Na última década o emprego de nanotecnologia tem crescido exponencialmente em função das suas evidentes vantagens: maior eficácia terapêutica, menor toxicidade e liberação modificada do fármaco. Tais características permitem elevar os níveis do fármaco no compartimento intracelular, além de possibilitar sua liberação modificada no sítio específico. Essas vantagens vem ao encontro da otimização do tratamento da leishmaniose devido à falta de medicamentos seguros e de adequada atividade farmacológica. O objetivo do presente projeto constituiu-se na preparação e na avaliação das características físico-químicas da nanopartícula polimérica associada ao novo fármaco hidroximetilnitrofural (NFOH), desenvolvimento e validação do método analítico para a determinação da eficiência de encapsulação, avaliação a atividade leishmanicida in vitro em promastigotas, em macrófagos infectados por amastigotas de L. amazonensis e citotoxicidade do NFOH livre e nanoestruturado. As nanopartículas poliméricas de poli (butil cianoacrilato) (PBCA) obtidas apresentaram potencial zeta de -10,1 mV, tamanho médio de 151,5 nm, polidispersividade de 0,104 e distribuição unimodal muito próximos ao encontrado na literatura. O método analítico validado apresentou especificidade, linearidade, precisão, exatidão e robustez, mostrando-se adequado para a quantificação do NFOH em nanopartículas, o resultado final da eficiência de encapsulação foi de 64,5%. Os testes realizados em promastigotas e macrófagos infectados por amastigotas de L. amazonensis revelaram a maior atividade do fármaco nanoestruturado em relação ao fármaco livre e ao placebo. Os ensaios de citotoxicidade comprovaram que o fármaco, sistema nanoestruturado contendo NFOH e placebo apresentam baixa toxicidade. Logo, as nanopartículas obtidas contendo NFOH são uma alternativa promissora para o tratamento da leishmaniose. / In the last decade the use of nanotechnology has grown exponentially as a function of its obvious advantages: high therapeutic efficacy, lower toxicity and modified release of the drug. This feature allows raising the levels of the drug in the intracellular compartment, and enables the modified release of the drug in its specific site. These advantages come to meet the optimization of the treatment of leishmaniasis due to lack of drugs that are safe and appropriate pharmacological activity. The goal of this project consisted in the preparation and evaluation of physical and chemical characteristics of polymeric nanoparticle associated with new drug hidroxymethylnitrofurazone (NFOH), development and validation of analytical method for the determination of encapsulation efficiency, evaluating the leishmanicidal activity in vitro in promastigotes and in macrophages infected with amastigotes of L. amazonensis and finally cytotoxicity of free and nanostructured NFOH. The polymeric nanoparticles of poly(butyl cyanoacrylate) (PBCA) obtained showed zeta potential of -10.1 mV, average size of 151.1 nm, polydispersity of 0.104 and unimodal distribution very similar to that found in the literature. The validated method showed specificity, linearity, precision, accuracy and robustness, making it adequate for the quantification of NFOH nanoparticles, the final outcome of the encapsulation efficiency was 64.5%. Tests conducted on promastigotes and macrophages infected with amastigotes of L. amazonensis revealed the highest activity of nanostructured drug compared to free drug and placebo. The cytotoxicity assays showed that the NFOH, nanostructured system containing NFOH and placebo had low toxicity. Thus, the obtained nanoparticles containing NFOH are a promising alternative for the treatment of leishmaniasis.

