celle des filtres prototypes, ce qui peut être expliqué par une différence de vitesse de filtration entre les deux échelles, (iv) le filtre G4 de la CTA-extraction contient une concentration de microorganismes 10 fois plus élevée que celle du filtre G4 de la CTA-soufflage après 6 mois de fonctionnement
Filtration performances of Air Handling Units (AHU) filters regarding particles and microbial aerosols have been studied, as well as the influence of the AHU operational conditions on behavior of microorganisms collected on the filters. A lab-scale AHU with two successive filtration stages was developed and validated for the study of prototype filters with industrial geometries. Three types of filters of different efficiency have been considered : G4, F7 and F9 according to EN 779 Standard. Two configurations of filters were considered: 1) G4 pleated/F7 bag and 2) F7/F9 bag. Filters were sequentially clogged by alumina particles which assured a mineral fraction, and then by micronized rice particles which provides the fungi Penicillium chrysogenum and assures an organic fraction which acts as a substrate for microorganisms. Finally, a microbial aerosol composed by endospores of Bacillus subtilis and spores of Aspergillus niger was nebulized for filters contamination. After clogging, stops and restarts of ventilation were simulated for different durations (10 days or 6 weeks). During restarts of ventilation, particles and microbial aerosols samplings were performed downstream of the filters. Main results are: (i) level of clogging is significantly less important for the 2nd filtration stage than for the first one, (ii) survival of B. Subtilis, growth of P. Chrysogenum and decline of A.niger on the filters whatever the period of time studied, and (iii) during restarts of ventilation, microbial aerosols releasing was not detected for sampled fraction. Moreover, two full-scale AHU were studied during 6 months. One of the AHU studied is equipped with two filters in series: a G4 pleated filter in 1st stage and a F7 bag filter in 2nd stage. This AHU treats the outdoor air to blow it towards the indoor environments. The other one extracts the indoor air to reject it back outdoors. The filters pressure drop, relative humidity and temperature of the air were measured continuously. Filters efficiency regarding particles and microbial aerosols were measured once a month. An original methodology for the monthly estimation of the concentration of microorganisms on the filters was implemented. Main results are: (i) no significant evolution of the filter pressure drop in 2nd stage, (ii) efficiency of G4 filters are comparable to the prototype filtersone, (iii) efficiency of F7 filters are lower than prototype filters one, which can be explained by differences of filtration velocity between the two scales, (iv) after 6 months of operation, concentration of microorganisms on G4 filter of the AHU of extraction is 10 times higher than the G4 filter one of AHU who treats outdoor air

The various topics investigated in the course of the preparation of this thesis can by unified under the common theme of fibrous fIltration enhancement from both experimental and theoretical perspectives. Fibrous filtration is by far the most common method of gas pUrification in use today and further improvements will require a better understanding of the various mechanisms contributing to the collection of particles. The lack of agreement between experimental results and the latest theoretical models found in the literature which have been put forward to predict fIlter efficiency led to the development of a complex computer simulation of a fIltration process. The model simultaneously accounts for particle collection in the inertial impaction, interception and Brownian diffusion regimes and also recognizes that real fIlters do not consist of a simple array of fibres, but are a complex mixture of fibres positioned randomly in space. Test fIlters carefully manufactured from well characterized glass fibre components were used to challenge monosize sodium chloride aerosols. Since most of the filtration parameters are known, our model was used and directly compared with the leading theoretical models and our experimental results. The enhancement of fibrous filters by gradual clogging was investigated. The filtration characteristics; pressure drop and upstream & downstream concentrations were monitored as loading progressed. A discussion of the changes in the quality factor which was found to be dependent upon aerosol size is given. The fractal dimension of the particle deposits on individual fibres was measured and found to be dependent on the fIltration dynamics present. The fundamental forces of electrostatic filtration (Coulomb, image and polarization forces) were clearly demonstrated in a system of test aerosols and fibrous fIlters which were identical except for the amount of charges the particles and fibres contained. The size ranges in which these forces are effective were accurately measured.

This thesis contains the results and discussion of an exploratory investigation into the application of Crossflow Microfiltration (CFMF) for solid/liquid separation in biological wastewater treatment systems. The principal objective of the study was to assess the influence of CFMF on the performance of identified biological wastewater treatment systems. It was not the objective to optimise filtration performance. A literature review indicated that the crossflow mode of filtration has been widely accepted as a unit operation in the fermentation industry. The filtration mode is now being applied not only for solid/liquid separation but also for separations on a molecular and ionic level. Very few applications of crossflow filtration in the context of biological wastewater treatment solid/liquid separation are reported in the literature. The reasons for this limited experience would appear to be the scale involved and the perceived high costs; separations in the fermentation industry are usually conducted at relatively small scale (laboratory or pilot-scale) and involve high-value products, justifying high capital and operating costs. Also, the high level of separation performance attained is perhaps not necessary for many wastewater treatment applications. No doubt these reservations are largely valid. However, these arguments cannot be applied equally to all filtration methods and wastewater treatment schemes. For example, the costs of microfiltration are substantially less than ultrafiltration or reverse osmosis, and in certain cases effluents with extremely low suspended solids contents may be required. In the light of these observations an investigation of CFMF for solid/liquid separation in biological wastewater treatment systems appears justified. Two biological treatment systems were selected for study: the Upflow Anaerobic Sludge Bed (UASB) reactor and the Activated Sludge system. The envisaged benefits accruing from the application of CFMF were different in each case.

Cette étude s'est concentrée sur la performance d'un filtre antimicrobien en fibres de polypropylène contenant de la pyrithione de zinc (PP/ZPT) au laboratoire et comparée à celle d'un filtre similaire (PP) avec la même classification F7 (EN779:2002). La performance de filtration à l'échelle du laboratoire des 2 filtres testés pendant le colmatage avec des particules PM10 a été quantifiée dans un dispositif expérimental avec mesure de la perte de charge du filtre et comptage des particules en amont et en aval des filtres. La croissance microbienne sur des filtres neufs et usagés, tous deux contaminés par aérosolisation avec un consortium microbien composé de deux bactéries (Staphylococcus epidermidis Gram positif, Serratia marcescens Gram négatif et spores fongiques (Penicillium chrysogenum). L'influence de trois paramètres sur la survie microbienne sur les filtres a été examinée : l'humidité relative de l'air, la présence ou l'absence de pyrithione de zinc (ZPT) en tant que substances antimicrobiennes et la présence de particules organiques. Des analyses quantitatives par unité formant colonies ont été utilisées pour déterminer la survie après 8 jours du consortium bactéries-champignons collecté par le filtre. Les deux filtres ont présenté des performances de filtration similaires en termes de variation de perte de charge et d'efficacité de collecte des particules pendant leur colmatage avec des particules PM10, ce qui signifie que le traitement antimicrobien n'a pas dégradé les performances de filtration du filtre. A faible valeur d'humidité de conditionnement (50% RH), avec des filtres neufs ou usagés, avec ou sans traitement antimicrobien, la population microbienne sur les filtres diminue et éventuellement ne survivra pas (Serratia). Lorsque l'humidité relative du conditionnement est élevée (90% RH), les bactéries ne se développent pas sur les filtres neufs, et seuls les champignons ont pu se développer. L'effet du traitement antimicrobien avec la pyrithione de zinc est confirmé pour les filtres neufs, en particulier en ce qui concerne les champignons Penicillium. Pour les filtres usagés, les résultats indiquent que le traitement antimicrobien n'est pas plus efficace avec une croissance significative du Penicillium, l'espèce endémique des particules de riz micronisées (PM10) collectées par les filtres ; les deux populations de bactéries diminuent significativement avec ou sans traitement antimicrobien.Dans une deuxième étape, les performances de filtration des 2 filtres testés précédemment ont été étudiées dans des conditions réalistes avec un air extérieur semi-urbain sur une période de 7 mois. Le comportement des microorganismes extérieurs sur les filtres (croissance/mortalité) a été observé. Deux unités de filtration fonctionnaient à IMT Atlantique, l'une contenant le filtre PP/ZPT et l'autre le filtre PP. Chaque unité filtrait le même air semi-urbain. Les deux unités de filtration ont fonctionné en continu et plusieurs paramètres ont été surveillés tout au long de la période d'exploitation : température, humidité relative, chute de pression du filtre, efficacité de collecte des particules du filtre, concentration massique des particules à l'entrée et concentrations microbiennes ; en outre, la concentration microbienne sur les filtres a été quantifiée 3 fois (tous les 2 mois) à partir d'une méthodologie innovante basée sur des coupons de média. Les performances de filtration des deux filtres testés en termes de changement de perte de charges et d'efficacité de collecte de particules étaient différentes de celles obtenues à l'échelle du laboratoire. La méthodologie des coupons a permis d'étudier le comportement des micro-organismes tout au long de l'étude. L'effet antimicrobien de la pyrithione de zinc a été confirmé concernant l'inhibition des champignons sans influence du niveau d'encrassement du filtre (dépôt de masse de particules)
This study focused on the performance of a marketed antimicrobial polypropylene fibers filter containing zinc pyrithione (PP/ZPT) at the laboratory and compared to those of a similar filter (PP) with same classification F7 (EN779:2002). The filtration performance at laboratory scale of the 2 tested filters during clogging with PM10 particles was quantified in an experimental set-up with filter pressure drop measurement and particle counting up and downstream of the filters. The microbial growth onto new and used filters, both contaminated by aerosolization with a microbial consortium composed of two bacteria (Staphylococcus epidermidis Gram positive, Serratia marcescens Gram negative and fungal spores (Penicillium chrysogenum). The influence of three parameters on the microbial survival onto filters was examined: the air relative humidity, the presence or absence of Zinc pyrithione (ZPT) as antimicrobial substances and the presence of organic particles. Quantitative analyses by colony forming unit were used to determine the survival after 8 days of the bacteria–fungi consortium collected by the filter. The two filters revealed similar filtration performance in terms of change in pressure drop and particle collection efficiency during their clogging with PM10 particles, meaning that the antimicrobial treatment did not degrade the filtration performance of the filter. At low humidity value of conditioning (50% RH), with new or used filters, with or without antimicrobial treatment, the microbial population onto the filters decreases and possibly will not survive (Serratia). At high humidity value of conditioning (90% RH), the bacteria do not grow onto the new filters, and only the fungi was able to develop. The effect of the antimicrobial treatment with zinc pyrithione is confirmed for new filters in particular regarding the fungi Penicillium. For used filters, the results indicate that the antimicrobial treatment is no more efficient with a significant growth of the Penicillium, the endemic species of the micronized rice particles (PM10) collected by the filters; the two populations of bacteria significantly decrease with or without antimicrobial treatment. In a second step, the filtration performances of the 2 filters tested previously was investigated in realistic conditions with a semi-urban outdoor air over a 7 months period. The behavior of the outdoor microorganisms onto the filters (growth/mortality) was observed. Two filtration units were operating at IMT Atlantique location, one containing the PP/ZPT filter and the second the PP filter. Each unit filtered the same semi-urban air. Both filtration units operated continuously and several parameters were monitored throughout the operating period: temperature, relative humidity, filter pressure drop, filter particle collection efficiency, inlet particle mass concentration, and microbial concentrations; in addition, the microbial concentration onto the filters was quantified for 3 times (every 2 months) from an innovative methodology based on media coupons. The filtration performances of the two tested filters in terms of changes in pressure drop and particle collection efficiency were different than those obtained in the Laboratory scale. The methodology of coupons permitted to study the behavior of the microorganisms throughout the study. The antimicrobial effect of the zinc pyrithione was confirmed regarding the inhibition of the fungi cultivated on the DRBC agar with no influence of the level of clogging of the filter (mass of particles deposit)

