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Forshaw, Paula Louise. "Kinetic studies of probe molecule adsorption on activated carbons." Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324940.
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Onugha, Leonard C. "Kinetic models for protein adsorption on porous cylindrical particles." Thesis, Swansea University, 2002. https://cronfa.swan.ac.uk/Record/cronfa42788.
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Most chromatographic purification techniques for macromolecuies (biopolymers) operate on the principles of adsorption. The rate of the adsorption process depends on mass transfer kinetics. Previous models of the adsorption kinetics have assumed that the adsorbent/packing particles used are spherical. Adsorbents which are fibrous or consist of rod-like particles offer potential advantages over the spherical particles. Whatman UK Ltd. market a semi-rigid cellulosic range of chromatographic adsorbents for macromolecule separation (Express-Ion) which are of this type, i.e. may be likened in shape to cylinders. The major aim of this study is to develop detailed kinetic models for the pore diffusion and mass transfer processes governing the adsorption kinetics of proteins that will predict the concentration-time profiles for the adsorption in both stirred tank and packed column modes of operation using semi-rigid cylindrical adsorbents. 1 he models have been developed to allow for particle size distribution within adsorbent samples, and for the delay and mixing that occurs in the flow line of the equipment. The stirred cell model constructed has been validated by fitting theoretical data to experimental curves obtained for the adsorption of bovine serum albumin on the anion exchanger Express-Ion D. This system was characterised by determining adsorption isotherms and the physical parameters of the adsorbent. The effects of varying the protein concentration, effective pore diffusivity, liquid film mass transfer coefficient, particle dispersity, number of particle size groups, stirrer speed, and the equilibrium isotherm parameters on the adsorption profiles has been studied. A packed bed variant model has also been constructed and used to predict the effect of process parameters on the breakthrough curve in a packed bed (chromatographic) mode, and to study the effects of particle geometry on the adsorption process.
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Mendiratta, Neeraj K. "Kinetic Studies of Sulfide Mineral Oxidation and Xanthate Adsorption." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/27545.
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Sulfide minerals are a major source of metals; however, certain sulfide minerals, such as pyrite and pyrrhotite, are less desirable. Froth flotation is a commonly used separation technique, which requires the use of several reagents to float and depress different sulfide minerals. Xanthate, a thiol collector, has gained immense usage in sulfide minerals flotation. However, some sulfides are naturally hydrophobic and may float without a collector.
Iron sulfides, such as pyrite and pyrrhotite, are few of the most abundant minerals, yet economically insignificant. Their existence with other sulfide minerals leads to an inefficient separation process as well as environmental problems, such as acid mine drainage during mining and processing and SO2 emissions during smelting process. A part of the present study is focused on understanding their behavior, which leads to undesired flotation and difficulties in separation. The major reasons for the undesired flotation are attributed to the collectorless hydrophobicity and the activation with heavy metal ions.
To better understand the collectorless hydrophobicity of pyrite, Electrochemical Impedance Spectroscopy (EIS) of freshly fractured pyrite electrodes was used to study the oxidation and reduction of the mineral. The EIS results showed that the rate of reaction increases with oxidation and reduction. At moderate oxidizing potentials, the rate of reaction is too slow to replenish hydrophilic iron species leaving hydrophobic sulfur species on the surface. However, at higher potentials, iron species are replaced fast enough to depress its flotation. Effects of pH and polishing were also explored using EIS.
Besides collectorless hydrophobicity, the activation of pyrrhotite with nickel ions and interaction with xanthate ions makes the separation more difficult. DETA and SO2 are commonly used as pyrrhotite depressants; however, the mechanism is not very well understood. Contact angle measurements, cyclic voltammetry and Tafel studies have been used to elucidate the depressing action of DETA and SO2. It was observed that DETA and SO2 complement each other in maintaining lower pulp potentials and removing polysulfides. DETA also helps in deactivating pyrrhotite. Therefore, the combined use of DETA and SO2 leads to the inhibition of both the collectorless flotation and the adsorption of xanthate.
The adsorption of xanthate on sulfide minerals is a mixed-potential mechanism, i.e., the anodic oxidation of xanthate requires a cathodic counterpart. Normally, the cathodic reaction is provided by the reduction of oxygen. However, oxygen can be replaced by other oxidants. Ferric ions are normally present in the flotation pulp. Their source could be either iron from the grinding circuit or the ore itself. The galvanic studies were carried out to test the possibility of using ferric ions as oxidants and positive results were obtained.
Tafel studies were carried out to measure the activation energies for the adsorption of ethylxanthate on several sulfide minerals. Pyrite, pyrrhotite (pure and nickel activated), chalcocite and covellite were studied in 10-4 M ethylxanthate solution at pH 6.8 at temperatures in the range of 22 â 30 0C. The Tafel studies showed that xanthate adsorbs as dixanthogen (X2) on pyrite and pyrrhotite, nickel dixanthate (NiX2) on nickel-activated pyrrhotite and cuprous xanthate (CuX) on both chalcocite and covellite. However, the mechanism for xanthate adsorption on each mineral is different. The free energy of reaction estimated from the activation energies are in good agreement with thermodynamically calculated ones.Ph. D.
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Benavente, Martha. "Adsorption of Metallic Ions onto Chitosan : Equilibrium and Kinetic Studies." Licentiate thesis, Stockholm : Kemiteknik, Chemical and Engineering and Technology, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4746.
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Yüzak, Yaprak. "Adsorption/desorption kinetic studies of vapours on porous carbon materials." Thesis, University of Newcastle Upon Tyne, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273521.
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Phillips, Youye. "Kinetic and adsorption behaviour of the anodic bromine formation reaction." Thesis, University of Ottawa (Canada), 1994. http://hdl.handle.net/10393/9485.
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Manning, Robert James. "Protein adsorption on self-assembled monolayers : a kinetic and conformational study." Thesis, University of Sheffield, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419605.
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Welagedara, Asanka. "Phosphorus Removal and Methylene Blue Adsorption by Porous Calcium Silicate Hydrate." Thesis, KTH, Mark- och vattenteknik (flyttat 20130630), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-171836.
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Nutrients (nitrogen and phosphorus) should be removed and recycled from wastewater in order to reduce the nutrient load to recipient waters, avoiding contamination of groundwater and conserve resources. There is a need to pay more attention to phosphorus (P) removal and recycling from wastewater due to limited availability of phosphorus recourses. For such purpose reactive filter media can be used to remove nutrient from wastewater as a sustainable technology. The present study was aimed to evaluate calcium silicate hydrate crystallization in Absol as a reactive filter media for removal and recycle of phosphorus from household wastewater and assess physical and chemical characteristics of Absol. A study of the color removing capacity of Absol was also performed. Several batch experiments were done for comparing absorption mechanism. Collected data were applied to Langmuir and Freundlich isotherm models to study type of adsorption isotherms and pseudofirst- order and second order models were run for study of adsorption kinetics. The experiment demonstrated a very high P and Methylene Blue (MB) sorption capacity. The amount of adsorbed P and MB vary with initial solution concentrations, contact time, and adsorbent dosage. Both equilibrium data (P, MB) were fitted very well in the Langmuir isotherm equation, confirming the monolayer physical sorption and adsorption kinetic followed by the pseudo-second order kinetic model. It is concluded that Absol can have potential to be use for the removal of P, textile dye contaminants and probably also pharmaceuticals present in wastewater.
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Tsige, Seyoum. "Kinetic Selectivity Effects of Binary Mixtures on Nanotube Bundles: Internal and External Adsorption." OpenSIUC, 2010. https://opensiuc.lib.siu.edu/theses/220.
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Kinetic selectivity effects that take place during the adsorption of binary mixture of gas particles in the inside and on the external surface of a single-walled carbon nanotube as well as on surface of a bundle of single-walled carbon nanotubes has been studied using a kinetic Monte Carlo technique and a lattice-gas model. We considered a homogeneous one-dimensional lattice and a heterogeneous two-dimensional lattice to represent adsorbing surfaces on a single carbon nanotube and on a bundle of carbon nanotubes respectively. We restricted adsorption/desorption only to the end sites, in the case of "pore-like" adsorption. In this work, we present effect of gas-gas interactions on the adsorption kinetics of binary mixtures on surface of carbon nanotubes. It was found that interactions caused significant change in an effective binding energy of both chemical species and as a result, change in the chemical species' adsorption rate and fractional equilibrium coverage was observed when partial pressures for the chemical species were not very low or very high. Low and high partial pressures (chemical potentials) caused long-range and short-range interactions respectively; in such cases dynamics of the system was little affected. Simulation results of adsorption kinetics of binary mixtures in pore and on the heterogeneous surface formed by two adjacent carbon nanotubes are also presented.
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Luxton, Todd Peter. "Oxyanion Adsorption by Iron and Ruthenium Oxides: A Macroscopic, Spectroscopic, and Kinetic Investigation." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/28394.
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The adsorption and desorption behavior of trace element contaminants was evaluated
solids-goethite and ruthenium oxide. The importance of anion displacement as a mechanism
responsible for arsenic release from iron oxides was investigated on goethite. The adsorption
and polymerization of silicate on goethite was examined as a function of surface concentration
determine the influence of adsorbed silicate monomers and polymers on arsenite adsorption
desorption. A kinetic model was employed to describe arsenite adsorption and desorption
absence and presence of silicate. The potential environmental impacts of the research
discussed. Hydrous and crystalline ruthenium oxides were extensively characterized
traditional colloidal surface characterization techniques, dissolution experiments, and macro-
spectroscopic experiments. The two ruthenium oxide phases exhibited large specific
areas, a high density of reactive surface functional groups and the presence of multiple
oxidation states in both solids. Enhanced dissolution of hydrous ruthenium oxide occurred
presence of oxalate and ascorbate. While enhanced dissolution of the crystalline phase
only in the presence of oxalate at pH 3. Results from the dissolution experiments were
develop possible mechanisms for the oxalate and ascorbate promoted dissolution of ruthenium
oxides. Macroscopic adsorption studies of arsenate adsorption on both ruthenium oxides
examined over a broad pH (3-10) and initial solution concentration range (0.01 to
Results from the adsorption studies indicate arsenate forms a stable surface complex with
ruthenium oxide phases. Extended x-ray absorption fine structure spectroscopy and Pressurejump
relaxation studies indicates arsenate is specifically adsorbed the ruthenium oxide
Chromate adsorption on ruthenium oxides was investigated as a function of pH and
chromate solution concentration. Macroscopic adsorption studies and zeta
measurements suggest chromate forms an inner-sphere surface complex with both oxide
X-ray absorption near edge spectroscopy data indicates chromate (Cr(VI)) is reduced
chromium (Cr(III)) on the ruthenium oxide surface. Modeling of the first Cr shell indicated
two oxygen backscattering distances similar to the Cr-O atomic distances reported for
coordinated to Cr(VI) and Cr(III) providing additional evidence for Cr(VI) reduction.Ph. D.
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Burde, Jared. "Physisorption Kinetics in Carbon Nanotube Bundles." OpenSIUC, 2011. https://opensiuc.lib.siu.edu/theses/641.
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Carbon nanotube bundles hold great promise for adsorption applications. However, most of the work done thus far has focused on the equilibrium properties of adsorption; the kinetics of adsorption is still not well understood. There also exist large discrepancies in the reported uptake of particles in the internal adsorption sites of carbon nanotube bundles. The purpose of this project was to elucidate the kinetics of adsorption in carbon nanotube bundles and to determine what kinetic factors, if any, may have caused the variations in experimental results. We studied the adsorption of particles in carbon nanotube bundles using analytical and computational techniques. By employing these separate but parallel methods, we were able to constantly compare and verify our results. We calculated and simulated the behavior of the system throughout its evolution and then analyzed our results to determine which system parameters had the greatest effect on the kinetics of adsorption. Our analytical and computational results showed good agreement with each other and with the experimental isotherm data provided by our collaborators. As a result of this project, we now know that the equilibration time of a system depends primarily on the binding energy of the adsorbates and the temperature. Specifically, the highest adsorption rates and shortest equilibration times are observed in systems with low binding energies and high temperatures. We also discovered that equilibration time for internal adsorption phases can be several orders of magnitude larger than those for external phases, which may have led to the disagreements in reported experimental results. Because of this work, we now better understand the process of equilibration.
