Dissertations / Theses on the topic 'Sorption purification'

L’hexafluorure d’uranium (UF6), est le seul composé utilisé à l’état gazeux dans les procédés d’enrichissement pour la production du combustible nucléaire. Pour le bon déroulement de l’étape d’enrichissement, la qualité de UF6 est primordiale. Cette étude s’est intéressée principalement aux impuretés volatiles sous forme de fluorures et oxyfluorures et leur réactivité avec des matériaux en présence ou non de l’UF6. La nature des produits adsorbés et de réactions a été identifiée. Les mécanismes physico-chimiques mis en jeux lors de la sorption ont été investigués. Les performances (capacité de sorption, sélectivité et régénération) de ces matériaux absorbants et adsorbants ont été évaluées en vue de leur utilisation comme filtre UF6 dans les usines de conversion
Uranium hexafluoride (UF6), is the only compound used in the gaseous state in the process of enrichment to produce nuclear fuel. For the success of the enrichment step, the UF6 quality is paramount. This study is mainly concerned with volatile impurities in form of fluorides and oxyfluorides and their reactivity with the materials in presence or not of UF6. The nature of the adsorbed compounds and reactions products was identified. The physico-chemical mechanisms of sorption were investigated. The performances (sorption capacity, selectivity and regeneration) of the absorbent and adsorbent materials have been evaluated to be used as UF6 filters in conversion plants

This thesis is concerned with applying engineering principles to the use of polymeric nanoporous adsorbents for use in blood purification to obtain original knowledge. Styrene divinylbenzene copolymer nanoporous adsorbents offer a potential means to remove middle molecular (MM) sized molecules when in direct contact with blood. (Continues...).

Metal–organic materials (MOMs), a type of porous crystalline structure composed of organic ligands jointed with metal ions, have captured the interest of scientists as potentially useful in gas sorption applications. Some of the most crucial avenues of investigation are in H2 storage (for use as a clean burning fuel source) and CO2 capture and sequestration (to remove the greenhouse gas from the environment). A major advantage of MOMs for such applications is their high variability in terms of physical dimensions and chemical moieties, based on composition and synthesis conditions, making them potentially customizable for specific application if necessary structural characteristics are known. Computational experimentation is an important avenue for determining such specifications as it allows examination of gas/MOM interaction at the molecular level. In this dissertation a number of MOM structure are computationally studied in order to elucidate gas sorption mechanisms. These systems were probed by classical simulation using grand canonical Monte Carlo with a carefully chosen set of intermolecular interaction parameters. While the focus of this work is specifically H2 and CO2 sorptive behavior, the insights gained from simulation extend beyond these specific applications. Addressed first are a series of MOMs with rht topology, which possesses asymmetric copper paddle-wheels and easily functionalized linkers. Beginning with a prototypical structure and then branching out into more chemically interesting variants revealed surprising gas sorption behavior about the metal paddle-wheels (with a definite preference for one copper over its counterpart). A synthetic strategy for controlling the preferred open-metal sorption site through the inclusion of electron rich functionality in the linker bodies, was also revealed. An additional MOM with similar composition components, exhibiting zyg topology, also showed this metal preference effect on the asymmetric paddle-wheels. A second class of MOMs, composed of square-pillared grids and known as the SIFSIX series (due to the inclusion of SiF62− as pillaring units) was also examined. These structures have been shown excellent results for CO2 sorption making the elucidation of the sorptive mechanisms of great interest. Six different structures were examined, probing the effects of linker length, metal selection, and interpenitration of unbonded scaffolds. The nature of the CO2-MOM sorption interactions were revealed through simulation and provided insights regarding the synergistic effect of pore dimensions and SiF62− functionality for specifying specific behavior (i.e. high selectivity vs. high uptake). A final MOM, composed of Y3+ ions and chemically complex linkers, was also examined. Disorder in the crystallographic data (e.g. single atoms with multiple positions) indicated the coexistance of notably different unit cells in the same system. Nevertheless, simulations revealed favored sorption sites in conjunction with results from physical experimentation.