L’obiettivo del lavoro svolto è quello di identificare una modalità economica ed applicabile per la pulizia e rigenerazione di filtri di profondità, in particolare nella filtrazione di solidi da correnti gassose. Si ha attualmente mancanza di un tale metodo, che consentirebbe di poter rigenerare il filtro senza che debba essere necessariamente sostituito. Il lavoro consiste in un approccio sperimentale che studia una singola fibra impolverata da particelle solide. Sono stati proposti dei modelli che descrivono le interazioni tra particella, fibra e liquido. Da questo è stato ricavato un criterio teorico per determinare la riuscita o meno della rimozione di una singola particella solida adesa ad una fibra posta verticalmente e sottoposta al passaggio di un film di liquido con un determinato spessore. L’apparato sperimentale predisposto permette il fissaggio della fibra, sulla quale vengono fatte scorrere le gocce del liquido di pulizia. Tali gocce sono osservate nella discesa con una fotocamera ad alta frequenza. L'appartato sperimentale ha permesso di variare i principali parametri sperimentali e di testare diverse combinazioni fibra-particelle. Il parametro chiave nella pulizia è stato individuato nella forza di adesione, dipendente dal liquido utilizzato per la pulizia. Dal punto di vista geometrico, la geometria più affine alla pulizia si è rivelata la geometria cilindrica di piccolo diametro a sfavore di una geometria planare. L’utilizzo di gocce di liquido più grandi e l’uso di un numero elevato di gocce permette di migliorare il livello di pulizia: entrambi i fattori possono restituire un vantaggio nella pulizia ma si contrappongono al costo materiale del liquido. Nel complesso, la metodologia di pulizia proposta si è rivelata promettente, con ampie possibilità di essere estesa a filtri industriali.

Thesis (M.S.)--West Virginia University, 2000.
Title from document title page. Document formatted into pages; contains ix, 87 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 69-73).

La fabrication de membranes nanofibreuses par un procédé d’électrospinning plus respectueux de l’environnement, ou plus « vert », est de nos jours un défi. L’électrospinning est un procédé qui permet, généralement à partir d’une solution de polymère, d’obtenir des membranes non-tissées dont le diamètre des fibres est compris entre 50 nm et quelques micromètres. Deux stratégies nouvelles ont été développées pour répondre à ce besoin croissant. La première consiste à fabriquer des membranes à partir de polymères bio- sourcés tandis que la deuxième vise à employer des solvants exclusivement aqueux. Cette deuxième stratégie permet de s’affranchir des vapeurs de solvants souvent toxiques utilisés au cours du procédé. Dans ce cadre, des membranes ont été fabriquées à partir de suspensions aqueuses de polymères non-hydrosolubles, d’une part, et à partir d’acide tannique, une molécule non-polymérique bio-sourcée en exploitant les interactions supramoléculaires. Ces stratégies plus « vertes » rendent moins dangereuse et moins couteuse l’utilisation d’émetteurs multi-jets et permettent, de ce fait, une meilleure industrialisation du procédé d’électrospinning. Les membranes développées ont été fabriquées pour des applications de microfiltration liquide. En effet, les membranes d’électrospinning peuvent allier des tailles de pores submicroniques à des porosités supérieures à 80% contrairement aux membranes de microfiltration commerciales (porosité < 40%). La fabrication de membranes de filtration par un procédé d’électrospinning multi-jet « vert » permet ainsi d’accroitre les débits de production et de filtration tout en respectant davantage l’environnement
The fabrication of nanofibrous mats by an environmentally friendly, or in other words by a “green”, electrospinning process is nowadays a challenge. Electrospinning is a process allowing the fabrication, generally from a polymer solution, of nonwoven mats composed of fibers having diameters ranging between 50 nm and a few micrometers. Two new strategies have been developed to answer such a growing need. The first one consists in electrospinning bio-sourced polymers while the second one is based on the electrospinning of aqueous solutions exclusively. This second strategy allows avoiding toxic vapors coming from the evaporation of toxic solvents often used during the process. In this context, mats were electrospun from solutions composed of aqueous suspensions of water insoluble polymers, on one hand, and composed of tannic acid, a non-polymeric bio-based molecule exploiting supramolecular interactions. These new environmentally friendly strategies turn the electrospinning process in a less dangerous and less expensive one, and, as a result, ease the use of multi-jet setups and enable a better industrialization of the electrospinning process. Membranes have been developed for liquid microfiltration applications. As a matter of fact, electrospinning membranes can combine submicron pore sizes with porosities greater than 80% unlike commercial microfiltration membranes (porosity < 40%). The fabrication of liquid filtration membranes by a multi-jet "green" electrospinning process, thus, makes it possible to increase the production rates of electrospinning mats and filtration rates while respecting the environment

This thesis focuses on the incorporation of carbon nanoparticles within continuous fibre reinforcements by liquid composite moulding processes, in order to provide enhanced electrical and delamination properties to the multiscale composites. The mechanisms controlling the flow and filtration of these nanoparticles during liquid composite moulding are studied, in order to develop a predictive 1-D model which allows design of the processing of these composite materials. Five different carbon nanoparticles at 0.25 wt% loading, three unmodified and one surface modified carbon nanotube systems and one carbon nanofibre system, were utilised to modify a commercial two-component epoxy resin utilised to impregnate carbon and glass reinforcements at high fibre volume fraction by resin transfer moulding. The dispersion of the nanofillers in the prepolymer was carried out by ultrasonication, high shear mixing or triple roll milling or a combination of the three. Electrical conductivity measurements of the carbon nanoparticle liquid suspensions during dispersion, alongside optical microscopy imaging and rheological analysis of these allowed the selection of the concentration of nanofiller and the appropriate dispersion technique for each nanoparticle system. The resin transfer moulding process required adaptation to incorporate the dispersion and modify degassing steps, especially when utilising unmodified carbon nanoparticles suspensions, due to their higher viscosity and tendency to be filtered. Nanoparticle filtration was identified by electrical conductivity measurements and microscopy of specimens cut at increasing distances from the inlet. Cake filtration was observed for some of the unmodified systems, whereas deep bed filtration occurred for the surface modified CNT material. Property graded composites were obtained due to filtration, where the average electrical conductivity of the carbon and glass composites produced increased by a factor of two or one order of magnitude respectively. The effect of filler on the delamination properties of the carbon fibre composites was tested under mode I. The results do not show a statistically significant improvement of delamination resistance with the presence of nanoparticles, although localised toughening mechanisms such as nanoparticle pull-out and crack bridging as well as inelastic deformation have been observed on fracture surfaces. Particle filtration and gradients in concentration resulted in non-linear flow behaviour. An 1-D analytical and a finite difference model, based on Darcy’s law accompanied by particle mass conservation and filtration kinetics were developed to describe the flow and filtration of carbon nanoparticle filled thermosets. The numerical model describes the non-linear problem by incorporating material property update laws, i.e. permeability, porosity and viscosity variations on concentration of retained and suspended particles with location and time. The finite difference model is consistent and converges to the analytical solution. The range of applicability of the analytical model is limited to lower filtration coefficients and shorter filling lengths, providing an approximate solution for through thickness infusion; whereas the numerical model presents a solution outside this range, i.e. in-plane filling processes. These models allow process design, with specified carbon nanoparticle concentration distributions achieved via modifying the nanofiller loading at the inlet as a function of time.

Master of Science
Department of Chemical Engineering
James H. Edgar
I am a current employee for a chemical company that makes complex inorganic color pigments for a variety of uses. Some of the applications require iron as a base for a black color variant; but several require a purity level that precludes iron. One such product that cannot have iron in it is a computer based application that requires absolute purity of only the copper-chrome based powder with no impurities. This color is a powder that is primarily composed of copper and chrome and has the distinct advantage that it has little-to-no magnetic susceptibility. This makes it ideal for mixing with a form of acrylic for coating circuit boards and other computer applications as a magnetic field could severely damage circuits. Unfortunately, the presence of impurities (particularly ferromagnetic iron) can increase the magnetic susceptibility of the powder. We are here to discuss the search for a system to filter out such impurities.

This thesis reports the investigation of liquid-to-gas and liquid-to-solid phase transitions of liquid hydrocarbon fuels and their ethanol blends, both in the bulk phase and as single droplets. The key point has been to develop an understanding of the fuels' macroscopic behavior by studying them at the molecular and at the single droplet level. A key work in this thesis is the investigation of different ratio ethanol/gasoline blends at the molecular level. At the macroscopic level, the vapor pressure, and hence the evaporation of the blends, is influenced by the strength of intermolecular interactions. Thus, information on the molecular interactions between ethanol and gasoline are inferred by using IR and excess IR spectroscopy. The spectroscopic data suggest that the hydrogen bonding between ethanol molecules is weakened upon gasoline addition, but the hydrogen bonds do not disappear. This can be explained by a formation of small ethanol clusters that interact via Van der Waals forces with the surrounding gasoline molecules. In addition, Raman spectroscopy is performed on the same blends, and the Raman spectra are compared with the IR ones. Two different approaches for data evaluation, with the scope of determining the ethanol content in the blends, are tested and compared: Firstly, the calibration of the intensity ratio of characteristic peaks as function of composition; secondly, a principal component regression (PCR). Both methods are found to have comparable uncertainty. For the evaluation of the Raman spectra, the PCR method yielded better accuracy than the intensity ratio approach. In addition, a detailed investigation of the influence of noise in the signal is presented. When the full IR spectra were evaluated by PCR, even high noise levels did not reduce the measurement accuracy significantly. Later, with the aim of studying the evaporation dynamics of fuel blends, at the single droplet level, electrodynamic balance (EDB) and optical tweezers are used to trap ethanol/gasoline droplets, containing different ethanol percentages. A longer lifetime is observed for droplets containing a greater fraction of ethanol. In order to explain the experimental evaporation trends obtained, a theoretical model is used to predict the evaporation rates of pure ethanol and pure gasoline droplets in dry nitrogen gas. Also a theoretical estimation of the saturation of the environment, with other aerosols, in the tweezers is carried out. Lastly, the liquid-to-solid phase transition of some long chain alkanes, commonly present in diesel or gasoline, is investigated both at the molecular and at the single droplet level. Firstly, by using Raman spectroscopy the solidification of these hydrocarbons in the bulk phase is observed. Distinctive features associating the solid even hydrocarbons to a triclinic structure and the odd ones to an orthorhombic structure can be observed in the spectra. Secondly, the liquid-to-solid phase transition of single hydrocarbons droplets is investigated. Freezing time and surface area resulted to be inversely proportional in dodecane droplets. This might suggest a surface freezing mechanism. Furthermore, differences in the scattering patterns, depending on the freezing mechanism, are pointed out. Droplets freezing homogeneously show a different scattering pattern with respect to droplets that froze heterogeneously.