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Hiratsuka, Tatsumasa. "Kinetic Nature of Capillary Condensation in Nanopores." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225638.
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Thompson, Natalie A. "Comparative Study of Metal Carbonate Based Adsorbents Recovering Phosphate from Water." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535633479315897.
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Lule, Guzide Meltem. "Investigation Of Adsorption Of Pesticides By Organozeolite From Wastewater." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12613952/index.pdf.
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The aim of this study was to determine the adsorption capacity of activated carbon and organo-zeolites for removal of pesticides in water.
In order to prepare organo-zeolite, two kinds of cationic surfactants, namely, hexadecyltrimethyl ammonium bromide (HTAB) and dodecyltrimethyl ammonium bromide (DTAB) were used. Adsorption studies of cationic surfactant on zeolite were investigated in respect to initial concentration of cationic surfactant, time, and temperature. It has been found that the best fitted isotherm equation was Langmuir equation. The observed adsorption rates were found to be equal to the second order kinetic model. The activation energies of cationic surfactant adsorption was determined by using Arrhenius equation.
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PORRAS, KAREN MELISSA GARCES. "THERMODYNAMIC AND KINETIC STUDIES OF THE LEAD AND CADMIUM ADSORPTION IN HUMIC ACID EXTRACTED FROM COAL." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=26730@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
Dentre os contaminantes químicos liberados nos corpos de água, chumbo e cádmio são extremamente prejudiciais para os seres vivos. As sustâncias húmicas, devido à sua estrutura molecular complexa, que compreende grupos carboxílicos, fenólicos e éter, são adsorventes eficazes para poluentes orgânicos e metais. Neste contexto, o principal objetivo do presente trabalho foi avaliar o potencial do ácido húmico (AH) como adsorvente para chumbo e cádmio em meio aquoso e determinar os parâmetros cinéticos e termodinâmicos do processo. AH foi extraído de uma amostra de carvão, coletada na área de mineração do Estado de Santa Catarina, previamente oxidada com HNO3 concentrado em condições de refluxo, conforme a metodologia recomendada pela IHSS. O AH obtido foi caraterizado por técnicas de análise elementar, FTRI, análise termogravimétrica e MEV. Os resultados da caracterização foram similares aos relatados na literatura. Foram realizados ensaios de adsorção para cada cátion, em diferentes níveis de pH da solução, e a partir desta avaliação previa ficou determinado o valor de pH em 5. Os ensaios de adsorção com variação da concentração inicial dos cátions foram realizados separadamente para cada metal em batelada, empregando as seguintes condições: 50 mL de uma solução de cátion (0 a 100 mg L-1), 50 mg de AH, agitação mecânica (175 rpm) e temperatura constante (25 graus Celsius). Após 24 horas, os sistemas foram centrifugados e a concentração de cada metal no sobrenadante foi determinada por espectrometria de absorção atómica. As isotermas obtidas para Pb e Cd apresentaram uma curva em forma de L, o que indica que os sítios adsorventes disponíveis no AH tendem à saturação. Comparativamente a capacidade de adsorção máxima para o Pb foi mais elevada (77 mg g-1) do que aquela apresentada para o Cd (12 mg g-1). Tal fato indica uma maior afinidade dos sítios de adsorção do AH para o Pb. Comparativamente, foram feitos ensaios de adsorção com AH de Leonardita (padrão da IHSS) e carvão mineral oxidado. Para a determinação dos parâmetros termodinâmicos, foram realizados ensaios de adsorção em três temperaturas diferentes (15, 25, 35 graus Celsius). O processo de adsorção foi de natureza endotérmico, com um valor de entalpia de 7,86 kJ mol-1 e um valor de entropia de 23,11 J mol-1 K-1. A cinética de adsorção segue um modelo cinético de pseudo-segunda ordem com constates de taxa de 0,065 mg g-1 min-1 e 0,025 mg g-1 min-1 para Pb (Co 17,60 mg L-1) e Cd (Co 6,41 mg L-1), respetivamente. Os resultados obtidos no presente estudo mostram que o AH de carvão mineral pode eventualmente ser empregado para a remoção de metais pesados em meio aquoso, porem estudos sobre otimização de seu potencial devem ser todavia realizados.
Among the released chemical contaminants into water bodies, lead and cadmium are extremely harmful to living things. The humic substances, due to their complex molecular structure that comprises both aliphatic and aromatic moieties as well as carboxylic, phenolic and ether groups are effective adsorbents for organic pollutants and metals. In this context, the main objective of this study was to evaluate the potential of humic acid (HA), extracted from previously oxidized coal, as adsorbent for lead and cadmium in aqueous solutions and determine the kinetic and thermodynamic parameters of the process. HA was extracted from a coal sample, collected in the mining area of the State of Santa Catarina, previously oxidized with HNO3 concentrated in reflux conditions, according to the methodology recommended by the IHSS. The HA obtained was characterized by elemental analysis techniques, FTRI, thermogravimetric analysis and SEM. The characterization results were similar to those reported in the literature. Adsorption experiments were carried out for each cation in different pH levels, and from this evaluation it was determined the value of pH at 5. The adsorption experiments with a variation of the initial concentration of cations were performed separately for each metal by employing the following conditions: 50 ml of a cation solution (0 to 100 mg L-1), 50 mg of HA, mechanical agitation (175 rpm) and constant temperature (25 Celsius degrees). After 24 hours, the system was centrifuged and the concentration of each metal in the supernatant was determined by atomic absorption spectrometry (AA). The isotherms obtained for Pb and Cd showed a L-shaped curve, indicating that the available sorptive sites on HA tending to a saturation point. Compared maximum adsorption capacity for Pb was higher (77mg g-1) than that shown for Cd (12mg g- 1). This fact indicates a higher affinity the adsorption sites of HA for Pb. Comparatively, adsorption experiments were performed with HA Leonardite (standard IHSS) and oxidized coal. For the determination of the thermodynamic parameters, adsorption experiments were performed at three different temperatures (15, 25, 35 Celsius Degrees). The adsorption process is endothermic nature, with a value of enthalpy of 7.86 kJ mol-1 and a value of entropy 80.54 mol-1 K-1. The adsorption kinetics follows a kinetic model of the pseudo-second-order with rate constants 0.065 g mg-1 min-1 and 0.025 mg g-1 min-1 for Pb (Co 17.60 mg L-1) and Cd ( Co 6.41 mg L-1), respectively. The results obtained in this study show that the coal HA can optionally be employed for removing heavy metals from aqueous media, but studies for their potential should however be realized.
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Hendra, Adhi Pratama. "Comparison of Cs Adsorption Characteristics of Soils in Japan and Indonesia." Kyoto University, 2019. http://hdl.handle.net/2433/242915.
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abu-lail, laila I. "removal of chloroform and MTBE from water by adsorption onto granular zeolites: equilibrium, kinetic, and mathematical modeling study." Digital WPI, 2011. https://digitalcommons.wpi.edu/etd-dissertations/7.
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Many parts of the world are facing water crises due to the lack of clean drinking water. Growing industrialization in many areas and extensive use of chemicals for various concerns has increased the burden of deleterious contaminants in drinking water especially in developing countries. It is reported that nearly half of the population in developing countries suffers from health problems associated with lack of potable drinking water as well as the presence of microbiologically contaminated water [1] . Synthetic and natural organic contaminants are considered among the most undesirable contaminants found in water. Various treatment processes are applied for the removal of organic contaminants from water including reverse osmosis membranes, ion exchange, oxidation, nanofiltration, and adsorption. The adsorption process is a widely-used technology for the removal of organic compounds from water. In this work, the adsorption of chloroform and methyl tertiary butyl ether (MTBE) onto granular zeolites was investigated. Zeolites were specifically chosen because they have shown higher efficiency in removing certain organics from water than granular activated carbon (GAC). Batch adsorption experiments to evaluate the effectiveness of several granular zeolites for the removal of MTBE and chloroform from water were conducted and the results compared with GAC performance. Results of these batch equilibrium experiments showed that ZSM-5 was the granular zeolite adsorbent with the greatest removal capacity for MTBE and chloroform from water, and outperformed GAC. Fixed-bed adsorption experiments with MTBE and chloroform were performed using granular ZSM-5. Breakthrough curves obtained from these column experiments were used to understand and predict the dynamic behavior of fixed bed adsorbers with granular ZSM-5. The ii film pore and surface diffusion model (FPSDM) was fit to the breakthrough curve data obtained from the fixed bed adsorption experiments. The FPSDM model takes into account the effects of axial dispersion, film diffusion, and intraparticle diffusion mechanisms during fixed bed adsorption. Generally, good agreement was obtained between the FPSDM simulated results and experimental breakthrough profiles. This study demonstrated that film diffusion is the primary controlling mass transfer mechanism and therefore must be accurately determined for good breakthrough predictions.
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Jung, Linda Suna. "Quantitative kinetic analyses of adsorption and desorption processes at the liquid-solid interface with surface plasmon resonance /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/11583.
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Konggidinata, Mas Iwan. "Application and Modifications of Ordered Mesoporous Carbon (OMC) for BTEX Removal| Characterization, Adsorption Mechanisms, and Kinetic Studies." Thesis, University of Louisiana at Lafayette, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10266612.
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Chemical and petrochemical industries produce substantial amounts of wastewater every day. This wastewater contains organic pollutants such as benzene, toluene, ethylbenzene and xylenes (BTEX) that are toxic to human and aquatic life. Ordered Mesoporous Carbon (OMC), an adsorbent that possesses the characteristics of an ideal adsorbent was investigated to understand its properties and suitability for BTEX removal. Adsorption isotherms, adsorption kinetics, the effects of BTEX initial concentrations, and temperatures on the adsorption process were studied. The OMCs were characterized using surface area and pore size analyzer, transmission electron microscopy (TEM), elemental analysis, thermogravimetric analysis (TGA), and fourier transform infrared spectroscopy (FTIR). The results suggested that the Langmuir isotherm and pseudo-second-order models described the experimental data. The thermodynamic parameters, Gibbs free energy (ΔG), the enthalpy change (ΔH), and the entropy change (ΔS) of adsorption indicated that the adsorption processes were physical, endothermic, and spontaneous. In addition, OMC had 27% higher total adsorption capacities compared to GAC. Physical modifications on OMC were performed by varying the ratios of boric acid to sucrose. The BTEX adsorption capacities were improved from 8% to 15% with the addition of boric acid. The highest total adsorption capacity was 116.6 mg g -1 using OMC-2. Chemical modification of OMC using citric acid showed increase in adsorption capacity by 21.7% compared to OMC-2.
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Palli, Amar D. "Heteroatom removal from nonaqueous systems by sorption processes a comparative study of kinetic models." Ohio : Ohio University, 1995. http://www.ohiolink.edu/etd/view.cgi?ohiou1179950186.
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Vega, Bernardo José Jiménez. "Cinética de adsorção de Pb e Cd em solo argiloso laterítico." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3145/tde-18012017-092047/.