Osnovni cilj istraživanja u okviru doktorske disertacije je definisanjekriterijuma na osnovu optimizacije usvojenog stepena sorbiranja idegradacije za modele transporta farmaceutika u aluvijalnim podzemnimvodama, koji služe kao polazna osnova za postavke budućih izvorištapodzemne vode. Dobijeni su novi podaci i informacije koje će se koristiti zaprocenu ponašanja farmaceutika, kao i za projektovanje i optimizaciju novihsistema za efikasnu zaštitu i upravljanje podzemnim vodama. Potpuno novirezultati se odnose na određivanje stepena eliminacije farmaceutika tokomprimene metode rečne obalske filtracije, kao i teorijsko i eksperimentalnopoređenje realnih podataka o stepenu sorbiranja i razgradnje farmaceutika.
The main goal of dissertation is to define new criteria based on theoptimization of applied sorption and degradation degree for groundwaterpharmaceuticals transport model, which serve as a basis for developmentand design of the future drinking water facilities. New data and information’sare obtained and can be used for assessment of pharmaceutical behavior inalluvial groundwater and for design of new and innovative systems for moreefficient protection and groundwater management. Novel results are referredon the determination of the pharmaceuticals elimination during river bankfiltration and on the theoretical and experimental comparison of real data forthe sorption and degradation capacity of selected pharmaceuticals.

Le travail presente dans ce memoire traite de l'utilisation de la bacterie acidophile thiobacillus ferrooxidans pour la biosoption des metaux toxiques contenus dans les effluents industriels et la mise au point d'un procede de traitement d'effluent utilisant cette bacterie. Les proprietes de resistance et de biosorption de t. Ferrooxidans vis-a-vis du cadmium et du chrome sont etudiees. Les resultats montrent que la souche bacterienne utilisee (dsm 583) resiste et s'adapte a de fortes concentrations en metaux et que d'importantes quantites de metal sont fixees (respectivement 0. 2 g de cd#2#+ et 0. 5 g de cr#6#+ par gramme de biomasse seche). Des cliches realises par microscopie electronique a transmission permettent d'observer des precipites a la surface des bacteries indiquant un mecanisme de bioprecipitation des metaux. Cette hypothese est confirmee par des tests d'elution des metaux fixes et la mise au point d'un modele empirique, par la methodologie des plans d'experiences, de la biosorption des metaux en fonction de cinq parametres (temperature, ph, vitesse d'agitation, concentration et etat physiologique de la biomasse). L'optimisation du modele empirique conduit a des quantites fixees superieures a 1g/g de biomasse seche et montre des differences dans les conditions optimales de biosorption suivant le metal etudie. Un procede de traitement d'effluent utilisant t. Ferrooxidans est alors propose et la production de la biomasse necessaire a ce procede particulierement etudiee. Un reacteur electrochimique de regeneration du substrat de la bacterie est concu et realise et permet de produire 3 a 5 fois plus de biomasse qu'une culture classique sans regeneration. La regeneration du milieu de culture est ensuite commandee par un regulateur automatique non lineaire ce qui permet d'obtenir de fortes concentrations en bacteries dans l'etat physiologique desire et d'envisager la mise au point d'un pilote de traitement d'effluent continu et selectif quant aux metaux elimines