Thin liquid films (TLFs) of water are ubiquitous in daily lives as well as in many industrial processes. They can be formed between two identical phases, as in colloid films between two macroscopic surfaces and foam films between two air bubbles; and between two dissimilar phases, as in wetting films. Stability of the colloids, foams, and wetting films is determined by the surface forces in the TLFs. Depending on the nature of the surfaces involved, the stabilities can be predicted using combinations of three different forces, i.e., the van der Waals, electrical double layer (EDL), and hydrophobic forces. The objective of the present work is to study the roles of these forces in determining the stabilities of the TLFs of water confined between i) an air bubble and a hydrophobic surface and ii) an oil drop and a hydrophobic surface, with particular interest in studying the role of the hydrophobic force. The first part of the study involves the measurement of the surface forces in the TLFs confined between bitumen drops and mineral surfaces. Deformation of bitumen drops has been monitored by interferometry while it approaches a flat surface. By analyzing the spatiotemporal film profiles, both the capillary and hydrodynamic forces have been calculated using the Young-Laplace equation and the Reynolds lubrication approximation, respectively, with the surface forces being determined by subtracting the latter from the former. The results are useful for better understanding the effects of electrolyte and pH on bitumen liberation and recovery by flotation and for developing a filtration model from first principles. The second part of the study involves the surface force measurement in wetting (flotation) films. Surface forces in the TLFs of water on silica surfaces have been measured using the force apparatus for deformable surfaces (FADS) using an air bubble as a force sensor. The measurements have been conducted in the presence of various cationic surfactants such as dodecylamine hydrochloride (DAH), and alkyltrimethylammonium chloride (CnTACl), electrolytes, and polymers. The results show that film stability and hence the kinetics of film thinning can be greatly improved by the control of bubble ζ-potentials, whose role in flotation has long been neglected in flotation studies. Force measurements have also been conducted in the TLFs of water confined between oil drops and hydrophobic surfaces. Stability of this type of film plays an important role in a process of using oil drops rather than air bubbles to collect hydrophobic particles from aqueous phase. The force measurements conducted in the present work show that hydrophobic forces are much stronger in water films formed between oil drops and hydrophobic surfaces than in water films formed between air bubbles and hydrophobic surfaces, which can be attributed to the differences in the Hamaker constants involved.
Doctor of Philosophy
When two macroscopic surfaces in water are brought to a close proximity, a thin liquid film (TLF) is formed in between, with its stability being determined by the surface forces present in the film. TLFs are ubiquitous in daily lives and play a decisive role in many industrial processes such as mineral flotation, food processing, oil extraction, heat transfer, etc. In the present work, the surface forces present in wetting films have been measured by approaching an air bubble (or an oil drop) slowly toward a flat surface while monitoring the curvature changes during film thinning by interferometry and calculating the capillary forces using the Young-Laplace equations. By analyzing the results in view of the Frumkin-Derjaguin isotherm and the extended DLVO theory, it was possible to determine the changes in the van der Waals, electrical double-layer (EDL), and hydrophobic forces during film thinning. The results show that both the EDL and the long-range component of the hydrophobic force control the kinetics of film thinning and rupture while the contact angle formation is controlled by the van der Waals force and the short-range hydrophobic force. It has been found also that n-alkane drops form substantially larger contact angles than air bubbles on a hydrophobic surface due to the fact that the van der Waals force is attractive in the drop-surface interactions while the same is repulsive in the bubble-surface interactions. These observations have a profound implication in flotation, that is, oil drops can recover hydrophobic particles from an aqueous phase better than air bubbles.

Doutoramento em Química
Water-soluble organic matter (WSOM) from atmospheric particles comprises a complex array of molecular structures that play an important role on the physic-chemical properties of atmospheric particles and, therefore, are linked to several global-relevant atmospheric processes which impact the climate and public health. Due to the large variety of sources and formation processes, adequate knowledge on WSOM composition and its effects on the properties of atmospheric aerosol are still limited. Therefore, this thesis aims at providing new insights on the molecular composition of WSOM from fine atmospheric aerosols typical of an urban area (Aveiro, Portugal). In a first step, adsorption phenomena of semivolatile organic compounds on quartz fibre filters employed in the collection of atmospheric aerosols were assessed. Afterwards, atmospheric aerosol samples were collected during fifteen months, on a weekly basis. A mass balance of aerosol samples was performed in order to set the relative contribution of elemental carbon, WSOM and water-insoluble organic matter to the aerosol mass collected at the urban area of Aveiro, with a special focus on the assessment of the influence of different meteorological conditions. In order to assess the chemical complexity of the WSOM from urban aerosols, their structural characteristics were studied by means of Fourier transform infrared infrared - Attenuated Total Reflectance (FTIR-ATR) and solid-state cross polarization with magic angle spinning 13C nuclear magnetic resonance (CPMAS 13C NMR) spectroscopies, as well as their elemental composition. The structural characterization of aerosol WSOM samples collected in the urban area highlighted a highly complex mixture of functional groups. It was concluded that aliphatic and aromatic structures, hydroxyl groups and carboxyl groups are characteristic to all samples. The semi-quantitative assessment of the CPMAS 13C NMR data showed different distributions of the various functional groups between the aerosol samples collected at different seasons. Moreover, the presence of signals typical of lignin-derived structures in both CPMAS 13C NMR and FTIR-ATR spectra of the WSOM samples from the colder seasons, highlights the major contribution of biomass burning processes in domestic fireplaces, during low temperature conditions, into the bulk chemical properties of WSOM from urban aerosols. A comprehensive two-dimensional liquid chromatography (LC x LC) method, on-line coupled to a diode array, fluorescence, and evaporative light scattering detectors, was employed for resolving the chemical heterogeneity of the aerosol WSOM samples and, simultaneously, to map the hydrophobicity versus the molecular weight distribution of the samples. The LC x LC method employed a mixed-mode hydrophilic interaction column operating under aqueous reversed phase mode in the first dimension, and a size-exclusion column in the second dimension, which was found to be useful for separating the aerosol WSOM samples into various fractions with distinct molecular weight and hydrophobic features. The estimative of the average molecular weight (Mw) distribution of the urban aerosol WSOM samples ranged from 48 to 942 Da and from 45 to 1241 Da in terms of UV absorption and fluorescence detection, respectively. Findings suggest that smaller Mw group fractions seem to be related to a more hydrophobic nature.
A matéria orgânica solúvel em água (MOSA) de aerossóis atmosféricos é composta por um conjunto complexo de estruturas moleculares que influenciam as propriedades físico-químicas das partículas atmosféricas e, por conseguinte, desempenham um importante papel em diversos processos atmosféricos globalmente relevantes, afectando o clima e a saúde pública. Devido a uma ampla variedade de fontes e processos de formação, é ainda escasso o conhecimento acerca da composição estrutural da MOSA e do respectivo efeito nas propriedades dos aerossóis atmosféricos. Assim, esta tese pretende fornecer novas perspetivas sobre a composição molecular da MOSA presente na fracção fina de partículas atmosféricas características de uma área urbana (Aveiro, Portugal). Para o efeito, numa primeira fase do trabalho, foi avaliada a ocorrência de eventuais fenómenos de adsorção de compostos orgânicos semi-voláteis nos filtros de fibra de quartzo utilizados na colheita das amostras de partículas atmosféricas. Posteriormente, e na mesma área urbana, foi efectuada a colheita de amostras de aerossóis atmosféricos, durante um período de 15 meses, numa base de amostragem semanal e em contínuo. Foram efectuados balanços mássicos que permitiram descrever a importância das fracções de carbono elementar, MOSA e matéria orgânica insolúvel em água, na massa total de aerossóis atmosféricos recolhidos na zona urbana de Aveiro, tendo-se dado especial relevo ao estudo dos efeitos de diferentes condições meteorológicas. Na tentativa de entender a complexidade da MOSA de aerossóis urbanos, foram efectuados estudos de caracterização estrutural com recurso às espectroscopias de infravermelho com transformadas de Fourier (FTIR) acoplada a um sistema de reflectância total atenuada (ATR, sigla inglesa de Attenuated Total Reflectance) (FTIR-ATR) e de ressonância magnética nuclear de 13C com polarização cruzada (CP, sigla inglesa de Cross Polarization) e rotação em torno do ângulo mágico (MAS, sigla inglesa de Magic Angle Spinning) (RMN CPMAS de 13C) de estado sólido, mas também através da avaliação da respectiva composição elementar. A caracterização estrutural da MOSA dos aerossóis recolhidos na zona urbana confirmou o carácter heterogéneo deste tipo de matéria orgânica, traduzido por uma multiplicidade de grupos funcionais. De um modo geral, foi possível concluir que as estruturas alifáticas, as estruturas aromáticas, os grupos hidroxilo e os grupos carboxilo constituem funcionalidades comuns às amostras estudadas. A avaliação semi-quantitativa dos dados de RMN CPMAS de 13C mostrou igualmente diferentes distribuições dos diversos grupos funcionais, entre as amostras de aerossóis colhidos em diferentes períodos sazonais. A presença de sinais típicos de estruturas derivadas de lignina nos espectros de RMN CPMAS de 13C e FTIR-ATR das amostras de MOSA típicas de estações sazonais mais frias sugere que as propriedades de MOSA de partículas atmosféricas são influenciadas pelos processos de queima da madeira para aquecimento doméstico. Complementarmente às técnicas espectroscópicas anteriormente referidas, foi também utilizada a técnica de cromatografia líquida bidimensional abrangente (LC x LC) acoplada aos detectors de fotodíodos, fluorescência e evaporativo com dispersão de luz, com o objectivo de resolver a heterogeneidade das amostras de MOSA e, simultaneamente, mapear a hidrofobicidade versus distribuição de tamanhos moleculares das amostras. A utilização de uma coluna de cromatografia de interacção hidrofílica operada sob condições de fase reversa na primeira dimensão e de uma coluna de cromatografia de exclusão por tamanhos na segunda dimensão, revelou-se muito útil para a separação das amostras de MOSA em frações com hidrofobicidades e tamanhos moleculares distintos. A distribuição de massa molar média (Mw) obtida neste estudo variou entre 48 e 942 Da e 45 a 1241 Da, em termos de detecção por UV e fluorescência, respectivamente. Os resultados obtidos sugerem ainda que as fracções com menor valor de Mw tendem a ter um carácter relativamente mais hidrofóbico.

