Browsing by Author "Cunha, Camila Cristina Rodrigues Ferreira da"

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    Aqueous chlorination of herbicide metribuzin : Identification and elucidation of new disinfection by-products, degradation pathway and toxicity evaluation.
    (2021) Barros, André Luis Corrêa de; Rodrigues, Daniel Aparecido da Silva; Cunha, Camila Cristina Rodrigues Ferreira da; Chagas, Igor Aparecido Santana das; Espirito Santo, Daiana Rocha do; Silva, Silvana de Queiroz; Afonso, Robson José de Cássia Franco
    A widely used herbicide, metribuzin, was evaluated for degradation, mineralization and disinfection byproducts (DBPs) formation during aqueous chlorination. In addition, to assess the toxicity effects of chlorination on metribuzin solution the following tests were performed: acute toxicity using Artemia salina nauplii; cell viability using MTT assay; estrogenicity using a re-engineered Bioluminescent Yeast Estrogen Screen (BLYES) and a constitutively bioluminescent strain (BLYR); mutagenicity and developmental toxicity using Q(SAR) methodology. Metribuzin at 10 mg·L−1 was degraded by chlorination, achieving 93% of removal at 30 min of reaction. TOC analysis showed that the herbicide does not suffer complete mineralization, even after 24 h of contact with free chlorine. Seventeen DBPs were detected and their structural formulae were elucidated by high resolution mass spectrometry. Toxicity effects for chlorinated solutions increased when compared to the unreacted metribuzin solution. DBPs were more toxic to Artemia salina nauplii, increasing around 20% on nauplii mortality. It was also observed high estrogenicity to human receptors in BLYES assays and mutagenic and developmental toxicant effects to animals and humans in Q(SAR) methodology, suggesting that DBPs are potentially more toxic than the precursor metribuzin. Metribuzin solutions at 10 mg·L−1 showed equivalent 17-β-estradiol values ranged from 0.061 to 6.71 μg·L−1 after to be chlorinated at different reaction times.
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    Biodegradation of sulfamethoxazole by microalgae-bacteria consortium in wastewater treatment plant effluents.
    (2020) Rodrigues, Daniel Aparecido da Silva; Cunha, Camila Cristina Rodrigues Ferreira da; Freitas, Mylena Gomes; Barros, André Luis Corrêa de; Castro, Paulo Bernardo Neves e; Pereira, Andressa Rezende; Silva, Silvana de Queiroz; Santiago, Aníbal da Fonseca; Afonso, Robson José de Cássia Franco
    Sulfamethoxazole (SMX) has been commonly detected in wastewater treatment plant (WWTP) effluents. SMX and other antibiotics can be considered as environmental contaminants of emerging concern. Due to their toxicity effects and their potential for the development of bacterial resistance their presence in aquatic compartment becomes a threat to human health. This study evaluated the bioremediation of SMX in WWTP effluents using a tertiary treatment composed by microalgae-bacteria consortium under low intensity artificial LED illumination, and also the assessment of sulfonamide resistance gene (sul1). The removal of SMX from WWTP effluents were 54.34 ± 2.35%, in which the microalgae-bacteria consortium improves the removal performance of SMX. The main process of SMX removal can be attributed to the symbiotic biodegradation by bacteria due to the increase of oxygen released by the microalgae photosynthetic process. Therefore, the microalgae-bacteria consortium used in this study, demonstrated to be a promising alternative for bioremediation of SMX, with potential for removal others contaminants from wastewater effluent. However, the residual SMX and the relative abundance of antibiotics resistance genes (ARG) found in this study suggest that SMX contributes to selective pressure for ARG maintenance and proliferation inWWTP effluent. Thus, further studies to removal ARG from WWTP effluent are needed.
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    Determinação dos teores de água em amostras de minério de ferro, manganês e de oxihidróxidos de ferro sintéticos.
    (2016) Cunha, Camila Cristina Rodrigues Ferreira da; Costa, Geraldo Magela da; Costa, Geraldo Magela da; Dutra, Flávio de Castro; Leão, Versiane Albis
    A quantificação de água em amostras de minerais e minérios tem grande importância em termos industriais e comerciais, além de importância química e científica. Sendo assim, o presente trabalho visou à determinação dos teores de água adsorvida e absorvida em diversas amostras de minério de ferro, minério de manganês e de oxihidróxidos de ferro sintéticos. A quantificação de água foi avaliada pelo método de perda de massa, análise termogravimétrica (TGA), Karl Fischer volumétrico (KF) colocando-se a amostra diretamente dentro de um vaso de reação e posteriormente em um forno tubular. Estes últimos experimentos foram feitos com o intuito de verificar se a temperatura de 105ºC efetivamente remove toda a umidade e investigar a presença de hidrohematita e protohematita. Obteve-se o perfil de liberação de água das amostras investigadas, o que possibilitou concluir a respeito da temperatura máxima para a retirada de água adsorvida e absorvida. Os teores determinados pelo método de Karl Fischer direto foram superiores aos obtidos pelo método TGA. Os resultados demonstraram que os teores de água adsorvida e absorvida são subestimados pelo TGA. Por outro lado, não foi possível estabelecer uma temperatura adequada para secar completamente as amostras, tendo em vista o pequeno número de amostras investigadas. Pode-se comprovar que a perda de água é dependente da temperatura e do tempo, e os resultados para a goethita sintética sugerem que os minérios podem ser aquecidos até 180ºC sem que ocorra a desidroxilação deste mineral. Além disso, sugere que o tempo de duas horas (especificado pela norma ISO 2596:2006 para o método de perda de massa) não é suficiente para remover toda água adsorvida e absorvida. Os teores de água das amostras de minério de ferro, goethita sintética e natural foram determinados por titulação de Karl Fischer com forno acoplado após aquecimento das amostras a 400ºC, 600ºC e 900ºC. Verificou-se que a secagem a 400ºC remove toda a água da goethita, portanto sugere-se que não há água ou hidroxilas na estrutura da hematita formada, comprovando a inexistência da protohematita e hidrohematita nas amostras investigadas.