Os ésteres são importantes compostos orgânicos, obtidos por síntese química ou extraídos de alguns produtos naturais utilizando-se solvente em meio adequado. Estudos mostram que enzimas, em particular lipases, podem ser aplicadas na síntese de diversos ésteres. O principal objetivo deste trabalho foi a obtenção de acetato de butila, um éster de aroma característico de abacaxi, utilizando lipase de Geotrichum candidum produzida em fermentação submersa e imobilizada em matriz polimérica de alginato de bário e gelatina reticulada com glutaraldeído. A caracterização bioquímica foi realizada tanto para a lipase na forma livre como para a lipase na forma imobilizada. O rendimento em conversão molar de substrato foi determinado por cromatografia gasosa. A enzima apresentou atividade enzimática máxima após 48 horas de fermentação de 37,7 U/mL. Os valores ótimos para pH e temperatura da enzima na forma livre e imobilizada foram pH 6,5 e 40 °C e pH 7,5 e 45 °C, respectivamente. A enzima na forma livre foi estável do pH 6,0 ao 8,0 e à temperatura de 35 a 45 °C, já na forma imobilizada, foi estável do pH 5,5 ao 8,5 e na faixa de temperatura de 30 a 55 °C. A lipase imobilizada teve seus parâmetros cinéticos determinados, e os valores obtidos para o Km e Vmax, foram 0,115 mmol e 0,718 µmol.mL-1.min-1, respectivamente. As melhores condições de síntese do bioaroma para a enzima na forma livre foram: temperatura de 30 °C, 12,5% de enzima em relação à quantidade de butanol utilizada, proporção molar do substrato 60% de acetato de vinila em um período de 24 horas. O rendimento alcançado neste caso foi de 97,2 % de conversão molar em acetato de butila. Para a enzima imobilizada as melhores condições foram: temperatura de 45 °C, 12,5% de enzima em relação à quantidade de butanol utilizada, proporção molar do substrato 60% de acetato de vinila em um período de 24 horas. O rendimento alcançado neste caso foi de 99,1%, que demonstra que lipase produzida por Geotrichum candidum na forma imobilizada apresenta excelente capacidade de sintetizar acetato de butila (bioaroma de abacaxi). / Esters are important organic compounds obtained by chemical synthesis or derived from some natural products using a solvent in appropriate medium. Studies have shown that enzymes, particularly lipases, ca be applied in the synthesis of various esters. The main objective of this study was to obtain butyl acetate, a characteristic ester aroma of pineapple, using lipase from Geotrichum candidum produced in submerged fermentation and immobilized in a barium alginate and gelatin polymer matrix crosslinked with glutaraldehyde. The biochemical characterization was performed for both free and immobilized lipases. The yield in molar conversion of substrate was determined by gas chromatography. The enzyme showed maximum enzymatic activity after 48 hours of fermentation of 37.7 U/mL. The optimum values for pH and temperature of the enzyme in free and immobilize form were pH 6.5 and 40 °C and pH 7.5 and 45 °C, respectively. The enzyme was stable in free form from pH 6.0 to 8.0 and at temperatures from 35 to 45 °C, and in the immobilized form from pH 5.5 to 8.5 and at temperatures from 30 to 55 °C. Kinetic parameters of the immobilized lipase were determined, and the values obtained for Km and Vmax were 0.115 mmol and 0.718 µmol.mL-1.min-1, respectively. The best conditions for the synthesis of flavor by enzyme in free form were: 30 °C of temperature, 12.5% of enzyme for the amount of butanol used, and molar ratio of substrate 60% of vinyl acetate in a 24 hours period. The yield achieved in this case was 97.2% of molar conversion in butyl acetate. For the immobilized enzyme the best conditions were: 45 °C of temperature, 12.5% of enzyme for the amount of butanol used, and molar ratio of substrate 60% of vinyl acetate in a 24 hours period. The yield achieved in this case was 99.1%, demonstrating that lipase produced by Geotrichum candidum in immobilized form has an excellent ability to synthesize butyl acetate (pineapple flavor).