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A adsorção de metais em solos tem sido estudada no escopo da geotecnia ambiental principalmente para prever formação de plumas, estudar viabilidade de técnicas de remediação e projetar revestimentos impermeabilizantes em sistemas de disposição de resíduos, entre outros. A consideração da adsorção como um fenômeno imediato e reversível é geralmente aceitável nessas aplicações, porém tem-se verificado que para solos tropicais o estudo da cinética pode melhorar as retroanálises de dados de campo e as interpretações de resultados experimentais. Este trabalho apresenta aspectos teóricos da cinética de adsorção, incluindo fatores que afetam a cinética de adsorção, modelos para determinar os mecanismos que controlam a cinética de adsorção e modelos de cinética de adsorção. A adsorção e a cinética de adsorção de cádmio e chumbo em um Latossolo roxo foram investigadas por meio de ensaios de adsorção tipo Batch. As concentrações iniciais nas soluções variaram de 2 mg/L até 2000 mg/L. OS tempos de contatos variaram de 5 minutos até 6 meses. Também foram realizados ensaios de extração e digestão química. A seguir, foram aplicados modelos para determinar os mecanismos que controlam a cinética de adsorção e também foram ajustados modelos de cinética de adsorção aos dados experimentais. Os resultados mostram que a adsorção pode ser representada por dois distintos comportamentos: curto prazo, até cerca de 8 horas, e longo prazo, para tempos superiores. A adsorção não específica aumenta com o aumento da concentração do contaminante na fase sólida no caso do cádmio, enquanto para o chumbo esta relação não ficou clara. Os modelos de cinética de adsorção testados representam apenas o comportamento de curto prazo e o ajuste desses modelos aos dados experimentais, mesmo para a adsorção de curto prazo, varia consideravelmente em função do método matemático utilizado. Finalmente, concluiu-se que a cinética de adsorção é bem representada por uma função tipo potência com expoente negativo.Metal adsorption in soils has been studied in the scope of environmental geotechnics mainly to predict migration of contaminant plumes, to study feasibility of remediation techniques, and to design waste disposal sites. The consideration of adsorption as an immediate and reversible phenomenon is generally accepted in those applications; however, the study of adsorption kinetics in tropical soils may improve back-calculation of field data and interpretation of experimental results. This study presents theoretical aspects of adsorption kinetics, including factors that affect adsorption kinetics, models to determine mechanisms that control adsorption kinetics and adsorption kinetics models. Adsorption and adsorption kinetics of cadmium and lead in a Brazilian lateritic red clay were investigated by means of Batch adsorption tests on. Initial solutions concentrations varied from 2 mg/L to 2000 mg/L. Contact times varied from 5 minutes to 6 months. Chemical extraction and digestion tests were also performed. Models were then applied to experimental data to determine the mechanisms that control adsorption kinetics and adsorption kinetics models were also fitted to experimental data. The results show that adsorption can be represented by two different behaviors: a short time behavior, until circa 8 hours, and a long time behavior, for longer times. For cadmium, the importance of non specific adsorption increases as the contaminant concentration in the solid phase increases, while this relation is not clear for lead. The investigated adsorption kinetics models can only represent the short time behavior, and fitting of these models, even for short-time adsorption, depends considerably on the utilized mathematical method. Finally, adsorption kinetics can be well represented by a power function with negative exponent.
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Jiang, Ping. "Mercury Sulfide Dissolution in Environmental Conditions: Thermodynamic and Kinetic Approaches." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/3027.
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Mercury (Hg) is a global contaminant of ecosystems and human health risk, with complicated biogeochemical processes. Mercury sulfide (HgS) dissolution has been suggested as a key process in Hg cycling, as it could potentially increase the pool of inorganic Hg (iHg) for the production of methylmercury (MeHg). Despite previous sporadic observations of enhanced HgS dissolution under certain conditions, much remains unclear on mechanisms of HgS dissolution. The objective of my research was to advance the mechanistic understanding of HgS dissolution, concerning re-adsorption of released Hg, effects of thiol-ligands, and Hg speciation.
Considering the lack of feasible techniques to differentiate dissolution and re-adsorption processes, I first developed an efficient method using isotope tracer and isotope dilution techniques to investigate the re-adsorption of released Hg during HgS dissolution. The HgS dissolution rate with consideration of re-adsorption was two times the rate calculated from detecting Hg alone in the presence of O2, indicating the importance of Hg re-adsorption during HgS dissolution. I further examined the role of Hg-ligand complexation in HgS dissolution and Hg(II) re-adsorption using a thermodynamic adsorption method, selecting L-cysteine (Cys) as a model compound for low molecular weight ligands and Waskish fulvic acid (FA) for natural dissolved organic matter (DOM). My results suggest that the presence of Cys enhanced HgS dissolution through the decreased re-adsorption of Hg-Cys complex, whereas Waskish FA inhibited HgS dissolution, possibly because of the adsorption of FA on HgS surface that covered dissolution sites.
I further employed a geochemical modeling method to study Hg speciation and the relation of iHg speciation to MeHg, aiming to provide a methodological example for potentially evaluating the implications of Hg species distribution during HgS dissolution on MeHg production. I applied geochemical model PHREEQC to the Florida Everglades, a well-studied wetland with model input parameters available, to determine the distribution of iHg in surface water at different sites. The modeling results suggest that sulfide and DOM govern iHg speciation, and the Hg-sulfide and Hg-DOM species are related to MeHg in environmental media but not fish, suggesting the importance of iHg speciation in MeHg production and the complexity of Hg bioaccumulation.
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Gallaba, Gallaba Mudiyanselage Dinuka Harshana. "AN EXPERIMENTAL STUDY OF STRUCTURAL DEFORMATION AND “GATE OPENING” OF ZEOLITIC IMIDAZOLATE FRAMEWORK-8 UPON GAS SORPTION: THERMODYNAMIC AND KINETIC EVIDENCE." OpenSIUC, 2020. https://opensiuc.lib.siu.edu/dissertations/1858.
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Volumetric adsorption experiments were conducted over three sorbates in Zeolitic Imidazolate Framework – 8 (ZIF-8). The sorption isotherms were measured at low temperatures. The study included carbon monoxide sorption in ZIF-8, xenon in ZIF-8, and methane sorption in ZIF-8. As a metal-organic framework that has been investigated thoroughly for its remarkable characteristics, ZIF-8 interactions with the above three sorbates has revealed some new features. Each of these systems offered a unique opportunity to study the physical properties of the sorbate and ZIF-8 and the thermodynamic responses of the system for its unique characteristics. The fundamental understating of sorbents-sorbate not only reveals some of the remarkable properties but also opens up new frontiers for researches in practical applications such as gas storage separation and other sorption-based fields of interest. The investigation into CO-ZIF-8 system has confirmed some of the predictions made on a similar system and analysis on the ZIF-8 structure. The measured adsorption isotherms have confirmed the existence of three pre-saturation subs steps, which were explained in terms of effects from the structural transition and polarity of the sorbate. The behavior of isosteric heat of adsorption and the equilibration time revealed a strong connection between steps in the isotherm and the structural changes of ZIF-8 due to organic linker rotation and volume expansion, also known as “Gate-Opening” in some cases. In both Xe-ZIF-8 and CH4 -ZIF-8 systems, the sorption isotherms revealed two substeps before the saturation. This is the first time such a feature was resolved experimentally in these systems although many previous studies have predicted the feature. The experimental observations on characteristics of the Xe -ZIF-8 system are also verified by computer simulations. Unlike the CO-ZIF-8 system, Xe-ZIF-8 interactions do not trigger the organic linker rotation of ZIF-8 structure, but it influenced the expansion of the ZIF-8 structure. In CH4 – ZIF-8 system the isotherms’ substeps were not as steep as Xe system but the loading dependence of isosteric heat of adsorption and equilibration time revealed features that are similar to CO. The lack of sorption-combined structural analysis of CH4-ZIF-8 prevent us from concluding the actual nature of the changes occurring which are related to the substeps and other thermodynamic and kinetic features. In all three systems, our measurements of the adsorption kinetics, we observed a non-monotonic behavior of the equilibration time as a function of sorbent loading. For CO the loading dependence of equilibration time exhibit peaks at loadings that correspond to the intermediate and higher loading sub-steps, and CH4 showed similar behavior at the loading corresponds to its intermediate substep region. The sharp peaks can be interpreted as packing rearrangement of adsorbed phase molecule in both cases and for CO there may be some contributions from the linker flipping and structural transition. The structural effect of kinetics is yet to be confirmed by a structural analysis for the CH4 system.
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Yan, Song. "Spectroscopic and kinetic studies of the adsorption and coadsorption of some small molecules on Zn(0001) and Ag(111) surfaces." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303758.
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Pritzker, Mark David. "Thermodynamic and kinetic studies of galena in the presence and absence of potassium ethyl xanthate." Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/76476.
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A study of the electrochemistry of the PbS-H₂O and PbS-KEX-H₂O systems has been made by carrying out thermodynamic calculations, electrochemical experiments and microflotation tests. Particular attention has been paid to how well this system can be described by equilibrium thermodynamics.
The thermodynamic calculations are more comprehensive than previous ones of this type since they are based on a mass balance which includes both insoluble and soluble species. The data they provide include equilibrium concentrations of all dissolved species at any Eh and pH and an Eh-pH stability diagram for each collector addition. Also, two- and three-dimensional plots showing the effect of Eh and pH on xanthate uptake by the galena surface have been presented for the first time. These are particularly useful because they can be directly compared to observed flotation data.
The results of voltammetry, IGP and potential-step experiments suggest that the oxidation of galena at pH 6.8 and 9.2 begins at a potential below the value predicted by bulk thermodynamics with the electrosorption of OH⁻ and the formation of a metal-deficient sulfide and a surface lead oxide. When oxidation becomes extensive enough, bulk products, Sº and PbO, begin to nucleate. Thiosulfate is detected at pH 9.2, but only becomes significant at high potentials.
The electrochemical experiments indicate that xanthate adsorbs onto galena via a one-electron transfer chemisorption reaction in the first monolayer and via the formation of PbX₂ in subsequent layers. It also appears that galena oxidation and xanthate adsorption are competitive processes that tend to inhibit each other.
Ground galena exhibits natural floatability at pH 9.2 as long as oxidation extends to the formation of a metal-deficient sulfide, but not to bulk PbO. When 10⁻⁵ M xanthate is added, the upper potential limit for flotation agrees well with the value predicted from thermodynamics for the decomposition of PbX₂. The lower limit, on the other hand, is at least 200 mv lower than any of the predicted values.
PbS dissolves anodically at pH 1.1 and 4.6 to form Pb²⁺ and Sº first by a random surface process and then by a nucleation and growth mechanism once oxidation becomes extensive enough. At pH 0, the relation between the open-circuit potential and mineral solubility, as predicted by the thermodynamic calculations, agrees quantitatively with that determined experimentally. However, as the pH is increased to 1.1 and 4.6, the system becomes increasingly less reversible.Ph. D.
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Grima, N. M. M. "Kinetic and mass transfer studies of ozone degradation of organics in liquid/gas-ozone and liquid/solid-ozone systems." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/3351.
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This work was concerned with the determination of mass transfer and kinetic parameters of ozone reactions with four organic compounds from different families, namely reactive dye RO16, triclocarban, naphthalene and methanol. In order to understand the mechanisms of ozone reactions with the organic pollutants, a radical scavenger (t-butanol) was used and the pH was varied from 2 to 9. Ozone solubility (CAL*) is an important parameter that affects both mass transfer rates and chemical reaction kinetics. In order to determine accurate values of the CAL* in the current work, a set of experiments were devised and a correlation between CAL* and the gas phase ozone concentration of the form CAL*(mol/L) = 0.0456 CO3 (g/m3 NTP) was obtained at 20°C. This work has also revealed that t-butanol did not only inhibit hydroxyl radical reactions but also increased mass transfer due to it increasing the specific surface area (aL). Values of the aL were determined to be 2.7 and 3.5 m2/m3 in the absence and presence of t-butanol respectively. It was noticed that the volumetric mass transfer coefficient (kLa) has increased following the addition of t-butanol. Ozone decomposition was studied at pH values of 2 to 9 in a 500 mL reactor initially saturated with ozone. Ozone decomposition was found to follow a second order reaction at pH values less than 7 whilst it was first order at pH 9. When the t-butanol was added, the decomposition of ozone progressed at a lower reaction order of 1.5 for pH values less than 7 and at the same order without t-butanol at pH 9. Ozone decomposition was found significant at high pHs due to high hydroxide ion concentration, which promotes ozone decomposition at high pHs. The reaction rate constant (k) of RO16 ozonation in the absence of t-butanol was determined. The result suggests that RO16 degradation occurs solely by molecular ozone and indirect reactions by radicals are insignificant. The chemical reaction of triclocarban with ozone was found to follow second order reaction kinetics. The degradation of naphthalene using the liquid/gas-ozone (LGO) system was studied. This result showed that hydroxyl radicals seemed to have limited effect on naphthalene degradation which was also observed when a radical scavenger (t-butanol) was used. Reaction rate constants were calculated and were found around 100 times higher than values reported in the literature due to differences in experimental conditions. From the results of the experimental investigation on the degradation of methanol by ozone it was found that the rate constant (k) of the degradation reaction increased at pH 9. The reaction stoichiometry was found to have a value of 1 mol/mol. The two steps of the liquid/solid-ozone (LSO) system were studied on beds of silica gel and a zeolitic material (D915) and the ozone adsorption process was modeled and found that particle rate controls ozone adsorption step but liquid rate controls the water treatment step. Ozone desorption with pure deionised water was studied. The water flow rate was found to accelerate the desorption rates but pH was found to decrease the desorption rates. In contrast, the effect of pH was insignificant in the presence of t-butanol. Determination of the adsorption isotherms for RO16, naphthalene and methanol revealed that RO16 did not exhibit adsorption on silica gel, but both naphthalene and methanol showed adsorption on D915 described by Langmuir model.
