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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

A kinetic study of the transfer of acetone between toluene and water phases

Puyear, Donald Empson January 1965 (has links)
The purpose of this investigation was to apply the techniques of chemical kinetics to the transfer of acetone between water and toluene phases, and thereby attempt to develop mechanisms and evaluate resistances to such transfer. An extraction cell was constructed which consisted of a 20-liter glass battery jar with independently driven impellers in each phase and a stationary phase divider at the interface. Extraction tests were conducted on the toluene-acetone-water system in the cell at 4, 15, and 30℃ at initial acetone concentrations ranging from 0.008 to 0.035 gram acetone per gram solvent. In all tests the stirrer bars were in contra-rotation at approximately 60 revolutions per minute. Initial unidirectional transfer rates were correlated with initial acetone concentrations and the correlations were used to predict the net rate of mass transfer at other than initial conditions. The results of this investigation led to the following conclusions: The flux of acetone from toluene solution to pure water, gm/min, sq cm, at 30℃ (F<sub>t</sub>) may be represented by the equation F<sub>t</sub> = 0.0403 C<sub>t</sub> where C<sub>t</sub> is gm acetone/gm toluene. The flux of acetone from an aqueous solution to pure toluene at 30℃ may be represented by the equation F<sub>w</sub> = 10 (- 0.0333 + 43.34 C<sub>w</sub>) / 10⁴ for aqueous acetone concentrations between 0.010 and 0.035 gram acetone per gram water, and by F<sub>w</sub> = 0.0251 C<sub>w</sub> for aqueous acetone concentrations below 0.010 gram acetone per gram water. For the range of concentration and driving force studied, the transfer of acetone between solutions in toluene and in water at 30℃ may be evaluated as the difference in the unidirectional fluxes. A mechanism for the transfer of acetone between toluene and water is proposed which involves, for transfer in each direction, (1) eddy diffusion of the acetone to the region of the interface, (2) transfer of a small amount of solvent from the opposite side of the interface, (3) a change in solvation of the acetone involving solvent from the opposite phase dissolved at the interface, (4) molecular diffusion into the opposite phase, and (5) eddy diffusion of the solvated acetone away from the region of the interface into the bulk of the receiving phase. Neither accepted theories, which predict that the coefficient of mass transfer will vary as a simple function of molecular diffusivity, nor correlations based on the rate of stirring and physical properties of the phases accounted for the large increase in the flux of acetone from water to toluene with increasing initial acetone concentrations in the aqueous phase. / Ph. D.
82

Internal pressure's role in the selectivity of the bromine radical

Hulvey, Glenn A. 10 June 2009 (has links)
The results of our studies demonstrate a link between selectivity in free radical brominations and the internal pressure of solvent. The study encompassed l8 solvents and/or mixtures over which the rate constant ratio for SH2 ring opening of cyclopropylbenzene (kC) vs hydrogen abstraction from toluene (kH) by bromine atom was found to vary by nearly a factor of twenty as a function of solvent. The observed rate constant ratios correlate with the cohesive energy density of the solvent, which is approximately equal to the internal pressure (kC/kH is found to increase with increasing solvent pressure) for the solvents used in this study. A similar competition pitting cyclopropylbenzene against p-chlorotoluene shows the same solvent effect. It is suggested that the observed variation in selectivity "with solvent pressure occurs because the volume of activation with kC is more negative than for kH by about 20 cm3/mol. / Master of Science
83

Variations in the biodegradation potential of toluene with increasing depth in an unsaturated subsurface environment

