• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 5
  • 5
  • 2
  • 2
  • Tagged with
  • 14
  • 14
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 2
  • 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.
1

Occurrence, Prevalence, and Disinfection Potential of Tetracycline Resistance Genes and Tetracycline Resistant Bacteria in a Subtropical Watershed

Sullivan, Bailey Ann 02 October 2013 (has links)
Antibiotics are an important method for protecting human health. Unfortunately, the development of antibiotic resistance has decreased the effectiveness of antibiotics in treating disease and preventing deaths associated with bacterial infection. The objective of this dissertation research was to gain a better understanding of anthropogenic influences on occurrence of tetracycline resistance and use of traditional disinfection methods for the reduction of tetracycline resistant bacteria and genes. Culture based and molecular methods were used to evaluate the occurrence of tetracycline resistance in a rapidly urbanizing watershed, identify the dominant resistant organisms and resistance genes in the watershed, and evaluate the use of UV and chlorine to reduce the concentration of resistant bacteria and resistance genes. Results from this research showed that tetracycline resistance was prevalent and is maintained in this study area. Several bacterial species (Aeromonas, Acinetobacter, Chryseobacterium, E. coli, Pseudomonas, and Serratia) made up the resistant population. The results also indicated that tet(W) was the major resistance gene in this watershed and that a majority of the resistant bacteria were capable of transferring their resistance. Landuse did not cause a difference in occurrence of resistant bacteria or resistance genes which suggests that a rapidly urbanizing watershed could experience resistance. It was also identified that environmental media (sediment and water) influence the occurrence and prevalence of resistant bacteria and resistance genes. The results indicate that streambed sediment may act as a reservoir for resistance and resistance might be transported in the water. Finally, the results showed that neither UV nor chlorine disinfection were effective in reducing tet(W) concentrations though the results varied greatly among species. Results from this research indicate that preventing the occurrence and distribution of resistance gene in the environment is difficult, and resistance will most likely be maintained. Therefore, in order to prevent the spread of antibiotic resistance, it will be important to prevent antibiotic resistance from becoming established in the environment. This can be done by educating the public about the importance of misusing and mismanaging antibiotics. Additionally, classifying antibiotics for either human or veterinary use may help slow the development of resistance. This should prevent clinically important antibiotics from being used in sub-therapeutic doses, which could decrease the selective pressure in the environment. Also clinically relevant bacteria can be prevented from interacting with resistant bacteria in the environment by disinfecting human waste.
2

Elucidation of Dissolved Organic Matter Interactions with Model Contaminants of Emerging Concern

Hernandez Ruiz, Selene January 2011 (has links)
This study examined the interaction of model cationic, neutral and anionic endocrine disrupting compounds, pharmaceuticals and personal care products (EDC/PPCPs) with bulk and fractionated freshwater and waste water dissolved organic matter (DOM). The chemical composition of the freshwater DOM (Suwannee River, GA, SROM) proved to be rich in plant-derived hydrophobic aromatics, while the wastewater DOM (WWOM) contained a greater proportion of microbial biomolecular products, presumably resulting mainly from human waste. Studies focused on the fluorescence quenching of excitation-emission matrices (EEMs) of WWOM indicated that interaction with bis-phenol A (BPA), carbamazepine (CBZ), and ibuprofen (IBU) occurred preferentially with soluble protein-like and fulvic acid-like constituents. However, upon introduction to bulk SROM, BPA and CBZ were observed to quench humic acid-like regions of the EEMs, while negatively charged ibuprofen preferentially quenched the protein-like and fulvic acid components irrespective of DOM source and/or fraction. Despite this evidence of EDC/PPCP interactions with both DOM types, the strength of bonds formed was generally not sufficient to preclude full recovery and quantification of all three contaminants by liquid chromatography tandem mass spectrometry (LC-MSMS). An important exception, however, was for the hydrophilic acid fraction (HiA) of both DOM types, whose apparent bonding to cationic CBZ and anionic IBU significantly diminished LC-MSMS recovery. Thus, water sources rich in HiA character might produce a concentration underestimation of ionized EDC/PPCPs even with the use of sophisticated instruments such as LC-MSMS.The results of this research are consistent with the evolving ""supramolecular"" theory of natural organic matter, which postulates that organic matter itself is comprised of fragments of partially degraded biomolecules that are aggregated into ""supramolecular"" structures of apparent higher molar mass via relatively weak electrostatic, hydrophobic, and van der Waals interaction. Our findings suggest that EDC/PPCP contaminants, which comprise many of the same functional groups as waste water and freshwater DOM, may be incorporated into such DOM supramolecular structures, likely via the same types of intermolecular bonding, when they are present in natural waters under environmentally-relevant conditions.
3