Metal-Organic Frameworks (MOFs) are three-dimensional porous nanomaterials with a variety of applications, including catalysis, gas storage and separation, and sustainable energy. Their potential as air filtration systems is of interest for designer carbon capture materials. The chemical constituents (i.e. organic ligands) can be functionalized to create rationally designed CO2 sequestration platforms, for example. Hardware and software alike at the bleeding edge of supercomputing are utilized for designing first principles-based molecular models for the simulation of gas sorption in these frameworks. The classical potentials developed herein are named PHAST -- Potentials with High Accuracy, Speed, and Transferability, and thus are designed via a "bottom-up" approach. Specifically, models for N2 and CH4 are constructed and presented. Extensive verification and validation leads to insights and range of applicability. Through this experience, the PHAST models are improved upon further to be more applicable in heterogeneous environments. Given this, the models are applied to reproducing high level ab initio energies for gas sorption trajectories of helium atoms in a variety of rare-gas clusters, the geometries of which being representative of sorption-like environments commonly encountered in a porous nanomaterial. This work seeks to push forward the state of classical and first principles materials modeling. Additionally, the characterization of a new type of tunable radical metal--carbene is presented. Here, a cobalt(II)--porphyrin complex, [Co(Por)], was investigated to understand its role as an effective catalyst in stereoselective cyclopropanation of a diazoacetate reagent. Density functional theory along with natural bond order analysis and charge decomposition analysis gave insight into the electronics of the catalytic intermediate. The bonding pattern unveiled a new class of radical metal--carbene complex, with a doublet cobalt into which a triplet carbene sigma donates, and subsequent back-bonding occurs into a pi* antibonding orbital. This is a different type of interaction not seen in the three existing classes of metal-carbene complexes, namely Fischer, Schrock, and Grubbs. Finally, the virtual engineering of enhanced chemical warfare agent (CWA) detection systems is discussed. As part of a U.S. Department of Defense supported research project, in silico chemical modifications to a previously synthesized zinc-porphyrin, ZnCS1, were made to attempt to achieve preferential binding of the nerve agent sarin versus its simulant, DIMP (diisopropyl methylphosphonate). Upon modification, a combination of steric effects and induced hydrogen bonding allowed for the selective binding of sarin. The success of this work demonstrates the role that high performance computing can play in national security research, without the associated costs and high security required for experimentation.

The effect of inclusion of explicit polarization is investigated through several theoret- ical studies of crystalline porous materials herein. In addition to the use of Monte Carlo simulation for such studies, a robust molecular dynamics software is presented which is suitable for analyzing time dependent properties of gases or other molecules in porous materials and other condensed phase systems. Metal-organic frameworks (MOFs) are the main focus of the work included here, a relatively young class of materials originally in- troduced in the early 1990s. These are usually three dimensional crystalline nanoporous materials that exhibit unique properties such as gas separation, storage and catalysis. They are synthesized by the combination of a metal ion e.g. Cu2+ with an organic linker e.g. benzene dicarboxylate. They are a very popular topic of scientific research due to the diversity in possible structures and manifold utility – finding applications in electron transfer, sensing, drug release etc. Industrially, MOFs like HKUST-1 and others are on the global market for use in gas storage and separation in fuel cell and raw materials processing. These materials are often ideal candidates for computer simulation owing to their crystalline nature – a very large atomic system (that is, moles of particles) can be under- stood by only evaluating one or a few unit cells of the MOF, usually less than 5,000 atoms, and macroscopic properties such as gas sorption capacity and diffusion coefficients can be calculated through extrapolation of atomistic interactions in a mathematically infinite lattice. The software developed by the space group as of 2005, Massively Parallel Monte Carlo (MPMC), allows for sophisticated calculation of repulsion dispersion, electrostatic and polarization energies. In this work, Monte Carlo Molecular Dynamics (MCMD) is in- troduced, which can hybridize both methods to explore the phase space of a system with ease and better efficiency, as well as explore the effects of MOF flexibility and dynamic properties which to-date are rarely studied. Studies involving primarily CO2, H2 and CH4 will be presented, but other gases investigated include C2 H2 , C2 H4 , C2 H6 , N2 , H2 O and others. Metal-organic materials with a wide variety of composition and structure will also be presented. Finally, features of the software MCMD will be presented for use by future studies.

Дисертаційна робота присвячена розробці та науковому обгрунтуванню методу для ефективного видалення сполук арсену різних ступенів окиснення та гуматів з природних вод. В дисертації теоретично (на основі літературних даних та розрахунків) та експериментально (в результаті сорбційних досліджень) обгрунтовано вибір сполук феруму, як основного сорбуючого компоненту для видалення сполук арсену з водного середовища. Різними способами (гетерогенне осадження, гомогенне осадження, гідротермальний метод) синтезовано ряд ферумвмісних сорбційних матеріалів, серед яких порошкові, зернисті на основі активованого вугілля та суспензійні сорбенти. Визначено, що використання комбінації «дрібнодисперсний ферум(ІІІ) оксигідроксид/мембрана» дозволяє вилучати сполуки арсену з модельних та підземних вод до санітарних вимог за вихідних концентрацій арсену 500-16733 мкг/дм3 та відділяти відпрацьований дрібнодисперсний ферумвмісний сорбент від води і захищає мембрани від засмічування.