As reações de adição aldólica entre a cetimina 1 e aldeídos aromáticos foram inicialmente efetuadas à temperatura ambiente, em sistema bifásico constituído por uma fase aquosa básica (KOH 10% ou NaOH 5% m/v) e por uma fase orgânica (aldeído), na ausência de solventes e de catalisadores, observando-se baixa conversão em produto. Porém, quando se utilizou o catalisador aliquat®-336, foi possível reduzir a concentração da base (NaOH 1%), com conversão total da imina em produto que, na maioria dos casos, era uma mistura de duas oxazolidinas isoméricas de estereoquímica cis e trans. Esses compostos puderam ser isolados e purificados por recristalização de etanol ou metanol. Em todas as reações efetuadas com benzaldeído, m-clorobenzaldeído e p-nitrobenzaldeído, não se observou excesso diastereomérico significativo. No entanto, as reações com p-clorobenzaldeído mostraram-se diastereosseletivas, conduzindo, à temperatura ambiente, quase que exclusivamente à oxazolidina de estereoquímica cis. A comparação entre o resultado de reações efetuadas a curto e longo tempo de reação, ou em diferentes temperaturas, permitiu concluir que o aldol de estereoquímica anti é o produto cinético, o qual se transforma lentamente na oxazolidina cis. O produto termodinâmico (aldol syn) cicliza rapidamente, não sendo observado nos espectros de RMN de H dos produtos brutos de reação, mas sim seu produto ciclizado, a oxazolidina trans. Tentativas de obter os produtos de reação com excesso enantiomérico, pelo emprego de catalisadores de transferência de fase assimétricos, não foram bem sucedidas. / The aldol addition reactions of ketimine 1 with four aromatic aldehydes could be performed at room temperature, in the presence of an alkaline aqueous solution (KOH 10% or NaOH 5% m/v), and in the absence of organic solvents or catalysts. Under this conditions, conversion to product was often incomplete. However, when the reaction was performed in the presence of aliquat®-336, the base concentration could be reduced (1% m/v), and the ketimine was completely converted into a mixture of diastereomeric oxazolidines, that could be isolated and purified by crystallization from ethanol or methanol. Although no significative diastereomeric excess was observed for the reactions of 1 with benzaldehyde, m-chlorobenzaldehyde or p-nitrobenzaldehyde, for reactions with p-chlorobenzaldehyde the cis oxazolidine was almost exclusively formed. The comparison of diastereomeric ratio at shorter or longer reaction times seems to indicate that the aldol anti adduct is the kinetic product and that cyclization to the corresponding cis oxazolidine is slower than the retro-aldol reaction. On the other hand, in lieu of the thermodynamic product (aldol syn), only the corresponding cyclized product (oxazolidine trans) could be visualized in the H NMR spectra of the crude product, as a result of a fast cyclization step. Attempts to produce enantiomeric enriched oxazolidines by performing the aldol reactions in the presence of chiral catalysts were unsuccessful.

Os processos industriais de polimerização em emulsão são normalmente realizados em reatores batelada ou semi batelada ou em tanques agitados contínuos (CSTR). Os reatores contínuos têm a vantagem de terem menor porte e de propiciarem melhor controle de qualidade do produto através da redução de variações de batelada a batelada. Além disso, as oscilações periódicas autosustentadas na conversão de monômero e no tamanho da partícula, que são normalmente observadas em reatores do tipo CSTR, podem ser minimizadas em reatores tubulares mediante o uso de dispositivos de mistura estáticos adequados combinados com escoamento pulsado (oscilatório). O objetivo deste trabalho é apresentar o desenvolvimento de uma copolimerização em emulsão de acetato de vinila e acrilato de butila em uma coluna pulsada com pratos perfurados (CPPP). A fim de aumentar a sua flexibilidade operacional, a coluna é composta de 5 seções, cada uma apresentando controles independentes de alimentação lateral e temperatura. Dependendo da estratégia de alimentação de monômero, pode-se notar uma deriva de composição durante o processo de copolimerização em emulsão do acetato de vinila e acrilato de butila devido às grandes diferenças entre estes monômeros em suas razões de reatividade e nas solubilidades na fase aquosa. Neste caso, a CPPP propicia diferentes possibilidades de alimentação que permitem controlar a composição do copolímero através da alimentação do monômero mais reativo ao longo da coluna. Por esta razão, foi avaliado neste estudo o efeito do número de correntes de alimentação sobre as propriedades do polímero. Diferentes