A direct injection nebulizer was constructed in our laboratory and was evaluated as an interface between a liquid chromatography column and an inductively coupled plasma-atomic emission spectrometer (ICP-AES). Optimum operating conditions, detection limits, and reproducibility in water and in organic solvents were studied. The detection limits in water were similar to a commercially available device. The detection limits of elements in organic solvents were about ten times higher than those in water. The DIN-ICP system stave more uniform response towards different species of Phosphorus and osmium than did a Meinhard nebulizer-ICP system, even when great differences in volatilitN existed between the species. A Potential application to the speciation of cisplatin and its analogs was also investigated.
Department of Chemistry

The toxicology of aerosols in occupational settings is often performed through particle collection on a filter followed by reconstitution into cell culture media which can alter the biological effects. Current in vitro exposure systems require additional instruments to control temperature and humidity, making the system bulky and difficult to take to the field. The Portable In Vitro Exposure Cassette (PIVEC) was designed for personal monitoring, characterized using copper nanoparticles, tested with alveolar cells, and set-up for real-time monitoring. Three differently sized copper nanoparticles, 40-800 nm, were dispersed as a dry aerosol and measured gravimetrically and on a number concentration basis to determine the deposition efficiency of the PIVEC. A549 cells, a human alveolar adenocarcinoma epithelial line, were exposed to the aerosols and oxidative stress and cell viability were monitored post-exposure. The deposition efficiency ranged from 0.5% to 18% depending on method of analysis and size of particle. Oxidative stress increased within the first two hours post exposure, however there was no significant difference in cell viability at the four hour time point at deposited doses up to 1.63 mg/cm2. Validation of the PIVEC was done in the laboratory using diesel exhaust. Metal oxide fuel additives are used to reduce emissions; however, additives have been shown to increase emitted nanoparticles. The PIVEC was used to determine the potential cytotoxicity and oxidative activity changes in A549 cells after exposure to either model particles or exhaust generated with or without a commercial, nano-cerium oxide based additive. Acellular experiments suggest a correlation between the deposition and the type of fuel used for the newly designed PIVEC. Cellular results suggest a decrease in cytotoxicity and no statistically significant effect on reactive oxygen species generation with the use of the nano-cerium oxide additive. Rapid monitoring of oxidative stress was performed using an enzyme-based biosensor. The functionalized biosensor uses cytochrome c to measure reactive oxygen species through electrochemical detection during aerosol exposures. When compared to a traditional biological assay, the biosensor response was similar. The PIVEC is a unique device, designed to monitor aerosols using air-liquid interface in vitro techniques including a real-time monitor for oxidative stress.

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Universidade Federal de Sao Carlos
The monitoring of indoor air quality (QIA) is a subject that has been disseminated in the current research. The objectives of them are the development of common methodologies to identify possible pollution agents at different locations. However, there are few works that develop methodologies in an attempt to mitigate the effects of indoor air pollution. Based on this problem, this study aimed to evaluate the effectiveness of filters doped with silver nanoparticles in the elimination of bacteria and fungi (bioaerosols) present in particulate matter from indoor environments, since it is known that nanosized silver particles have pronounced bactericidal and fungicidal effect. To achieve these goals, fabrics considered common were initially acquired in malls and were evaluated in terms of their filtration properties (permeability, loss, collection efficiency). It was subsequently performed the synthesis of silver nanoparticles suspension followed by immersion in the suspension of the chosen fabric. After drying, they were used to collect air suspended particulate material in a bathroom of the Department of Chemical Engineering of the Federal University of São Carlos. From the results it was verified that the filters doped with silver nanoparticles were able to significantly eradicate microorganisms present in air suspended particulate material. The elimination of microorganisms ranged from 22 to 82% for the mesh PV and 71 to 100% for the cotton fabric.
O monitoramento da qualidade de ar interno (QAI) é um assunto que vem se difundindo nas pesquisas atuais. Os objetivos destas pesquisas comumente são o desenvolvimento de metodologias para identificar possíveis fontes de poluição em diferentes locais. Entretanto, poucos são os estudos que abordam o desenvolvimento de metodologias que tentam amenizar os efeitos da poluição em ambientes fechados. Com base nesta problemática, este trabalho teve como objetivo avaliar a eficácia de filtros impregnados com nanopartículas de prata na eliminação de bactérias e fungos (bioaerossóis) presentes no material particulado de ambientes internos, uma vez que se sabe que partículas nanométricas de prata possuem pronunciado efeito bactericida e fungicida. Para alcançar este objetivo foram adquiridos em centros comerciais tecidos considerados comuns e estes foram avaliados em termos de suas propriedades de filtração (permeabilidade, perda de carga, eficiência de coleta), e posteriormente foram realizadas as sínteses de nanopartículas de prata seguidas da imersão em suspensão de nanopartícula dos filtros escolhidos. Após a secagem dos mesmos foi realizada a coleta do material particulado a qual foi feita em um banheiro do Departamento de Engenharia Química da Universidade Federal de São Carlos. Através dos resultados foi possível verificar que os filtros impregnados com nanopartículas de prata foram capazes de erradicar micro-organismos presentes no material particulado de forma significativa. A eliminação dos micro-organismos variou de 22 a 82% para o tecido malha PV e de 71 a 100% para o tecido algodão.

Afin de permettre la mise en place d’une filière de valorisation du CO2 issu de l’industrie sidérurgique, cette étude a pour but de proposer un nouveau procédé de dépoussiérage des fumées de hauts fourneaux qui serait placé à la suite des filières actuelles de traitement pour améliorer leur épuration. L’originalité de la technologie retenue, un lit granulaire arrosé, permet de maintenir la perte de charge constante en facilitant le réentraînement en continu des particules collectées à l’aide d’un écoulement de liquide (formant un film à la surface des collecteurs) pour ainsi pallier le problème de colmatage. Une étude hydrodynamique et des mesures d’efficacité vis-à-vis de particules de diamètre compris entre 0,5 et 10 µm ont montré que la perte de charge et l’efficacité initiale augmentaient avec la diminution du diamètre des collecteurs, ce qui est en accord avec les résultats de la littérature pour des lits granulaires secs. La présence d’un filet d’eau augmente l’efficacité initiale de collecte au détriment toutefois d’une perte de charge plus élevée. Ces observations sont liées à la diminution de la porosité du lit lorsque ce dernier est arrosé par un débit d’eau. Un bon compromis entre perte de charge et efficacité a été trouvé avec un lit composé de 50 cm de billes de 5 mm de diamètre et un débit d’eau de 12 L.min-1 pour un débit de gaz à traiter de 20 m3.h-1. Des essais de colmatage longue durée ont mis en évidence que l’efficacité du lit reste globalement constante au cours du temps, à une valeur proche de la valeur initiale. La perte de charge, bien que supérieure en début d’expérience à celle d’un lit granulaire sec, se stabilise rapidement à une valeur bien plus faible que celle mesurée pour un lit sec pour une même masse de particules collectées. Les expériences ayant été menées sur 30 h dans des conditions défavorables, nous pouvons nous attendre à ce que dans des conditions réelles de fonctionnement la perte de charge soit stable sur des temps beaucoup plus longs. Ainsi la présence de l’eau remplit bien le rôle prévu en limitant l’évolution du colmatage du lit granulaire par le réentrainement des particules collectées par le lit. Cette étude s’est achevée par le développement d’un modèle permettant de déterminer la perte de charge et l’efficacité initiale d’un lit granulaire arrosé, ce qui a abouti sur un exemple de pré-dimensionnement à échelle industrielle
In order to enable the establishment of a CO2 recovery chain sector from the steel industry, this study aims to propose a new filtration device for the dust removal of blast furnace fumes that would be placed after the current treatment chain to improve their purification. The originality of the chosen technology, a trickle bed, permits to maintain a constant pressure drop by re-entraining continuously the particles trapped on collectors thanks to a water film flow to overcome the clogging problem. A hydrodynamic study and efficiency measurements lead with particles (in a range of diameters between 0.5 and 10 μm) showed that the pressure drop and the initial efficiency increase with the decrease of the collector diameter, which is in agreement with the results of the literature for dry granular beds. The presence of water increases the initial collection efficiency at the expense of a higher pressure drop. These observations are related to the decrease of the bed porosity in presence of a water flow. A good compromise between pressure drop and efficiency was found for an air flow rate of 20 m3.h-1, a liquid flow rate of 12 L.min-1 and using a 50 cm bed composed of glass beads of 5 mm diameter. Long-term clogging tests showed that the efficiency of the bed remains globally constant over time at a value close to the initial one. The pressure drop, although higher at the beginning of the experiment than that of a dry granular bed, stabilizes rapidly at a much lower value than that measured for a dry granular bed for the same mass of particles collected. The experiments have been carried out over 30 h under disadvantageous conditions, and we can expect that under real operating conditions the pressure drop will be stable over much longer times. Thus, the presence of water plays its part by limiting the clogging evolution of the granular bed by the re-entrainment of particles collected by the bed. This study was completed by the development of a model to determine the pressure drop and initial efficiency of a trickle bed, which resulted in an example of pre-sizing of a process on an industrial scale

Processes at the air-water/ice interface are known to play a very important role in the release of reactive halogen species with atmospheric aerosols serving as catalysts. The ability to make different types of ice with various morphologies, hence, different adsorption and surface properties in vacuum, provide a useful way to probe the catalytic effect of ice in atmospheric reactions. Also, the use of the liquid jet technique provides the rare opportunity to probe liquid samples at the interface; hitherto impossible to investigate with traditional surface science techniques. Studies of reactions on both ice and liquid surfaces at ambient conditions are usually complicated by the rapid desorption and adsorption processes due to the high evaporation rates at the surface. To gain a better understanding and improve modeling of several atmospheric relevant reactions, it is therefore important to develop laboratory techniques that provide an opportunity to investigate non-thermal reactions on both ice and liquid surfaces. Detailed investigation of the interactions of atmospheric relevant molecules (methyl iodide and hydrogen chloride) on water ice at low temperature in UHV conditions has been carried out. These interactions were studied using different techniques such as temperature programmed desorption (TPD), electron stimulated desorption (ESD) and resonance enhanced multiphoton ionization (REMPI). Unlike probing reactions on ice surfaces, investigating air/liquid interfaces present several challenges. This is because traditional surface science techniques require an ultra high vacuum environment to prevent distortion of information due to interference from equilibrium vapor above the liquid surface during data acquisition. The liquid jet technique facilitates the direct study of continually renewed liquid surfaces in high vacuum, thereby preventing the constant changing of the properties and composition of the liquid surface due to the aging process (diffusion of impurities or liquid constituent). A linear time-of-flight mass spectrometer has been used to monitor ion ejection during laser irradiation of liquid jet containing aqueous solutions and pure water. Since these ions are ejected exclusively from the surface of the liquid and the cluster distributions observed are influenced by the local structure, these experiments provide a sensitive probe of the liquid vacuum interface of these solutions. Though the research is fundamental, the results obtained from these investigations indicate how the discontinuity of bulk properties on the surface of both ice and aqueous solutions affects interfacial reactions.

