1,2-dichloroethane (DCA) is one of the most widely used and produced chemicals of the modern world. It is used as a metal degreaser, solvent, chemical intermediate as well as a fuel additive. This carcinogen is toxic to both terrestrial and aquatic ecosystems and accidental spills and poor handling has resulted in contamination of the environment. Thus far several bacteria in the Northern hemisphere have been identified that are capable of utilizing this compound as a sole carbon and energy source. This report focuses on the isolation and characterization of bacterial isolates from the Southern hemisphere that are capable of degrading DCA as well as the global distribution of the DCA catabolic route. Samples obtained from waste water treatment plants were batch cultured in minimal medium containing DCA and repeatedly sub-cultured every five days over a 25 day period. A halogen release assay was performed in order to determine whether individual isolates possessed dehalogenase activity. Confirmation of DCA utilization by bacterial isolates positive for dehalogenase activity was done by sub-culturing back into minimal medium containing DCA. Enzyme activities were confirmed with cell free extracts using all of the intermediates in the proposed DCA degradative pathway and compared to a known DCA degrading microorganism. Biochemical tests and 16SrDNA sequencing indicated that all the South African isolates belonged to the genus Ancylobacter and were different from each other. Based on enzyme activities, it was found that the South African isolates may possess a similar degradative route as other DCA degrading microorganisms. Primers based on genes involved in DCA degradation were synthesized and PCR analysis was performed. It was found that all isolates possessed an identical hydrolytic dehalogenase gene whereas the other genes in the pathway could not be PCR amplified. Southern hybridization using probes based on known genes indicated that some of the isolates had homologous genes. Pulsed field gel electrophoresis (PFGE) and random amplified polymorphic DNA (RAPD) analysis indicated that the five South African isolates of Ancylobacter aquaticus are distinguishable from each other. This study is the first report indicating that microbes from different geographical locations use similar metabolic routes for DCA degradation. The first gene of the pathway (dhlA) has undergone global distribution which may be due to widespread environmental contamination. / Thesis (Ph.D)-University of KwaZulu-Natal, Westville, 2009.

No description available.

1,2-dichloroethane (1,2-DCA) is a popular industrial chlorinated organic chemical. Because 1,2-DCA is a dense non-aqueous phase liquid and easily accumulated in deep soil and water, it is difficult to be removed from the contaminated sites. In this study, aerobic and anaerobic microcosm batch experiments were performed to evaluate the feasibility of biodegradation of 1,2-DCA by adding different growth substrates. The aerobic microcosm results show that approximately 90% of 1,2-DCA removal was observed in the natural degradation group (A1) and the aerobic sludge addition group (A3) after 7 days of incubation. Up to 95% of 1,2-DCA removal could be observed in the substrate supplement group in after 14 days of incubation. In the anaerobic microcosm studies, 50% of 1,2-DCA removal could be obtained in all groups after 10 days except for the natural degradation group (B1). Moreover, the degradation efficiency for the anaerobic sludge group (B3) reached 80% of 1,2-DCA removal in 5 days. The DGGE profiles show that the microbial diversity varied with time and the sugar supplement groups (A2, B2) exhibited the most microbial diversity. Bacterial clones results revealed that the 1,2-DCA biodegradable microbial strains were presented in the microcosms, such as Klebsiella, Pseudomonas, Rhodoferax and Xanthobactor. The real-time PCR results indicated that the Dehalococcoides spp. was the major bacterium that was responsible for the degradation of 1,2-DCA in the anaerobic substrate supplement group (B2). Desulfitobacterium spp. could be the dominant 1,2-DCA degrading bacterium for the aerobic substrate supplement group (A2) and all of the anaerobic groups (B1, B2, B3, B4).

