Estudo cinético e de adsorção de íons metálicos em nanofibrilas de celulose
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2022-09-08
Autores
Orsi, Blenda Lopes
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Universidade Estadual Paulista (Unesp)
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Com o avanço dos processos tecnológicos e consequentemente industriais, o descarte de metais em compartimentos ambientais tem se mostrado um problema devido as consequências negativas aos seres vivos, podendo culminar na morte dependendo do tipo de metal, suas propriedades e interações com o meio. Para auxiliar no monitoramento ambiental, o desenvolvimento de técnicas e modelos utilizando materiais de baixo custo a fácil acesso mostram-se metodologias atrativas. A celulose é o biopolímero natural mais abundante do mundo podendo ser obtido diretamente das plantas ou resíduos, como bagaço da cana e restos de madeira. Portanto este estudo tem como objetivo avaliar a eficiência da nanocelulose para a adsorção de íons metálicos presente em soluções aquosas. A produção da celulose em escala nano se deu a partir do uso do moinho SuperMassColloider, que utilizando-se da moagem diminui o diâmetro de suas fibras, e o preparo de filmes deste material, a partir de secagem em estufa. Sua caracterização por DRX, FTIR, MEV, EDS e AFM mostraram a fabricação de uma celulose em escala nano com parâmetros dentro dos obtidos por literatura. Os testes analíticos envolveram o estudo do equilíbrio químico, avaliando o tempo de contato até o equilíbrio ser estabelecido, com valores obtidos a partir da leitura em ICP OES. Foram preparadas soluções multielementares de íons metálicos (zinco, cobre, cádmio, chumbo, manganês e níquel) com pH 6, força iônica 0,01 mol L-1 e temperatura constante de 25°C, a fim de analisar os modelos cinéticos de adsorção de pseudoprimeira ordem, pseudosegunda ordem, Elovich, Weber-Morris e Boyd, com a finalidade de verificar o melhor modelo que se aplica ao mecanismo de adsorção entre o adsorvente e o adsorvato. O estudo em questão obteve um resultado favorável para a adsorção dos íons metálicos selecionados, com porcentagem de remoção no equilíbrio variando conforme o metal, zinco (87%), chumbo (95,6%), níquel (90,7%), manganês (95,5%), cobre (98,4%), cádmio (87,7%). Dentre os modelos comparados o que mais se adequou foi o de pseudosegunda ordem, enquanto o de Weber e Morris se adequou ao explicar o mecanismo de adsorção, tendo em alguns casos sido complementado pelos resultados de Boyd, principalmente para os tempos iniciais.
With the advance of industrial, technological, agricultural and urbanization processes, the disposal of metals in soil and water resources has proved to be a problem due to the physiological consequences to living beings, which can lead to death depending on the type of metal and its properties. With the growth of this, the development of techniques and models of environmental monitoring have gained prominence, especially those that use low cost and easy to access materials. Cellulose and its by-products have proven to be a good option to be applied in environmental monitoring, because their hydroxyls allow the adsorption of metals and, if necessary, the modification of their bonds from other binders. It is the most abundant natural biopolymer in the world and can be obtained directly from plants or residues such as sugarcane bagasse and wood debris. Therefore, this study aims to evaluate the efficiency of nanocellulose for the adsorption of metal ions present in aqueous solutions. The production of cellulose in nano scale occurred from the use of the SuperMassColloider mill, which uses grinding process to decrease the diameter of its fibers, and the preparation of films of this material, from the technique of drying in the oven. Its characterization by XRD, FTIR, SEM, EDS and AFM showed the manufacture of a nano scale cellulose with parameters within the expected and comparable with literature values. The analytical tests involved the study of chemical balance, evaluating the contact time until the balance is established. Considering the percentage of removal of metal ions of multielemental solution (zinc, copper, cadmium, lead, manganese, and nickel) with pH 6, ionic strength 0.01M and constant temperature of 25°C. Kinetic adsorption models of pseudofirst order, pseudosecond order, Weber and Morris, Elovich and Boyd were applied in order to analyze the best model that applies to the system under analysis and the adsorption mechanism that occurs in the adsorbent. The study in question obtained a favorable result for adsorption of the selected metal ions, with a percentage of removal in balance varying according to metal, zinc (87%), lead (95.6%), nickel (90.7%), manganese (95.5%), copper (98.4%), cadmium (87.7%). The kinetic model that best fit the results obtained was pseudosecond order, while the Weber and Morris mechanism was adapted to the kinetic mechanism, having in some cases been complemented by Boyd's results, especially for the initial times.
With the advance of industrial, technological, agricultural and urbanization processes, the disposal of metals in soil and water resources has proved to be a problem due to the physiological consequences to living beings, which can lead to death depending on the type of metal and its properties. With the growth of this, the development of techniques and models of environmental monitoring have gained prominence, especially those that use low cost and easy to access materials. Cellulose and its by-products have proven to be a good option to be applied in environmental monitoring, because their hydroxyls allow the adsorption of metals and, if necessary, the modification of their bonds from other binders. It is the most abundant natural biopolymer in the world and can be obtained directly from plants or residues such as sugarcane bagasse and wood debris. Therefore, this study aims to evaluate the efficiency of nanocellulose for the adsorption of metal ions present in aqueous solutions. The production of cellulose in nano scale occurred from the use of the SuperMassColloider mill, which uses grinding process to decrease the diameter of its fibers, and the preparation of films of this material, from the technique of drying in the oven. Its characterization by XRD, FTIR, SEM, EDS and AFM showed the manufacture of a nano scale cellulose with parameters within the expected and comparable with literature values. The analytical tests involved the study of chemical balance, evaluating the contact time until the balance is established. Considering the percentage of removal of metal ions of multielemental solution (zinc, copper, cadmium, lead, manganese, and nickel) with pH 6, ionic strength 0.01M and constant temperature of 25°C. Kinetic adsorption models of pseudofirst order, pseudosecond order, Weber and Morris, Elovich and Boyd were applied in order to analyze the best model that applies to the system under analysis and the adsorption mechanism that occurs in the adsorbent. The study in question obtained a favorable result for adsorption of the selected metal ions, with a percentage of removal in balance varying according to metal, zinc (87%), lead (95.6%), nickel (90.7%), manganese (95.5%), copper (98.4%), cadmium (87.7%). The kinetic model that best fit the results obtained was pseudosecond order, while the Weber and Morris mechanism was adapted to the kinetic mechanism, having in some cases been complemented by Boyd's results, especially for the initial times.
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Monitoramento ambiental, Nanotecnologia