A direct injection nebulizer (DIN) was constructed in our laboratory and was evaluated as an interface between a liquid chromatography column and an inductively coupled plasma-atomic emission spectrometer (ICP-AES). Optimum operating conditions, detection limits and reproducibility of the DIN closely matched literature data for a somewhat different commercial device. In addition, when using the DIN for sample introduction, the ICP detection exhibited uniform response towards phosphorous compounds of different volatilities.
Department of Chemistry

ENGLISH ABSTRACT: Leaching of nickel laterite was conducted with a solution of ammonia and ammonium carbonate in a closed vessel. The vessel used in this study was designed to leach and perform solid-liquid separation at the same time. For solid-liquid separation, stainless steel sintered metal filter media were used. The sintered metal filter medium was selected for its high strength to withstand pressure, chemical resistance to caustic solution and back flushing properties. Optimum leaching conditions were determined by varying temperature, ammonia concentration, ammonium carbonate concentration and oxygen pressure. After leaching and filtration, the pH of the leach liquor was measured and samples were analyzed for dissolved metals (Ni, Fe and Co) using atomic absorption spectrophotometry. The most significant variable effect on leaching of nickel was the ammonia concentration. The maximum dissolution of nickel from the unroasted ore was 11.90% at 4 M NH3, 100oC, 2 M (NH4)2CO3 and 2 bar O2 pressure. Optimization from the leaching data was done using response profiling and desirability in Statistica software. Optimum leaching conditions were determined to be 3 M NH3, 2 M (NH4)2CO2, 100oC and 2 bar O2 pressure. The mineralogy of the ore before and after leaching was studied to understand why nickel extraction from unroasted ore was poor. XRF analysis of solids after leaching showed that iron, silicon, and magnesium remained the same. The only metal which showed significant decrease from solids was nickel. XRD analysis of solids after and before leaching showed that most mineral phases present in the ore are not affected by the leaching solution. SEM with EDS detection was used to determine nickel distribution within the ore. The results showed that nickel is mostly associated with iron. The iron is surrounded by magnesium and silicon. Silicate minerals do not react with ammonia and ammonium carbonate solution. From filtration experiments, the filtration differential pressure had no significant effect on the filtration rate. An average filtration rate of 0.29±0.07 ml/min.cm2 was obtained. The filtration rate from these experiments was very low. The main reason was due to quick pore clogging of sintered metals. Pore clogging was found to be mainly on the surface of the filter medium. Laterites have been found to have low permeability due a lot of clay present in the ore. Rheological studies on this ore showed that the ore has shear thickening behavior. However, a very clear filtrate was obtained. After each leach and filtration experiment, the sintered metals was unblocked by back flushing with water and air. Back flushing was successful because all 18 experiments were carried out using the same sintered filter medium. The effect of roasting the ore prior to leaching was investigated using optimum conditions obtained when leaching the unroasted ore. There was a slight improvement in nickel extraction when the ore was roasted. The average percentage extraction of nickel from 3 experimental runs was 19.25%±0.19 at 100oC, 3M NH3, 2M (NH4)2CO3, and 5 bar oxygen pressure. Some part of nickel in the ore was unextractable due to association of nickel with recrystallized silicate minerals in the reduced ore. Roasting improved permeability of the ore. The filtration rate improved significantly after roasting the ore. The average filtration rate was 2.60±0.05 ml/min.cm2. Dissolution kinetics of the unroasted and roasted saprolitic laterite were investigated with regard to the effects of temperature, ammonia concentration, ammonium carbonate concentration, and oxygen pressure. For the unroasted ore, it was found that dissolution rate and degree of nickel extraction increases with increasing temperature. Increase in ammonia concentration improves the degree of nickel extraction. Nevertheless, nickel extraction does not depend entirely on ammonia concentration because even when ammonia concentration is high and ammonium carbonate concentration is zero nickel extraction is low. An increase in ammonium carbonate concentration also increases the degree of nickel extraction. Ammonium carbonate is critical for the extraction, since ammonium ions in the solution prevent hydrolysis of the nickel ammine complex. Oxygen did not have a significant effect on the degree of nickel extraction. The leaching of nickel laterite was found to be a two stage leaching process. In the first stage, the dissolution of nickel is faster but after 15 minutes, the reaction rate is reduced. The reaction rate is reduced by inert minerals which host nickel. These minerals contain iron magnesium and silicon. The fast dissolution of nickel in the first stage represents leaching of free nickel in the ore. The data for the second stage of leaching was analyzed by the shrinking core model, and the results suggested that the dissolution rate is controlled by mixture kinetics (ash layer diffusion and surface reaction control). The activation energy for the dissolution reaction was calculated as 56.5 KJ/mol. The reaction order with respect to ammonia and ammonium carbonate were determined to be 0.3 and 0.26 respectively. For the roasted ore, the highest degree of nickel extraction was obtained at 60oC, 3M NH3, 2M (NH4)2CO3, and 5 bar oxygen pressure. The percentage extraction under these conditions was 28.7%. Temperature did not have a significant effect on the leaching rate. An increase in NH3 and (NH4)2CO3 increased the final extraction of nickel but did not have any effect on leaching rate in the first stage of leaching. In the absence of ammonium carbonate, nickel extraction is almost zero. The experimental data did not give linear fit to the shrinking core models investigated for the unroasted ore. The reason for this could be due to the sampling time interval which was too far apart, or the leaching behavior of roasted nickel is complicated and cannot explained by shrinking core model alone. Leaching experiments demonstrate that for a high degree metal extraction and improved reaction kinetics with ammonia and ammonium carbonate, the solution temperature should be high (>100oC) for the unroasted ore. In order to leach at high temperature with ammonia and ammonium carbonate a closed vessel is required to prevent reagent loses. The reaction kinetics showed that the reaction is controlled mostly by ash layer diffusion; this indicates that a low degree of nickel extraction in the unroasted saprolitic laterite is due to inert minerals (ash layer) which host nickel within the ore. In order to obtain a high degree of nickel extraction, the ore needs to be roasted under reducing conditions. Roasting conditions need to be carefully controlled to ensure high dissolution of nickel. In fact optimum roasting conditions which will give maximum dissolution of nickel, must be determined before working with the bulk of the ore.
AFRIKAANSE OPSOMMING: Logingstoetse van saprolitiese lateriet met 'n oplossing van ammonia en ammonium karbonaat is gedoen in 'n druk houer. Die logingsvat vir hierdie studie is ontwikkel om die loging sowel as die vloeistof – vastestof skeiding te doen. Gesinterde metaal filter medium was gebruik vir die vloeistof – vastestof skeiding aangesien dit die volgende eienskappe vertoon; die vermoë om druk te weerstaan, die chemiese weerstand teen bytsoda oplossing, asook voordelige terugspoel eienskappe. Optimum loogkondisies is bepaal deur die temperatuur, ammoniak konsentrasie, ammonium karbonaat konsentrasie, en suurstof druk te varieer. Na loging en filtrasie is die pH van die loogvloeistof gemeet en monsters is deur atoom absorpsie spektrofotometrie geanaliseer vir opgeloste metale (Ni, Fe en Co). Die veranderlike wat die grootste effek op die loging van nikkel gehad het was die ammoniak konsentrasie. Die maksimum herwinning van nikkel van uit ongeroosterde erts was 11.9 % by 4 M NH3, 100 oC, 2 M (NH4)2CO3 en 2 bar O2 druk. Optimisering van die loogdata is gedoen deur die respons profiel te analiseer met Statistica sagteware. Optimum loogkondisies was bepaal as 3 M NH3, 2 M (NH4)2CO2, 100 oC en 2 bar O2 druk. Die mineralogie van die erts voor en na loging is bestudeer om te bepaal waarom die nikel opbrengs van ongeroosterde erts so laag was. XRF analise van die vastestof na loging het gewys dat yster, silikon en magnesium nie deur loging affekteer is nie. Slegs nikkel het 'n merkwaardige afname getoon. XRD analsiese van die vastestof voor en na loging wys dat die meeste mineraal fases teenwoordig in die erts nie deur die loogoplossing affekteer is nie. SEM met EDS deteksie is gebruik om die nikkel verspreiding in die erts te bepaal. Die resultate wys dat nikkel meestal met yster assosieer. Die yster is omring deur magnesium en silikon. Silikaat minerale reageer nie met ammoniak en ammonium karbonaat oplossing nie. In filtrasie eksperimente is daar gevind dat die filtrasie differensiële druk geen noemenswaardige effek op die filtrasie tempo gehad het nie. Die gemiddelde filtrasietempo was 0.29+0.07 ml/min.cm2. Die filtrasie tempo van hierdie eksperimente was baie laag, hoofsaaklik as gevolg van blokkasie van porieë van die sinter metaal filter medium. Dit is gevind dat blokkasie van porieë hoofsaaklik op die oppervlak van die filter medium plaasvind. Lateriedes toon 'n lae deurlaatbaarheid as gevolg van die erts se hoë klei inhoud. Rheologiese studies op hierdie erts wys dat die erts skuif verdikking (“shear thickening”) gedrag vertoon. 'n Baie helder filtraat is egter verkry. Die gesinterde metale is na elke loog en filtrasie eksperiment skoongemaak deur terugspoeling met water en lug. Hierdie procedure was suksesvol, aangesien al 18 eksperimente met dieselfde filter medium uitgevoer is. Die effek van erts roostering voor loging is ondersoek by die optimum kondisies wat verkry was vir die loging van ongeroosterde erts. Nikkel ekstraksie het effens verbeter met geroosterde erts. Die gemiddelde persentasie ekstraksie van nikkel van drie eksperimentele lopies was 19.25 % + 0.19 by 100 oC, 3 M NH3, 2 M (NH4)2CO3, en 5 bar suurstofdruk. 'n Gedeelte van die nikkel in die erts was onherwinbaar as gevolg van die assosiasie van nikkel met her-gekristaliseerde sillikaat-minerale in die gereduseerde erts. Die porositeit van die erts is verbeter deur dit te rooster. Die filtrasie tempo het merkwaardig verbeter nadat die erts gerooster is. Die gemiddelde filtrasie tempo was 2.6+0.05 ml/min.cm2. Kinetika vir die oplossing van ongeroosterde en geroosterde saprolitiese lateriet is ondersoek, met in ag geneem die effekte van temperatuur, ammonia konsentrasie, ammonium karbonaat konsentrasie en suurstofdruk. Vir ongeroosterde erts is gevind dat die oplossingstempo en graad van nikkel ekstraksie toeneem met toenemende temperatuur. Toename in ammoniak konsentrasie lei tot 'n toename in nikkel ekstraksie, maar nikkel ekstraksie is nie alleenlik afhanklik van ammoniak nie. 'n Toename in ammonium karbonaat konsentrasie lei ook tot 'n toename in nikkel ekstraksie. Ammonium karbonaat is krities vir die ekstraksie, aangesien ammonium ione in die oplossing die hidrolise van die nikkel-amien kompleks verhoed. Suurstof het nie 'n merkwaardige effek op die totale nikkel ekstraksie gehad nie. Vir die bepaling van reaksie kinetika is 100˚C gebruik as die logingstemperatuur. Die loging van saprolitiese nikkel lateriet vind in twee stadia plaas. In die eerste fase is die oplossing van nikkel vinnig, maar na 15 minute neem die reaksietempo af. Die reaksietempo word verlaag deur inerte minerale wat teenwoordig is in die nikkel erts. Hierdie minerale bevat yster, magnesium en silikon. Die vinnige oplossing van nikkel in die eerste fase verteenwoordig die loging van vry nikkel in die erts. Die data vir die tweede stadium is geanaliseer deur die krimpende kern model, en die resultate dui aan dat die oplossingstempo deur 'n gemengde meganisme beheer word (as laag diffusie en oppervlak reaksie beheer). Die aktiveringsengergie vir die oplossingsreaksie was bereken as 56.5 kJ/mol. Die reaksieorde ten opsigte van ammoniak en ammonium karbonaat is onderskeidelik bepaal as 0.3 en 0.26. Die hoogste graad van nikkel ekstraksie vir die geroosterde erts is verkry by 60oC, 3 M NH3, 2 M (NH4)2CO3, en 5 bar O2 druk. Die persentasie ekstraksie by hierdie kondisies was 28.7 %. Temperatuur het nie 'n merkwaardige effek op loogtempo gehad nie. 'n Toename in NH3 en (NH4)2CO3 het die graad van nikkel ekstraksie laat toeneem, maar het nie enige effek op die loogtempo gehad nie. In die afwesigheid van ammonium karbonaat het byna geen nikkel ekstraksie plaasgevind nie. Die eksperimentele data het nie 'n lineêre passing vir die krimpende kern model soos vir die ongeroosterde erts ondersoek gegee nie. Die rede hiervoor is dat die monsternemings interval te groot was, of dat die logings karakteristiek van geroosterde nikel gekompliseerd is en nie alleen deur die krimpende kern model voorspel kan word nie. Logings eksperimente wys dat die temperatuur hoog moet wees (> 100 oC) om 'n hoë graad van nikkel ekstraksie te verkry met die ongeroosterde erts. 'n Geslote reaktor word benodig om by 'n hoë temperatuur met ammoniak en ammonium karbonaat te loog om reagens verliese te verhoed. Die reaksie kinetika word grootliks deur aslaag diffusie beheer. Hieruit kan gesien word dat 'n lae graad van nikkel ekstraksie uit die ongeroosterde saprolitiese lateriet die gevolg is van nie-reaktiewe minerale (aslaag) waarin die nikkel binne die erts bevat word. Om 'n hoë graad van nikkel ekstraksie te verkry moet die erts onder reduserende kondisies gerooster word. Rooster kondisies moet versigtig beheer word om hoë oplossing van nikkel te verseker. Optimum rooster kondisies om maksimum nikkel oplossing te verkry, moet bepaal word voordat daar met groter hoeveelhede erts gewerk kan word.