Gullic, David Bryan 04 March 2009 (has links)
A microcosm study was performed to investigate the biodegradation potential of BTX compounds in unsaturated soils under aerobic and anaerobic conditions. Toluene was used as a model compound at concentrations of 100 to 200 mg/L. An uncontaminated, groseclose soil ranging in depth from 0 to 18 feet was used in order to observe differences in microbial degradation abilities in shallow subsurface environments. Several metabolic groups were investigated including aerobes, denitrifyers and sulfate reducers. Bacterial densities of these groups were determined at each soil depth. Physical and chemical parameters of the subsurface environments were also investigated to observe their impact on microbial biodegradation potentials. These included changes in soil particle size, moisture content, and pH with increasing depth. Substantial toluene biodegradation took place in some, but not all soils under both aerobic and denitrifying conditions. Biodegradation rates varied considerably among aerobes and denitrifyers in similar environments. In acidic, poorly drained clay soils of 3, 6 and 9 feet, denitrifyers readily degraded toluene while aerobic microorganisms were unable to mineralize the compcund. Evidence of toluene biodegradation by anaerobic bacteria including sulfate reducers was also observed in moist, clay soils although the rates were much slower. Currently, in situ bioremediation techniques for benzene, toluene and xylene compounds almost always rely on indigenous, aerobic organisms to degrade the contaminants. However, results of this study indicate that aerobic organisms capable of biodegradation may not exist in some subsurface environments, even in soils very close to the surface. The physical/chemical properties of unsaturated environments have significant impacts on microbial capabilities as well as the biodegradation potential of contaminants. / Master of Science
84

High-Temperature, High-Pressure Viscosities and Densities of Toluene

Rowane, Aaron J 01 January 2016 (has links)
High-temperature, high-pressure (HTHP) conditions are exemplified in ultra-deep petroleum reservoirs and can be exhibited within diesel engines. Accurate pure component hydrocarbon data is essential in understanding the overall behavior of petroleum and diesel fuel at these conditions. The present study focuses on the HTHP properties of toluene since this hydrocarbon is frequently used to increase the octane rating of gasoline and toluene occurs naturally in crude oil. In this thesis experimental densities and viscosity are presented to 535 K and 300 MPa extending the database of toluene viscosity data to higher temperature than previous studies. The data is correlated to a Tait-like equation and a Padѐ approximate in conjunction with a single mapping of the isotherms. Free-volume theory and a superposition of the viscosity in relation to the Leonnard-Jones repulsive force are both used to model the toluene viscosity data. It was found that the data are in good agreement with the available literature data.
85

Influência das condições meteorológicas na concentração do benzeno e tolueno na Região Metropolitana de São Paulo: interação com outros poluentes / Influence of meteorological conditions on the concentration of benzene and toluene in the Metropolitan Region of São Paulo: interaction with other pollutants