The aim of this study was to access the efficacy of an enhanced in situ bioremediation technology at a 1,2-dichloroethane (1,2-DCA) polluted site in southern Taiwan. A water-soluble substrate was injected into the groundwater to provide carbon sources for microbial growth. After substrate injection, increased total organic carbon (TOC) concentrations and microbial populations including Dehalococcoides spp. and Desulfitobacterium spp. were observed in the groundwater. Microbial diversity was analyzed using denaturing gradient gel electrophoresis (DGGE) and 16S rDNA sequencing to identify the bacterial strains. The results showed that after 4.5 months of substrate injection, the reduction-oxidation potential (ORP) changed from aerobic to anaerobic conditions. The less oxygen-tolerable 1,2-DCA degrading bacteria Dehalococcoides spp. started to accumulate in groundwater. However, the more oxygen-tolerable Desulfitobacterium spp. didn¡¦t show a prominent change, although the ORP was suitable for Desulfitobacterium spp. to carry out reductive dechlorination. The DGGE results indicate that with the injected carbon sources and mineral nutrients, both the groundwater microbial diversity and the amount of dominant bacteria were increased. The 16S rDNA sequencing demonstrated that the amount and diversity of 1,2-DCA degradation-related bacteria also increased with the injection of substrate. Six groups of 1,2-DCA degradation related reactions were found: dechlorination, chlorinated-compound degradation, denitrification, iron-reduction, sulfate-reduction and methane-utilizing. Four species that can directly degrade 1,2-DCA were found: Dehalobacter sp., Dehalococcoides sp., Nitrosospira sp. and Pseudomonas sp. Moreover, 11 methane-utilizing bacterial species were also discovered. The presence of these methane-utilizing bacteria not only might assist the process of denitrification and sulfate-reduction, but also could diminish the emission of the greenhouse gas. The results of this study confirmed that the addition of substrates could affect the groundwater oxidation-reduction state and enhance the bioremediation at the 1,2-DCA-contaminated site. Thus, enhanced in situ bioremediation is a feasible technology for site remediation.

A new treatment technology, called Advanced Reduction Process (ARP), was developed by combining UV irradiation with reducing reagents to produce highly reactive species that degrade contaminants rapidly. Vinyl chloride (VC) and 1,2-dichloroethane (1,2-DCA) pose threats to humans and the environment due to their high toxicity and carcinogenicity. In this study, batch experiments were conducted under anaerobic conditions to investigate the degradations of VC and 1,2-DCA with various ARP that combined UV with dithionite, sulfite, sulfide or ferrous iron. Complete degradation of both target compounds was achieved by all ARP and the reactions were found to follow pseudo-first-order decay kinetics. The effects of pH, sulfite dose, UV light intensity and initial contaminant concentration on the degradation kinetics were investigated in the photochemical degradation of VC and 1,2-DCA by the sulfite/UV ARP. The rate constants were generally promoted by raising the solution pH. The optimal pH conditions for VC and 1,2-DCA degradation were pH 9 and pH 11,respectively. Higher sulfite dose and light intensity were found to increase the rate constants linearly for both target contaminants. A near reciprocal relation between the rate constant and initial concentration of target compounds was observed in the degradation of 1,2-DCA. The rate constant was observed to be generally independent of VC concentration, but with a slight increase at lower concentrations. A degradation mechanism was proposed that described reactions between target contaminants and reactive species such as the sulfite radical and hydrated electron that were produced in the photolysis of sulfite solution. A mechanistic model that described major reactions in the ARP system was developed and explained the dependence of the rate constant on those experimental factors. Chloride ion and chloroethane were detected as the major degradation products at acid and neutral pH. An increase in pH promoted the extent of dechlorination with complete dechlorination being observed at pH 11 for both VC and 1,2-DCA. Due to the rapid degradation kinetics in these ARPs, this new treatment technology may be applied to remove various contaminants in water and wastewater.

Thickness shear mode (TSM) sensors, also known as quartz crystal micro-balances (QCM) are a class of acoustic wave sensors that have been used for gas phase sensing. In this thesis this device is used to measure vapor-liquid equilibrium data for copolymers of poly(styrene-butadiene) at 294K. Copolymers of poly(styrene-butadiene) with varying percentages of styrene (85%, 45% and 21 %) were studied with benzene, n-hexane, dichloroethane and chloroform as solvents. Literature data for pure polystyrene/benzene and polystyrene/chloroform and polybutadiene/benzene were obtained to complement the measured data. Obtained experimental data were fit with a modified Flory-Huggins model and compared with the predictions of three models (UNIFAC-FV, Entropic-FV, and GK-FV). Flory-Huggins model gave a good quantitative fit for the solvent activities in the copolymer solutions.