Наявність органічних сполук в стічних водах, що надходять у водойми, повинна бути знижена до надзвичайно малих концентрацій для попередження негативних екологічних наслідків. Глибоке очищення води від органічних речовин може бути здійснено шляхом застосування адсорбційної технології. На сьогоднішній день дослідження можливостей синтезу сорбентів з відходів глиноземних виробництв для очищення стічних вод набувають все більшої популярності. Метою магістерської роботи є модифікування поверхні активованого вугілля та використання його в технології глибокого очищення стічних вод фармацевтичного виробництва. Основними завданнями магістерської дисертації є:  вибір методу модифікування та встановлення основних параметрів процесу модифікування;  виявлення типу модифікатору;  встановлення морфології та складу отриманого зразку модифікованого вугілля;  дослідження структурно-сорбційних характеристик поверхні модифікованого активованого вугілля;  виявлення основних параметрів (тривалість процесу, температурний режим, концентрація модифікатору) сорбційного процесу;  дослідження ефективості застосування отриманих зразків модифікованого вугілля для очищення води від левамізолу, норсульфазолу та стрептоциду;  створення технологічної схеми глибокого очищення води від левамізолу, норсульфазолута стрептоциду. Об’єкт дослідження – процес модифікації вуглецевмісного сорбенту, дослідження закономірностей його застосування для глибокого вилучення органічних сполук. Предмет дослідження – активоване вугілля, «червоний шлам» Миколаївського глиноземного заводу, модельні розчини фармацевтичних стічних вод (левамізолу, норсульфазолу та стрептоциду). Синтезовано сорбент з використанням відходів глиноземного виробництв та перевірено його ефективністі в порівнянні з торговою маркою активованого вугілля. Встановлено, що ефективнішим є модифіковане активоване вугілля. Модифікування поверхні АВ призводить до збільшення сорбційної ємності сорбенту. Результати досліджень відображено у матеріалах міжнародних конференцій.
To prevent negative environmental effects the presence of synthetic organic compounds in sewage that enters into ponds should be reduced to extremely low concentrations. Deep water purification from toxic organic substances can be done by applying adsorption technology. Today research opportunities synthesis of sorbents from waste alumina production for wastewater treatment are becoming more popular. The purpose of the master's work is to modify the surface of activated carbon and use it in the technology of deep sewage treatment of pharmaceutical production. The main tasks of the master's thesis are:  the choice of the modification method and the establishment of the main parameters of the modification process;  detection of modifier type;  establishment of morphology and composition of the obtained sample of modified coal;  research of structural–sorption characteristics of the surface of modified activated carbon;  establishment of the basic parameters (duration of the process, temperature mode, concentration of the modifier) of the sorption process;  checking the effectiveness of the application of the obtained samples of modified coal for water purification from levamisole, norsulfazolum and streptocide;  creation of a technological scheme of deep water purification from levamisole, norsulfazolum, streptocide. The object of the study – the process of modification of carbon-containing sorbent, the study of the laws of its application for the deep removal of organic compounds. The subject of research - activated carbon, "red mud" of Mykolayiv Alumina Factory, model solutions of pharmaceutical wastewater (levamisole, norsulfazole and streptocide) The sorbent was synthesized using waste from alumina production and its efficiency compared to the trademark of activated carbon was checked. Found that the modified activated carbon is more efficient. Modification of the AC surface leads to an increase sorbent capacity of the sorbent. The results of the research were made public at international conferences.