Sanchez, Dayana Yordy 26 February 2019 (has links)
Os hidrocarbonetos (HCs) aromáticos monocíclicos, como o benzeno e o tolueno, estão entre os compostos orgânicos voláteis (COVs) de grande interesse tanto para estudos dereatividade atmosférica, devido à contribuição para formação de smog fotoquímico, quanto por efeitos nocivos diretos à saúde humana. A evaporação e queima incompleta de combustíveis é a principal fonte de benzeno e tolueno, além de atividades industriais e uso de solventes. A Região Metropolitana de São Paulo (RMSP) é uma das maiores aglomerações urbanas do mundo com 21 milhões de habitantes e frota de mais de 7 milhões de veículos. A poluição do ar, com destaque para eventos de smog fotoquímico com altas concentrações de ozônio, tem sido um dos grandes problemas ambientais da RMSP. Devido à importância do benzeno e tolueno, a Companhia Ambiental do Estado de São Paulo (CETESB) iniciou o monitoramento destes compostos com frequência horária na estação Pinheiros, em conjunto com o monitoramento de outros poluentes. Neste trabalho avaliou-se o efeito das condições meteorológicas na variabilidade temporal da concentração do benzeno e tolueno medidos na estação Pinheiros durante o ano 2017, e as interações com outros poluentes (NO2,O3e CO). As concentrações mais altas foram observadas no período do inverno e a primavera (julho, agosto e setembro), decorrentes das condições desfavoráveis à dispersão dos poluentes, com máximos de 2,81 e 14,2 ppbv para benzeno e tolueno respectivamente, 3,70 ppm para CO, 203 e 208 g/m3para NO2 e O3, respectivamente. Os valores de concentração máxima do benzeno, tolueno, CO e NO2 foram obtidos entre as 08 e 10 h da manhã e depois das 20 h, coincidindo com os horários de maior tráfego, e, portanto, aumento das emissões por queima de combustíveis. Valores mínimos foram obtidos entre as 13 e 18 h, associados à diluição e remoção em função do aumento da altura da camada de mistura e/ou da velocidade do vento nestes horários; assim como processos de remoção por reações fotoquímicas. A variação diária da concentração do O3,apresentou níveis mínimos de manhã cedo entre as 6 e 8 horas, iniciando uma subida por volta das 10 horas, atingindo os valores máximos as 15 horas. O benzeno e tolueno apresentaram correlação positiva significativa (r > 0,8) com o CO, reforçando influência das emissões veiculares. Análise mais detalhada para agosto de 2017 mostrou a complexidade das condições meteorológicas afetando a concentração dos compostos estudados, envolvendo eventos sinóticos como a passagem de frentes frias (FF) determinantes na diminuição na concentração de benzeno e tolueno. Enquanto que dias em que as alturas da camada limite convectiva e estável foram abaixo de 500m apresentaram concentrações mais altas de poluentes. / Monocyclic aromatic hydrocarbons (HCs), such as benzene and toluene, are among the volatile organic compounds (VOCs) of great interest for both atmospheric reactivity studies, due to their contribution to the formation of photochemical smog, and for direct harmful effects on human health. The evaporation and incomplete burning of fuels is the main source of benzene and toluene, as well as industrial activities and the use of solvents. The Metropolitan Region of São Paulo (RMSP) is one of the largest urban agglomerations in the world with 21 million inhabitants and more than 7 million vehicles. Air pollution, especially photochemical smog events with high concentrations of ozone, has been one of the major environmental problems for RMSP. Due to the importance of benzene and toluene, the Environmental Company of the State of São Paulo (CETESB) began an hourly monitoring of these pollutants, among others, at Pinheiros Station. This work evaluated the meteorological conditions effects on the temporal variability of the benzene and toluene concentration and their interaction with other pollutants (NO2, O3 and CO) measured at the Pinheiros station during 2017. The highest concentrations were observed during winter (July, August and September), due to the unfavorable conditions for dispersion of pollutants, with maximums of 2.81 and 14.2 ppbv for benzene and toluene, respectively, 3.70 ppm for CO; 203 and 208 g/m3 for NO2 and O3, respectively. The maximum concentration values of benzene and toluene were obtained between 08 and 10 a.m. and after 8 p.m., due to the heaviest traffic, at that time, which increases fuel-burning emissions. The minimum values were obtained between 1 and 6 p.m., which was associated to the dilution and transport as a function of the increase of the height of the mixture layer and/or the wind speed, as well as processes of removal by photochemical reactions. These compounds showed a significant positive correlation (r> 0.8) with CO, reinforcing the influence of vehicular emissions. More detailed analyses for August 2017 showed the complexity of the meteorological conditions affecting the concentration of the studied compounds. For example, synoptic events such as the passage of cold fronts (FF) caused the decrease in the concentration of benzene and toluene, while higher concentrations of benzene and toluene were associated with convective and stable layer conditions below 500 m.
86

Produção e ação de biossurfactante produzido por bactérias em meios salinos contaminados por hidrocarbonetos aromáticos / Production and action of biosurfactant produced by bacteria in saline media contaminated with aromatic hydrocarbons

