Mestrado em Química - PPGQ

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Navegando Mestrado em Química - PPGQ por Assunto "Adsorvente alternativo"

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    Avaliação da fibra da bucha vegetal (Luffa cylindrica) e das folhas de taboa (Typha angustifolia L.) como materiais adsorventes para a remoção do agrotóxico tebuconazol de água contaminada
    (Universidade Federal de Goiás, 2019-03-18) Silva, Thiago Felipe; Freitas, Silvia de Sousa; http://lattes.cnpq.br/4503172443143993; Freitas, Silvia de Sousa; Alves, Vanessa Nunes; Sarmento, Antover Panazzolo
    Agrochemicals are industrialized products made up of a broad junction of chemicals used to combat pest resistance in plantations. The high consumption and the inappropriate disposal of these products can generate great environmental impacts. Adsorption processes employing alternative materials have been evaluated to remove them from the environment, especially from water sources for human consumption. In this work, the adsorption capacity of the materials: bush (Luffa cylindrica) and taboa (Typha angustifolia L.) was evaluated for the removal of the tebuconazole pesticide from aqueous medium. The analytical methodology used to quantify the pesticide in the solution, after the removal, was High Performance Liquid Chromatography with UV-vis detector (HPLC-UV). The values of LD and LQ in the chromatographic method were 0.01 mg L-1 and 0.10 mg L-1 , respectively. The materials were characterized by the FTIR technique, being observed in both materials the presence of functional groups characteristic of lignocellulosic compounds. The micrographs (SEM) indicated the heterogeneity and irregularity of the surface in both materials. The pH at the zero charge point (pHPCZ) was 6.15 for bush (Luffa cylindrica) and 6.62 for taboa (Typha angustifolia L.). The ability to remove tebuconazole from the aqueous medium by the materials was evaluated as a function of the adsorbent dosage, contact time and concentration of the pesticide. The dosages of 20 and 10 g L-1 were used in the adsorption tests with the bush (Luffa cylindrica) and taboa (Typha angustifolia L.), respectively. The kinetic study showed that the adsorption equilibrium was obtained after 40 minutes of contact and the experimental data were better adjusted by the Avrami model, for both materials. Regarding the study of tebuconazole concentration, it was observed that the removal is little influenced by the increase in tebuconazole concentration in the medium, remaining relatively constant in the concentration range evaluated, for both materials. The experimental data were well adjusted by all models of isotherms evaluated (Langmuir, Freundlich and Sips), with R 2> 0.99. The maximum adsorption capacity (Qmax) of tebuconazole was 8.5651 mg g-1 for bush (Luffa cylindrica) and 13.6419 mg g-1 for taboa (Typha angustifolia L.).The use of the adsorbents to remove the pesticide in natural water sample presented results very similar to those observed when using deionized water, showing that the removal efficiency of these materials is not affected by the type of aqueous matrix. The alternative column adsorption process showed satisfactory removal results (~ 51% removal for bush and ~ 75% removal with taboa), in a significantly shorter time (3-4 min) in relation to the batch process (40 min). Thus, it can be concluded that the adsorbent materials evaluated, bush (Luffa cylindrica) and the taboa (Typha angustifolia L.) can be used for the removal of the tebuconazole pesticide from aqueous medium.