Comparação entre diferentes processos de degradação do antibiótico sulfametoxazol / Comparison between different processes for degradation of antibiotic sulfamethoxazole

Hussain, Sajjad 28 February 2014 (has links)
A ocorrência de produtos farmacêuticos e de cuidados pessoais no meio ambiente tem levado a preocupações sobre seu impacto ambiental e à saúde pública. O sulfametoxazol (SMX) é um fármaco que tem sido encontrado amplamente no ambiente. Neste estudo foi verificada a eficácia de vários processos, a saber eletroquímico, eletroquímico foto assistido, fotoquímico, Fenton e foto-Fenton, para a degradação de SMX em solução aquosa. A degradação eletroquímica e eletroquímica foto assistida foram realizadas em uma célula de fluxo do tipo filtro-prensa, usando um ânodo dimensionalmente estável comercial com composição nominal Ti/Ru0,3Ti0,7O2. Durante ambos os processos, efeitos de diferentes parâmetros foram analisados, como a natureza do eletrólito, a concentração de eletrólito suporte (NaCl) e a densidade de corrente aplicada. Os experimentos fotoquímicos, Fenton e foto-Fenton foram realizados em um reator de vidro cilíndrico de compartimento único. O efeito das concentrações inicias de Fe2+ e de H2O2 foram estudados para os processos Fenton e foto-Fenton. Similarmente, o efeito do pH inicial, a concentração inicial do SMX e a temperatura foram investigados para todos os processos. A variação da concentração de SMX foi determinada por cromatografia líquida de alta eficiência (CLAE) e a quantidade de matéria orgânica foi monitorada por análise de carbono orgânico total (COT). Os resultados obtidos indicaram que o SMX foi completamente degradado, porém, o COT foi apenas parcialmente removido em todos os processos. No período de tempo de ensaio estabelecido o aumento da densidade de corrente e da concentração de NaCl mais eficiente para a degradação e remoção de COT nos processos eletroquímicos. A quantidade de Fe2+ e H2O2 aumenta a eficiência do processo Fenton e foto-Fenton, e meio ácido foi favorável para todos os processos. O consumo de energia elétrica, baseado no parâmetro EEO (energia por ordem) mostrou que os processos eletroquímicos são energeticamente mais eficientes do que os fotoquímicos. As degradações acompanhadas por CLAE acoplado à espectrometria de massas, permitiu que vários intermediários fossem identificados, sendo então proposta uma sequência reacional para a degradação do SMX. O radical hidroxila e o cloro ativo atacam os anéis benzílico e isoxazólico, tendo sido demonstrado que os compostos iniciais formados foram os compostos hidrolisados e clorados. Os íons inorgânicos, tais como: NO3-, NH4+ e SO42-, também foram identificados durante os processos de degradação. / The occurrence of pharmaceuticals and personal care products in the environment has raised concerns about their impact upon environmental and public health. Sulfamethoxazole (SMX) is a pharmaceutical that has been found widely in the environment. This study investigated the effectiveness of various processes such as electrochemical, photo assisted electrochemical, photochemical, Fenton photo-Fenton to SMX degradation in aqueous solution. The electrochemical and photo-assisted electrochemical degradations were performed in a filter press type flow cell using a dimensionally stable anode with nominal composition of Ti/Ru0.3Ti0.7O2. During both these processes the effects of different parameters were analyzed, such as, nature of the electrolyte concentration of the supporting electrolyte (NaCl) and the applied current density. The photochemical, Fenton and photo - Fenton experiments were carried out in a single compartment cylindrical glass reactor. The effects initial iron concentrations and H2O2 were studied for Fenton and photo-Fenton processes. Similarly the effect of initial pH, initial concentration of SMX and temperature were investigated for all processes. The variation of SMX concentration was determined by high performance liquid chromatography (HPLC) and the amount of organic matter was monitored by analysis of total organic carbon (TOC). The results indicated that SMX was completely degraded, but TOC was partially removed in all processes studied, during experimental period the increase of the current density and NaCl concentration enhanced the degradation and TOC removal in the electrochemical processes. The amount of iron and H2O2 increases the efficiency of Fenton and photo-Fenton processes and acidic media was favorable for all processes. The electrical energy consumption parameter based on EEO (energy per order) was also evaluated and it was observed that the electrochemical processes are more energetically efficient than the photochemical. The degradations followed by HPLC coupled with mass spectrometry, in which several intermediates were identified and proposed a reaction sequence for the degradation of SMX. The hydroxyl radical and active chlorine attack benzene and isoxazólico rings, and has been demonstrated that the initial compounds formed were hydrolyzed and chlorinated compounds. Inorganic ions such NO3-, NH4+ and SO42- were also identified during degradation processes.
4