[ES] En la presente tesis doctoral se ha evaluado el uso de nuevos soportes celulósicos y silíceos como sistemas de filtración para la estabilización y conservación de alimentos líquidos con el fin de afrontar dos grandes retos de la industria de bebidas. Por un lado, evitar o minimizar los cambios en las propiedades nutricionales, estructurales y organolépticas de los alimentos, ocasionados por la pasteurización térmica tradicional, y ofrecer una alternativa al problema de la baja viabilidad debida a los altos costos de inversión/producción al aplicar nuevas tecnologías no térmicas. Por ello, esta tesis doctoral se centra en el desarrollo y evaluación de una nueva tecnología no térmica de conservación de alimentos líquidos basada en la filtración. Se han desarrollado sistemas de filtración a partir de soportes celulósicos y silíceos, sin funcionalizar o funcionalizados con compuestos antimicrobianos. En el primer capítulo se evaluó el uso de materiales de celulosa como soportes filtrantes para el tratamiento de alimentos líquidos. Como primera aproximación se desarrolló un material poroso nano-micro tubular a partir de la extracción y deslignificación del material celulósico presente en el corazón o raquis de la mazorca de maíz. El uso de este soporte resultó ser efectivo como material filtrante para el tratamiento de agua y zumo de naranja, en un sistema de flujo continuo, eliminando la carga microbiana. La aplicación de este soporte como sistema de filtración presenta diversas ventajas como su capacidad de retención microbiana, la reutilización de sub-productos del maíz y, por tanto, su respeto al medioambiente. Sin embargo, sería necesario optimizar el proceso de filtrado para evitar la frecuente obturación de sus poros que requirió varios ciclos de lavado durante el proceso, así como establecer un método de regeneración del material para incrementar su vida útil. Además, este sistema afectó al color del zumo filtrado, que no se mantuvo constante durante el proceso, lo que supone una importante desventaja que es necesaria abordar. Como segunda aproximación, se evaluó el potencial de la inmovilización de una molécula bioactiva sobre membranas de celulosa, para mejorar la capacidad de retención microbiana del material celulósico, así como permitir su reutilización. Los filtros de celulosa funcionalizados con poliaminas demostraron ser eficaces en la eliminación de patógenos en agua, debido a las cargas positivas generadas por los grupos amina inmovilizados en la superficie de las membranas, que atraen y retienen las bacterias cargadas negativamente. Dada la fácil preparación y procedimiento de uso de las membranas de celulosa funcionalizadas con poliaminas, éstas podrían ser consideradas una buena opción para el desarrollo de sistemas de tratamiento de aguas in situ, rápidos, de fácil manejo y de bajo coste. El segundo capítulo describe el desarrollo y aplicación de partículas de sílice funcionalizadas con compuestos de aceites esenciales, con el fin de diseñar coadyuvantes de filtración con actividad antimicrobiana. La filtración de diversas matrices alimentarias (agua, cerveza y zumo de manzana) a través de los soportes funcionalizados con los antimicrobianos naturales demostró ser eficaz en la reducción del recuento de la cepa patógena Escherichia coli, así como frente a la microflora endógena de la cerveza y el zumo (bacterias acidolácticas, aerobios mesófilos, psicrófilos, mohos y levaduras). La eficacia en el control microbiano se debe a la combinación de la adsorción física y la inactivación por contacto con los compuestos de aceites esenciales inmovilizados. Además, la evaluación de las propiedades físico-químicas y sensoriales de los alimentos líquidos demostró un efecto poco significativo, éste depende del tamaño de las partículas de sílice usadas y de la molécula bioactiva inmovilizada. Por lo tanto, el sistema de conservaci�
[CAT] En la present tesi doctoral s'ha avaluat l'ús de nous suports cel·lulòsics i silicis com a sistemes de filtració per a l'estabilització i conservació d'aliments líquids, amb la finalitat d'afrontar dos grans reptes de la indústria de begudes. D'una banda, evitar o minimitzar els canvis en les propietats nutricionals, estructurals i organolèptiques dels aliments, ocasionats per la pasteurització tèrmica tradicional, i oferir una alternativa al problema de la baixa viabilitat deguda als alts costos d'inversió/producció en aplicar noves tecnologies no tèrmiques. Per això, aquesta tesi doctoral es centra en el desenvolupament i avaluació d'una nova tecnologia no tèrmica de conservació d'aliments líquids basada en la filtració. S'han desenvolupat sistemes de filtració a partir de suports cel·lulòsics i silicis, sense funcionalitzar o funcionalitzats amb compostos antimicrobians. En el primer capítol es va avaluar l'ús de materials de cel·lulosa com a suports filtrants per al tractament d'aliments líquids. Com a primera aproximació es va desenvolupar un material porós nano-micro tubular a partir de l'extracció i deslignificació del material cel·lulòsic present en el cor o raquis de la panolla de dacsa. L'ús d'aquest suport va resultar ser efectiu com a material filtrant per al tractament d'aigua i suc de taronja, en un sistema de flux continu, eliminant la càrrega microbiana. L'aplicació d'aquest suport com a sistema de filtració presenta diversos avantatges com la seua capacitat de retenció microbiana, la reutilització de subproductes de la dacsa i, per tant, el seu respecte al medi ambient. No obstant això, seria necessari optimitzar el procés de filtrat per a evitar la freqüent obturació dels seus porus que va requerir diversos cicles de rentada durant el procés, així com establir un mètode de regeneració del material per a incrementar la seua vida útil. A més, aquest sistema va afectar el color del suc filtrat, que no es va mantenir constant durant el procés, la qual cosa suposa un important desavantatge que és necessari abordar. Com a segona aproximació, es va avaluar el potencial de la immobilització d'una molècula bioactiva sobre membranes de cel·lulosa, per a millorar la capacitat de retenció microbiana del material cel·lulòsic, així com permetre la seua reutilització. Els filtres de cel·lulosa funcionalitzats amb poliamines van demostrar ser eficaces en l'eliminació de patògens en aigua, a causa de les càrregues positives generades pels grups amina immobilitzats en la superfície de les membranes, que atrauen i retenen els bacteris carregats negativament. Donada la fàcil preparació i procediment d'ús de les membranes de cel·lulosa funcionalitzades amb poliamines, aquestes podrien ser considerades una bona opció per al desenvolupament de sistemes de tractament d'aigües in situ, ràpids, de fàcil maneig i de baix cost. El segon capítol descriu el desenvolupament i aplicació de partícules de sílice funcionalitzades amb compostos d'olis essencials, amb la finalitat de dissenyar coadjuvants de filtració amb activitat antimicrobiana. La filtració de diverses matrius alimentàries (aigua, cervesa i suc de poma) a través dels suports funcionalitzats amb els antimicrobians naturals va demostrar ser eficaç en la reducció del recompte del cep patogen Escherichia coli, així com enfront de la microflora endògena de la cervesa i el suc (bacteris àcid làctics, aerobis mesòfils, psicròfils, floridures i llevats). L'eficàcia en el control microbià es deu a la combinació de l'adsorció física i la inactivació per contacte amb els compostos d'olis essencials immobilitzats. A més, l'avaluació de les propietats fisicoquímiques i sensorials dels aliments líquids estudiats va demostrar un efecte poc significatiu, aquest depèn de la grandària de les partícules de sílice usades i de la molècula bioactiva immobilitzada. Per tant, el sistema de conserv
[EN] In the present doctoral thesis the use of new cellulosic and silica supports as filtering systems for the stabilization and preservation of liquid foods has been evaluated to overcome two major challenges of the beverage industry. On the one hand, avoid or minimize the changes in the nutritional, structural and organoleptic properties of food caused by traditional thermal pasteurization, and offer an alternative to the problem of low viability due to high investment/production costs when applying new non-thermal technologies. Therefore, this doctoral thesis focuses on the development and evaluation of a new non-thermal technology for the preservation of liquid foods based on filtration. The filtering systems have been developed from cellulosic and silica supports, non-modified or functionalized with antimicrobial compounds. In the first chapter, the use of cellulose materials as filtering supports for the treatment of liquid foods was evaluated. As first approximation, a porous nano-micro tubular material was developed from the extraction and delignification of the cellulosic material present in the corn stalk. The use of this support was effective as filtering material for the treatment of water and orange juice, in a continuous flow system, eliminating the microbial load. The application of this support as filtering system has several advantages, such as its microbial retention capacity, the reuse of corn by-products and, therefore, its respect for the environment. However, it would be necessary to optimize the filtering process to avoid the frequent clogging of its pores that required several washing cycles during the process, as well as to establish a method of material regeneration to increase its life. In addition, this system affected the color of the filtered juice, which did not remain constant during the process, representing an important disadvantage that must be addressed. As a second approach, the potential of the immobilization of a bioactive molecule on cellulose membranes was evaluated to improve the microbial retention capacity of the cellulosic material, as well as to allow its reuse. The cellulose filters functionalized with polyamines proved to be effective in eliminating pathogens in water, due to the positive charges generated by the amine groups immobilized on the surface of the membranes, which attract and retain the negatively charged bacteria. Given the easy preparation and usage of the polyamines-functionalized cellulose membranes, these could be considered a good option for the development of fast, easy to use and low cost in situ water treatment systems. The second chapter describes the development and application of silica particles functionalized with essential oil components to design filtering aids with antimicrobial activity. The filtration of various food matrices (water, beer and apple juice) through the supports functionalized with natural antimicrobials proved to be effective in reducing the load of the pathogenic strain Escherichia coli, as well as reducing the endogenous microflora of beer and the juice (lactic acid bacteria, mesophilic, psychrophilic, mold and yeast). The removal capability is due to the combination of physical adsorption and contact inactivation with the essential oil compounds immobilized. In addition, the evaluation of the physicochemical and sensory properties of the liquid foods studied showed a not significant effect, it depends on the size of the silica particles used and the immobilized bioactive molecule. Therefore, the proposed preservation system has a high potential for cold beverage pasteurization processes.
N. Peña-Gomez would like to thank for financial support in the frame of her PhD project to Operational Programme of the European Social Fund (ESF) 2014-2020, the Agencia Estatal de Investigación, Generalitat Valenciana and FEDER-EU (Projects RTI2018-101599-B-C21 and AGL2015-70235-C2-1-R). The authors also thank the Electronic Microscopy & Microanalysis Laboratory at Patras University for support.
Peña Gomez, N. (2020). Development of polymeric and silica filtering materials functionalized with antimicrobial compounds for the elimination of microorganisms in liquid food [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/137041
TESIS