Ellen Cristina Souza 21 August 2013 (has links)
A contaminação da água e do solo por hidrocarbonetos aromáticos tem aumentado ao longo dos anos, devido ao seu uso nos mais diversos segmentos industriais. Hidrocarbonetos, tais como tolueno, são descritos como extremamente poluentes, tóxicos e potencialmente mutagénicos e carcinogénicos para os seres humanos. Os hidrocarbonetos são compostos lipófilicos difíceis de serem eliminados, contudo, estes aromáticos podem ser removidos de ambientes contaminados por meio de biorremediação utilizando bactérias produtoras de surfactante. Biossurfatantes são surfactantes principalmente produzidos por microrganismos, as quais promovem a quebra das moléculas de hidrocarbonetos, através da formação de micelas, aumentando a sua mobilidade, a biodisponibilidade e sua exposição à bactérias favorecendo a biodegradação do hidrocarboneto. A produção deste tensoativo exige meios de fermentação e oxigênio para o metabolismo microbiano. Por tanto, aeração e agitação são variáveis operacionais importantes para garantir um coeficiente de transferência de massa de oxigénio eficaz (kLa). Para esta finalidade, o kLa foi determinado experimentalmente em diferentes meios de fermentação, especificamente meio salino básico, meio de baixa salinidade, meio Bushnell-Haas e água do mar, por diversas variáveis operacionais. Ensaios foram realizados em agitador rotativo para selecionar, dentre os diferentes tipos de bactérias, nomeadamente Bacillus subtilis, Bacillus licheniformis e Bacillus megatherium, o melhor produtor de biossurfactante na presença de tolueno, nos meios de fermentação descritos acima, formulados com diferentes salinidades. A presença de tolueno inibiu o crescimento de microrganismo deslocando seu metabolismo para a produção de biossurfactante. Assim, B. subtilis foi capaz de reduzir a tensão superficial (TS) em 29,49 ± 0,55 unidades, produzindo cerca de 3,52 ± 0,06 mg/L de biossurfactante. Ao elevar o processo para um fermentador de bancada, a quantidade de tolueno no meio de baixa salinidade foi reduzido drasticamente após 12 horas de crescimento (de 45 ml para 7,43 ml), quando B. subtilis foi utilizado, reduzindo o TS em 22,6 unidades (com concentração de biossurfactante de 3,02 mg/L). Os resultados obtidos mostraram que o B. subtilis pode ser considerado um microrganismo promissor para ser utilizado na biorremediação de locais contaminados por tolueno / Contamination of water and soil by aromatic hydrocarbons has been increasing along the years, due to its use in various industrial segments. Hydrocarbons, such as toluene, are described as extremely polluting, toxic, potentially carcinogenic and mutagenic to humans. Hydrocarbons are lipophilic compounds difficult to be disposed of; however, the aromatic ones can be removed from contaminated environments via bioremediation using surfactant-producing bacteria. Biosurfactants are surfactants produced mainly by microorganisms, which promote the breaking of hydrocarbons molecules, by means of the formation of micelles, increasing their mobility, bioavailability and exposure to bacteria favoring hydrocarbon biodegradation. This tensoactive production requires oxygen and fermentation media for the microorganism metabolism. Thus, aeration and agitation are important operating variables to ensure an effective oxygen mass transfer coefficient (kLa). To this purpose, such a response was experimentally determined in this study in different fermentation media, specifically basal saline medium, low saline medium, Bushnell-Haas medium and sea water, and correlated with the above operating variables. Rotary shaker essays were performed to select, among different bacteria, namely Bacillus subtilis, Bacillus megatherium and Bacillus licheniformis, the best biosurfactant producer in the presence of toluene, in fermentative broths described above, formulated with different salinities. The presence of toluene inhibited the growth of microorganism shifting the metabolism to the production of biosurfactant. Thus, B. subtilis was able to reduce the surface tension (ST) in 29.49 ± 0.55 units producing up to 3.52 ± 0.06 mg/L of biosurfactant. Scaling up the process to a bench fermentor, the quantity of toluene in the low salinity medium was reduced drastically after 12 h of growth (from 45 mL to 7.43 mL), when B. subtilis was used, reducing the ST in 22.6 units (biosurfactant concentration of 3.02 mg/L). The results obtained showed that B. subtilis can be considered a promising microorganism to be used for the bioremediation of sites contaminated by toluene.
87

Simulation of the diffusion of endocrine disrupting compounds in silicalite by molecular dynamics