Dans le cadre de cette thèse, nous nous proposons d'examiner le comportement de deux silices bi-fonctionnalisées présentant une mésostructure (i.e., MCM-41) ou non (i.e., gel de silice, dénommé ici SiO2), ainsi que leur réactivité vis-à-vis des espèces de chrome. Les groupements fonctionnels sélectionnés pour modifier les échantillons de silice afin d'atteindre ce but sont d'une part, le mercaptopropyle et l'acide propylsulfonique (MCM-SH,SO3H), et d'autre part le mercaptopropyle et l'éthylènediaminetriacetate (SiO2-SH/ED3A). La recherche a débuté avec des matériaux structurellement ordonnés, de type MCM-41, offrant une très grande aire spécifique tout en assurant un accès rapide et aisé vers les groupements fonctionnels. Sur la base d'une MCM-41 modifiée par des fonctions thiol oxydées à divers degrés, un ensemble d'échantillons d'adsorbants caractérisés par différents rapport de groupements greffés thiol/acide sulfonique (teneur constante en soufre = 1 mmol g-1) ont été synthétisés. Une attention particulière a été portée à la caractérisation de la composition chimique de surface, pour laquelle on s'attend à une forte influence sur les propriétés de sorption. Une méthode simple, basée sur une seule technique instrumentale (titrage conductimétrique), a été appliquée pour la détermination simultanée des groupements thiol et sulfonique sur MCM-SH,SO3H. Dans un second temps, les conditions expérimentales susceptibles de permettre un piégeage effectif de Cr(VI) sur MCM-SH,SO3H ont été définies, en étudiant notamment l'effet du pH, du rapport solide/solution, ou encore de la composition de l'adsorbant (i.e., rapport SH/SO3H). Sur la base des données collectées, un mécanisme de réduction-sorption expliquant le processus d'immobilisation a été proposé. Dans une seconde approche, un autre type de silice bi-fonctionnelle (SiO2-SH,ED3A) a été suggéré afin d'améliorer l'affinité (propriétés de sorption) du matériau vis-à-vis des espèces Cr(III) générées lors de la réduction de Cr(VI). Le gel de silice a été choisi comme matrice pour greffer des quantités contrôlées de groupements mercaptopropyls et éthylènediaminetriacetate à sa surface. La performance de tel adsorbants bi-fonctionnels a été évaluée au regard de paramètres expérimentaux variés susceptibles d'influencer le processus de sorption-réduction (pH, rapport solide/solution, concentration) afin de déterminer le mécanisme de séquestration et de le comparer avec les adsorbants précédents. Finalement, on montrera comment le second adsorbant présente également l'avantage de pouvoir être utilisé dans des conditions dynamiques (expériences en colonne)
The present work proposes to examine chemical characteristics and behavior of two bifunctionalized silicas exhibiting either a mesostructure (i.e., MCM-41) or not (i.e., silica gel, denoted here SiO2) with respect to the immobilization of chromium species. The organo-functional groups selected to achieve this goal are mercaptopropyl and propylsulfonic acid moieties (MCM-SH,SO3H), on one hand, and mercaptopropyl and ethylenediaminetriacetate groups (SiO2-SH/ED3A) on the other hand. The research has been started with structurally ordered materials, of MCM-41 type, to ensure high surface area and easy and fast accessibility to the functional groups. On the basis of thiol-modified MCM-41, a set of sorbent samples containing different ratio of grafted mercaptopropyl and propylsulfonic acid groups (constant concentration of sulfur = 1 mmol g-1) has been synthesized. Special attention was first given to the characterization of surface chemical contents, which are expected to have a strong influence on sorption parameters. A simple, one-instrument method (conductometric titration) has been applied to the simultaneous determination of thiol- and sulfonic group on MCM-SH,SO3H. Then, the experimental conditions that are likely to provide effective sequestration of Cr(VI) on MCM-SH,SO3H have been defined, notably by studying the effect of pH, solid-to-solution ratio, or composition of the adsorbent (i.e., SH/SO3H ratio). On the basis of received data, a reduction-sorption mechanism explaining the uptake process has been proposed. In a second approach, a second type of bi-functional silica (SiO2-SH,ED3A) was suggested so as to improve the affinity (sorption properties) of the material to the reductively-generated Cr(III) species. Silica-gel was chosen as the matrix to graft controlled amounts of mercaptopropyl and ethylenediaminetriacetate groups at its surface. The performance of such bi-functional adsorbent was evaluated with respect to various experimental parameters likely to affect the reduction-sorption process (pH, solid-to-solution ratio, concentration) in order to determine the uptake mechanism and to compare it with the above adsorbent. Finally, it will be seen how this second adsorbent also offers the advantage of being usable in flowing conditions (column experiments)