Control of Emerging Contaminants by Granular Activated Carbon and the Impact of Natural Organic Matter

Zhang, Juan 17 August 2012 (has links)
This research ranked the adsorbability of 115 emerging contaminants by granular activated carbon (GAC) from drinking water, mainly the organic chemicals identified on the Contaminant Candidate List 3 (CCL3), using classical and quantum quantitative structure activity relationships (QSAR). 80% of the investigated contaminants were classified as cost effectively treatable by GAC based on the models. A rapid small-scale column test (RSSCT) conducted with Lake Ontario water spiked with 8 selected emerging contaminants showed the modeling results were accurate. This research also tested the hypothesis that GAC exhaustion for geosmin and 2-methylisoborneol would be due entirely to natural organic matter, and would occur independently of the presence of these two compounds. RSSCT results confirmed this hypothesis. Mathematical modeling supported this observation by demonstrating that the ratio of the effluent concentration to the influent concentration of a trace organic contaminant is only dependent on the NOM loading state at any bed depth.
5

Control of Emerging Contaminants by Granular Activated Carbon and the Impact of Natural Organic Matter

Zhang, Juan 17 August 2012 (has links)
This research ranked the adsorbability of 115 emerging contaminants by granular activated carbon (GAC) from drinking water, mainly the organic chemicals identified on the Contaminant Candidate List 3 (CCL3), using classical and quantum quantitative structure activity relationships (QSAR). 80% of the investigated contaminants were classified as cost effectively treatable by GAC based on the models. A rapid small-scale column test (RSSCT) conducted with Lake Ontario water spiked with 8 selected emerging contaminants showed the modeling results were accurate. This research also tested the hypothesis that GAC exhaustion for geosmin and 2-methylisoborneol would be due entirely to natural organic matter, and would occur independently of the presence of these two compounds. RSSCT results confirmed this hypothesis. Mathematical modeling supported this observation by demonstrating that the ratio of the effluent concentration to the influent concentration of a trace organic contaminant is only dependent on the NOM loading state at any bed depth.
6

Comparação entre diferentes processos de degradação do antibiótico sulfametoxazol / Comparison between different processes for degradation of antibiotic sulfamethoxazole