Gabry, Thomas Jacques Andre 26 April 2012 (has links)
In this thesis we investigated the separation of two endocrine disrupting chemicals (EDC), bisphenol-A (BPA) and nonylphenol (NP) from water over the defect free silicalite zeolite. Two force-fields were investigated, the OPLS-AA force-field which is an all-atom one, and the OPLS-UA force-field which is a united atom one. In order to be able to simulate BPA, we simulated and studied the diffusion of different molecules in silicalite. We compared two famous bulk water models, the non-rigid TIP3P modified for CHARMM model and the rigid SPC model, to literature and simulated the diffusion of these water molecules at temperatures from 300K to 600K. We found that these models coupled with our parameters for silicalite compared poorly with literature except for values calculated by Yazaydin et al. The mean-square displacements (MSDs) were more important in the x-direction (sinusoidal channel) than in the expected y-direction (straight channels) for both models resulting in small self-diffusion coefficient values. Results tended to improve as temperature increased. We believe that the high number of hydrogen bonds, implying the presence of clusters of water molecules, is responsible for the poor self-diffusion coefficient. The charges chosen to describe our silicalite zeolite, +2.05, may also be a reason of our small self-diffusion coefficient. We then investigated the self-diffusion of aromatic molecules at 300 and 400K. Benzene, phenol and toluene were studied. We found self-diffusion coefficients for benzene that did not compare well to experiments but that was close to simulation work done by Rungsirisakun et al. Our diffusion coefficients for benzene were several orders of magnitude bigger than the experimental values found in literature for both force-fields. The diffusion patterns for both phenol and toluene did not allow us to calculate self-diffusion coefficients for both investigated force-fields. We believe that the jumps in the MSDs of these molecules are due to the rotation that they undergo in the nanopores. Phenol anchors to the framework by hydrogen-bonds between the hydrogen of its alcohol group and the oxygen of the framework. The diffusion seems to happen when the alcohol group is in a line with one channel. The same diffusion phenomenon was seen for toluene molecule but was related to the methyl group attached to its benzene ring. When this group is in front of a channel, the energetic barrier is reduced and the molecule can diffuse through it. Finally bigger molecules were simulated and studied. Neopentane seemed to have a very low self-diffusion coefficient in silicalite if it could move at all. We report values of self-diffusion of 1.3 10-14 m2.s-1 at both 300K and 400K. This value seems a little high compared to benzene experimental self-diffusion coefficient values that are in the same order of magnitude at both temperatures. The linear nonylphenol molecule that we simulated seemed to diffuse through silicalite with patterns that were close to the one seen for phenol. The hydrogen bonding between its alcohol group and the framework slows down its diffusion in silicalite. With the same reasoning as for phenol we decided not to calculate diffusion coefficient for NP. The last molecule investigated was bisphenol-A (BPA). We found that BPA almost did not diffuse through silicalite. The size of the molecule can explain why it did not diffuse, but we believe that the angle between the two phenol groups should be able to bend enough for it to diffuse, slowly, through silicalite. Our conclusion is that the two phenol groups at both ends of the molecules are the most important factor in its very slow diffusion. Hydrogen bonding is taking place at both ends making it very hard for the molecule to move in the framework. We decided to generate self-diffusion coefficients for this molecule because the diffusion process did not have jumps. We found self-diffusion coefficient that are 3.10-15 m2.s-1 and 15. 10-15 m2.s-1 at 300 and 400K respectively for the OPLS-AA force-field, and 11.6.10-15 m2.s-1 and 6.68.10-15 m2.s-1 at 300 and 400K respectively for the OPLS-UA force-field. The last result was unexpected as we thought that the self-diffusion coefficient was going to increase with temperature. We believe that running much longer simulations for every molecule that we studied should give more reasonable and reliable results as the self-diffusion coefficients values are very small.
88