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Aguiar, Franklin Pessoa. "Modificação da sílica propiletilenodiamina com formaldeído, estudo do equilíbrio e da cinética de adsorção dos íons cádmio, chumbo e cromato." Universidade Federal da Paraíba, 2009. http://tede.biblioteca.ufpb.br:8080/handle/tede/7177.
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In this work, modified silica gel with the group aminopropiletanoimina was used as retention capacity for the ions cadmium, lead and cromate. The tests were accomplished in aqueous solutions under different conditions of pH, in constant temperature of 298±1 K. The number of mol of the organic chain anchored to the matrix was 0,97mmol /g. The analysis of the curves TG, for the degradation interval between 0,12 and 0,4, shows certain constancy of the value of the activation energy with the increase of the value of the conversion degree, however, the comparison of the activation energies calculated by the method of FWO and by the method of Coats-Redfern shows different results for all the models of simple mechanisms, for that, it is believed that the process in such area conversion doesn't happen through a simple mechanism, but through a complex process where more than one mechanism is acting in the dynamics of the degradation reaction. Based in the number of mols of cadmium, lead and cromate adsorbed, it can settle down the following order: cadmium > cromate > lead. The analysis of the kinetics of the reaction for the three ions shows that the processes of adsorption follow a kinetic law of speed of pseudo-second order with the constants of speed cadmium > lead > cromate. The balance of the process of adsorption is not described by the same model of adsorption; the lead and the cromate are described reasonably well by Langmuir, but for the cadmium it was not found any model to describe the behavior of the process of adsorption satisfactorily.
Neste trabalho, sílica gel modificada com o grupo aminopropiletanoimina foi utilizada como adsorvente para os íons cádmio, chumbo e cromato. Os testes foram realizados em soluções aquosas sob diferentes condições de pH em temperatura constante de 298±1 K. O número de mol da cadeia orgânica ancorada à matriz foi de 0,97mmol /g. A análise das curvas TG, para o intervalo de degradação entre 0,12 e 0,4, mostra certa constância do valor da energia de ativação com o aumento do valor do grau de conversão, entretanto, a comparação das energias de ativação calculadas pelo método de FWO e pelo método de Coats-Redfern mostra resultados diferentes para todos os modelos de mecanismos simples, por isso, acredita-se que o processo em tal região de conversão não ocorre a través de um mecanismo simples, mas sim, através de um processo complexo onde mais de um mecanismo está atuando na dinâmica da reação de degradação. Com base no número de moles de cádmio, chumbo e cromato adsorvidos pode-se estabelecer a seguinte ordem: cádmio > cromato > chumbo. A análise da cinética da reação para os três íons mostra que os processos de adsorção seguem uma lei cinética de velocidade de pseudo-segunda ordem com as constantes de velocidade de cádmio > chumbo > cromato. O equilíbrio do processo de adsorção não é descrito pelo mesmo modelo de adsorção; o chumbo e o cromato são descritos razoavelmente bem pelo Langmuir, mas, para o cádmio não foi encontrado nenhum modelo que descrevesse o comportamento do processo de adsorção satisfatoriamente.
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Lalley, Jacob. "Phosphate Remediation and Recovery from Lake Water using Modified Iron Oxide-based Adsorbents." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1427812939.
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Annaduzzaman, Md. "Chitosan biopolymer as an adsorbent for drinking water treatment : Investigation on Arsenic and Uranium." Licentiate thesis, KTH, Mark- och vattenteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-167973.
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In many countries over the world (including Sweden), metal toxicity in freshwater resources causes a severe drinking water quality problem and poses a threat to the environment and human health. Among the different toxic metals in the water resources of Sweden, arsenic and uranium are the biggest threats to health. These elements, over long time consumption, may even lead to cancer and/or neurological disorder. Most of the wells are installed in crystalline and sedimentary bedrock and the received water comes from water bearing fractures in the bedrock. The handling of such water is an issue and there is a need to reduce the arsenic and uranium exposure by improving processes and technologies. It is a very serious problem demanding a safe, sustainable and eco-friendly arsenic and uranium removal technology prior to drinking water supply. Different treatment systems are available, but many of them are not suitable due to their high cost, operation complexity and waste management issues. Through this study, chitosan biopolymer the second largest abundant polysaccharide on earth after cellulose, was verified as a potential adsorbent for arsenic(V) and uranium(VI) removal from water solution. Adsorbent characterizations were also conducted by XRD, FTIR, SEM, UV-visible spectrum and TGA/DTA investigations. Bench-scale batch experiments were conducted using chitosan biopolymer (DDA-85%) as an adsorbent to determine the arsenic(V) and uranium(VI) removal efficiency, by allowing four important effective parameters e.g. chitosan dosages, pH, contact time and contaminant concentration. The adsorption data at optimum conditions were fitted with Langmuir, Freundlich and Dubinin-Radushkhevic (D-R) isotherm and Lagergren pseudo-first-order and pseudo-second-order kinetic model to investigate the adsorption process. The characterization of materials assured the presence of effective amino, hydroxyl, and carboxyl groups of chitosan. Another advanntage is that the materials are bio-degradable. The results show that the arsenic(V) and uranium(VI) removal efficiency was 100% and 97.45% after 300 minutes with optimum pH of 6.0 and 7.0 respectively. The optimum adsorbent dosages and initial concentration were 60 and 80g/L and 100 and 250 µg/L respectively. The adsorption process was suitably described by Freundlich isotherm (R2 = 0.9933) and Langmuir isotherm (R2 = 0.9858) correspondingly for arsenic(V) uranium(VI) compared to other isotherms. This is an important indicator of homogeneous monolayer adsorption of metals. For both of arsenic(V) and uranium(VI), pseudo-second-order explained the adsorption kinetics better than pseudo-first-order and the second-order kinetic regression coefficient (R2) were 0.9959 and 0.9672 correspondingly. Connecting to the above mentioned results, it can be summed up that the chitosan biopolymer (DDA 85%) can be used as an inexpensive, sustainable and environment-friendly treatment option for arsenic(V) and uranium(VI) contaminated drinking water.I många länder världen runt (även i Sverige) orsakar metallers toxicitet besvärliga vattenkvalitetsproblem och utgör ett hot mot människors hälsa. Bland de toxiska metaller som finns i svenska vatten utgör arsenik och uran i dricksvatten allvarliga hälsorisker vid långvarig exposition då de kan orsaka cancer och neurologiska problem. Flertalet brunnar är installerade i kristallint berg och sedimentära bergarter och vattnet kommer vanligen från sprickor i berggrunden. Hanteringen av sådant vatten kan kräva reduktion av expositionen för arsenik- och uraninnehåll genom förbättrade processer och teknologier. Detta är ett angeläget problem som kräver en säker, pålitlig och ekovänlig teknologi att tillämpas innan vattnet distribueras. En rad olika behandlingssystem är tillgängliga men många av dem är inte lämpliga beroende på deras höga kostnad, den komplicerade tillämpningen och problem med hanteringen av restprodukter. I denna studie has biopolymeren chitosan, den näst vanligaste polymeren efter cellulosa, konstaterats vara en möjlig adsorbent för att avlägsna arsenik(V) och uran(VI) från vatten. Karakterisering av adsorbenten har också genomförts genom XRD, FTIR, SEM, UV och strålning i synligt ljus samt TGA/DTA undersökningar. Batch-tester i bänkskala har genomförts med användning av chitosan (DDA-85%) som adsorbent för att bestämma dess förmåga att avlägsna arsenik(V) och uran(VI)genom att variera fyra parametrar, nämligen kontakttid, pH, dos av chitosan och halt av föroreningen. Adsorptionsdata vid optimala förhållanden bestämdes genom tillämpning av Langmuir, Freundlich och Dubinin-Radushkhevic (D-R) isotermerna. Vidare tillämpades Lagergrens pseudo-first-order och pseudo-second-order kinetiska modell för att undersöka adsorptionsprocessen. Karakteriseringen av materialet visade förefintligheten av effektiva amino- (N-H), hydroxyl- (O-H) samt karboxylgrupper (C=O) i chitosan-polysackariden och att det är lätt nedbrytbart. Preliminära resultat visar att reduktionen av arsenik(V) och uran(VI) var 100 respektive 97,45 % efter 300 minuters kontakttid med optimalt pH på 6,0 respektive 7,0. De optimala doserna av adsorbent och den initiala koncentrationen var 60 och 80 g/L och 100 och 250 µg/L. Adsorptions process beskrevs bäst av Freundlich-isotermen för arsenik(V) (R2 = 0.9933) och med Langmuir-isotermen för uran(VI) (R2 = 0,9858) jämfört med andra isotermer vilket var en viktig indikation på en homogen monolager-adsorption. För både arsenik(V) och uran(VI) beskrev pseudo-second order adsorptionen bättre än pseudo-first-order. Second-order kinetiska regressionskoefficienten (R2) var 0.9959 och 0.9872 respektive. De ovanstående resultaten visar sammanfattningsvis att chitosan (DDA-85%) kan användas som en billig, pålitlig och miljövänlig behandlingsmetod av vatten för arsenik(V) och uran(VI).
QC 20150526
ChitoClean
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Li, Nigel. "A study of the kinetic interactions of complex metal ion : humic and magnetite ternary systems." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/a-study-of-the-kinetic-interactions-of-complex-metal-ion--humic-and-magnetite-ternary-systems(a3666dd0-eeee-47fe-90c9-a80925da2f7a).html.
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The sorption of humic acid (HA) and HA size fractions onto magnetite has been studied. There is considerable irreversibility in the interaction of the humic with the magnetite surface, but the presence of Eu3+ ions has no effect on the sorption of humic onto magnetite. The magnitude of the sorption to magnetite increases with HA fraction size for all ionic strengths between 0.01 and 3 mol dm-3. Increasing ionic strength also increases sorption. Asymmetric Flow Field Flow Fractionation analysis of HA sorption to magnetite after 1 day revealed preferential sorption of lower molecular weight material. Eu3+ sorption onto magnetite was studied as a function of Eu concentration, which showed an increase in relative sorption as Eu concentration decreased. The behaviour of Eu3+ in ternary (HA/Eu3+/magnetite) systems is heavily influenced by HA, and from the data there is direct evidence for ternary complex formation. Larger HA size fractions retain more Eu3+ in solution than the smaller fractions. The binding strengths of HA size fractions were determined through ion exchange resin experiments: generally the larger fractions (> 10 kDa) showed stronger binding than the smaller components, but the unfractionated sample showed the strongest binding.First order dissociation rate constants have been determined for the whole HA and HA size fractions. The dissociation rate constants are independent of HA fraction size, but the larger species bind more Eu non-exchangeably. Time series ultrafiltration of Eu3+/whole humic mixtures has shown a shift in the distribution of metal ions to larger size fractions after a few days. Two ternary system kinetic speciation models have been developed to predict the behaviour of HA and Eu3+ in ternary systems. The two differ in their description of the multi-component behaviour of the binary HA-mineral interaction. The first assumes a single HA species and two surface binding sites and was found to perform better overall than the second, which has a single surface sorption site and two HA species in solution. The exchangeable binding strengths for the different HA samples calculated from both models showed similarities to those measured experimentally.
