Síntese, caracterização e avaliação das propriedades fotocatalíticas de nanocompósitos de Fe2O3-SnO2 sintetizados pelo método poliol
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Data
2021-10-27
Autores
Lima, Vinícius Bertuzzo
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Universidade Estadual Paulista (Unesp)
Resumo
A fotocatálise baseada em materiais semicondutores vem sendo bastante estudada com vistas a aplicação em dispositivos que promovem a restauração de aquíferos por meio da degradação dos resíduos industriais despejados, tais como corantes orgânicos. Para o presente estudo foram selecionados dois destes materiais multifuncionais: Fe2O3, SnO2, com o objetivo de serem avaliados como agentes descorantes da Rodamina-B. Além da preparação pelo método Poliol de partículas do Fe2O3 e do SnO2, produziu-se também o compósito Fe2O3-SnO2, cujo desempenho descorante foi analisado comparativamente aos seus componentes na atuação individual. Após uma primeira síntese dos materiais, novos parâmetros foram testados chegando a menores tempos de refluxo para a síntese de partículas de Fe2O3 e mais baixas temperaturas para a obtenção do nanocompósito desejado. Para avaliação da decomposição térmica dos materiais diretamente sintetizados, foram feitas as análises térmicas simultâneas TGA/DTA até 1000°C, nas quais se constatou a conversão em α-Fe2O3 em temperatura próxima de 400°C e a conversão em SnO2 em torno de 650°C, para os casos de síntese dos óxidos isolados. No caso do compósito obtido pela síntese conjunta observou-se a necessidade de aplicação de tratamento em temperatura mínima de 700°C. A análise por difração de raios X e microscopia eletrônica de varredura dos materiais sintetizados e tratados termicamente revelou tratar-se de partículas nanoestruturadas dos respectivos óxidos. Análises por adsorção de nitrogênio gasoso (BET) mostraram curvas de histerese com características de material não poroso. Os cálculos indicaram área superficial específica de 18, 45 e 20 m²/g para as amostras preparadas de Fe2O3, SnO2 e o compósito, respectivamente. Por meio de dados de refletância difusa estimou-se os band gaps de 1,9 eV, 3,5 eV e 1,8 eV para Fe2O3, SnO2 e para o Fe2O3-SnO2, respectivamente. Os ensaios de descoramento de Rodamina-B feitos em pH 5,5 e sob irradiação de luz visível e ultravioleta mostraram o desempenho de cada um dos materiais preparados. As partículas de Fe2O3 apresentaram uma capacidade grande de adsorção física do corante testado, reduzindo a absorção de luz em 75% nos primeiros 15 minutos de exposição. Porém, sua capacidade de descoramento se manteve estável ao longo dos 75 minutos seguintes. Os ensaios realizados na presença do SnO2 mostraram descoramento máximo de 45%. Após 120 minutos de exposição. O descoramento obtido para o nanocompósito ao fim de 180 minutos foi de 20%. Este comportamento foi atribuído ao total revestimento da superfície das partículas do óxido de ferro com as nanopartículas de SnO2.