Sajjad Hussain 28 February 2014 (has links)
A ocorrência de produtos farmacêuticos e de cuidados pessoais no meio ambiente tem levado a preocupações sobre seu impacto ambiental e à saúde pública. O sulfametoxazol (SMX) é um fármaco que tem sido encontrado amplamente no ambiente. Neste estudo foi verificada a eficácia de vários processos, a saber eletroquímico, eletroquímico foto assistido, fotoquímico, Fenton e foto-Fenton, para a degradação de SMX em solução aquosa. A degradação eletroquímica e eletroquímica foto assistida foram realizadas em uma célula de fluxo do tipo filtro-prensa, usando um ânodo dimensionalmente estável comercial com composição nominal Ti/Ru0,3Ti0,7O2. Durante ambos os processos, efeitos de diferentes parâmetros foram analisados, como a natureza do eletrólito, a concentração de eletrólito suporte (NaCl) e a densidade de corrente aplicada. Os experimentos fotoquímicos, Fenton e foto-Fenton foram realizados em um reator de vidro cilíndrico de compartimento único. O efeito das concentrações inicias de Fe2+ e de H2O2 foram estudados para os processos Fenton e foto-Fenton. Similarmente, o efeito do pH inicial, a concentração inicial do SMX e a temperatura foram investigados para todos os processos. A variação da concentração de SMX foi determinada por cromatografia líquida de alta eficiência (CLAE) e a quantidade de matéria orgânica foi monitorada por análise de carbono orgânico total (COT). Os resultados obtidos indicaram que o SMX foi completamente degradado, porém, o COT foi apenas parcialmente removido em todos os processos. No período de tempo de ensaio estabelecido o aumento da densidade de corrente e da concentração de NaCl mais eficiente para a degradação e remoção de COT nos processos eletroquímicos. A quantidade de Fe2+ e H2O2 aumenta a eficiência do processo Fenton e foto-Fenton, e meio ácido foi favorável para todos os processos. O consumo de energia elétrica, baseado no parâmetro EEO (energia por ordem) mostrou que os processos eletroquímicos são energeticamente mais eficientes do que os fotoquímicos. As degradações acompanhadas por CLAE acoplado à espectrometria de massas, permitiu que vários intermediários fossem identificados, sendo então proposta uma sequência reacional para a degradação do SMX. O radical hidroxila e o cloro ativo atacam os anéis benzílico e isoxazólico, tendo sido demonstrado que os compostos iniciais formados foram os compostos hidrolisados e clorados. Os íons inorgânicos, tais como: NO3-, NH4+ e SO42-, também foram identificados durante os processos de degradação. / The occurrence of pharmaceuticals and personal care products in the environment has raised concerns about their impact upon environmental and public health. Sulfamethoxazole (SMX) is a pharmaceutical that has been found widely in the environment. This study investigated the effectiveness of various processes such as electrochemical, photo assisted electrochemical, photochemical, Fenton photo-Fenton to SMX degradation in aqueous solution. The electrochemical and photo-assisted electrochemical degradations were performed in a filter press type flow cell using a dimensionally stable anode with nominal composition of Ti/Ru0.3Ti0.7O2. During both these processes the effects of different parameters were analyzed, such as, nature of the electrolyte concentration of the supporting electrolyte (NaCl) and the applied current density. The photochemical, Fenton and photo - Fenton experiments were carried out in a single compartment cylindrical glass reactor. The effects initial iron concentrations and H2O2 were studied for Fenton and photo-Fenton processes. Similarly the effect of initial pH, initial concentration of SMX and temperature were investigated for all processes. The variation of SMX concentration was determined by high performance liquid chromatography (HPLC) and the amount of organic matter was monitored by analysis of total organic carbon (TOC). The results indicated that SMX was completely degraded, but TOC was partially removed in all processes studied, during experimental period the increase of the current density and NaCl concentration enhanced the degradation and TOC removal in the electrochemical processes. The amount of iron and H2O2 increases the efficiency of Fenton and photo-Fenton processes and acidic media was favorable for all processes. The electrical energy consumption parameter based on EEO (energy per order) was also evaluated and it was observed that the electrochemical processes are more energetically efficient than the photochemical. The degradations followed by HPLC coupled with mass spectrometry, in which several intermediates were identified and proposed a reaction sequence for the degradation of SMX. The hydroxyl radical and active chlorine attack benzene and isoxazólico rings, and has been demonstrated that the initial compounds formed were hydrolyzed and chlorinated compounds. Inorganic ions such NO3-, NH4+ and SO42- were also identified during degradation processes.
7