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico
A biomassa lÃquida residual de processos agrÃcolas e agroindustriais em geral representa um recurso renovÃvel em quantidade expressiva sem uma destinaÃÃo econÃmica e ambientalmente sustentÃvel Como exemplo a soluÃÃo quanto aos estoques de glicerina resultante da transesterificaÃÃo de Ãleos vegetais para obtenÃÃo do biodiesel tem sido postergada pela carÃncia de alternativas de engenharia apropriadas ao aproveitamento adequado dessa biomassa Por essa razÃo foi iniciado o desenvolvimento de um reator de gaseificaÃÃo destinado à biomassa lÃquida pela via da oxidaÃÃo parcial onde à empregada uma tecnologia de combustÃo nÃo convencional a CombustÃo de FiltraÃÃo como base de projeto para a concepÃÃo do reator em que a biomassa de referÃncia utilizada foi o glicerol (C3H8O3) Este trabalho eminentemente experimental foi realizado com a construÃÃo de um protÃtipo de reator de gaseificaÃÃo em escala de laboratÃrio em que seu queimador à preenchido completamente por esferas cerÃmicas de alumina (Al2O3) formando assim uma matriz porosa inerte que fica parcialmente imersa no glicerol na sua extremidade inferior e que envolve um trocador de calor instalado na parte superior do reator O processo à investigado no sentido de identificar algumas caracterÃsticas fundamentais de projeto tais como: limite de operaÃÃo do reator em termos de misturas arcombustÃvel; presenÃa de fenÃmenos de instabilidade; velocidade de propagaÃÃo da onda de combustÃo; e influÃncia dos principais parÃmetros de operaÃÃo, razÃo de equivalÃncia taxa de consumo de combustÃvel e vazÃes de ar e Ãgua na reaÃÃo Embora toda a experimentaÃÃo tenha se restringido a ensaiar o gaseificador para produÃÃo de gÃs de sÃntese pelo mÃtodo da oxidaÃÃo parcial a investigaÃÃo teÃrica foi mais abrangente englobando a reforma autotÃrmica Os experimentos respaldados por instrumentos de monitoramento e anÃlise cromatogrÃfica foram apoiados por um estudo teÃrico a partir de um modelo analÃtico simplificado com base na reaÃÃo global de oxidaÃÃo parcial associada à reaÃÃo de deslocamento ÃguaâgÃs Resultados experimentais demonstraram a viabilidade do processo constatando estabilidade operacional em ampla faixa de razÃo de equivalÃncia e eficiÃncia de conversÃo (>20%) do glicerol em gÃs de sÃntese mantendo extraÃÃo de energia da reaÃÃo
The residual liquid biomass from agricultural and agroindustrial processes in general way represents a renewable resource in significant amount without an economically and environmentally sustainable destination For instance the solution concerning glycerin stocks remaining from the vegetable oil transesterification for obtaining biodiesel has been postponed due to the lack of engineering alternatives appropriate to the proper utilization of this biomass Therefore the development of a liquid biomass gasification reactor based on partial oxidation has been initiated where a non conventional combustion technology has been employed Filtration Combustion as a design basis for the reactor conception in which the reference biomass used was glycerol This work eminently experimental was carried out to build a gasification reactor prototype in laboratory scale in which its burner is completely filled by ceramic spheres of alumina (Al2O3) thus forming a inert porous matrix which is partially immersed in glycerol at its bottom end and which involves a heat exchanger installed at the top of the reactor The process is investigated to identify some key design features such as: reactor operation limit in terms of fuel-air mixtures; occurrence of instability phenomena; combustion wave propagation velocity; and influence of the main operation parameters equivalence ratio fuel consumption rate and air and water flow rates into the reaction Although all experimentation has been restricted to test the gasifier for the production of synthesis gas by partial oxidation method theoretical investigation was broader comprising the autothermal reforming The experiments supported by monitoring instruments and chromatographic analysis were supported by a theoretical study based on a simplified analytical model considering the global reaction of partial oxidation associated with water-gas shift reaction Experimental results have demonstrated the feasibility of the process providing operational stability over a wide range of equivalence ratio and conversion efficiency (>20%) of glycerol to syngas while maintaining energy extraction from reaction

This study is mainly focused on the investigation of which are the main characteristics affecting the membranes’ performances and how they are influenced by the presence of different organic solvents. Two different PDMS membranes were prepared and studied, the two materials have the same chemical structure but different number of active sites for the cross-linking process. This choice was made to investigate how the swelling of a polymer can affect membrane characteristics. The first experiment performed with these PDMS membranes was the dynamic vapor sorption of organic solvents. Both hydrocarbons and alcohols were tested in order to understand how the polymeric material interacts with the different chemical species. It is evident from the results, the higher affinity between polymer and hydrocarbons with respect to alcohols. The sorption isotherms so obtained were modelled using different theories, trying to estimate the strengths and limits of each of them. From the same sorption experiments, kinetic data for the evaluation of transport phenomena were obtained and Fick’s law was applied to calculate values of the diffusion coefficient. In the second part of this study, the same membranes were tested in presence of pure liquid organic solvents, performing some filtration experiments. Fluxes through the membranes were measured and an evaluation of rejection and Molecular Weight Cut Off were given. In the end, the membranes were tested in presence of organic solvents binary mixtures. As before, fluxes through the membranes were measured and selectivities were calculated. It was possible to observe how these membranes are not able to separate hydrocarbons but they show higher selectivity in presence of a mixture of a hydrocarbon and an alcohol. In conclusion, this research provides a guidance on which experiments can be performed to characterize a membrane material and help to understand how many different parameters can affect the separation process.

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Universidade Federal de Sao Carlos
The increase in the air pollution in the last decades is causing a strong increase in the monitoring and control of emissions of particulate matter in the atmosphere, in order to minimize the problems caused to the environment and to the human health. Particularly, the behavior nanometric particles in the air needs special attention. The fiber filters, one of the oldest methods of particle removal, are, in principle, capable to operate in this size range, but data on their performance are still scarce. In this work, the behavior of an industrial filter of polyester and of a high efficiency (HEPA) filter was studied with the intention of evaluating their performance operating in the removal of nanometric particles from aerosols. The polyester filter had a porosity of 0.884, a thickness of 4.5 mm and diameter of fiber of 16 m and the HEPA filter the porosity of 0.920, thickness of 0.4 mm and diameter of fibers between 0.075 and 2.35 µm. The test aerosol was composed by monodispersed NaCl particles, obtained from the Electrospray Aerosol Generator, model 3480, from TSI, using salt solutions in concentrations from 0.5 to 5.0 g/L. The size of the generated particles varied from 8.4 to 94.8 nm. To determine this diameter, images in an Electronic Transmission Microscope were obtained and analyzed in the image analyzer Image Pro Plus, 3.0. The filtration device was built in acrylic with a filtration area of 40 cm2. The performance of the filters was evaluated through the analysis of the collection efficiency of the nanometric particles, by counting the particles before and after the filter, using a TSI Condensation Nuclei Particle Counter , model 3007. The filter of polyester showed a maximum collection efficiency of 0.990. The HEPA filter demonstrated its capacity to collect particles in this size range, obtaining larger efficiencies than 0.99994. The increase of the filtration velocity, as well as the increase of the diameter of the particles resulted in smaller efficiencies in both filters, typical behavior of filters operating in the range of predominance of the diffusional mechanism. When compared to theoretical models form the literature, it was verified poor fitting. Therefore, it is suggested an adjustment to the LIU and RUBOW (1990) model, and an effective increase in the mechanism of direct interception caused by the Brownian motion was introduced. In the case of the HEPA filters, considering the observed discrepancy between theory and experiment, an approach that took into account the fiber size distribution of the filter was proposed. In both cases a sensitive improvement was verified in the adjustment of the theoretical prediction to the experimental data
A crescente escalada da poluição do ar nas últimas décadas vem causando um sensível aumento no monitoramento e no controle de emissões de material particulado na atmosfera, visando minimizar os problemas causados ao meio ambiente e à saúde humana. Particularmente, o comportamento de partículas nanométricas no ar necessita atenção especial. Os filtros de fibras, um dos métodos mais antigos de remoção de material particulado, são, em princípio, capazes de atuar nessa faixa de tamanho, mas dados sobre seu desempenho são ainda escassos. Neste trabalho estudou-se o comportamento de um filtro industrial de poliéster e de um filtro de alta eficiência (HEPA) com o intuito de avaliar o desempenho dos mesmos operando na remoção de partículas nanométricas de aerossóis. O filtro de poliéster tinha porosidade de 0,884, espessura de 4,5 mm e diâmetro de fibra de 16µm e o filtro HEPA uma porosidade de 0,920, espessura de 0,4 mm e diâmetro de fibras entre 0,075 e 2,35 µm. O aerossol de teste era composto por partículas monodispersas de NaCl, que foram obtidas a partir de um gerador de partículas Electrospray Aerosol Generator, modelo 3480, da TSI, utilizando soluções de sal nas concentrações de 0,5 a 5,0 g/L. O tamanho das partículas geradas variou de 8,4 a 94,8 nm. Para determinar este diâmetro foram obtidas imagens do Microscópio Eletrônico de Transmissão e analisadas no Programa Image Pro Plus, 3.0. O dispositivo de filtração foi construído em acrílico com área de filtração de 40 cm2. O desempenho dos filtros foi avaliado através da análise da eficiência de remoção das partículas nanométricas, através da contagem de partículas, utilizando um contador de partículas, da TSI, modelo 3007. O filtro de poliéster apresentou eficiência de coleta máxima de 0,990. O filtro HEPA demonstrou possui uma grande capacidade de coletar partículas nesta faixa de tamanho, obtendo eficiências maiores que 0,99994. O aumento da velocidade de filtração, bem como o aumento do diâmetro das partículas proporcionou queda na eficiência em ambos os filtros, comportamento típico de filtros operando na região de predominância do mecanismo difusional. Quando avaliados os modelos presentes na literatura, verificou-se que os mesmos não se ajustaram aos dados experimentais. Portanto, propôs-se um ajuste ao modelo de LIU & RUBOW (1990), considerando um aumento efetivo no mecanismo de interceptação direta causado pelo movimento Browniano. No caso dos filtros HEPA, frente à observada discrepância entre teoria e experimentos, foi proposto um equacionamento que levou em conta a distribuição de tamanho das fibras do filtro. Em ambos os casos verificou-se uma sensível melhora no ajuste da previsão teórica aos dados experimentais