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Liličenko, Nadežda [Verfasser]. "Adsorption kinetic investigations of phthalocyanine derivatives self assembled monolayers (SAMs) on gold: Temperature influence on the SAM formation process and quality / Nadežda Liličenko." Kassel : Universitätsbibliothek Kassel, 2015. http://d-nb.info/1075466954/34.
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Dittler, Roy Frank. "Reducing Ultra-High-Purity (UHP) Gas Consumption by Characterization of Trace Contaminant Kinetic and Transport Behavior in UHP Fabrication Environments." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/321322.
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Trends show that the fraction of the world's population with electronic devices using modern integrated circuits is increasing at a rapid rate. To meet consumer demands: less expensive, faster, and smaller electronics; while still making a profit, manufacturers must shrink transistor dimensions while increasing the number of transistors per integrated circuit; a trend predicted by Gorden E. Moore more than 44 years prior. As CMOS transistors scale down in size, new techniques such as atomic-layer deposition (ALD) are used to grow features one atomic layer at a time. ALD and other manufacturing processes are requiring increasingly stringent purities of process gases and liquids in order to minimize circuit killing defects which reduces yield and drives up manufacturing cost. Circuit killing defects caused by impurity incursions into UHP gas distribution system can come from a variety of sources and one of the impurity transport mechanisms investigated was back diffusion; the transport of impurities against convective flow. Once impurity incursions transpire, entire production lines are shut down and purging with UHP gas is initiated; a process that can take months thus resulting in tens of millions of dollars in lost revenue and substantial environment, safety, and health (ESH) impacts associated with high purge gas consumption. A combination of experimental investigation and process simulation was used to analyze the effect of various operational parameters on impurity back diffusion into UHP gas distribution systems. Advanced and highly sensitive analytical equipment, such as the Tiger Optics MTO 1000 H2O cavity ring-down spectrometer (CRDS), was used in experiments to measure real time back diffusing moisture concentrations exiting an electro-polished stainless-steel (EPSS) UHP distribution pipe. Design and operating parameters; main and lateral flow rates, system pressure, restrictive flow orifice (RFO) aperture size, and lateral length were changed to impact the extent of back diffusing impurities from a venting lateral. The process model developed in this work was validated by comparing its predictions with data from the experiment test bed. The process model includes convection, molecular diffusion in the bulk, surface diffusion, boundary layer transport, and all modes of dispersion; applicable in both laminar and turbulent flow regimes. Fluid dynamic properties were directly measured or were obtained by solving Navier-Stokes and continuity equations. Surface diffusion as well as convection and dispersion in the bulk fluid played a strong role in the transport of moisture from vents and lateral branches into the main line. In this analysis, a dimensionless number (Peclet Number) was derived and applied as the key indicator of the relative significance of various transport mechanisms in moisture back-diffusion. Guidelines and critical values of Peclet number were identified for assuring the operating conditions meet the purity requirements at the point of use while minimizing UHP gas usage. These guidelines allowed the determination of lateral lengths, lateral diameters, flow rates, and restrictive flow device configurations to minimize contamination and UHP gas consumption. Once a distribution system is contaminated, a significant amount of purge time is required to recover the system background due to the strong interactions between moisture molecules and the inner surfaces of the components in a gas distribution system. Because of the very high cost of UHP gases and factory downtime, it is critical for high-volume semiconductor manufacturers to reduce purge gas usage as well as purge time during the dry-down process. The removal of moisture contamination in UHP gas distribution systems was approached by using a novel technique dubbed pressure cyclic purge (PCP). EPSS piping was contaminated with moisture, from a controlled source, and then purged using a conventional purge technique or a PCP technique. Moisture removal rates and overall moisture removal was determined by measuring gas phase moisture concentration in real time via a CRDS moisture analyzer. When compared to conventional purge, PCP reduced the time required and purge gas needed to clean the UHP gas distribution systems. However, results indicate that indiscriminately initiating PCP can have less than ideal or even detrimental results. An investigation of purge techniques on the removal of gas phase, chemisorbed, and physisorbed moisture, coupled with the model predictions, led to the testing of hybrid PCP. The hybrid PCP approach proved to be the most adaptable purge technique and was used in next phase of testing and modeling. Experiments and modeling progressed to include testing the effectiveness of hybrid PCP in systems with laterals; more specifically, laterals that are "dead volumes" and results show that hybrid PCP becomes more purge time and purge gas efficient in systems with increasing number and size of dead volumes. The process model was used as a dry-down optimization tool requiring inputs of; geometry and size, temperature, starting contamination level, pressure swing limits of inline equipment, target cleanliness, and optimization goals; such as, minimizing pure time, minimizing purge gas usage, or minimizing total dry-down cost.
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Nguyen, Minh Tuan. "Support acidity effects of NiMo sulfide catalysts in hydrodenitrogenation of quinoline, indole and Coker Gas Oil." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1209/document.
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L'objectif de la thèse est d'identifier les effets de l'acidité de catalyseurs sulfures supportés en hydrodésazotation (HDN) afin d'améliorer les performances catalytiques.Un modèle cinétique de Langmuir-Hinshelwood y compris le transfert de masse liquide-vapeur a été utilisé pour analyser les données cinétiques obtenues à partir de l'HDN de la quinoléine et de l'indole sur NiMo(P)/Al2O3 et NiMo(P)/ASA. Les résultats de la modélisation cinétique a montré que le NiMo(P)/ASA a favorisé l'hydrogénation du 1,2,3,4-tétrahydroquinoléine en decahydroquinoléine, qui est l'étape limitant de vitesse de l'HDN de la quinoléine. Cependant, l'effet de promotion du NiMo(P)/ASA pour les étapes d'hydrogénation de l'HDN de l'indole n'a pas été mis en évidence. En plus, le NiMo(P)/ASA a favorisé fortement les réactions d'élimination de l'atome d'azote. Les composés azotés adsorbent plus fortement sur NiMo (P)/ASA. La caractérisation par spectroscopie infrarouge de CO a suggéré que ces résultats pourraient être liés à la modification des propriétés électroniques de la phase NiMoS due à l'acidité plus élevée de l'ASA.La quinoléine est un fort inhibiteur pour l'HDN de l'indole alors que l'effet inhibiteur de l'indole sur l'HDN de la quinoléine était négligeable sur NiMo(P)/Al2O3 et plus important sur NiMo(P)/ASA. L'HDN d'un mélange de Straight Run et Coker Gazole a permis d'évaluer le mécanisme réactionnel et de comparer la réactivité vers HDN de différents composés. L'HDN des composés neutres a été inhibée par une adsorption forte des composés basiques. Les composés de type carbazole et quinoléine étaient réfractaires. Le NiMo(P)/ASA a probablement favorisé plus les craquages et montré une désactivation plus rapide que le NiMo(P)/Al2O3The thesis objective is to identify the support acidity effects of sulfide catalysts in hydrodenitrogenation (HDN) reactions in order to improve the HDN catalysts.Kinetic data obtained from quinoline and indole HDN, over NiMo(P)/Al2O3 and NiMo(P)/ASA catalysts were analyzed by a Langmuir-Hinshelwood kinetic model, including liquid-vapor mass transfer, in order to estimate kinetic and adsorption parameters. Kinetic modeling results indicated that the NiMo(P)/ASA catalyst favored the hydrogenation of 1,2,3,4-tetrahydroquinoline into decahydroquinoline, which is the rate limiting step of quinoline HDN. However, the promoting effect of the NiMo(P)/ASA in hydrogenation steps of indole HDN was not evidenced. In quinoline and indole HDN, the NiMo(P)/ASA showed a strong promoting effect in N-removal reactions. Nitrogen compounds adsorb more strongly over NiMo(P)/ASA. Characterization by Infra-Red spectroscopy of CO suggested that these results might be related to the modification of the electronic properties of promoted NiMoS phase due to higher acidity of ASA.The HDN of quinoline-indole mixture showed a strong inhibiting effect of quinoline on indole HDN whereas the inhibiting effect of indole on quinoline HDN was negligible over NiMo(P)/Al2O3 and more important over NiMo(P)/ASA. The HDN of a mixture of Straight Run and Coker Gas Oil allowed an access to the HDN mechanism and comparison of reactivity towards HDN of different compounds. The HDN of neutral compounds was inhibited by the stronger adsorption of basic compounds. Carbazole-type and quinoline-type compounds were refractory. The NiMo(P)/ASA likely favored more cracking reactions and as well showed a faster deactivation rate than the Al2O3 counter catalyst
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Ambati, Jyotrhirmai. "STUDIES ON SILICON NMR CHARACTERIZATION AND KINETIC MODELING OF THE STRUCTURAL EVOLUTION OF SILOXANE-BASED MATERIALS AND THEIR APPLICATIONS IN DRUG DELIVERY AND ADSORPTION." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_diss/203.
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This dissertation presents studies of the synthetic processes and applications of siloxane-based materials. Kinetic investigations of bridged organoalkoxysilanes that are precursors to organic-inorganic hybrid polysilsesquioxanes are a primary focus. Quick gelation despite extensive cyclization is found during the polymerization of bridged silane precursors except for silanes with certain short bridges. This work is an attempt to characterize and understand some of the distinct features of bridged silanes using experimental characterization, kinetic modeling and simulation. In addition to this, the dissertation shows how the properties of siloxane- materials can be engineered for drug delivery and adsorption.
The phase behavior of polymerizing mixtures is first investigated to identify the solutions that favor kinetic characterization. Microphase separation is found to cause gradual loss of NMR signal for certain initial compositions. Distortionless Enhancement by Polarization Transfer 29Si NMR is employed to identify the products of polymerization of some short-bridged silanes under no signal loss conditions. This technique requires knowing indirect 29Si-1H scalar coupling constants which sometimes cannot be measured due to second-order effects. However, the B3LYP density functional method with 6-31G basis set is found to predict accurate 29Si-1H coupling constants of organoalkoxysilanes and siloxanes. The scalar coupling constants thus estimated are employed to resolve non-trivial coupled NMR spectra and quantitative kinetic modeling is performed using the DEPT Si NMR transients. In order to investigate the role of the organic bridging group, the structural evolution of bridged and non-bridged silanes are compared using Monte Carlo simulations. Kinetic and simulation models suggest that cyclization plays a key role right from the onset of polymerization for bridged silanes even more than in non-bridged silanes. The simulations indicate that the carbosiloxane rings formed from short-bridged precursors slow down but do not prevent gelation.
The tuning of siloxane-based materials for adsorption technologies are also discussed here. In the first example, antioxidant enzyme loading is investigated as a means to reduce oxidative stress generated by silica nanoparticle drug carriers. Materials are engineered for promising enzyme loading and protection from proteolysis. Second, the potential of copper sulfate impregnation to enhance adsorption of ammonia by silica is explored by molecular simulation.
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Deligny, Julien. "Hydrogénation de composés aromatiques en présence de Ni/Al2O3 : approche théorique et expérimentale." Thesis, Poitiers, 2018. http://www.theses.fr/2018POIT2261.