números de correntes laterais de alimentação de monômero foram empregadas nos ensaios experimentais. Diferenças na uniformidade da composição do copolímero podem ser notadas dependendo do número de correntes laterais de alimentação aplicadas em cada teste. A fim de permitir variações de temperatura, somente a temperatura de entrada das camisas de resfriamento foi fixada. Para simular as reações foi utilizado um modelo matemático desenvolvido baseado no modelo de escoamento pistonado (plug-flow) axialmente disperso. No presente trabalho, um balanço de energia foi incluído ao modelo matemático anterior de modo que a influência de diferentes perfis de temperatura pudesse ser considerada. O efeito das correntes laterais de alimentação de monômero sobre as propriedades do copolímero puderam ser previstas com suficiente precisão pelas simulações do modelo, as quais foram também validadas pelos resultados experimentais. Com base nas simulações matemáticas, um perfil ótimo de alimentação pôde ser calculado e experimentalmente aplicado na CPPP permitindo a produção de um copolímero mais homogêneo. Os resultados também permitiram a validação do modelo matemático como uma ferramenta confiável na predição de ensaios experimentais. Além disso, as vantagens da CPPP puderam ser verificadas pelo seu desempenho adequado como reator tubular para processos contínuos de copolimerização em emulsão. Finalmente, os resultados indicaram a possibilidade de melhorias adicionais nas propriedades do polímero através do emprego de diferentes temperaturas e perfis de alimentação de outros reagentes ao longo da coluna. / Industrial emulsion polymerization processes are usually performed in batch or semi-batch stirred tanks, or in continuous stirred tank reactors (CSTR). Continuous reactors have the advantage of being smaller and providing a better product quality control by the reduction of the batch-to-batch variations. In addition, periodical self-sustained oscillations in monomer conversion and in particle size that are usually observed in CSTR can be minimized in tubular reactors presenting good radial mixing. Such conditions can be achieved in tubular reactors by using adequate static mixing devices combined with pulsed (oscillatory) flow. The aim of this work is to report the development of a continuous emulsion copolymerization of vinyl acetate and butyl acrylate performed in a pulsed sieve plate column (PSPC). In order to improve its operational flexibility, the column is composed of five sections, each one presenting independent lateral feed and temperature controls. Depending on the monomer feeding strategy, a composition drift can be noticed during the emulsion copolymerization process of vinyl acetate and butyl acrylate, due to the large differences in reactivity ratios and aqueous phase solubility between these monomers. In this case, the PSPC provides different operational feeding possibilities which allow controlling the copolymer composition by feeding the more reactive monomer along the column. For this reason, in this study the effect of the number of lateral feed streams on the polymer properties was evaluated. Different numbers of lateral monomer feed streams were employed in the experimental runs. Differences in the uniformity of the copolymer composition can be noticed along the reactor depending on the number of lateral feed streams applied in each test. In order to allow temperature variations, during each reaction only the inlet temperature of the cooling jackets was fixed. A developed mathematical model based on the axially dispersed plug-flow model was used to simulate the reactions. In the present study the energy balance was included in the mathematical model so that the influence of different temperature profiles could be taken into account. The effect of lateral monomer feed streams over the copolymer properties could be predicted with sufficient accuracy by model simulations which were also validated by the experimental results. Based on mathematical simulations, an optimal feeding profile could be calculated and experimentally applied in the PSPC allowing the production of a more homogeneous copolymer. The results also permitted the validation of the mathematical model as a reliable tool in the prediction of experimental runs. Furthermore, the advantages of the PSPC could be verified by its adequate performance as a tubular reactor for continuous emulsion copolymerization processes. Finally, the results indicate the possibility of further improvements in other polymer properties by employing different temperature and feeding profiles of other reagents along the column.