Recently, because of the increase of environmental concerns in process design, the need to enhance conversion to product and prevent generation of wasteful byproducts in the reactor network has become urgent. This prevents high cost treatment and separation costs downstream in the process. Therefore, in this thesis I focus on making production of vinyl chloride monomer (VCM) more efficient and on possible ways of industrial organochlorine waste (OCW) recycling. In particular, in the first experiment, we investigate how catalyst and its structure can affect product output. Infrared spectroscopy and X-ray diffraction analysis were utilized to investigate the structure of the γ-Al2O3 carrier with CuCl2 catalyst on its surface. Structure of the two catalysts, HarshowX1 and MEDC-B, and their effect on the mechanism of ethylene oxidative chlorination reaction into 1,2-dichlorethane were studied. Differential thermal analysis and mass spectroscopy were applied to study the structure and the mechanism differences between the deposited and permeated CuCl2 catalysts. The second experiment deals with ecological processing and recycling methods of wasteful byproduct that can be called chlororganic wastes. Typical waste products are 1,2-dichloroethane, 1,1,2-trichloroethane, vinylidene, and vinyl chloride monomer. Polymerization and copolymerization of typical waste products with their C5-C9 fraction resulted in non-toxic polymer products that can be used in construction and road-building industries. The possibility of joint chlorine and sulfide-containing chemical wastes recycling into polysulfide oligomeric products is discussed. This comprehensive recycling allows utilizing 80-90% of all wastes generated during synthesis of chlorinated products in the chemical industry. The results of the studies aim to improve the conversion of ethylene to vinyl chloride and minimize the formation of byproducts.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-07-17T10:50:47Z No. of bitstreams: 1 RENATO PIMENTEL FIGUEIREDO - DISSERTAÇÃO (PPGEQ) 2009.pdf: 975618 bytes, checksum: b13e64667a70305e542a6dbc48ab446d (MD5) / Made available in DSpace on 2018-07-17T10:50:47Z (GMT). No. of bitstreams: 1 RENATO PIMENTEL FIGUEIREDO - DISSERTAÇÃO (PPGEQ) 2009.pdf: 975618 bytes, checksum: b13e64667a70305e542a6dbc48ab446d (MD5) Previous issue date: 2009-01-22 / No processo de produção de monocloreto de vinila (MVC) utilizado pela BRASKEM, após a reação de pirólise do 1,2-dicloroetano (EDC) os componentes mais leves do que o EDC são separados em uma coluna de destilação chamada de coluna de leves ou coluna de separação cloropreno – EDC. Estes componentes são principalmente o cloropreno, 1,1-dicloroetano (1,1-EDC) e o benzeno, A coluna de separação de leves foi modelada diversas vezes nestes últimos vinte e um anos pela BRASKEM, algumas vezes com sucesso e em outras sem alcançar o objetivo pretendido. O primeiro sucesso foi a demonstração que o uso de nitrogênio podia economizar vapor, aumentando, contudo a geração de subproduto. Com a evolução da consciência sobre o meio ambiente e da preservação dos recursos naturais e da redução da geração de subprodutos tornou-se uma exigência buscar a redução do consumo dos recursos naturais e da redução da geração de subproduto através da otimização dos processos. Esta coluna é uma das três do processo de produção de MVC que remove o subproduto gerado na produção do MVC. Sua otimização pode diminuir o consumo de recursos naturais e evitar uma geração a maior de subprodutos. A evolução dos modelos e dos bancos de dados com maior numero de componentes e propriedades permitiu nova abordagem para simulação da coluna. O uso de simuladores comerciais tem se mostrado como uma excelente oportunidade de obtenção de resultados consistentes com um tempo de desenvolvimento da solução menor do que a construção de modelos próprios. Neste trabalho usando o ASPEN versão 2006.5 no modo de cálculo da coluna com RateFrac, Rate-based com Soave Redlich Kwong ao invés de equilíbrio, simulamos a coluna de leves e comparamos com os resultados obtidos em teste industrial na BRASKEM, demonstrando que os resultados do modelo são robustos. A otimização da coluna foi feita tendo como restrição a concentração na corrente de fundo para o cloropreno e o 1,1-EDC, concentração máxima de 1,2-EDC no destilado e vazão máxima de destilado (subproduto). A otimização ajudou a ampliar os resultados obtidos no teste industrial, chegando a um valor de 721 mil dólares por ano de economia obtida com a redução do consumo de vapor, de nitrogênio e da