Programa de Pós-Graduação em Química - PPGQ

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Para o desenvolvimento, cultural, econômico e tecnológico de uma sociedade é preciso unir esforços em diferentes áreas do conhecimento através de ensino e pesquisa de qualidade, realizadas por profissionais críticos, capazes de entender as necessidades regionais, nacionais e ao mesmo tempo conjungando-as com as necessidades mundiais. Nesse contexto, as Instituições de Ensino Superior devem exercer o papel de preparar profissionais capazes de transformar, gerar, construir, sistematizar, inovar e socializar conhecimentos no sentido de promover desenvolvimento sustentável. Esses parâmetros, como é sabido de todos, só são alcançados com investimento forte em educação.

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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.
Avaliação e desenvolvimento de um método para extração seletiva de cromo utilizando a luffa cylindrica como bioadsorvente
(Universidade Federal de Goiás, 2016-04-20) Sousa Neto, J. A.; Alves, Vanessa Nunes; http://lattes.cnpq.br/7058376443471599; Alves, Vanessa Nunes; http://lattes.cnpq.br/7058376443471599; Coelho, Luciana Melo; Muñoz, Rodrigo Alejandro Abarza
This work describes the development of a method in solid phase extraction for Cr (III) determination in food and environmental samples using Luffa cylindrica as bioadsorbent. In the first chapter, a characterization study to evaluate the use of Luffa cylindrica "in natura" as bioadsorbent for chromium ions (III and VI) adsorption in aqueous systems was conducted. Through characterization, specifically in relation to the determination of pH(PCZ), it became clear that the material has positively charged surface in solutions with pH below 6.0 and above this value, the surface is negatively charged. From this evidence, a study was conducted to evaluate the effect of pH solution on the chromium inorganic species adsorption has been noted that from pH = 4.0 it is possible to separate the chromium species (III and VI) and trivalent species exclusively adsorbed. Thus, we conducted several characterization tests such as Infrared Spectroscopy, X-rays Diffraction by the powder method, Elemental Analysis, Scanning Electron Microscopy and Energy Dispersive Spectroscopy to evaluate the physicochemical characteristics of Luffa cylindrica. The results of the kinetic study and the adsorption isotherms showed that the chromium III ions adsorption of Luffa cylindrica possibly occurs through an interaction of the chemical type. Furthermore, the parameters as stirring time and adsorbent mass were evaluated to obtain the best conditions of the adsorption process. Quantification of chromium before and after the adsorption process was performed by Flame Atomic Absorption Spectrometry. From the results, it was observed that requires 30 minutes to achieve sorption equilibrium and adsorption kinetics followed a pseudo-second-order. Study of possible interferences Ba2+, Co2+, Cu2+, Fe3+ and Mn2+ ions were performed in order to observe the selectivity of the material relative to the analyte of interest. The second chapter was developed a flow method of solid phase extraction for selective extraction and determination of Cr (III) ions in food and environmental samples. Multivariate techniques were used to evaluate the chemical variables and extraction flow system: adsorbent mass, separation flow rate, concentration and volume of eluent, through a 24factorial design. The results showed that the adsorbent mass and eluent volume was significantly influence in the flow system and has been used for optimization a Doehlert design of these variables indicating optimal values as 170 mg of adsorbent mass and 1348μL eluent (HNO3 1 mol L-1). The other variables, separation flow rate and eluent concentration were maintained at the values 2 mL min-1 and 1 mol L-1, respectively. The possible presence of interfering ions, Cu2+, Fe3+, Mn2+, Zn2+, Ca2+, Mg2+, Na+, K+, Cr6+ was studied in order to verify the selectivity of the analysis method. Through the calculated values for the interfering factor (IF) was determined good selectivity of the proposed method. The analytical performance was evaluated by the parameters, detection limit (LOD), quantification limit (LOQ), accuracy (D.P.R) and the values were 19.2 ug L-1; 63.99 ug L-1 and 0.19%, respectively, with the linear range of the method equal to 63.90 to 2000 ug L-1. Finally, the accuracy of the method was evaluated from analysis of water certificate reference material (APS-1071) and sediment (APS-1066). Recovery tests were performed on samples of water, energy and isotonic values having been found in the range from 87.60 to 107.35%. Keywords:Chromium, Luffa cylindrica, solid phase extraction.