Fotodegradação do contaminante emergente 2-(tiocianometiltio) benzotiazol (TCMTB) por meio de fotólise direta

Bertoldi, Crislaine Fabiana January 2017 (has links)
Os contaminantes emergentes são considerados compostos onipresentes em águas, portanto investigar a degradação e comportamento dessas substâncias torna-se necessária, pois é reportado que estes compostos causam efeitos adversos em seres vivos. O composto 2-(tiocianometiltio) benzotiazol (TCMTB), considerado um contaminante emergente, é amplamente empregado na indústria do couro como biocida com a finalidade de inibir o desenvolvimento de microrganismos na pele. Sendo assim, o objetivo do presente trabalho foi estudar a degradação do contaminante emergente TCMTB, por meio das técnicas de fotólise direta com radiação UV, radiação solar e oxidação com ozônio. Experimentos de fotólise direta do TCMTB, em soluções aquosas com diferentes concentrações, em efluente do processo de remolho e efluente simulado do remolho, foram conduzidos em reator com lâmpada de vapor de mercúrio (250 W). O teste de hidrólise foi realizado protegido da luz, a temperatura ambiente com diferentes concentrações do TCMTB para observar o comportamento do contaminante na ausência de luz. O maior coeficiente de absorção molar foi medido e identificado em 220 e 280 nm como 20489 e 11317 M-1 cm-1, respectivamente, para pH 5,0. Os resultados experimentais da fotodegradação mostraram que TCMTB foi rapidamente degradado por fotólise direta em soluções aquosas em 30 min de tratamento fotolítico. Os resultados do estudo do pH, demonstraram que pH interfere no processo fotoquímico, uma vez que em condições alcalinas o composto é mais estável e a taxa de fotodegradação diminui. Os ensaios com o efluente do processo de remolho mostraram que a degradação do TCMTB tem comportamento semelhante às soluções aquosas. O efluente simulado do remolho mostrou que uma alta concentração do contaminante leva a um maior tempo de irradiação de luz para a degradação. A aplicação de luz natural evidenciou degradação mais lenta, mas ainda assim, foi possível observar degradação de até 96% para a concentração de 6 mg L-1 em 420 min. A utilização do oxidante ozônio como tratamento, alcançou 40% de remoção do contaminante em 30 min, assinalando a alta estabilidade do composto. Portanto, este trabalho aponta o potencial do uso de fotólise direta (luz v artificial), ou radiação solar (luz natural) para a degradação de contaminantes emergentes como o 2 (tiocianometiltio) benzotiazol (TCMTB). / Emerging contaminants are considered omnipresent compounds in water, thus investigate the degradation and behavior of these substances becomes necessary as it is reported that these compounds cause adverse effects on living beings. The 2- (thiocyanomethylthio) benzothiazole compound (TCMTB), considered an emerging contaminant, is widely used in the leather industry as a microbicide for the purpose of inhibiting the development of microorganisms in the skin and leather. In this context, the purpose of the present work was to study the degradation of the emerging contaminant TCMTB by direct photolysis with UV radiation, solar radiation and ozone. Experiments of direct photolysis of the TCMTB in aqueous solutions with different concentrations, in the effluent from the soaking process were conducted in a reactor with mercury vapor lamp (250 W). The hydrolysis test was performed protected from light at room temperature with different concentrations of TCMTB to observe the behavior of the contaminant in the absence of light. The highest molar absorption coefficient was measured and identified at 220 and 280 nm as 20489 and 11317 M-1 cm -1, respectively, at pH 5.0. The experimental results of photodegradation showed that TCMTB was rapidly degraded by direct photolysis in aqueous solutions in 30 min of photolytic treatment. The results of the pH study showed that pH interfered in the photochemical process, since under alkaline conditions the compound is more stable and the photodegradation rate decreases. Assays of the direct photolysis in effluent from the soaking process have shown that TCMTB degradation behaves similarly to aqueous solutions. The direct photolysis of the the simulated effluent from the soaking showed that a high concentration of the contaminant leads to a longer time of light irradiation for degradation. The application of natural light evidenced slower degradation, however, it was possible to observe degradation of up to 96% for the 6 mg L-1 concentration with 420 min. The use of the ozone oxidant as a treatment, achieved 40% removal of the contaminant for 30 min of treatment, indicating the high stability of the compound. Therefore, this work highlights the potential of the use of direct photolysis (artificial light), or solar radiation (natural light) for the vii degradation of emerging contaminants such as 2 (thiocyanomethylthio) benzothiazole (TCMTB).
8