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Les fluides spéciaux (mélanges d’hydrocarbures utilisés comme solvants pour applications diverses) sont produits à partir de l’hydrodésaromatisation des charges pétrolières (naphta et distillats moyens) initialement riches en aromatiques. Leur mise en marché respecte une exigence environnementale (moins de 100 ppm en aromatique) parfois difficile à atteindre compte tenu de la composition initiale de la charge. Par conséquent, à partir de l’identification des molécules réfractaires à l’hydrogénation, un choix de molécules modèles réparti selon trois familles, les monoaromatiques (toluène, indane, tétraline, cyclohexylbenzène, nonylbenzène), les diaromatiques (naphtalène, biphényle) et les triaromatiques (phénanthrène), a permis d’étudier leur réactivité dans les conditions opératoires d’hydrogénation.A partir d’une approche expérimentale couplée à la modélisation cinétique, les schémas réactionnels et une échelle de réactivité ont été établis pour ces molécules modèles. Leur transformation conduit majoritairement du produit totalement hydrogénés. Les monoaromatiques sont les plus réactifs alors que les triaromatiques sont les moins réactifs. Néanmoins, en mélange, le pouvoir inhibiteur d’une molécule sur l’hydrogénation des autres aromatique augmente avec son aromaticité. Le phénanthrène est alors la molécule la plus inhibitrice. Les polyaromatiques engendrent alors une accumulation de monoaromatiques rendant difficile l’hydrogénation totale des charges pétrolières. Ceci est dû à des effets de compétition à l’adsorption à la surface du catalyseur entre les aromatiques qui ont été chiffrés en déterminant à partir d’un modèle suivant le formalisme de Langmuir-HinshelwoodSpecial fluids (hydrocarbon mixture used as solvents for various applications) are produced from deep hydrodearomatization of petroleum distillates (naphta and middle distillates) with high aromatic contents. Their commercialization follows a stringent environmental regulation (less than 100 ppm of aromatics) that is not always reachable due to the initial feedstock composition. Therefore, from the refractory molecules identification for hydrogenation, a selection of three families of model molecules, monoaromatics (toluene, indane, tetralin, cyclohexylbenzene, and nonylbenzene), diaromatics (naphthalene, biphenyl) and triaromatics (phenanthrene) allowed to study their reactivity in the hydrogenation operating conditions.By an experimental approach coupled with kinetic modeling, reaction schemes and a reactivity scale were established for these model molecules. Their transformation leads to the major formation of the saturated product. Monoaromatics are the most reactive while triaromatics are the less reactive. However, in mixture, the inhibiting strength of a molecule on the other aromatic hydrogenation increases with their aromaticity. Therefore, phenanthrene is the strongest inhibitor. Polyaromatics provoke an accumulation of monoaromatics generating a challenging petroleum distillates total hydrogenation. This is due to competitive adsorption effects at the catalyst surface between aromatics that was quantified from a model following the Langmuir-Hinshelwood formalism
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Santos, Alan Silva dos. "Transformation de composés modèles soufrés et oléfiniques représentatifs d'une essence de FCC. Approche expérimentale et théorique." Thesis, Poitiers, 2017. http://www.theses.fr/2017POIT2276/document.
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Une des voies privilégiées pour réduire la teneur en soufre dans les essences commerciales est l'hydrodésulfuration sélective (HDS) des essences issues du procédé de FCC. Une essence étant composée d'un mélange de composés soufrés (1000 ppm) et d'oléfines (20-40%pds). Il est important de comprendre leur transformation de manière à améliorer l'HDS tout en minimisant l'hydrogénation (HYD) des oléfines. Par conséquent, la transformation de plusieurs molécules modèles soufrées (2-méthylthiophène, 3-méthylthiophène et le benzothiophène) et oléfiniques (hex-1-ène, 4-méthylpent-1-ène, 3,3-diméthylbut-1-ène et 2,3-diméthylbut-2-ène) a été étudiée dans les conditions opératoires d'HDS. Par une approche expérimentale couplée à de la modélisation cinétique, nous avons établi une échelle de réactivité entre les composés soufrés d'une part et les oléfines d'autre part. Le benzothiophène est le composé le plus réactif, mais aussi celui qui est le plus inhibiteur pour la transformation des autres composés soufrés. Concernant les oléfines, l'hex-1-ène est la plus réactive par rapport aux autres oléfines ramifiées. Lorsque ces composés sont en mélange, on constate des inhibitions mutuelles plus au moins conséquentes selon la structure des composés modèles. Ces effets qui résultent de compétitions à l'adsorption entre les molécules à la surface du catalyseur ont été modélisés et quantifiés (constantes cinétique et d'adsorption) à partir d'un modèle unique en considérant le formalisme de Langmuir-HinshelwoodA preferred route to reduce the sulfur content on the commercial gasoline is the selective hydrodesulfurization (HDS) process of FCC gasoline. A typical gasoline is composed by a mixture of sulfur (1000 ppm) and olefins (20-40%wt) compounds. Therefore, it is important to understand their transformation in order to improve the HDS and minimizing the olefin hydrogenation (HYD). Consequently, the transformation of various sulfur (2-methylthiophene, 3-methylthiophene and benzothiophene) and olefins (hex-1-ene, 4-methylpent-1-ene, 3,3-dimethylbut-1-ene and 2,3-dimethylbut-2-ene) has been studied under HDS operating conditions.By experimental and theoretical (kinetic modeling) approaches, a reactivity scale has been established between the sulfur compounds on one hand and olefins compounds on the other hand. The benzothiophene is the most reactive compound. However it is the most inhibitor compound for the transformation of others sulfur compounds. Regarding the olefins, the hex-1-ene is the most reactive compound among the others branched compounds. A mutual inhibition has been observed when those compounds are studied in mixture according with their structures. These effects result from competitive adsorption between the molecules on the catalyst surface. These results could be modeled and quantified (adsorption and kinetic constants) from a unique model considering the Langmuir-Hinshelwood formalism
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Freitas, Patricia Antonio de Menezes. "Estudos de adsorção de di-2-piridil cetona saliciloilhidrazona (DPKSH) em resinas amberlite xad-2 e xad-7. Extração de íons cobre em fase sólida envolvendo a xad-7 modificada com DPKSH." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/46/46133/tde-31012008-155245/.
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Di-2-piridil cetona saliciloilhidrazona (DPKSH) é uma hidrazona que forma compostos de coordenação com diversos íons metálicos. As resinas Amberlite XAD-2 e XAD-7 são polímeros não-iônicos que podem ser usados para a pré-concentração de íons metálicos. A adsorção de DPKSH nessas matrizes poliméricas foi etudada utilizando a espectrofotometria. A quantidade de DPKSH adsorvida nessas resinas foi calculada a partir da diferença entre a concentração inicial a concentração remanescente na solução sobrenadante, após o contato com a fase sólida em diferentes intervalos de tempo. Modelos cinéticos de pseudo-primeira e pseudo-segunda ordens foram aplicados aos dados experimentais coletados no estudo cinético. Outros experimentos realizados com tempo constante, mas variando a concentração inicial de DPKSH, forneceram dados experimentais que foram aplicados a três modelos de isotermas (Langmuir, Freundlich and Dubinin-Radushkevich) e alguns parâmetros termodinâmicos foram calculados para descrever a adsorção. Para a XAD-7, um estudo cinético mais completo foi realizado incluindo concentrações iniciais de DPKSH. A resina XAD-7 modificada com DPKSH foi então utilizada para estudar a retenção de íons Cu(II) usando três sistemas diferentes: (a) espectrofotometria direta; (b) uma coluna de vidro parcialmente preenchida com a resina modificada e (c) usando a técnica de análise por injeção em fluxo (FIA) com uma mini-coluna preenchida com a fase sólida. Finalmente, Cu(II) foi determinado em amostras sintéticas e comerciais de aguardente.Di-2-pyridyl ketone salicyloylhydrazone (DPKSH) is a hydrazone which forms coordination compounds with several metallic ions. Amberlite XAD-2 and XAD-7 resins are non-ionic polymers which can be used to pre-concentrate metallic ions. Adsorption of DPKSH onto these polymeric matrices was investigated using the spectrophotometry. The amount of DPKSH adsorbed onto the resins was calculated as the difference between the initial concentration and the remained concentration in the supernatant solution, after the contact with the solid phase at different intervals of time. Kinetic models of pseudo-first and -second orders and intra-particle diffusion model were applied on experimental data collected from the kinetic study. Other experiments carried out under a constant time, but changing the initial DPKSH concentration, led to experimental data which were applied to three different isotherm models (Langmuir, Freundlich and Dubinin-Radushkevich) and some thermodynamic parameters were calculated and used to describe the adsorption. For XAD-7 a more complete kinetic study was carried out including different initial concentrations of DPKSH. The resin XAD-7 modified with DPKSH was then applied to study the retention of Cu(II) ions using three differents systems: (a) direct spetrophotometry; (b) a glass column filled with the modified resin and (c) using the flow injection analysis (FIA) with a mini-column partially filled with the solid phase. Finally, Cu(II) was determined in commercial and synthesized samples of sugar cane brandy.
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Strey, Leonardo. "Biossorção de íons metálicos em águas utilizando casca de pinus como material adsorvente alternativo." Universidade Estadual do Oeste do Paraná, 2013. http://tede.unioeste.br:8080/tede/handle/tede/1253.
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Previous issue date: 2013-08-01Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
This work proposes the use of the bark of Pinus elliottii, a residue of wood processing, as biosorbent in the removal of metal ions Cd2+, Pb2+ and Cr3+solutions fortified, as an alternative to conventional treatment methods, such as precipitation, ion exchange, electrochemical treatment, flocculation and filtration. The biosorbent was characterized by scanning electron microscopy (SEM), infrared spectroscopy (FT-IR) and point of zero charge (pHPCZ). Adsorption tests were performed aiming to determine the optimal conditions of pH, mass of adsorbent and contact time for the adsorption process. The adsorption kinetics was evaluated by pseudofirst and pseudosecond order models, Elovich and intraparticle diffusion. Adsorption isotherms for each metal were constructed, which were linearized according to mathematical models of Langmuir, Freundlich and Dubinin-Radusckevich. To compare this biosorbent with a commercial adsorbent, comparative studies with activated charcoal were performed . Furthermore, we evaluated the ability of desorption of materials and the influence of temperature on adsorption of metals studied by pine bark. The characterization of the biosorbent by SEM showed a rough and heterogeneous surface, important adsorption characteristics. From the FT-IR was identified compounds such as lignin, cellulose and hemicellulose, which favor the adsorption process. The pHPZC obtained was 3.5. The mass tests showed that 8 g L-1 biosorbent are sufficient for efficient removal of metal ions in solution. From the tests of pH, optimum conditions were obtained: 7.0 for Cd and 5.0 to Pb and Cr. The equilibrium time for adsorptive process were 40, 20 and 80 min for Cd, Pb and Cr, respectively. With the application of kinetic models is possible to suggest that the main limiting step for adsorption of these metal ions may be the chemisorption. The mathematical models that best fitted for the adsorption pine bark were Dubinin-Radushkevich for Cd, Freundlich for Pb, and Langmuir and Freundlich for Cr. The increase in temperature increased removal efficiency and, furthermore, with the thermodynamic parameters, it was found that the adsorption process is controlled by chemisorption. Desorption values were low, indicating a strong interaction of the metal with the surface of the adsorbent. In comparative studies with activated coal its possible to concluded that, despite the bark of Pinus elliottii present an adsorption efficiency less than this, the same satisfactory results of adsorption and removal of metal ions present in solutions fortified. Thus, it is concluded that the use of the bark of Pinus elliottii as biosorbents showed a promising alternative for the decontamination of contaminated water bodies by metal ions Cd, Pb and Cr
O presente trabalho propõe a utilização da casca de Pinus elliottii, um resíduo do beneficiamento da madeira, como biossorvente na remoção dos íons metálicos Cd2+, Pb2+ e Cr3+ de meio aquoso, como alternativa aos métodos convencionais de tratamento, como a precipitação, troca iônica, tratamento eletroquímico, floculação e filtração. O biossorvente foi caracterizado por meio de microscopia eletrônica de varredura (MEV), espectroscopia na região do infravermelho (FT-IR) e ponto de carga zero (pHPCZ). Após a caracterização foram realizados testes de adsorção objetivando determinar as condições ideais de pH, massa de adsorvente e tempo de contato para o processo de adsorção. A cinética de adsorção foi avaliada pelos modelos de pseudoprimeira ordem, pseudossegunda ordem, Elovich e difusão intrapartícula. Foram construídas as isotermas de adsorção para cada metal, as quais foram linearizadas conforme os modelos matemáticos de Langmuir, Freundlich e Dubinin-Radusckevich. Visando comparar este biossorvente com um adsorvente comercial, foram realizados estudos comparativos com o carvão ativado. Além disso, foram avaliados a capacidade de dessorção dos materiais e a influência da temperatura no processo de adsorção dos metais em estudo pela casca de pinus. A caracterização do biossorvente por meio da técnica de MEV mostrou uma superfície irregular e heterogênea, importantes características de adsorção. A partir da FT-IR foi possível identificar grupos funcionais comuns a estrutura da lignina, celulose e hemicelulose, os quais favorecem o processo de adsorção. O pHPCZ obtido foi de 3,5. Os testes de massa demonstraram que 8 g L-1 do biossorvente são suficientes para uma remoção eficiente dos íons metálicos em solução. A partir dos testes de pH, as condições ideais obtidas foram: 7,0 para Cd e, 5,0 para Pb e Cr. Os tempos de equilíbrio para o processo adsortivo foram 40, 20 e 80 min, para Cd, Pb e Cr, respectivamente. Com a aplicação dos modelos cinéticos sugere-se que a etapa limitante para a adsorção destes íons metálicos pode ser a quimiossorção. Os modelos matemáticos que melhor se ajustaram para a adsorção em casca de pinus foram Dubinin-Radushkevich para o Cd, Freundlich para Pb e, Langmuir e Freundlich para o Cr. O incremento na temperatura aumentou eficiência de remoção e, além disso, com os parâmetros termodinâmicos, concluiu-se que o processo de adsorção é controlado pela quimissorção. Os valores de dessorção foram baixos, indicando uma forte interação dos metais com a superfície do adsorvente. Com os estudos comparativos com o carvão ativado foi possível concluir que apesar da casca de Pinus elliottii apresentar uma eficiência de adsorção menor que este, a mesma apresentou resultados satisfatórios de adsorção e remoção dos íons metálicos presentes nas soluções fortificadas. Assim, conclui-se que a utilização da casca de Pinus elliottii como biossorvente mostrou-se uma alternativa promissora para descontaminação de corpos hídricos contaminados pelos íons metálicos Cd, Pb e Cr
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Pradhan, Nirakar. "Hydrogen and lactic acid synthesis through capnophilic lactic fermentation by Thermotoga neapolitana." Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1145/document.