Desenvolvimento de método adaptado de extração com ponteiras descartáveis para determinação de íons Pb(II) e Mn(II) utilizando taboa (Typha angustifólia L.) como adsorvente
(Universidade Federal de Goiás, 2020-12-18) Ferreira, Marina Mesquita; Alves, Vanessa Nunes; http://lattes.cnpq.br/7058376443471599; Alves, Vanessa Nunes; Lemos, Valfredo Azevedo; Freitas, Sílvia de Sousa
In this work, the extraction technique with disposable tips (DPX - from English disposable pipette extraction) was used using Typha angustifolia L. (cattail) as an adsorbent. An adapted DPX method was developed for the determination of Pb(II) and Mn(II) ions in aqueous samples, using the Flame Atomic Absorption Spectrometry (FAAS) technique for quantification. The characterization of the cattail was performed through X-Ray Diffraction, Infrared Spectroscopy, X-Ray Fluorescence Spectroscopy, Determination of the pH at the Zero Charge Point and Buoyancy, with results consistent with those observed in the literature. The zero load point of the material was determined at 6.39. The pH of the solution was univariate optimized by selecting the solutions of Pb(II) and Mn(II) ions at a concentration of 1.0 mg L-1 at pH 8. Tests to optimize the parameters that influence the adsorption and desorption of the ions were made in a multivariate manner. Through Doehlert planning, it was possible to obtain optimal values for mass of adsorbent and number of adsorption cycles, being defined in 30 mg and 7 cycles, respectively, for Pb(II) and Mn(II) ions and the concentration of HNO3 and number of desorption cycles, in 0.8 mol L-1 and 7 cycles. The kinetic study indicated that the adsorption of the Pb(II) and Mn(II) ions obey a pseudo-first order and Avrami kinetics, respectively. The maximum adsorption capacity was obtained through the construction of adsorption isotherms, with values of 29.17 and 5.64 mg g-1 being found for the Pb(II) and Mn(II) ions, respectively. Under optimized conditions the extraction method presented detection limits of 17.51 μg L-1 (Pb (II)) and 35.02 μg L-1 (Mn (II)), quantification limits of 58.37 μg L-1 (Pb (II)) and 116.7 μg L-1 (Mn (II)), and a pre-concentration factor of 10 (Pb (II)) and 2 (Mn (II)), being a linear range of 116.7 to 2000 μg L-1 method for Mn (II) and from 58.37 to 2500 μg L-1 for Pb (II). Accuracy was evaluated separately in terms of repeatability and reproducibility, obtaining D.P.R. values of 0.31 and 0.25% for Pb (II), respectively, and 7.00 and 9.88% for Mn (II), respectively. The evaluation was evaluated by means of recovery tests in river water collected near a mining company, recovery values in the range of 80-120% and through the use of certified reference materials, indicating high reliability of the method.
Desenvolvimento de metodologia analítica utilizando sistema em fluxo e casca de arroz para pré-concentração de chumbo em amostras de sedimento
(Universidade Federal de Goiás, 2018-06-20) Furtado, Liliam Quelem Tavares; Coelho, Luciana Melo; http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4794563A2; Coelho, Luciana Melo; Alves, Vanessa Nunes; Silva, Sidnei Gonçalves da
The present work presents a study of use of the rice husk as adsorbent material for the determination of lead ions in sediment samples obtained at different points of Rio Doce region (Espírito Santo), using flow injection system. With detection metal determination wes used Atomic Flame Absorption Spectrometry. The physico-chemical characterization of the material was done by Infrared Region Spectroscopy, Scanning Electron Microscopy, X-ray Dispersive Energy Analysis and X-ray Diffraction and determination of the zero load point. In adsorptive processes, the pH directly influences the extraction of the ion and the study of this parameter indicated that in pH 6,00 better extraction conditions are obtained. After pH determination, a multivariate optimization 2 4 of the parameters influencing the ion adsorption process was performed. The variables evaluated were adsorbent mass, preconcentration flow, volume and eluent concentration. Subsequently, a univariate study of the mass and preconcentration flow variables was performed, as well as a study of the elution flow rate. The best responses for flow system operation were obtained using: adsorbent mass 70.0 mg, eluent concentration (HNO3) 0,50 mol L-1 , eluent volume 1000 μL, preconcentration flow 2.0 mL min-1 and elution flow 1.0 mL min-1 . From the optimized conditions, the procedure showed to be effective for the Pb2+ species, with limits of detection (LD) and quantification (LQ), respectively, equal to 0.015 and 0.05 mg L-1, with a relative standard deviation (DPR) of 6.821% and a preconcentration factor of 49.5. Recovery values were obtained between 87 - 100% for fortified sediment samples. In order to analyze the selectivity of the method, the evaluation of possible interferences was carried out, based on the calculation of the interference factor (FI). The Cu (II), Ni (II), Co (II), Fe (III) and Zn (II) ions were analyzed in different proportions. The procedure presented was satisfactory for preconcentration of Pb2+ ions, and it can be used for extraction of the same. As it proved to be fast, efficient, low cost, besides the reduction in reagent consumption and waste generation. Factors that favor the development of a system based on the principles of "Green Chemistry".