Photocatalysis based on semiconductor materials has been extensively studied with a view to its application in devices that promote the restoration of aquifers through the degradation of industrial waste discharged, such as organic dyes. For the present study, two of these multifunctional materials were selected: Fe2O3, SnO2, with the objective of being evaluated as bleaching agents for Rhodamine-B. In addition to the preparation by the Polyol method of Fe2O3 and SnO2 particles, the Fe2O3-SnO2 composite was also produced, whose bleaching performance was analyzed compared to its components in individual performance. After a first synthesis of materials, new parameters were tested, reaching shorter reflux times for the synthesis of Fe2O3 particles and lower temperatures to obtain the desired nanocomposite. To evaluate the thermal decomposition of directly synthesized materials, simultaneous TGA/DTA thermal analyzes were carried out up to 1000°C, in which the conversion to α-Fe2O3 was found at a temperature close to 400°C and the conversion to SnO2 around 650°C, for the cases of synthesis of isolated oxides. In the case of the composite obtained by the joint synthesis, the need to apply treatment at a minimum temperature of 700°C was observed. The X-ray diffraction and scanning electron microscopy analysis of the synthesized and heat-treated materials revealed that they were nanostructured particles of the respective oxides. Analyzes by adsorption of nitrogen gas (BET) showed hysteresis curves with characteristics of non-porous material and calculations indicated specific surface area of 18, 45 and 20 m²/g for the samples prepared with Fe2O3, SnO2 and the composite, respectively. Using diffuse reflectance data, band gaps of 1.9 eV, 3.5 eV and 1.8 eV were estimated for Fe2O3, SnO2 and for Fe2O3- SnO2, respectively. Rhodamine-B bleaching tests carried out at pH 5.5 and under visible and ultraviolet light irradiation showed the performance of each of the prepared materials. The Fe2O3 particles showed a large physical adsorption capacity of the dye tested, reducing light absorption by 75% in the first 15 minutes of exposure. However, its bleaching capacity remained stable over the next 75 minutes. The tests carried out in the presence of SnO2 showed a maximum bleaching of 45% after 120 minutes of exposure. The bleaching obtained for the nanocomposite after 180 minutes was 20%. This behavior was attributed to the total surface coating of the iron oxide particles with SnO2 nanoparticles
Photocatalysis based on semiconductor materials has been extensively studied with a view to its application in devices that promote the restoration of aquifers through the degradation of industrial waste discharged, such as organic dyes. For the present study, two of these multifunctional materials were selected: Fe2O3, SnO2, with the objective of being evaluated as bleaching agents for Rhodamine-B. In addition to the preparation by the Polyol method of Fe2O3 and SnO2 particles, the Fe2O3-SnO2 composite was also produced, whose bleaching performance was analyzed compared to its components in individual performance. After a first synthesis of materials, new parameters were tested, reaching shorter reflux times for the synthesis of Fe2O3 particles and lower temperatures to obtain the desired nanocomposite. To evaluate the thermal decomposition of directly synthesized materials, simultaneous TGA/DTA thermal analyzes were carried out up to 1000°C, in which the conversion to α-Fe2O3 was found at a temperature close to 400°C and the conversion to SnO2 around 650°C, for the cases of synthesis of isolated oxides. In the case of the composite obtained by the joint synthesis, the need to apply treatment at a minimum temperature of 700°C was observed. The X-ray diffraction and scanning electron microscopy analysis of the synthesized and heat-treated materials revealed that they were nanostructured particles of the respective oxides. Analyzes by adsorption of nitrogen gas (BET) showed hysteresis curves with characteristics of non-porous material and calculations indicated specific surface area of 18, 45 and 20 m²/g for the samples prepared with Fe2O3, SnO2 and the composite, respectively. Using diffuse reflectance data, band gaps of 1.9 eV, 3.5 eV and 1.8 eV were estimated for Fe2O3, SnO2 and for Fe2O3- SnO2, respectively. Rhodamine-B bleaching tests carried out at pH 5.5 and under visible and ultraviolet light irradiation showed the performance of each of the prepared materials. The Fe2O3 particles showed a large physical adsorption capacity of the dye tested, reducing light absorption by 75% in the first 15 minutes of exposure. However, its bleaching capacity remained stable over the next 75 minutes. The tests carried out in the presence of SnO2 showed a maximum bleaching of 45% after 120 minutes of exposure. The bleaching obtained for the nanocomposite after 180 minutes was 20%. This behavior was attributed to the total surface coating of the iron oxide particles with SnO2 nanoparticles
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Palavras-chave
Síntese de material nanoestruturado, Nanocompósitos, Fotocatálise, Descoramento da Rodamina-B, Método Poliol, Óxido de ferro III, Dióxido de estanho, Synthesis of nanostructured material, Nanocomposites, Photocatalysis, Bleaching performance of Rhodamine-B