Poly (co iso-butyl vinyl ether-alt-maleic anhydride), an alternating copolymer, was synthesised. For this class of copolymers the formation of an electron-donor complex is invoked to explain their microstructure in which the two comonomers strictly alternate. Due to its polarity, this copolymer constitutes a potential additive for imparting hydrophilic properties to a hydrophobic matrix. In order to obtain narrow molecular weight polymers and study the relation between the molecular weight of this additive and its ability to migrate to the host polymer surface, chain transfer agents were introduced in the system and also the Reversible Addition-Fragmentation chain Transfer (RAFT) process was employed. Free radical polymerisation was first carried out to allow for a comparison with the RAFT process and kinetics of copolymerisation was studied by NIR-FTIR and 1H NMR spectroscopy in order to analyse the rate of reaction of each comonomer. Dibenzyl trithiobenzoate, 3-benzyl sulfanyl thiocarbonyl sulfanyl-propionic acid and dibenzyl trithiobenzoate were used as RAFT agents. Results demonstrate that only benzyl dithiobenzoate is able to control the molecular weight of this copolymer and decrease its polydispersity index; possible reasons laying behind this result are discussed. It was also found that, in particular in the presence of benzyl dithiobenzoate, poly(iso-butyl vinyl ether) forms. This is an unusual phenomenon considering that the free radical polymerisation affords alternating copolymers and that iso-butyl vinyl ether is a monomer that polymerises through the cationic process. Experiments were carried out in various solvents in an attempt to counteract this side reaction, but no appreciable correlation between the properties of the solvents and the formation of homopolymer were found. Various hypothesis are considered, however it is likely that, in the conditions adopted, the presence of the RAFT agents alters the equilibrium constant of complex formation favouring the synthesis of the homopolymer. In addition to this side???reaction also inhibition of the copolymerisation reaction was at times encountered and an investigation into this phenomenon was also conducted.

The phenomenon of depropagation or reverse polymerization for multicomponent polymerizations has been studied in detail. The monomer Alpha-Methyl Styrene (AMS) has been copolymerized with Methyl Methacrylate (MMA) and Butyl Acrylate (BA) at temperatures ranging from 60oC to 140oC and the kinetics have been studied in the form of propagation/cross propagation and depropagation parameters. There have been multiple attempts with varying amounts of success in the past to determine the kinetic parameters for depropagating systems including work by Lowry and Wittmer as well as other modelling methodologies that are not as mechanistic. The most recent development of the mechanistic terminal model is that of the Kruger model. The model is robust and can take into account all special cases as well as all reactions being reversible. The kinetic parameters have been estimated for each of the three binary systems using the Kruger model (MMA/AMS, MMA/BA, BA/AMS). The Alfrey-Goldfinger model is inadequate to describe depropagating terpolymer systems and in order to study them, a new model was developed based upon the binary Kruger model. This new model takes into account a fully depropagating terpolymer system leading to a total of 15 parameters to be estimated. These 15 parameters have the same definitions as those estimated from the binary Kruger model, thus making accurate analysis of the binary systems crucial since these will be used as first estimates for the terpolymer system. Extensive experimental data (composition, conversion and molecular weights) was collected and analysed for the MMA/AMS and BA/AMS systems. For the BA/AMS system both the bulk and solution copolymerizations were studied in detail with the results from the Kruger model not showing a significant difference in the reactivity ratios between the two types of polymerization. For the MMA/AMS system, a bulk study only was done which revealed an interesting phenomenon that points toward a break down of the long chain approximations used for all of the models being studied. For both of these systems, extensive ¹H NMR analysis was done to determine the copolymer composition. Data collected in previous research for the MMA/BA system was reanalysed using the Kruger model and it was found that the parameter estimates did not differ significantly from the published values. Extensive benchmarking was done with the newly developed terpolymer model on non-depropagating systems using data from the literature to ensure it worked for the simplest cases. It was found that the model matched the parameter estimates from the literature and in some cases improving upon them to fit the data better. Along with the benchmarking a sensitivity analysis was done which revealed some interesting information. For the MMA/BA/AMS terpolymer system a set of experiments (based upon practical considerations) were performed and the composition of the polymer was determined using ¹³C NMR instead of the usual ¹H NMR due to the difficulty of peak separation for the complex terpolymer. Using the depropagating terpolymer composition data in conjunction with the parameter estimates from the three binary systems allowed for estimation of the 15 kinetic parameters, which showed only minor variation from the binary estimates.