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    Method development for simultaneous determination of polar and nonpolar pesticides in surface water by low-temperature partitioning extraction (LTPE) followed by HPLC-ESI-MS/MS.
    (2019) Barros, André Luis Corrêa de; Abreu, Cíntia Grossi de; Cunha, Camila Cristina Rodrigues Ferreira da; Rodrigues, Daniel Aparecido da Silva; Afonso, Robson José de Cássia Franco; Silva, Gilmare Antônia da
    During this research, chemometric approaches were applied for optimization of the low-temperature partitioning extraction (LTPE) for the simultaneous analysis of the pesticides: acephate, difenoconazole, fenamidone, fluazifop, fluazinam, methamidophos, and thiamethoxam from surface water samples and determination by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry. It was used the 23 full factorial and the Doehlert experimental designs. The extraction technique was optimized by evaluating the effects of the three variables: sample pH, ionic strength (addition of Na2HPO4), and organic solvent volume. Considering the interest to find an optimal condition for all analytes simultaneously, the best extraction parameters found were as follows: pH = 5.33, concentration of Na2HPO4 = 0.0088 mol L−1 and organic phase volume = 4.5 mL. The optimized methodology showed LOD and LOQ levels from 0.33 to 8.13 ng L−1 and from 1.09 to 26.84 ng L−1, respectively. The recovery values ranged from 38.37 and 99.83% and the RSD values varied from 2.33 to 18.92%. The method was applied to surface water analysis sampled in areas with intensive agricultural practices in Ouro Branco City, Minas Gerais, Brazil. The difenoconazole was detected in concentrations between 12.53 and 94.76 ng L−1.
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    Quantification of moisture contents in iron and manganese ores.
    (2013) Costa, Geraldo Magela da; Novack, Kátia Monteiro; Elias, Megg Madonyk Cota; Cunha, Camila Cristina Rodrigues Ferreira da
    The moisture contents of several synthetic and natural goethite-bearing samples were determined by the loss-of-mass method and by the Karl-Fischer titration. It was found that drying at 105°C did not remove all the water from these samples, and that temperatures above 200°C would be required to completely remove the adsorbed water. The multiple peaks observed in the TGA and DSC measurements are not due to the dehydroxylation of goethite, but are due to the release of adsorbed water. The decomposition of goethite into hematite occurs with the release of adsorbed water from room temperature up to the onset of the main dehydroxylation peak. The dehydroxylation occurs in a broad range of temperatures due to the existence of a particle-size distribution, surface hydroxyls and formation of a hematite coating. The determination of all adsorbed water is best performed by adding the powdered sample into the Karl- Fischer reaction vessel.
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    Removal of cephalexin and erythromycin antibiotics, and their resistance genes, by microalgae-bacteria consortium from wastewater treatment plant secondary effluents.
    (2021) Rodrigues, Daniel Aparecido da Silva; Cunha, Camila Cristina Rodrigues Ferreira da; Espirito Santo, Daiana Rocha do; Barros, André Luis Corrêa de; Pereira, Andressa Rezende; Silva, Silvana de Queiroz; Santiago, Aníbal da Fonseca; Afonso, Robson José de Cássia Franco
    Antibiotics have become a concern in the aquatic environments owing to the potential development of bacterial resistances. Thus, this study evaluated the removal of cephalexin (CEP) and erythromycin (ERY) from a local wastewater treatment plant (WWTP) effluent, mediated by microalgae-bacteria consortium. Likewise, the removal of correlated antibiotics resistance genes blaTEM and ermB was also assessed. The incubation results showed that the added concentrations of selected antibiotics did not restrain the consortium growth. Moreover, CEP and ERY were almost completely removed after the cultivation period, reaching total removals of 96.54% and 92.38%, respectively. The symbiotic interaction between microalgae and bacteria plays a role in the kinetics removal of CEP and ERY. The abundance of blaTEM and ermB was reduced by 0.56 and 1.75 logs, respectively. Lastly, our results suggest that technology based on natural microalgae-bacteria consortium could be a potential alternative to improve the quality of WWTP effluents.
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    Water determination in iron oxyhydroxides and iron ores by Karl Fischer titration.
    (2016) Cunha, Camila Cristina Rodrigues Ferreira da; Costa, Geraldo Magela da
    Protohematite (Fe2−x/3(OH) x O3−x 1 ≤ x < 0.5) and hydrohematite (Fe2−x/3(OH) x O3−x 0.5 ≤ x < 0) are iron-defective phases containing hydroxyl groups in their structures. These species were described in prior studies mainly with the aid of X-ray diffraction and Infrared spectroscopy. The existence of these phases in soils might have influence in redox processes, and they were considered as a possible water reservoir in Martian soils. In this study, we have used for the first time the Karl Fischer titration method to determine the amount of water released after heating several synthetic samples of goethite, hematite and natural iron ores at 105, 400, 600 and 900 °C. It was found that heating at 105 °C did not remove all moisture from the samples, and higher temperatures were necessary to completely remove all the absorbed water. The water contents determined at 400, 600 and 900 °C were found to be the same within the experimental errors, suggesting the inexistence of both protohematite and hydrohematite in the investigated samples. Therefore, the above-mentioned effects of these phases in soils might have to be reevaluated.