Desenvolvimento de um método de extração e pré-concentração em fluxo para determinação de cádmio em amostras de interesse alimentício utilizando a palha do café como adsorvente
(Universidade Federal de Goiás, 2017-03-29) Soares, Maria Dalva Americano; Carvalho, Dayene do Carmo; http://lattes.cnpq.br/5513978376671756; Alves, Vanessa Nunes; http://lattes.cnpq.br/7058376443471599; Alves, Vanessa Nunes; Freitas, Silvia de Sousa; Coelho, Nívia Maria Melo
The present work presents a study on the use of dry coffee straw and straw from sticky coffee, also known as "bark" of the coffee as adsorbent for metallic ions. Initially, the experiments were carried out in batch and the metal quantification before and after the adsorption experiments was done using Atomic Flame Absorption Spectrometry (FAAS). The adsorption of the ions Cd (II), was evaluated and the results indicated that the coffee straw dried in natura, presented an outstanding performance. The optimization parameters studied in the adsorption of the corresponding ion were the pH of the solution and time of contact, presenting the maximum adsorption occurrence in the pH value between 5 to 9 and better contact time starting from 60 minutes. The physical-chemical characterization of the material was done through the use of Infrared Spectroscopy, X-ray Dispersive Energy Analysis, X-Ray Diffraction Analysis, EDX Elemental Analysis and the zero load point determination. The adsorption kinetics best fit the pseudo-second order model and the adsorption isotherms developed with the objective of determining the maximum adsorptive capacity showed a better fit to the Langmuir model. From data obtained in the batch experiments, the dry coffee straw was used in the development of a solid phase extraction method for adsorption of cadmium. In order to evaluate the chemical and flow variables that possibly influence the system, the multivariate method was used. The variables studied were adsorbent mass, eluent concentration, eluent volume and pre-concentration flow, through a factorial design 24, indicating the eluent volume and pre-concentration flow as the significant variables, which were studied later by means of Doehlert planning. Thus, the best conditions for flow system operation were: adsorbent mass 25 mg, (HCl) eluent concentration 1.0 mol L-1, eluent volume 250 μL and pre-concentration flow 2.0 mL min-1. For the purpose of analyzing the selectivity of the method, a study of the possible interferences was done, based on the calculation of the interference factor (IF). The Cu+2, Fe+2, Mn+2, Zn+2, Ca+2, Mg+2, Na+1, K+1, Cr+3 ions were analyzed in different proportions. The pre-concentration factor was calculated as being equal to 20.4; Limit of detection (LD) 7,86 μg L-1, Limit of quantification (LQ) 26,20 μg L-1, precision (DPR) 0,11, linear range between 26,20 - 2000 μg L-1. The accuracy of the method was tested through the analysis of the certified water reference material (APS - 1071).The recovery tests were carried out on samples of cashew, pineapple, orange and guava juices, and the values found were ranged from 100,72 to 109,7%. The method developed was satisfactory for pre-concentration of Cd (II) ions, for the simplicity, efficiency, low cost. Also, the used adsorbent can be easily found in nature and it can be reused.