Chitosan is a biopolymer resulting from the deacetylation of chitin, the second most abundant biopolymer in nature. Chitosan has been successfully used in systems to remove metal ions and other pollutants from wastewater. Chitosan has shown promise as a sorbent for radionuclides in some aqueous waste streams. The sorption of these radionuclides by chitosan is studied to determine if chitosan could be used as a sorbent for aqueous waste streams containing these metals. The effect of various experimental conditions including sorbent particle size, agitation rate, hydration, temperature, pH, metal concentration and sorbent concentration are examined in this study. Results showed that sorption depends on the availability of access sites, controlled by the specific surface area of the sorbent. Sorption was observed to decrease with increasing temperature. The sorption isotherms and kinetics for Co(II), Eu(III) and U(VI) sorption onto chitosan were determined experimentally by batch sorption. Isotherms were fitted using the Langmuir and Freundlich models. Kinetics were modeled using the pseudo- first order, pseudo-second order, Elovich, and intraparticle diffusion models in order to determine possible rate-limiting steps. Most data were well described by the pseudo- second order and Elovich models. Multi-linearity was observed in the intraparticle diffusion model. The sorption capacity of the metals on chitosan was found to follow the order Co < Eu < U.
Graduation date: 2013

Carbon has been used electrochemically in various forms for water treatment and the carbon aerogel is one of them. Carbon Aerogels (CA) are used as electrodes due to their high surface capacity and high electrical conductivity. They are also known as Carbon Nanofoams (CNF). CA electrodes attract oppositely charged ions that are nearby. This concept is known as Capacitive De-Ionization (CDI). The use of CA in CDI for water purification is well documented, but not much work has been done on regeneration of CA electrodes. Once saturated, these electrodes lose their ability to adsorb additional ions and it must be restored by regeneration. If they cannot be regenerated, they would need to be replaced, which would greatly increase the cost of the treatment they are expensive. The goal of this study is to obtain data to define optimal regeneration conditions and to develop predictive capability by examining desorption behavior of adsorbed ions on CA electrodes. This study focuses on desorption of adsorbed ions and regeneration of CA. Various experiments were conducted to explore the effects on regeneration of CA of shorting of electrodes, change of polarity of electrodes, flow speed of water over CA electrodes, and temperature of regeneration water. The optimal combination of experimental variables was identified and was used for remaining experiments that tested the effect of size, charge and mass of adsorbed ions on regeneration of CA. Also, the effect of thickness of CA and its pore size on regeneration of CA was studied. Results indicated that application of reverse potential for the first few minutes of the total regeneration time provided the greatest regeneration. Longer application of reverse potential did not result in higher regeneration. The regeneration behavior when no potential applied with and without shorting was as expected. Application of reverse potential with variable temperature or variable flow speed of water over CA surfaces provided results that were different from the ones that were obtained with no potential being applied with or without shorting of electrodes.

M. Tech. Engineering: Chemical.
Focuses on the emerging application of clinoptilolite in removing aspirin and cephalexin from municipal wastewater streams. The mechanisms of sorbent-organic compounds interaction was studied in detail. Specifically, this research aims to achieve the following objectives: I. to investigate the sorption capacity of surfactant modified clinoptilolite on the removal of aspirin and cephalexin ; II. To relate sorbents performance to process variables with sorbent properties and water quality ; III. to compare the sorption capacity of surfactant modified clinoptilolite to commercial emerging adsorbents on the removal of aspirin and cephalexin from aqueous solution ; IV. to apply existing mathematical models to describe isotherms and kinetic data in order to extract design parameters.