Selective toluene disproportionation over ZSM-5 zeolite

Albahar, Mohammed January 2018 (has links)
This research aimed at improving p-xylene selectivity in toluene disproportionation over ZSM-5 zeolite by exploring the effect of crystal size and various post synthetic modification methods. A comprehensive study of the effect of different modifications on the physicochemical properties of ZSM-5 was investigated using X-ray diffraction (XRD), pyridine adsorption, Fourier transform infra-red (FTIR), 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR), BET surface area by N2 adsorption, inductively coupled plasma (ICP) and scanning electron microscopy (SEM). The catalytic performance of each catalyst was studied in a fixed bed reactor at a temperature 475 °C, WHSV 3-83 h-1 and two different pressures (1 and 10 bar). ZSM-5 zeolites with different crystal sizes (5, 50 and 100 ÂÂμm) were synthesized in house and compared with the commercially obtained ZSM-5 having a crystal size of 0.5 ÂÂμm. The increase in crystal size improved p-xylene selectivity which was attributed to the diffusion constraints imposed by the longer diffusion path lengths of large crystals. The highest p-xylene selectivity (58 %) was achieved over ZSM-5 with the largest crystal size 100 ÂÂμm at the highest WHSV 83 h-1. However, it was accompanied by a low conversion (2 wt. %). ZSM-5 with crystal size of 5 ÂÂμm delivered the best results in terms of the combination of para-selectivity (40 %) and toluene conversion (15 wt. %). The p-xylene produced in the channels of ZSM-5 can quickly isomerise to o-xylene and m-xylene on the external unselective acid sites. Different post modification methods were applied in this study in attempt to suppress the fast isomerization reaction by deactivating the external acid sites. This was achieved to some extent by depositing an inert silica layer using different silica agents, amounts and number of modification cycles and as a result p-xylene selectivity was significantly improved (84 %), especially over large crystals 5 ÂÂμm. The decrease in Brà̧nsted acidity (FTIR) suggested the success of the silylation method. Furthermore, impregnation of lanthanum and phosphorus on ZSM-5 improved p-xylene selectivity (40 %). FTIR measurements showed a drastic drop in the number of Brà̧nsted and Lewis acid sites after loading phosphorus which led to a large reduction in toluene conversion. Lanthanum impregnation had less effect on conversion and increased selectivity with decreased Brà̧nsted sites and pore volume reduction showed by N2 adsorption suggesting some pore narrowing. There are several approaches that can be considered in future to further improve p-xylene selectivity. Improving the synthesis of large crystals to balance acidity and crystal size can lead to the enhancement of p-xylene selectivity. Also, performing toluene disproportionation on optimised pre-coked ZSM-5 large crystals at high pressure can help to maintain the conversion while increasing p-xylene selectivity. Another approach would be to apply silylation modification to extruded large crystals ZSM-5.
89

Produção e ação de biossurfactante produzido por bactérias em meios salinos contaminados por hidrocarbonetos aromáticos / Production and action of biosurfactant produced by bacteria in saline media contaminated with aromatic hydrocarbons