The occurrence of the pharmaceuticals and personal care products (PPCPs) and illicit drugs in western Hengchun Peninsula and Kenting tourist area of Taiwan

Tu, Bo-Wen 26 September 2012 (has links)
This study investigated the spatial distribution and seasonal variation of pharmaceuticals and personal care products (PPCPs) and illicit drugs in western Hengchun peninsula and Kenting coastal tourist area in Taiwan. We used solid phase extraction (SPE) followed by liquid-chromatography tandem mass spectrometry (HPLC-MS/MS) to determine 22 PPCPs and 10 illicit drugs in water samples. The detected concentrations of PPCPs and illicit drugs ranged from below detection limit to 9350 ng/L, and the most frequently five detected compounds in this area were ampicillin (79%), codeine (63%), caffeine (62%), carbamazepine (61%) and pseudoephedrine (57%). The impact of the special event- Kenting music festival, such as ¡§spring scream¡¨ was also discussed in this study, and the results from PCA and HCA both showed that the concentrations and distributions of PPCPs and illicit drugs were affected by the tourists. In addition, two wastewater treatments plants (WWTPs) were also investigated for seven days during Kenting music festival period. The results indicated that WWTPs did not show enough removal efficiencies in Kenting tourist area during the special event. The impact of the PPCPs and illicit drugs to the aquatic environment and ecology still needs to be further monitored.
9

Fotodegradação do contaminante emergente 2-(tiocianometiltio) benzotiazol (TCMTB) por meio de fotólise direta