Desenvolvimento de um método de extração em fase sólida in situ para determinação de Cr(III) em infusão de fitoterápicos
(Universidade Federal de Goiás, 2019-08-08) Siqueira, Alêssa Gomes; Costa, Bruno Elias dos Santos; http://lattes.cnpq.br/9995122149910490; Alves, Vanessa Nunes; http://lattes.cnpq.br/7058376443471599; Rezende, Hélen Cristine; Coelho, Luciana Melo; Alves, Vanessa Nunes; Costa, Bruno Elias dos Santos
This work presents the development of an in situ solid phase extraction method (SPE-ISS) for the determination of chromium (III) in herbal infusion samples using flame atomic absorption spectrometry (F AAS). Thus, in order to evaluate the inorganic composition of medicinal plant samples (calendula, chamomile, carqueja, green tea, leather hat, melissa and passiflora) we used the EDXRF (Dispersive Energy X-ray Fluorescence). the presence of plant essential metals in addition to toxic metals. Subsequently, a quantitative analysis of some metal ions was performed in infusion samples prepared from these plants, and Fe(III) was the only one found in considerable concentration, while Pb(II), Cr(III), and Cd(II) presented concentrations below the detection limit of the technique. Therefore, it is necessary to develop extraction and preconcentration methods that allow the determination of Cr(III) simply and safely, even when present in low concentrations. In this work, the SPE-ISS method was optimized by multivariate techniques, and the results showed that the formation of the Cr-PAN complex is favored at pH 9.5, with the complexant at 0.18 mmol L-1 concentration. For optimization of solid phase formation and extraction, factorial design and response surfaces were used, which pointed to the use of CTAB as phase transfer agent, NaClO4 0.26 mol L-1 as ionic pairer and agitation time of 7.5 minutes. Studies of possible interferents indicated negative interference of the metallic ions Al(III), Zn(II), Fe(III) and Ca(II). The analytical performance was evaluated by the parameters, preconcentration factor, detection limit (LD) and limit of quantification (LQ) and the values found were 1.66 μg L-1 and 5,5 μg L-1, respectively. The intra-day and inter-day precision (RPD) was 0.001% and 0.0004%, respectively, being the linear range of the method from 250 to 5000 μg L-1, presenting the potential to determine low chromium concentrations. Finally, the accuracy of the method was evaluated from analysis of certified reference water material (APS-1071), as well as recovery tests on water samples and herbal infusions 77.60 - 116%.
Desenvolvimento de um método por ponto nuvem dos hormônios naturais E1 e E2 em amostras de urina e determinação por CLAE/EC utilizando eletrodo de diamante dopado com boro
(Universidade Federal de Goiás, 2015-08-06) Amorim, Kamila Pereira de; Andrade, Leonardo Santos; http://lattes.cnpq.br/5360511377400279; Andrade, Leonardo Santos; Brocenschi, Ricardo Francisco; Alves, Vanessa Nunes
Cloud point extraction method (CPE) was used for the determination of estrone (E1) and 17β-estradiol (E2) hormones in human urine. The combination of the electrochemical detection techniques with high-performance liquid chromatography (HPLC-EC) was used for the detection and quantification of these hormones. A boron doped diamond electrode (BDD) pretreated cathodically was used as electrode material for all electrochemical measurements. The optimized chromatographic parameters resulted in a mobile phase composition of KH2PO4 (0.01 mol L-1; pH 5.0) / ACN (72:28 V/V), flow 1.2 ml min-1. An applied potential for electrochemical detection of 1.0 V x Ag/AgCl (3.0 mol L-1) was selected from hydrodynamic voltammograms constructed for each hormone changing the potential between 0.3 V and 1.2 V x Ag/AgCl (3.0 mol L-1). Limits of detection (S/N = 3) of 500 ng mL-1 and limits of quantification of 800 ng mL-1 were obtained for both E1 and E2 hormones without any extraction process. Urine samples at pH 5.0 and 7.0 were investigated aiming the influence of pH on the efficiency of the CPE process, and the optimum results for the most current signal of the hormones was obtained at pH 7.0. Extractor solvent volumes were changed in the 0.5-2.5 mL range, and the optimum results were obtained when using 1.0 mL of Tergitol TMN-6 surfactant (10% aqueous solution). From the equation of the calibration curves obtained with and without the CPE procedure it was possible to determine the pre-concentration factor (FC) and all the other parameters involving the efficiency of CPE method. A comparison of the efficiency of CPE method with direct liquid-liquid extraction with the organic solvent CCl4 was carried out and the results showed that the CPE method was quite superior to liquid-liquid extraction. The validation of the method was carried out from intra-day recovery experiments and inter-day and evaluated the accuracy, precision and repeatability. The proposed method was applied to individual samples of urine of 1 man, 1 pregnant woman, 1 woman in fertile age, and 1woman in lactating stage. The values of the variation coefficients of the recovery percentages were lower than 15%.