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Les énergies non-renouvelables ont été d’un apport capital dans l’industrialisation et l’urbanisation dans les derniers centenaires. L’exploitation excessive des réserves d’hydrocarbures et son impact environnemental ont contribué au developpement de plusieurs technologies durables à caractère néo-carbone neutre. A cet effet, les processus biologiques comme la fermentation pourraient être exploités pour convertir biologiquement le hydrates de carbone en énergies comme l’hydrogène (H2) ou des acides organiques commercialement rentables. Ce travail a étudié les techniques d’ingénierie pour améliorer la synthèse simultanée d’H2 et d’acide lactique à travers des conditions de fermentation capnophile lactique (CLF) par une souche de labo de Thermotoga neapolitana.En un premier temps, une comparaison génotypique entre la souche de labo et celle sauvage a révélé une ressemblance de 88,1 (±2,4) %. En plus, les analyses du génotypage par RiboPrint® et par spectroscopie de masse matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF MS) ont montré une différentiation génétique au-delà du niveau sous-espèce ; et par conséquent la souche de labo a été proposée comme sous-espèce, T. neapolitana subsp. lactica. Basé sur la caractérisation phénotypique, la souche de labo produisait 10-90% plus d’acide lactique que celle sauvage sous les mêmes conditions sans pour autant affecté le taux de production d’H2.La souche de labo a donc été étudiée pour aussi bien optimiser les conditions de croissance que pour estimer les paramètres cinétiques de croissance. Un nouveau modèle cinétique basé sur les principes de fermentation à l’obscurité (DF) et les expressions mathématiques Monod ont été développés pour permettre la simulation de la croissance en biomasse, la consommation de substrat, et la formation de produit. Le modèle n’a cependant pas pu faire une estimation des acides acétique et lactique avec précision du fait que le modèle DF n’a pas considéré la carboxylation de l’acide acétique en acide lactique par l’enzyme pyruvate ferrédoxine oxydoréductase (PFOR) sous les conditions CLF.Le model a été associé avec le mécanisme CLF et les paramètres cinétiques ont été recalibrés. Les paramètres cinétiques que sont le taux d’absorption spécifique maximum (k), la constante semi-saturation (ks), le coefficient en rendement biomasse (Y), et le taux de décomposition interne (kd) étaient de 1,30 l/h, 1,42 g/L, 0,12 et 0,02 l/h. Fait intéressant, le nouveau modèle CLF s’est parfaitement adapté avec les résultats expérimentaux et a estimé que près de 40-80% de la production d’acide lactique est attribué au recyclage de l’acide acétique et le CO2.En plus, l’adsorption de l’acide lactique par le carbone actif et les résines polymères anioniques a été appliquée avec succès comme technique de transformation en aval dans la récupération et la purification de l’acide lactique à partir du modèle de fermentation type T. neapolitana. Pour ce faire, ce travail de recherche constitue une étape majeure dans le domaine de la fermentation bactérienne utilisable pour de vastes applications scientifiques prenant en compte le développement d’énergies renouvelables et la production industrielle d’acide lactiqueThe environmental impact of excessive exploitation of fossil fuel reserves has inspired the innovation of several sustainable neo-carbon-neutral technologies. To that end, the biological processes like fermentation may be leveraged to bioconvert carbohydrate-rich feedstocks to fuels like hydrogen (H2) or commercially valuable organic acids like lactic acid. This research work investigated the engineering techniques for improving simultaneous synthesis of H2 and lactic acid under capnophilic (CO2-dependent) lactic fermentation (CLF) conditions by a lab strain of Thermotoga neapolitana.Primarily, the genotypic comparison between the lab strain and the wild-type revealed DNA homology of 88.1 (± 2.4)%. Genotyping by RiboPrint® and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analyses showed a genetic differentiation beyond subspecies level, hence the lab strain was proposed as a new subspecies, T. neapolitana subsp. lactica. The lab strain produced 10-90% more lactic acid, based on the phenotypic characterization, than the wild-type strain under similar operating conditions without impairing the H2 yield.The lab strain was then studied to optimize the growth conditions as well as to estimate the growth kinetic parameters. A new mathematical model based on the dark fermentation (DF) principles and Monod-like kinetic expressions was developed to enable the simulation of biomass growth, substrate consumption and product formation. The model failed to estimate acetic and lactic acid accurately, as the DF model did not consider the carboxylation of acetic acid to lactic acid by the pyruvate:ferredoxin oxidoreductase (PFOR) enzyme under CLF conditions. The model was then incorporated with the CLF mechanism and the kinetic parameters were recalibrated.The calibrated kinetic parameters, i.e. maximum specific uptake rate (k), semi-saturation constant (kS), biomass yield coefficient (Y) and endogenous decay rate (kd) were 1.30 1/h, 1.42 g/L, 0.12 and 0.02 1/h, respectively, under CLF conditions. The new CLF-based model fitted very well with the experimental results and estimated that about 40-80% of the lactic acid production is attributed to the recycling of acetic acid and CO2.In addition, the adsorption of lactic acid by activated carbon and anionic polymeric resins was successfully applied as a downstream processing technique for the recovery of lactic acid from a model T. neapolitana fermentation broth. This research work serves as a practical milestone in the field of microbial fermentation with a scope for wider scientific applications, including the development of bio-based renewable energy and industrial lactic acid production
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Danielson, Thomas Lee. "Investigation of Static and Dynamic Reaction Mechanisms at Interfaces and Surfaces Using Density Functional Theory and Kinetic Monte Carlo Simulations." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/71296.
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The following dissertation is divided into two parts. Part I deals with the modeling of helium trapping at oxide-iron interfaces in nanostructured ferritic alloys (NFAs) using density functional theory (DFT). The modelling that has been performed serves to increase the knowledge and understanding of the theory underlying the prevention of helium embrittlement in materials. Although the focus is for nuclear reactor materials, the theory can be applied to any material that may be in an environment where helium embrittlement is of concern. In addition to an improved theoretical understanding of helium embrittlement, the following DFT models will provide valuable thermodynamic and kinetic information. This information can be utilized in the development of large-scale models (such as kinetic Monte Carlo simulations) of the microstructural evolution of reactor components. Accurate modelling is an essential tool for the development of new reactor materials, as experiments for components can span decades for the lifetime of the reactor.
Part II of this dissertation deals with the development, and use of, kinetic Monte Carlo (KMC) simulations for improved efficiency in investigating catalytic chemical reactions on surfaces. An essential technique for the predictive development and discovery of catalysts relies on modelling of large-scale chemical reactions. This requires multi-scale modelling where a
common sequence of techniques would require parameterization obtained from DFT, simulation of the chemical reactions for millions of conditions using KMC (requiring millions of separate simulations), and finally simulation of the large scale reactor environment using computational fluid dynamics. The tools that have been developed will aid in the predictive discovery, development and modelling of catalysts through the use of KMC simulations. The algorithms that have been developed are versatile and thus, they can be applied to nearly any KMC simulation that would seek to overcome similar challenges as those posed by investigating catalysis (such as the need for millions of simulations, long simulation time and large discrepancies in transition probabilities).Ph. D.
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Lang, Matthew H. "Polyelectrolyte adsorption kinetics." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/5792.
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Lima, Camila Renata Machado de. "Estudos de adsor??o de tetraciclina e cromoglicato em part?culas de quitosana." Universidade Federal do Rio Grande do Norte, 2013. http://repositorio.ufrn.br:8080/jspui/handle/123456789/17693.
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Previous issue date: 2013-01-25Universidade Federal do Rio Grande do Norte
Among the polymers that stand out most in recent decades, chitosan, a biopolymer with physico-chemical and biological promising properties has been the subject of a broad field of research. Chitosan comes as a great choice in the field of adsorption, due to their adsorbents properties, low cost and abundance. The presence of amino groups in its chain govern the majority of their properties and define which application a sample of chitosan may be used, so it is essential to determine their average degree of deacetylation. In this work we developed kinetic and equilibrium studies to monitor and characterize the adsorption process of two drugs, tetracycline hydrochloride and sodium cromoglycate, in chitosan particles. Kinetic models and the adsorption isotherms were applied to the experimental data. For both studies, the zeta potential analyzes were also performed. The adsorption of each drug showed distinct aspects. Through the studies developed in this work was possible to describe a kinetic model for the adsorption of tetracycline on chitosan particles, thus demonstrating that it can be described by two kinetics of adsorption, one for protonated tetracycline and another one for unprotonated tetracycline. In the adsorption of sodium cromoglycate on chitosan particles, equilibrium studies were developed at different temperatures, allowing the determination of thermodynamic parameters
Dentre os pol?meros que mais se destacam nas ?ltimas d?cadas, a quitosana, um biopol?mero com propriedades f?sico-qu?micas e biol?gicas promissoras, tem sido alvo de um campo amplo de pesquisa. A quitosana se apresenta como uma ?tima escolha no campo de adsor??o, devido a suas propriedades adsorventes, baixo custo e abund?ncia. A presen?a de grupos aminos em sua cadeia governam a maioria das suas propriedades e definem em qual aplica??o dada amostra de quitosana poder? ser utilizada, assim torna-se imprescind?vel a determina??o do seu grau de desacetila??o m?dio. Neste trabalho foram desenvolvidos estudos cin?ticos e de equil?brio a fim de monitorar e caracterizar o processo de adsor??o de dois f?rmacos, o cloridrato de tetraciclina e o cromoglicato de s?dio, em part?culas de quitosana. Modelos cin?ticos e de isotermas de adsor??o foram aplicados nos dados experimentais. Para ambos os estudos, an?lises no potencial zeta tamb?m foram realizadas. A adsor??o de cada f?rmaco apresentou aspectos distintos. Atrav?s dos estudos desenvolvidos neste trabalho foi poss?vel descrever um modelo cin?tico para a adsor??o de tetraciclina em part?culas de quitosana, demonstrando que o mesmo pode ser descrito por duas cin?ticas de adsor??o, uma para a tetraciclina protonada e outra para a tetraciclina n?o protonada. Na adsor??o de cromoglicato de s?dio em part?culas de quitosana, estudos de equil?brio foram desenvolvidos a diferentes temperaturas, permitindo a determina??o de par?metros termodin?micos
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Borsato, Francimeiri Piva. "Avaliação do mecanismo de adsorção do metronidazol em carvão ativado da casca do coco babaçu." Universidade Estadual do Oeste do Paraná, 2018. http://tede.unioeste.br/handle/tede/3988.