Bertoldi, Crislaine Fabiana January 2017 (has links)
Os contaminantes emergentes são considerados compostos onipresentes em águas, portanto investigar a degradação e comportamento dessas substâncias torna-se necessária, pois é reportado que estes compostos causam efeitos adversos em seres vivos. O composto 2-(tiocianometiltio) benzotiazol (TCMTB), considerado um contaminante emergente, é amplamente empregado na indústria do couro como biocida com a finalidade de inibir o desenvolvimento de microrganismos na pele. Sendo assim, o objetivo do presente trabalho foi estudar a degradação do contaminante emergente TCMTB, por meio das técnicas de fotólise direta com radiação UV, radiação solar e oxidação com ozônio. Experimentos de fotólise direta do TCMTB, em soluções aquosas com diferentes concentrações, em efluente do processo de remolho e efluente simulado do remolho, foram conduzidos em reator com lâmpada de vapor de mercúrio (250 W). O teste de hidrólise foi realizado protegido da luz, a temperatura ambiente com diferentes concentrações do TCMTB para observar o comportamento do contaminante na ausência de luz. O maior coeficiente de absorção molar foi medido e identificado em 220 e 280 nm como 20489 e 11317 M-1 cm-1, respectivamente, para pH 5,0. Os resultados experimentais da fotodegradação mostraram que TCMTB foi rapidamente degradado por fotólise direta em soluções aquosas em 30 min de tratamento fotolítico. Os resultados do estudo do pH, demonstraram que pH interfere no processo fotoquímico, uma vez que em condições alcalinas o composto é mais estável e a taxa de fotodegradação diminui. Os ensaios com o efluente do processo de remolho mostraram que a degradação do TCMTB tem comportamento semelhante às soluções aquosas. O efluente simulado do remolho mostrou que uma alta concentração do contaminante leva a um maior tempo de irradiação de luz para a degradação. A aplicação de luz natural evidenciou degradação mais lenta, mas ainda assim, foi possível observar degradação de até 96% para a concentração de 6 mg L-1 em 420 min. A utilização do oxidante ozônio como tratamento, alcançou 40% de remoção do contaminante em 30 min, assinalando a alta estabilidade do composto. Portanto, este trabalho aponta o potencial do uso de fotólise direta (luz v artificial), ou radiação solar (luz natural) para a degradação de contaminantes emergentes como o 2 (tiocianometiltio) benzotiazol (TCMTB). / Emerging contaminants are considered omnipresent compounds in water, thus investigate the degradation and behavior of these substances becomes necessary as it is reported that these compounds cause adverse effects on living beings. The 2- (thiocyanomethylthio) benzothiazole compound (TCMTB), considered an emerging contaminant, is widely used in the leather industry as a microbicide for the purpose of inhibiting the development of microorganisms in the skin and leather. In this context, the purpose of the present work was to study the degradation of the emerging contaminant TCMTB by direct photolysis with UV radiation, solar radiation and ozone. Experiments of direct photolysis of the TCMTB in aqueous solutions with different concentrations, in the effluent from the soaking process were conducted in a reactor with mercury vapor lamp (250 W). The hydrolysis test was performed protected from light at room temperature with different concentrations of TCMTB to observe the behavior of the contaminant in the absence of light. The highest molar absorption coefficient was measured and identified at 220 and 280 nm as 20489 and 11317 M-1 cm -1, respectively, at pH 5.0. The experimental results of photodegradation showed that TCMTB was rapidly degraded by direct photolysis in aqueous solutions in 30 min of photolytic treatment. The results of the pH study showed that pH interfered in the photochemical process, since under alkaline conditions the compound is more stable and the photodegradation rate decreases. Assays of the direct photolysis in effluent from the soaking process have shown that TCMTB degradation behaves similarly to aqueous solutions. The direct photolysis of the the simulated effluent from the soaking showed that a high concentration of the contaminant leads to a longer time of light irradiation for degradation. The application of natural light evidenced slower degradation, however, it was possible to observe degradation of up to 96% for the 6 mg L-1 concentration with 420 min. The use of the ozone oxidant as a treatment, achieved 40% removal of the contaminant for 30 min of treatment, indicating the high stability of the compound. Therefore, this work highlights the potential of the use of direct photolysis (artificial light), or solar radiation (natural light) for the vii degradation of emerging contaminants such as 2 (thiocyanomethylthio) benzothiazole (TCMTB).
10

Fotodegradação do contaminante emergente 2-(tiocianometiltio) benzotiazol (TCMTB) por meio de fotólise direta