Desenvolvimento de uma metodologia para determinação de Pb2+ em matrizes aquosas utilizando nanopartículas magnéticas
(Universidade Federal de Goiás, 2018-04-20) Silva, Carolina Aparecida de Sousa; Alves, Vanessa Nunes; http://lattes.cnpq.br/7058376443471599; Alves, Vanessa Nunes; http://lattes.cnpq.br/7058376443471599; Coltro, Wendell Karlos Tomazelli; Coelho, Luciana Melo
The iron oxide (Fe3O4) nanoparticles are promising adsorbents and, in this work, they were synthesized, characterized and applied as adsorbents in the adsorption of lead ions (Pb2+) using solid phase magnetic extraction (MSPE). The iron oxide was synthesized by the coprecipitation method and the obtained nanoparticles presented the crystalline phase of the oxide, being proved by the characterization by X-Ray Diffraction, X-ray Dispersive Energy and Absorption Spectroscopy in the Infrared region. In order to obtain information on the surface charge of the synthesized material, the pH at the zero loading point (pHPCZ) was determined indicating that the oxide surface is negatively charged at pH values above 9.4. Once the best pH (9.0) for adsorption was defined, the influence of the variables agitation time and mass of the adsorbent were evaluated, fixing them in 4 min and 3.0 mg respectively, in order to obtain the best conditions of the adsorption. adsorption process. The maximum adsorption capacity was obtained by the construction of adsorption isotherms, and a value of 31.60 mg.g1 was found. Through the kinetic study, it was observed that the adsorption obeys a pseudo-first-order kinetics. After the adsorption was optimized, the best desorption parameters were evaluated, aiming the development of an extraction/preconcentration method. Thus, 500μL of 0.5 mol.L-1 nitric acid was used as the eluent. The analytical performance was evaluated by means of the parameters, limit of detection (L.D.), limit of quantification (L.Q.), precision (D.P.R) and values found were 5.44 μg.L-1 ; 16.48 μg.L-1 and 0.25%, respectively, with the linear range of the method being 16.48 -500 μg.L-1 . Finally, the accuracy of the method was evaluated from recovery tests on samples of mineral water, micellar water and facial makeup with recovery values in the range of 95.94 - 118%. In addition, analyzes of certified water reference material (APS-1071) were also made to verify the accuracy of the proposed method.
Determinação eletroquímica do agrotóxico tiabendazol extraído e pré-concentrado em amostras de tomate pela técnica de ponto nuvem usando eletrodo de diamante dopado com boro
(Universidade Federal de Goiás, 2019-03-29) Caixeta Neta, Antônia; Andrade, Leonardo Santos; http://lattes.cnpq.br/5360511377400279; Andrade, Leonardo Santos; Alves, Vanessa Nunes; Muñoz, Rodrigo Alejandro Abarza
In Brazil, there is a significant consumption of tomatoes and, according to the report of the Program of Analysis of the Residues of Agrochemicals in Food (PARA) available by ANVISA, the tiabendazole (TBZ) fungicide was detected in some tomato samples analyzed. The detection of this substance is considered to be prohibited, since the TBZ is authorized only for application in seeds of the plant and, therefore, could not be found in fruits. Thus, electrochemical methods can be used for the determination of pesticides in complex samples and in low concentration levels, because they produce fast and reliable measurements, consuming small amounts of reagents. In this work, a procedure for the electroanalytical determination of TBZ fungicide in tomato fruits using boron-doped diamond electrode (BDD) was developed and validated using the cloud extraction and preconcentration (CPE) technique. The analytical technique used in this determination was the High Performance Liquid Chromatography coupled to an electrochemical detector (HPLC-EC), by the use of the BDD electrode. In order to evaluate the main variables of the CPE process, it was used a 24 complete factorial planning to optimize the parameters. The CPE optimized condition was achieved by the use of Tergitol (19% V/V), NaCl (0.83 g), ultrasonic stirring time of 15 min and temperature of 36 °C. Under these conditions, the preconcentration factor obtained was 5.7. The limits of detection and quantification obtained were 2.7 × 10-8 mol L-1 and 5.5 × 10-8 mol L-1 , respectively. The average recoveries obtained in 3 days were satisfactory, varying between 80.7% and 115.1%, which demonstrates the good accuracy of the developed method. In the application of the method in commercial tomatoes, TBZ was detected in one of the samples analyzed. The differential pulse voltammetry (DPV) technique was also investigated for the electroanalytical determination of TBZ fungicide in tomato fruit (extracted and pre-concentrated by CPE) using BDD electrode in order to increase the analytical frequency. The use of DPV technique increased the analytical frequency by approximately 90 times compared to the HPLC/EC technique.