The phenomenon of depropagation or reverse polymerization for multicomponent polymerizations has been studied in detail. The monomer Alpha-Methyl Styrene (AMS) has been copolymerized with Methyl Methacrylate (MMA) and Butyl Acrylate (BA) at temperatures ranging from 60oC to 140oC and the kinetics have been studied in the form of propagation/cross propagation and depropagation parameters. There have been multiple attempts with varying amounts of success in the past to determine the kinetic parameters for depropagating systems including work by Lowry and Wittmer as well as other modelling methodologies that are not as mechanistic. The most recent development of the mechanistic terminal model is that of the Kruger model. The model is robust and can take into account all special cases as well as all reactions being reversible. The kinetic parameters have been estimated for each of the three binary systems using the Kruger model (MMA/AMS, MMA/BA, BA/AMS). The Alfrey-Goldfinger model is inadequate to describe depropagating terpolymer systems and in order to study them, a new model was developed based upon the binary Kruger model. This new model takes into account a fully depropagating terpolymer system leading to a total of 15 parameters to be estimated. These 15 parameters have the same definitions as those estimated from the binary Kruger model, thus making accurate analysis of the binary systems crucial since these will be used as first estimates for the terpolymer system. Extensive experimental data (composition, conversion and molecular weights) was collected and analysed for the MMA/AMS and BA/AMS systems. For the BA/AMS system both the bulk and solution copolymerizations were studied in detail with the results from the Kruger model not showing a significant difference in the reactivity ratios between the two types of polymerization. For the MMA/AMS system, a bulk study only was done which revealed an interesting phenomenon that points toward a break down of the long chain approximations used for all of the models being studied. For both of these systems, extensive ¹H NMR analysis was done to determine the copolymer composition. Data collected in previous research for the MMA/BA system was reanalysed using the Kruger model and it was found that the parameter estimates did not differ significantly from the published values. Extensive benchmarking was done with the newly developed terpolymer model on non-depropagating systems using data from the literature to ensure it worked for the simplest cases. It was found that the model matched the parameter estimates from the literature and in some cases improving upon them to fit the data better. Along with the benchmarking a sensitivity analysis was done which revealed some interesting information. For the MMA/BA/AMS terpolymer system a set of experiments (based upon practical considerations) were performed and the composition of the polymer was determined using ¹³C NMR instead of the usual ¹H NMR due to the difficulty of peak separation for the complex terpolymer. Using the depropagating terpolymer composition data in conjunction with the parameter estimates from the three binary systems allowed for estimation of the 15 kinetic parameters, which showed only minor variation from the binary estimates.

Nanofibers, which have high surface area to volume ratio and better mechanical properties, are nanomaterials that both industry and scientists have started to show great attention in the last two decades. They are used in many areas such as life and filtration sciences, sensors, and composite reinforcement etc. Among five main production types, electrospinning is the best candidate for further development with a wide range of opportunities to be applied to all types of polymers and ceramics. This method uses electrically charged jet of polymers or liquid states of polymers to produce fibers from micro dimensions down to nano dimensions. Electrospinning setup has mainly three parts / (i) an AC/DC high voltage equipment which creates high electrical potential, (ii) a syringe, and (iii) a collecting screen. The purpose of this study is to electrospin polystyrene/butyl rubber blends and to investigate the effects of electrospinning parameters on the fibers produced. In this study, polystyrene/butyl rubber blends were electrospun by changing the applied voltage, the tip-to-collector distance, the flowrate, and the butyl rubber content in the fiber. Finally, morphology of electrospun fibers was characterized by SEM. The average fiber diameters varied from 760 nm to nearly 10 &micro / m. Increasing butyl rubber content in the fiber resulted in a decrease in the final fiber diameter. Increasing applied voltage also caused a decrease in the final fiber diameter. The tip-to-collector distance did not affect the average fiber diameter. Increasing flowrate yielded fibers with larger diameters. Finally, the addition of non-ionic surfactant decreased the average fiber diameter.