Souza, Ellen Cristina 21 August 2013 (has links)
A contaminação da água e do solo por hidrocarbonetos aromáticos tem aumentado ao longo dos anos, devido ao seu uso nos mais diversos segmentos industriais. Hidrocarbonetos, tais como tolueno, são descritos como extremamente poluentes, tóxicos e potencialmente mutagénicos e carcinogénicos para os seres humanos. Os hidrocarbonetos são compostos lipófilicos difíceis de serem eliminados, contudo, estes aromáticos podem ser removidos de ambientes contaminados por meio de biorremediação utilizando bactérias produtoras de surfactante. Biossurfatantes são surfactantes principalmente produzidos por microrganismos, as quais promovem a quebra das moléculas de hidrocarbonetos, através da formação de micelas, aumentando a sua mobilidade, a biodisponibilidade e sua exposição à bactérias favorecendo a biodegradação do hidrocarboneto. A produção deste tensoativo exige meios de fermentação e oxigênio para o metabolismo microbiano. Por tanto, aeração e agitação são variáveis operacionais importantes para garantir um coeficiente de transferência de massa de oxigénio eficaz (kLa). Para esta finalidade, o kLa foi determinado experimentalmente em diferentes meios de fermentação, especificamente meio salino básico, meio de baixa salinidade, meio Bushnell-Haas e água do mar, por diversas variáveis operacionais. Ensaios foram realizados em agitador rotativo para selecionar, dentre os diferentes tipos de bactérias, nomeadamente Bacillus subtilis, Bacillus licheniformis e Bacillus megatherium, o melhor produtor de biossurfactante na presença de tolueno, nos meios de fermentação descritos acima, formulados com diferentes salinidades. A presença de tolueno inibiu o crescimento de microrganismo deslocando seu metabolismo para a produção de biossurfactante. Assim, B. subtilis foi capaz de reduzir a tensão superficial (TS) em 29,49 ± 0,55 unidades, produzindo cerca de 3,52 ± 0,06 mg/L de biossurfactante. Ao elevar o processo para um fermentador de bancada, a quantidade de tolueno no meio de baixa salinidade foi reduzido drasticamente após 12 horas de crescimento (de 45 ml para 7,43 ml), quando B. subtilis foi utilizado, reduzindo o TS em 22,6 unidades (com concentração de biossurfactante de 3,02 mg/L). Os resultados obtidos mostraram que o B. subtilis pode ser considerado um microrganismo promissor para ser utilizado na biorremediação de locais contaminados por tolueno / Contamination of water and soil by aromatic hydrocarbons has been increasing along the years, due to its use in various industrial segments. Hydrocarbons, such as toluene, are described as extremely polluting, toxic, potentially carcinogenic and mutagenic to humans. Hydrocarbons are lipophilic compounds difficult to be disposed of; however, the aromatic ones can be removed from contaminated environments via bioremediation using surfactant-producing bacteria. Biosurfactants are surfactants produced mainly by microorganisms, which promote the breaking of hydrocarbons molecules, by means of the formation of micelles, increasing their mobility, bioavailability and exposure to bacteria favoring hydrocarbon biodegradation. This tensoactive production requires oxygen and fermentation media for the microorganism metabolism. Thus, aeration and agitation are important operating variables to ensure an effective oxygen mass transfer coefficient (kLa). To this purpose, such a response was experimentally determined in this study in different fermentation media, specifically basal saline medium, low saline medium, Bushnell-Haas medium and sea water, and correlated with the above operating variables. Rotary shaker essays were performed to select, among different bacteria, namely Bacillus subtilis, Bacillus megatherium and Bacillus licheniformis, the best biosurfactant producer in the presence of toluene, in fermentative broths described above, formulated with different salinities. The presence of toluene inhibited the growth of microorganism shifting the metabolism to the production of biosurfactant. Thus, B. subtilis was able to reduce the surface tension (ST) in 29.49 ± 0.55 units producing up to 3.52 ± 0.06 mg/L of biosurfactant. Scaling up the process to a bench fermentor, the quantity of toluene in the low salinity medium was reduced drastically after 12 h of growth (from 45 mL to 7.43 mL), when B. subtilis was used, reducing the ST in 22.6 units (biosurfactant concentration of 3.02 mg/L). The results obtained showed that B. subtilis can be considered a promising microorganism to be used for the bioremediation of sites contaminated by toluene.
90

Optimized Extraction of 2-Arachidonyl Glycerol and Anandamide from Aortic Tissue and Plasma for Quantification by LC-MS/MS

Garst, Christopher, Fulmer, Makenie, Thewke, Doug, Brown, Stacy D. 28 August 2016 (has links)
Atherosclerosis is a disease characterized by plaque formation due to an accumulation of fat, cholesterol, and immune cells in the walls of arteries. If a plaque ruptures, an occlusive thrombosis may form that causes either a heart attack or stroke. Macrophages express CB-2 receptors, and are one type of immune cell that plays a role in plaque destabilization and rupture. Endocannabinoids anandamide (AEA) and 2-arachidonyl glycerol (2-AG) have been found to have activity on CB-1 and CB-2 receptors throughout the body and immune system. In this study, we investigated several sample preparation options for the LC-MS quantification of AEA and 2-AG from plasma and aortic tissue. The extractions considered included liquid–liquid (LLE), solid-phase (SPE), and supported liquid (SLE). Some extraction protocols yielded high analyte recovery and prevention of 1-AG/2-AG isomerization. Our results indicate that a liquid-liquid extraction using toluene yields the highest recovery for both analytes, coupled with low ionization suppression in the mass spectrometer. This extraction and corresponding LC-MS/MS assay provides a simple, high throughput mechanism for the quantification of 2-AG and AEA in matrices relevant to the study of endocannabinoids’ role in atherosclerosis.

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