geração de subproduto. A modelagem também identificou que a forma de operação do condensador com subresfriamento não é a condição ideal. A operação nas condições propostas na otimização, sem sub-resfriamento, pode gerar um ganho de 1,4 milhões de dólares por ano. / In the process of production of vinyl chloride monomer (VCM) used by BRASKEM, after the reaction of pyrolysis, of the 1,2-dicholoroethane (1,2-DCE), the components lighter than DCE are separated in a distillation column called the light’s column or separation’s column chloroprene - DCE. These components are mainly the chloroprene, 1,1-dichloroethane (1,1-DCE) and the benzene. The light’s column was modeled by BRASKEM several times on the last twenty one years, some of the times successfully and in other times not achieves the intended goal. The first success was the demonstration that the use of nitrogen could save steam, increasing, however the generation of by-product. With the evolution of consciousness on the environment, the need of natural resources preservation, and reducing the generation of byproducts, it became a requirement to seek reduction in consumption of natural resources and reducing the generation of by-product through the optimization of processes. This column is one of three of the production process of VCM that removes the by-product generated in VCM’s production. Its optimization can reduce the consumption of natural resources and avoid the generation of more by-products. The development of models and databases with greater number of components and properties allowed new approach to simulation of the column. The use of commercial simulators has been shown as an excellent opportunity to obtain solid results with a smaller time of development of the solution as the construction of own models. In this work using ASPEN version 2006.5 with RateFrac, calculation type Rate-based instead of equilibrium, using Soave-Redlich-Kwong , we simulated the light’s column and compared with the results obtained in industrial test in BRASKEM, demonstrating that the results of the model are robust. The optimization of the column was done with the restriction of the concentration in the bottom for chloroprene and 1,1-DCE, maximum concentration of 1,2-DCE in distilled and maximum flow of distilled (by-product). Optimization has helped to improve the results obtained in the test industry, reaching a value of 721 thousand dollars per year in savings with the reduction in the consumption of steam, nitrogen and the generation of by-product. The optimization also identified that the form of operation of the condenser with sub-cooling it is not the ideal condition. The operation without sub-cooling, as proposed in the optimization, can generate a gain of 1.4 million dollars per year.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-04-30T16:15:44Z No. of bitstreams: 1 TALLES CAIO LINHARES DE OLIVEIRA - DISSERTAÇÃO PPGEQ 2014..pdf: 2048638 bytes, checksum: 8906a39fa89dff7c77323f97499594a3 (MD5) / Made available in DSpace on 2018-04-30T16:15:44Z (GMT). No. of bitstreams: 1 TALLES CAIO LINHARES DE OLIVEIRA - DISSERTAÇÃO PPGEQ 2014..pdf: 2048638 bytes, checksum: 8906a39fa89dff7c77323f97499594a3 (MD5) Previous issue date: 2014-09 / CNPq / O monômero cloreto de vinila (MVC), matéria prima usada para a obtenção do policloreto de vinila (PVC), é produzido comercialmente em larga escala através da decomposição térmica do 1,2-dicloroetano (EDC) em um reator tubular inserido em um forno industrial. O PVC possui aplicações que vão desde produtos médico-hospitalares e embalagens para alimentos até peças de alta tecnologia como as usadas em equipamentos espaciais. O principal problema enfrentado na operação é a formação de uma camada de coque no interior do reator que limita o tempo de operação. O presente trabalho consiste no desenvolvimento de modelos matemáticos para a previsão do comportamento de um reator de craqueamento térmico de EDC. Um total de três modelos foram formulados, o primeiro modelo serviu para estruturação do algoritmo e para a análise geral da metodologia usada. No segundo modelo uma cinética reacional mais complexa envolvendo composto estáveis e radicais foi implementada, a deposição de coque foi considerada o que possibilitou estimar o seu impacto no tempo de produção e nas variáveis do processo como: pressão, temperatura e conversão. O último modelo foi desenvolvido utilizando técnicas de fluidodinâmica computacional (CFD) e forneceu as distribuições na direção radial e ao longo do reator para as variáveis do processo. Os resultados obtidos de