Bertoldi, Crislaine Fabiana January 2017 (has links)
Os contaminantes emergentes são considerados compostos onipresentes em águas, portanto investigar a degradação e comportamento dessas substâncias torna-se necessária, pois é reportado que estes compostos causam efeitos adversos em seres vivos. O composto 2-(tiocianometiltio) benzotiazol (TCMTB), considerado um contaminante emergente, é amplamente empregado na indústria do couro como biocida com a finalidade de inibir o desenvolvimento de microrganismos na pele. Sendo assim, o objetivo do presente trabalho foi estudar a degradação do contaminante emergente TCMTB, por meio das técnicas de fotólise direta com radiação UV, radiação solar e oxidação com ozônio. Experimentos de fotólise direta do TCMTB, em soluções aquosas com diferentes concentrações, em efluente do processo de remolho e efluente simulado do remolho, foram conduzidos em reator com lâmpada de vapor de mercúrio (250 W). O teste de hidrólise foi realizado protegido da luz, a temperatura ambiente com diferentes concentrações do TCMTB para observar o comportamento do contaminante na ausência de luz. O maior coeficiente de absorção molar foi medido e identificado em 220 e 280 nm como 20489 e 11317 M-1 cm-1, respectivamente, para pH 5,0. Os resultados experimentais da fotodegradação mostraram que TCMTB foi rapidamente degradado por fotólise direta em soluções aquosas em 30 min de tratamento fotolítico. Os resultados do estudo do pH, demonstraram que pH interfere no processo fotoquímico, uma vez que em condições alcalinas o composto é mais estável e a taxa de fotodegradação diminui. Os ensaios com o efluente do processo de remolho mostraram que a degradação do TCMTB tem comportamento semelhante às soluções aquosas. O efluente simulado do remolho mostrou que uma alta concentração do contaminante leva a um maior tempo de irradiação de luz para a degradação. A aplicação de luz natural evidenciou degradação mais lenta, mas ainda assim, foi possível observar degradação de até 96% para a concentração de 6 mg L-1 em 420 min. A utilização do oxidante ozônio como tratamento, alcançou 40% de remoção do contaminante em 30 min, assinalando a alta estabilidade do composto. Portanto, este trabalho aponta o potencial do uso de fotólise direta (luz v artificial), ou radiação solar (luz natural) para a degradação de contaminantes emergentes como o 2 (tiocianometiltio) benzotiazol (TCMTB). / Emerging contaminants are considered omnipresent compounds in water, thus investigate the degradation and behavior of these substances becomes necessary as it is reported that these compounds cause adverse effects on living beings. The 2- (thiocyanomethylthio) benzothiazole compound (TCMTB), considered an emerging contaminant, is widely used in the leather industry as a microbicide for the purpose of inhibiting the development of microorganisms in the skin and leather. In this context, the purpose of the present work was to study the degradation of the emerging contaminant TCMTB by direct photolysis with UV radiation, solar radiation and ozone. Experiments of direct photolysis of the TCMTB in aqueous solutions with different concentrations, in the effluent from the soaking process were conducted in a reactor with mercury vapor lamp (250 W). The hydrolysis test was performed protected from light at room temperature with different concentrations of TCMTB to observe the behavior of the contaminant in the absence of light. The highest molar absorption coefficient was measured and identified at 220 and 280 nm as 20489 and 11317 M-1 cm -1, respectively, at pH 5.0. The experimental results of photodegradation showed that TCMTB was rapidly degraded by direct photolysis in aqueous solutions in 30 min of photolytic treatment. The results of the pH study showed that pH interfered in the photochemical process, since under alkaline conditions the compound is more stable and the photodegradation rate decreases. Assays of the direct photolysis in effluent from the soaking process have shown that TCMTB degradation behaves similarly to aqueous solutions. The direct photolysis of the the simulated effluent from the soaking showed that a high concentration of the contaminant leads to a longer time of light irradiation for degradation. The application of natural light evidenced slower degradation, however, it was possible to observe degradation of up to 96% for the 6 mg L-1 concentration with 420 min. The use of the ozone oxidant as a treatment, achieved 40% removal of the contaminant for 30 min of treatment, indicating the high stability of the compound. Therefore, this work highlights the potential of the use of direct photolysis (artificial light), or solar radiation (natural light) for the vii degradation of emerging contaminants such as 2 (thiocyanomethylthio) benzothiazole (TCMTB).

Page generated in 0.119 seconds