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    Estudo da typha angustifolia l. como material vegetal adsorvente para a remoção dos agrotóxicos trifluralina, clorpirifós e α-endossulfam de meio aquoso
    (Universidade Federal de Goiás, 2016-02-26) Mendes, Marcia Felipe; Freitas , Sílvia de Sousa; http://lattes.cnpq.br/4503172443143993; Freitas, Sílvia de Sousa; Eiras, Sebastião de Paula; Alves, Vanessa Nunes
    Because of the toxicological relevance of pesticides introduced into the environment through agricultural practices, it is necessary to develop simple methodologies with low cost, enabling remove these pollutants from the environment, in particular of water intended for human consumption. The adsorption process is an efficient and low cost technique that have wide application. The adsorbent capacity of the leaves of Typha angustifolia L. herbaceous perennial plant belonging to the family Typhaceae, in Brazil it is also popularly known as taboa, was investigated for the removal of pesticides trifluralin, chlorpyrifos and α-endosulfan from aqueous medium. The the analytical method using solid phase extraction (SPE) and chromatography with electron capture detector (GC/ECD) was optimizates and validate. The validation criterions were reached and the analytical methos was considered efficient for trifluralin, chlorpyrifos and α-endosulfan quantification in an aqueous medium, providing credibility to the results obtained in the adsorption experiments. The adsorption capacity of T. angustifolia was evaluated under different parameters: treatment of the material, amount of material, contact time between the plant material and the pesticides solution and concentration of the pesticides solution. The results showed that treatment of the material with distilled water and was satisfactory and, for all doses evaluated the pesticide removal was efficient, with best results obtained at a dose of 3.0 g L-1 , equivalent to 60 mg of adsorbent in 20.0 mL of solution, in which the pesticide removal were between 73 and 80%. The adsorption kinetics of the pesticide by T. angustifolia showed that the adsorption equilibrium was reached in 40 minutes for all pesticides, removing up to 90% and using a very small amount of plant material (3 g L-1 ). The experimental data were evaluated using the kinetic models of pseudo-first order, pseudo-second order and Avrami. One of the limitations encountered in the concentration influence study is the limited solubility of the agrochemical in aqueous medium (between 0.33 and 1.00 mg L-1 ), resulting in the study of a small concentration range in the adsorption experiments. To study the pesticides adsorption mechanism by T. angustifolia material, the experimental data were applied to Langmuir, Freundlich and Sips non-linear isotherms models. Additional tests showed that the adsorption capacity is unaffected when using natural water in the adsorption experiments. The results indicate that the material obtained from of T. angustifolia leaves, has a great potential to be used as an alternative adsorbent material in pesticide contaminated aqueous solution treatment.
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    Estudo do bagaço de cevada e da palha de milho como materiais adsorventes alternativos para remoção do agrotóxico carbaril de meio aquoso contaminado
    (Universidade Federal de Goiás, 2018-08-17) Milhomem, Karoline Pinto; Freitas, Sílvia de Sousa; http://lattes.cnpq.br/4503172443143993; Sarmento, Antover Panazzolo; Coelho, Luciana Melo
    In this dissertation, the materials corn straw and barley bagasse were investigated as alternative adsorbents for removal of the carbaryl pesticide from aqueous medium. For this, both materials were ground to obtain uniform particles (granulometry between 20 and 48 mesh) and treated with hydrated ethyl alcohol. The quantification of the carbaryl pesticide was made by High Efficiency Liquid Chromatography with UV-vis detector. The values of LD and LQ for the determination of the carbaryl pesticide by liquid chromatography using the method used were 0.01 mg L-1 and 0.10 mg L-1, respectively. The characterization of the adsorbent materials by FTIR showed the presence of the functional groups: hydroxyl, carbonyl and methyl, very common in lignocellulosic materials. The pH at the zero loading point (pHPCZ) was 7.08 for barley bagasse and 6.44 for corn straw. The adsorption capacity of the investigated materials was evaluated under different parameters such as material dose (g L-1), contact time between the pesticide solution and the adsorbent material (min) and the concentration of the pesticide in the solution (mg L-1). An alternative adsorption procedure was also proposed with the adsorbents packaged in a column where different doses of the adsorbents were evaluated and finally the adsorption process was evaluated using natural water samples. From the study of the dose of the materials the dose of 20 g L-1, equivalent to 200 mg of the adsorbent material in 10 mL of solution was selected, where 45.1% of the carbaryl was obtained when the barley bagasse was used and 49.2% when corn straw was used. For both adsorbents the kinetic study showed that the adsorption of the carbaryl agrochemical is best represented by the Avrami kinetic model, indicating that the adsorption of the carbaryl is not constant, but follows multiple orders. The maximum adsorption capacity (Qmax) was obtained by the construction of adsorption isotherms, where it was verified that the experimental data of the process of adsorption of the carbaryl by the barley bagasse is better represented by the Langmuir model providing a value of Qmax of 6, 5244 mg g-1. For corn straw, the Sips model was the most adequate with a Qmax value of 1.2625 mg g -1. In the column adsorption procedure the barley bagasse was efficient in all the doses evaluated, obtaining practically the same rate of removal as the procedure performed in batch mode, however in a much shorter time. As for the adsorbent corn straw, the removal through the column procedure was much less effective, suggesting that for this material the batch procedure is more adequate. In the adsorption study using natural water samples as an aqueous matrix, it was verified that the adsorption process of the carbaryl by both adsorbents can be affected by the pH of the medium and also by the presence of other compounds present in the aqueous matrix. In general, the results indicate that the barleybagasse and corn straw materials can be used as adsorbent materials in the treatment of aqueous medium contaminated with the carbaryl pesticide.