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This work has evaluated the adsorption capability of three coal produced in the Universidade Estadual do Oeste do Paraná (tilapia bone residual coal, soybean bark coal and chestnut from Pará) and other kind of coal commercially obtained (babaçu coconut pealing coal) to remove the metronidazole from aqueous solution. The coal which better absorbed the metranidazole was the babaçu coconut peal one (CCCB) with temperature from 40ºC, 150 rpm of stirring and with no pH adjustment. Thus, the kinetic tests were performed by using the SOTAX dissolution apparatus, with 1000 mL of metronidazole solution, varying the concentration (200, 400, 650 and 850 mg/ L) and the temperature (30, 40, 45ºC), 1 g of the coal and 150 rpm of stirring. The equilibrium time observed was around 20 hours and in the first 4 hours a bigger amount of metranidazole was adsorbed, this inicial amount corresponds to the metranidazole adsorption in the outer layer of the CCCB. The results obtained from the adsorption kinetics were described by the intraparticule diffusion in which were verified the appearing of four well defined regions corresponding to the adsorption in the outer layer, in the macropores, in the CCCB mesopores and the equilibrium, respectively. In the equilibrium studies, were presented two adsorption mechanisms: monolayer and multilayer with increasing concentration of the adsorbate, corresponding to the hybrid model of Langmuir + BET. The removing process of metranidazole by using CCCB became economically viable due to the low cost in the obtention or production of the adsorbent, the easily extracetion of the babaçu coconut biomass and the excellent capability of maximum adsorptive to the metranidazole.
Neste trabalho, avaliou-se a capacidade de adsorção de três carvões produzidos na Universidade Estadual do Oeste do Paraná (carvão do resíduo ósseo de tilápia, carvão da casca da soja e o carvão da casca da castanha do Pará) e um carvão obtido comercialmente (carvão da casca do coco babaçu) para remoção do antibiótico metronidazol de solução aquosa. O carvão que melhor adsorveu o metronidazol foi o carvão da casca do coco babaçu (CCCB) com temperatura de 40ºC, 150 rpm de agitação e sem ajuste de pH. Dessa forma, os testes cinéticos foram realizados com o auxílio de um dissolutor (Sotax), utilizando 1000 mL de solução de metronidazol, variando a concentração (200, 400, 650 e 850 mg L-1) e a temperatura (30, 40 e 45ºC), 1 g do carvão e 150 rpm de agitação. O tempo de equilíbrio observado foi de aproximadamente 20 horas e nas primeiras 4 horas uma maior quantidade de metronidazol foi adsorvida, essa quantidade inicial corresponde à adsorção do metronidazol na camada externa do CCCB. Os dados obtidos a partir da cinética de adsorção foram descritos pelo modelo de difusão intrapartícula, no qual verificou-se o aparecimento de quatro regiões bem definidas correspondendo respectivamente a adsorção na camada externa, nos macroporos, nos mesoporos do CCCB e por último o equilíbrio. No estudo de equilíbrio, apresentou dois mecanismos de adsorção: monocamada e multicamadas com o aumento da concentração do adsorvato, correspondendo ao modelo híbrido de Langmuir+ BET. O processo de remoção de metronidazol utilizando o CCCB é economicamente viável visto o baixo custo na obtenção ou fabricação do adsorvente por ser extraído da biomassa do coco babaçu, além de possuir uma excelente capacidade máxima adsortiva para o antibiótico estudado.
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Costa, Diego Pinto. "Modelagem computacional aplicada na estimação de parâmetros cinéticos em processos químicos e cromatográficos." Universidade do Estado do Rio de Janeiro, 2012. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=4853.
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Conselho Nacional de Desenvolvimento Científico e TecnológicoA estimação de parâmetros cinéticos em processos químicos e cromatográficos utilizando técnicas numéricas assistidas por computadores tem conduzido para melhoria da eficiência e o favorecimento da compreensão das fenomenologias envolvidas nos mesmos. Na primeira parte deste trabalho será realizada a modelagem computacional do processo de produção de biodiesel via esterificação, sendo que, o método de otimização estocástica Random Restricted Window (R2W) será correlacionado com os dados experimentais da produção de biodiesel a partir da esterificação do ácido láurico com etanol anidro na presença do catalisador ácido nióbico (Nb2O5). Na segunda parte do mesmo será realizada a modelagem computacional do processo de cromatografia de adsorção (batch process) onde serão correlacionados os dados provenientes dos modelos cinéticos de HASHIM, CHASE e IKM2 com os dados experimentais da adsorção de amoxicilina com quitosana, e também serão correlacionados os dados experimentais da adsorção de Bovine Serum Albumin (BSA) com Streamline DEAE com os dados provenientes de uma nova aplicação do método R2W mediante a implementação de um modelo cinético reversível. Ademais, as constantes cinéticas para cada processo supracitado serão estimadas levando em consideração o valor mínimo da função resíduos quadrados.
The estimation of kinetic parameters in chemical and chromatographic processes using numerical techniques assisted by computers has led to the improved of efficiency and facilitating the understanding of phenomenologies involved in those. In the first part of this work will be carried out the computational modeling of production process of biodiesel by esterification, and that, the stochastic method of optimization Random Restricted Window (R2W) will be correlated with the experimental data of biodiesel production through the esterification of lauric acid with anhydrous ethanol in the presence of niobic acid (Nb2O5) as catalyst. In the second part of this will be carried out the computational modeling of the process of adsorption chromatographic (batch process) where will be correlated the data by the kinetic models of HASHIM, CHASE and IKM2 with the experimental data of amoxicillin adsorption with quitosan, and will also be correlated the experimental data of Bovine Serum Albumin (BSA) with Streamline DEAE with the data from a new application of R2W method through the implementation of a reversible kinetic model. Moreover, the kinetic constants for each process aforementioned will be estimated taking into account the minimum value of function of square residues.
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Brouette, Nicolas. "Influence des propriétés interfaciales de couches organiques sur l'adsorption de protéines globulaires." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209645.
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Dans ce travail, l'adsorption de protéines globulaires sur des surfaces modifiées a été investiguée par ellipsométrie et par réflectivité de neutrons.L'adsorption de myoglobine deutérée sur des monocouches hydrophobes d'OTS et de PS a été étudiée par réflectivité de neutrons pour des solutions de protéines de différentes concentrations (de 1 mg/ml à 0.01 mg/ml). A basse concentration, les protéines adsorbées se dénaturent et s'étalent sur le substrat hydrophobe et l'adsorption résulte en une fine couche dense en protéines. Sur le PS, les protéines s'étalent moins, ce qui est en accord avec la moindre hydrophobicité du PS. A haute concentration, une couche supplémentaire peu dénaturée est observée au-dessus de la première couche.
La cinétique d'adsorption primaire de HSA a été étudiée par ellipsométrie sur des brosses de PEG (Mw = 35700 Da) de différentes densités de greffage. Les résultats confirment que les brosses de PEG répriment l'adsorption de protéines. En outre, l'adsorption est très rapide sur le PS, tandis que sur les brosses, l'adsorption est plus lente. Le comportement à temps long de la quantité adsorbée Γ en fonction de la densité de greffage σ est en accord semi-quantitatif avec une théorie développée par Halperin et basée sur les différentes contributions à l'énergie libre d'une protéine adsorbée. Il a également été mis en évidence un régime pour lequel le taux d'adsorption dΓ/dt décroît exponentiellement avec la quantité de protéines adsorbées Γ.
L'adsorption de protéines (lysozyme, HSA et myoglobine) a ensuite été étudiée sur des brosses de PNIPAM en fonction des paramètres de la brosse et de la température. Les brosses ont été greffées par ATRP à partir d'une monocouche d'OEG (oligo éthylène glycol) silanisé contenant du brome comme initiateur. Il a été montré que l'adsorption primaire sur la surface de greffage est inférieure à 0.1 mg/m^2 et que l'adsorption ternaire dans la brosse, en dessous et au-dessus de la LCST, ne dépasse pas 1 mg/m^2 (~ 2% de fraction volumique en protéines). La résistance à l'adsorption a été associée à la présence d'une région hydrophile superficielle qui pourrait présenter une barrière cinétique à l'adsorption des protéines dans le cœur moins polaire de la brosse.
L'ensemble de ces résultats montre que les propriétés interfaciales du substrat jouent un rôle crucial dans les processus d'adsorption des protéines.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Graf, Barbara [Verfasser], Martin [Gutachter] Muhler, and Wolfgang [Gutachter] Grünert. "The coupling of transient kinetic measurements with adsorption calorimetry for clarification of the structure-response relationship in Fischer-Tropsch catalysts / Barbara Graf ; Gutachter: Martin Muhler, Wolfgang Grünert ; Fakultät für Chemie und Biochemie." Bochum : Ruhr-Universität Bochum, 2011. http://d-nb.info/1212660846/34.
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Borthwick, D. S. "Adsorption kinetics and thermodynamics from single crystal adsorption calorimetry." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596784.
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The interactions of CO, NO and O2 with Pt{111}, pt{211}, and Pt{411} have been investigated with Single Crystal Adsorption Calorimetry (SCAC). Coverage-dependent heat of adsorption and sticking probability data for 300 K are presented, and are discussed with respect to the kinetics and thermodynamics of adsorption and desorption. CO adsorption proceeds molecularly on both Pt{111} and Pt{411}, with initial sticking probabilities of 0.78 and 0.80, and initial heats of adsorption of 176 kJ mol-1 and 196 kJ mol-1, respectively. Both adsorbate layers are found to be non-localised, having identical pre-exponential factors of 2x1015 s-1. Discrepancies between isosteric and calorimetric heat of adsorption data at low coverage for CO/Pt{111} have been rationalised in terms of an entropy-driven localised/non-localised phase transition occurring above 300 K. Initial adsorption of NO occurs with a sticking probability of 0.84 on all three surfaces. The initial heat of adsorption for NO/Pt{411} indicates dissociative adsorption. The NO/Pt adsorbate layers are found to be highly localised, with pre-exponential factors in the range 1017 – 1020 s-1. This has been discussed in terms of desorption from highly compressed adsorbate layers in which co-operative effects are extant. O2 adsorption proceeds dissociatively on all three surfaces, with the initial heats of adsorption all above 300 kJ mol-1. Desorption occurs from localised adsorbate layers, with all systems having pre-exponential factors of 1018 s-1. A kinetic compensation effect has been observed for the data of this thesis, as well as that of the SCAC literature, and is discussed within the context of the chemisorption entropy-enthalpy compensation.
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Dalton, James Spencer. "The kinetics of surfactant adsorption." Thesis, University of Bristol, 1999. http://hdl.handle.net/1983/d2ce527d-0373-4191-b2d9-8e9e7d81dd9f.
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Ojwang, Dickson Odhiambo. "Prussian blue analogue copper hexacyanoferrate : Synthesis, structure characterization and its applications as battery electrode and CO2 adsorbent." Doctoral thesis, Stockholms universitet, Institutionen för material- och miljökemi (MMK), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-146335.
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Prussian blue (PB) and Prussian blue analogues (PBAs) are compounds with potential applications in a large variety of fields such as gas storage, poison antidotes, electrochromism, electrochemistry and molecular magnets. The compounds are easy to synthesize, cheap, environmentally friendly and have been pursued for both fundamental research and industrial purposes. Despite the multifunctionality of PB and PBAs, they have complicated compositions, which are largely dependent on the synthesis methods and storage conditions. Thus, performing investigations on such compounds with defined composition, stoichiometry and crystal structure is essential. This thesis has focused on synthesis and detailed structure characterization of copper hexacyanoferrate (CuHCF) via X-ray powder diffraction (XRPD), neutron powder diffraction (NPD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), inductively coupled plasma-optical emission spectroscopy (ICP-OES), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Mössbauer spectroscopy, extended X-ray absorption fine structure (EXAFS), infrared (IR) and Raman techniques. In addition, kinetics of thermal dehydration process, CO2 adsorption and CO2 adsorption kinetics were investigated. Moreover, in operando synchrotron X-ray diffraction experiments were performed to gain insight into the structure-electrochemistry relationships in an aqueous CuHCF/Zn battery during operation.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript.
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Enarsson, Lars-Erik. "Polyelectrolyte adsorption on oppositely charged surfaces - Conformation and adsorption kinetics." Licentiate thesis, Stockholm : Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4059.
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