Contamination of groundwater supplies by gasoline and other petroleum-derived hydrocarbons released from underground or aboveground storage tanks is a serious and widespread environmental problem. Corrosion, ground movement, and poor sealing can cause leaks in tanks and associated piping. Petroleum hydrocarbons contain methyl tertiary-butyl ether (MTBE) (a fuel oxygenate), benzene, toluene, ethylbenzene, and xylene isomers (BTEX), the major components of gasoline, which are hazardous substances regulated by many nations. MTBE possesses all the characteristics of a persistent compound in the subsurface: high solubility, low volatility, low sediment sorption, and resistance to biodegradation. The objectives of this study were to (1) evaluate the biodegradibility of MTBE under aerobic conditions, and (2) assess the potential of using the aerobic bioremediation technique to clean up aquifers contaminated by MTBE. In this study, microcosms were constructed to determine the feasibility of biodegrading MTBE by intrinsic microbial consortia (aquifer sediments) under aerobic and aerobic cometabolic conditions. In the cometabolic microcosms, propane, ethanol, and BTEX were applied as the primary substracts to enhance the biodegradation of MTBE. The inocula used in this microcosm study were aquifer sediments collected from the contaminated-zones of a petroleum-hydrocarbon (including MTBE) contaminated site. Microcosms were constructed with nutrient medium (or site groundwater), sediments, and MTBE solution in 70-mL serum bottles sealed with Teflon-lined rubber septa. MTBE was analyzed using purge-and-trap instrument following gas chromatography (GC)/flame ionization detector (FID). Results show that the indigenous microorganisms were able to biodegrade MTBE under aerobic conditions using MTBE as the sole primary substrate. Microcosms with site groundwater as the medium solution show higher MTBE biodegradation rate. This indicates that site groundwater might contain some trace minerals or organics, which could enhance the MTBE biodegradation rate. Results show that the addition of BTEX would also enhance the MTBE removal. However, no significant MTBE biodegradation was observed in microcosms with propane and ethanol as the primary substrates. This reveals that the supplement of the second carbon source might inhibit the degradation of MTBE due to the preferential removal of some organics over MTBE. Results from the microcosm study suggest that aerobic biodegradation plays an important role on the MTBE removal. Intrinsic bioremediation is a feasible technology to remediate the studied MTBE-contaminated site.

Contamination of soil/groundwater supplies by gasoline and other petroleum-derived hydrocarbons released from underground storage tanks (USTs) is a serious and widespread environmental problem. Corrosion, ground movement, and poor sealing can cause leaks in tanks and associated piping. Petroleum hydrocarbons contain methyl tertiary-butyl ether (MTBE) (a fuel oxygenate), benzene, toluene, ethylbenzene, and xylene isomers (BTEX), the major components of gasoline, which are hazardous substances regulated by many nations.The objective of this proposed study is to assess the potential of using a passive in situ oxidation barrier system. This passive active barrier system has advantages over conventional systems including less maintenance, cost-effectiveness, no above-ground facilities, no groundwater pumping and reinjection, and groundwater remediation in situ. The oxidation barrier system included a persulfate-releasing barrier, which contains persulfate-releasing materials. The slow-released persulfate would oxidize MTBE and benzene in aquifer. The persulfate-releasing materials would release persulfate when contacts with groundwater, thus oxidizes the MTBE and benzene. In the first part of this study, bench scale experiment was also performed to produce the persulfate-releasing materials high persulfate-releasing rate. The components of the persulfate-releasing materials and optimal concentrations of those components were determined in this study. Results indicate that the highest persulfate releasing rate can be obtained when the mass ratio of cement/sand/water was 1.4/0/0.7. Result obtained from the persulfate-releasing materials test and bench-scale were used for the design and operation of the following column experiments. Results from the column experiment indicate that approximately 98% of MTBE and 99% of benzene could be removed during the early persulfate-releasing stage. Results also reveal that the produced oxidation byproducts of MTBE, tert-butyl formate (TBF) and tert-butyl alcohol (TBA), can also be produce an acetone. Results from this study suggest that extra Fe(II) would cause the decrease in oxidation rates due to the reaction of sulfate with Fe(II). Results show that the parameters, which would affect the oxidation rate include persulfate concentration, oxidant reduction potential (ORP), conductivity, sulfate concentration, and contaminant concentration. The proposed treatment scheme would be expected to provide a more cost-effective alternative to remediate MTBE and other petroleum-hydrocarbon contaminated aquifers. Knowledge obtained from this study will aid in designing a persulfate oxidation system for site remediation.