La caractérisation et l’analyse des particules nano/micromètriques solides en suspension dans l’air ont récemment reçu une attention considérable. Le prélèvement représentatif des particules à analyser est une exigence fondamentale. L’échantillonneur d’aérosols récemment développé appelé Mini Particle Sampler (MPS), qui est équipé d’une grille poreuse de Transmission Electron Microscopy (TEM), rend l’échantillonnage de particules possible. Cependant, l’exploitation des résultats de ce système d’échantillonnage est encore à l’étape précoce. Cette thèse améliore et quantifie le système d’échantillonnage MPS. En outre, une nouvelle méthode de caractérisation de la masse de polluants est développée sur la base du système d’échantillonnage optimisé. L’efficacité d’échantillonnage des particules dont le diamètre de mobilité varie de 5à 100 nm est principalement étudiée. Selon l’analyse de sensibilité des paramètres dans l’ensemble de la configuration effectuée par la méthode Taguchi, la concentration en sel de l’atomiseur, la polarité à haute tension dans Differential Mobility Analyzer (DMA), la méthode d’évaluation de l’efficacité d’échantillonnage, la température d’échantillonnage, et la porosité de la grille TEM affectent le moins possible l’efficacité de collection. L apetite taille des pores du filtre, le débit élevé et les particules plus denses augmentent l’efficacité de collection des particules, qui sont les principaux paramètres. Basé sur l’étude des mécanismes de filtration des grilles TEM et la comparaison des modèles théoriques disponibles, une méthode d’analyse expérimentale de l’efficacité de collection combinée à la modélisation théorique est développée en considérant l’applicabilité du modèle. En utilisant cette méthode, les effets des principaux paramètres mentionnés ci-dessus sont comparés entre les expériences et les théories. La technologie d’échantillonnage est optimisée et l’efficacité minimale de collecte peut atteindre 40% en ajustant les paramètres du système d’échantillonnage. De plus, selon les méthodes de Monte-Carlo, les incertitudes sur l’efficacité de collection à partir des données mesurées et des modèles sont généralement inférieures à 1% et à 9%, respectivement. La plupart des données d’efficacité de collection mesurées sont couvertes par la plage d’incertitude d’efficience simulée par les modèles. L’analyse de sensibilité basée sur la variance de Sobol montre que la taille des pores et le débit de prélèvement contribuent de manière significative aux incertitudes et nécessitent un contrôle pour améliorer la précision de l’efficacité. En outre, le facteur de correction de Cunningham est également un paramètre de sensibilité. Sur la base du développement ci-dessus du système d’échantillonnage MPS, une méthode quantitative est proposée pour caractériser la concentration de masse élémentaire des particules micrométriques en suspension dans l’air par échantillonnage de particules etTEM - Energy Dispersive X-ray Spectroscopy (EDS). Le principe est de collecter les particules en suspension dans l’air sur une grille TEM, puis d’y ajouter une certaine masse de particules de référence, et de déterminer les pourcentages relatifs de tous les éléments (particules de référence et particules inconnues) via EDS. Indépendamment de la condition d’échantillonnage, la collecte quantitative et homogène des particules monodispersées RbCl, CsCl et NaCl sur la grille TEM a pu être réalisée. Pour toutes les conditions testées, lors du dépôt de divers types de particules en suspension quantifiées sur une grille TEM, les écarts absolus entre les pourcentages de masse des éléments théoriques et les rapports expérimentaux mesurés par EDS restent inférieurs à 10%, qui confirme que la méthode proposée pourrait être utilisée pour la caractérisation massique d’éléments dans un aérosol inconnu. Le RbCl a été préféré comme référence depuis sa rareté dans les particules aéroportées habituelles et sa faible toxicité
Characterization and analysis of airborne solid nano/micrometric particles have received considerable attention. The representative collection of particles to be analyzed is a fundamental requirement. The recently developed aerosol sampler called Mini Particle Sampler (MPS), which is equipped with a porous Transmission Electron Microscopy (TEM) grid, renders particle sampling convenient. However, the research for this useful sampling system is still in the initial stage. The thesis improves and quantifies the MPS sampling system. Besides, a new method of pollutant mass characterization is developed based on the optimizedsampling system. The sampling efficiency of the sampling system for particles with mobility diameters ranging from 5 to 100 nm is mainly investigated. According to the sensitivity analysis tof the parameters in the whole setup carried out by the Taguchi method, salt concentration of the atomizer, high-voltage polarity in the Differential Mobility Analyzer (DMA), sampling efficiency assessment method, sampling temperature, and porosity of the porous TEM gridminimally affect the collection efficiency. Small filter pore size, high flowrate, and denserparticles promote particle capturing, which are the main parameters. Based on the investigation of the filtration mechanisms of TEM grids and the comparison of available theoretical models, a method for experimental collection efficiency analysis combined with theoretical modeling is developed by considering the model’s applicability. Using this method, the effects of the main parameters mentioned above are compared between experiments andtheories. The sampling technology is optimized and the minimum collection efficiency isup to 40% by adjusting the parameter settings of the sampling system. In addition, accordingto the Monte-Carlo methods, sampling efficiency uncertainties from measured data andtheoretical models are generally less than 1% and 9%, respectively. Most sampling efficienciesmeasured data are covered by the efficiency uncertainty range simulated by models.Sobol variance-based sensitivity analysis shows that pore size and flowrate contribute significantly to the uncertainties, and require control to improve the efficiency precision. Besides, Cunningham correction factor is also a sensitivity parameter. Based on the above development of the MPS sampling system, a quantitative method is proposed to characterize the elemental mass concentration of airborne nano/micrometric particles via particle sampling and TEM - Energy Dispersive X-ray Spectroscopy (EDS). The principle is to collect airborne particles on a TEM grid, then add a certain mass of reference particles on it, and determine the relative percentages of all elements (reference and unknown particles) via EDS. Regardless of the sampling condition, the quantitative and homogeneously collection of monodisperse RbCl, CsCl, NaCl particles on the TEM grid could be achieved. For all the tested conditions, when depositing divers kinds of quantified airborne particles on one TEM grid, the absolute deviations between theoretical element mass percentages and experimental ratios measured by EDS remain lower than 10%, which confirms that the proposed method could be used for mass characterization of elements in an unknown aerosol. RbCl has been preferred as a reference since its rarity in usual airborne particles and having a low toxicity. The developed method has been used for characterizing aerosol released by the friction between serial pad and braking disc. The mass concentration of Fe in the braking aerosol is calculated as 0.105 μg/L using this method, which is consistent with the concentration range estimated from the data of Scanning Mobility Particle Sizer (SMPS) and Aerodynamic Particle Sizer (APS)

Thesis (M. Eng.)(Chemical Engineering)--University of Pretoria, 2006.
Accompanied by a CD-ROM containing Matlab programs. Includes bibliographical references. Available on the Internet via the World Wide Web.

Наведено результати аналізу сучасного стану і тенденцій розвитку вітчизняних та закордонних досягнень із досліджуваної проблеми, що дало можливість визначити напрямки подальших досліджень. Виконано аналіз причин утворення скупчень у порожнинах газопроводів, досліджено чинники та причини утворення гідратних утворень у порожнинах труб під час магістрального транспортування газу. Досліджено вплив скупчень на безпечність і режими експлуатації газопроводів. Ідентифіковано місця найбільш ймовірної появи скупчень. Проведено експериментальні дослідження з метою встановлення оптимальних інформативних параметрів виявлення гідратних утворень у порожнинах магістральних газопроводів. Розроблено дослідно-експериментальний взірець приладу для контролю наявності скупчень у порожнинах лінійної частини магістральних газопроводів.
Приведены результаты анализа современного состояния и тенденций развития отечественных и зарубежных достижений по исследуемой проблеме, который позволил определить направления дальнейших исследований. Выполнен анализ причин образования скоплений в полостях газопроводов, исследованы факторы и причины образования гидратных образований в полостях труб при магистральном транспорте газа. Исследовано влияние скоплений на безопасность и режимы эксплуатации газопроводов. Идентифицированы места наиболее вероятного появления скоплений . Проведены экспериментальные исследования с целью установления оптимальных информативных параметров обнаружения гидратных образований в полостях магистральных газопроводов. Разработан опытно-экспериментальный образец прибора для контроля наличия скоплений в полостях линейной части магистральных газопроводов.
The aim of the thesis is to solve the current problem of applied scientific research in the direction of improving methods of exploitation of main gas pipelines through the development and introduction of new methods and means of technical diagnostics clusters in the cavities of the linear part of main gas pipelines. The results of a current state analysis and domestic and foreign developments trends of the researching problem, that allowed to define further research areas. The object of the research is the presence of a main gas pipeline liquid clusters. The subject of research is the methods and means of diagnosing fluid in main gas pipelines. The causes of clusters in the gas pipelines cavities were analyzed, the factors and causes of hydrate formation in the pipes cavities have been investigated at the main gas transport. Provisions are made for protection: the method of determining the location and level of liquids and dirt in the cavity of main gas pipeline. To solve the problems and achieve the goal of a thesis uses methods of analytical modeling, correlation and regression analysis, interpolation data. Experimental study on developing a method of diagnosing clusters in the cavities of the linear part of main gas pipelines and generalization of results were carried out using the theory and practice of technical measurements and experimental design, methods of polynomial filtering of measurement results of mathematical statistics and probability theory, methods of numerical processing of the experimental results to enhance their credibility. Scientific novelty of the results of the thesis by the following provisions: 1. The first time the analytical method for determining the location and volume of fluid accumulation in the cavity of main gas pipelines. 2. For the first time developed a method of technical diagnostics of gas mains pipe cavity without interference in its work and violations of pumping gas is to use ultrasonic method of determining the level of liquid in place of its accumulation in the cavity of the pipe. 3. Improved functional diagram ultrasonic method of technical diagnostics linear part of main gas pipelines, which enabled regardless of environmental conditions, to obtain reliable information on the state of the pipeline. 4. Found a further development of methods of construction and use of technical equipment and diagnostic systems for the evaluation of the technical state of gas mains, which significantly increases the reliability of the transmission system. Solved in dissertation work tasks and the results obtained enable to increase the efficiency and reliability of gas transportation system by applying the proposed method of diagnosing fluid accumulations for their effective withdrawal from the cavities of gas mains pipes for further implementation of in qualitative diagnosis. The basic scientific positions and results are the essence of the thesis received the author alone. The author made the following research: - analyzed and systematized reasons of contamination in the cavity gas pipeline; - analyzed the methodological, technical and regulatory support of technical diagnosing gas pipeline; - developed analytical methods for determining the location and extent of accumulation of fluid in the cavity gas pipeline; - developed, tested and implemented in an industrial environment in the current gas pipeline experimental model, technology information and measuring system of monitoring the presence and amount of fluid in the cavity gas pipeline. The clusters influence on safety and the gas pipelines operation modes was researched. These researches showed that liquid presence makes negatively influence at all the gas-transport system items working, complicates the main gas realization process and substantially worsens gas quality. Besides, the water presence in a gas pipeline considerably complicates the pipelines in-line inspection diagnostics procedure because in such case cleansing and diagnostic pistons damage or their destructions is possible because of the hydraulic shots. The most probable occurrence clusters places were identified. Mainly, it takes place in the ascending overfall heights areas or in deepening. The experimental studies for determination of optimal informative parameters for detection hydrate formation in the pipelines cavities have been done. An acoustic method for the accumulations volume estimation was suggested for using which consists in experimental dependences establishment of the ultrasonic vibrations amplitude with non-technological including type and thickness and ambient temperature that enables high precision (more than 0,9) the non-technological accumulations presence and their volume determination regardless of the environment parameters. An experimental model device has been developed for the non-technical clusters cavities controlling in the pipelines linear parts.