todos os modelos estão em concordância com dados industriais disponíveis. Os modelos I e II podem ser usados para realização de testes no processo sem a necessidade de utilização de unidade piloto e como ponto de partida para a otimização nos fornos de craqueamento, enquanto o modelo em CFD pode contribuir para estudo de melhorias de projeto deste tipo de reator. / The vinyl chloride monomer (MVC) raw material used to obtain the polyvinyl chloride (PVC), is commercially produced on a large scale by thermal decomposition of 1,2dichloroethane (EDC) inserted into a tubular reactor in an oven industrial. PVC has applications ranging from medical products and food containers to high-tech parts like those used in space equipment. The main problem faced in the operation is the formation of a layer of coke inside the reactor which limits the time of operation. The present work is the development of mathematical models for predicting the behavior of reactor thermal cracking of EDC. A total of three models were formulated, the first model was used to structure the algorithm and the overall analysis of the methodology used. In the second model a more complex reaction kinetics involving radicals and stable compound was implemented, coke deposition was found which allowed to estimate their impact on production time and the process variables such as pressure, temperature and conversion. The last model was developed using computational fluid dynamics (CFD) and provided the distributions in the radial direction and along the reactor for the process variables. The results of all the models are in agreement with industrial data available. Models I and II can be used for testing the process without the need of using pilot unit and as a starting point to optimize the cracking furnaces while the CFD model study can contribute to improvements in the design of this type reactor.

>Magister Scientiae - MSc / Amperometric sensors for Tenofovir, a model nucleotide/ nucleoside reverse transcriptase inhibitor ARV drug, were studied based on the principle of ion-transfer electrochemistry at the membrane-stabilized oil/ water interface (O||W) in a four-electrode cell set-up. Solutions of the hydrophobic salts tetradodecylammonium tetrakis(4-chlorophenyl) borate (ETH500), ethyl violet tetraphenylborate (EthVTPB), tetrabutylammonium tetraphenylborate (TBATPB), tetraphenylphosphnium tetraphenylborate (TPphTPB) and three ionic liquids (Methyltrioctylammonium bis(trifluoromethyl sulfonyl)imide (IL1), 1-butyl-3- methylimdazolium bis(trifluoromethyl sulfonyl)imide (IL3) and 1-propyl-3- methylimdazolium bis(trifluoromethylsulfonyl)imide (IL4)) in nitrobenzene (NB), 1,2- dichloroethane (DCE), and 2-nitrophenyloctyl ether (NPOE) were each tested as O-phases. The cyclic voltammograms of the resulting O||W interfaces in aq. Li2SO4 or aq. MgSO4 were compared with respect to noise, potential window, and other parameters. The three ILs were also tested as self-sufficient salts without a solvent medium. In the end, the ETH500/ DCE salt/ solvent pair was found to yield the best behaved polarizable O||W interface in aq. MgSO4. The analytical characteristics of the resulting sensors to tenofovir without (Ag|ETH500/DCE||) and with the dibenzo-18-crown-6 (Ag|ETH5000/DB18C6/DCE|| in the O-phase were studied with respect to the two pairs of peaks in the CV, namely the WO ion transfer peak and the reverse OW peak. Both sensors exhibited operational stability of 90 min. After consideration of reasonable S/N ratio and sample throughput rates, the scan rate of 25 mV/ s was used in subsequent signal interrogation with CV. The final potential windows were 0.95 V wide for Ag|ETH500 (10 mM)/ DCE|| in aq. MgSO4 (50 mM) and 0.70 V wide for Ag|ETH500 (10 mM)/ DB18C6 (50 mM)/ DCE|| in aq. MgSO4 (50 mM). From plots of peak currents versus square of scan rate, tenofovir diffusion coefficients of about 2.48 × 10-11 cm2/ s were estimated, which indicated diffusion through the supporting membrane as the rate limiting process. Based on WO ion transfer peaks, the first one exhibited a detection limit of about 5 M, a linear range of 15 – 100 M, and sensitivity of 7.09 nA M-1 towards tenofovir, whereas for the second one these were respectively 3 M, 6.32 nA M-1, and 9 – 100 M. In this way, a four-electrode amperometric detection of ion transfer process at liquid | liquid interface, both under simple and ionophore-facilitated mode, has been demonstrated as promising for analysis of tenofovir as a representative of the nucleotide/ nucleoside reverse transcriptase inhibitor ARV drugs