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.
Micro extração em fase sólida dispersiva utilizando hematita como adsorvente para determinação de cromo em etanol combustível
(Universidade Federal de Goiás, 2019-02-21) Oliveira, Jordana de Assis Nunes; Alves, Vanessa Nunes; http://lattes.cnpq.br/7058376443471599; Alves, Vanessa Nunes; Tarley, César Ricardo Teixeira; Freitas, Sílvia de Sousa
A micro extração em fase sólida dispersiva é um tipo de extração em fase sólida que possui uma série de aplicações analíticas. Assim, neste trabalho é apresentado o desenvolvimento de um método de micro extração em fase sólida dispersiva utilizando nanopartículas de hematita como adsorvente para determinação de íons Cr(III) em amostras de etanol combustível, com detecção por espectrometria de absorção atômica com atomização por chama. A hematita foi sintetizada pelo método sol-gel e caracterizada por Difração de Raios X, Espectroscopia de Infravermelho, Espectroscopia de Energia de Fluorescência de Raios X, Microscopia Eletrônica de Varredura com Fonte de Emissão de Campo, Microscopia Eletrônica de Transmissão, Magnetização edeterminação do Potencial Zeta. O material sintetizado apresentou estrutura cristalina e fase única no difratograma de raios X, sendo condizente com a ficha cristalográfica comparada. As microscopias mostraram nanopartículas com morfologia de nano-ginger, apresentando crescimento em rede ramificada, com crescimento em diferentes planos. Através do potencial zeta, foi determinado o pH no ponto de carga zero do material em 4,49. Os parâmetros que influenciam na extração do íon Cr(III) foram selecionados e otimizados. O pH da solução foi otimizado pelo método univariado, sendo obtidas as melhores extrações para uma solução contendo o íon cromo na concentração de 0,5 mg L -1 em pH 9. As demais variáveis foram otimizadas pelo método multivariado. Inicialmente um planejamento fatorial 2 4 foi utilizado para avaliar as variáveis: massa do adsorvente, tempo de adsorção e dessorção e concentração do eluente (HNO 3 ). A massa do adsorvente não foi considerada significativa e, portanto, fixada em 3,0 mg. As demais variáveis foram consideradas significativas, e otimizadas através de um planejamento composto central, sendo seus melhores valores otimizados em 112,2 s, 81,5 s e 1,0 mol L -1 para tempo de adsorção, tempo de dessorção e concentração do eluente, respectivamente. O estudo cinético revelou que a adsorção obedece a uma cinética de pseudo-pimeira ordem. A capacidade máxima de adsorção foi obtida pela construção de isotermas de adsorção, sendo encontrado um valor de 38,27 mg g -1 . O desempenho analítico foi avaliado por meio dos parâmetros, limite de detecção, limite de quantificação, precisão intra-dia e fator de pré-concentração e os valores encontrados foram de 0,39 μg L -1 , 1,30 μg L -1 , 0,06 % e 50, respectivamente, sendo a faixa linear do método de 1,5 a 1000 μg L -1 . A exatidão do método foi avaliada a partir de análises de material de referência certificado de água (APS-1071), além dos testes de recuperação em amostras de etanol combustível, com valores de recuperação na faixa de 80-120%.

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Navegando Programa de Pós-Graduação em Química - PPGQ por Autor "Alves, Vanessa Nunes"

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