Nanopartículas de dióxido de titânio e prata imobilizadas em filmes de celulose não modificada: preparação, caracterização e aplicação na degradação de poluentes
Data
2022-08-05
Autores
Garcia, Arthur Matsudo 
Orientadores
Camilo, Fernanda Ferraz
Tipo
Tese de doutorado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Visando o emprego desses nanomateriais como nanocatalisadores heterogêneos em processos que envolvam a degradação de poluentes em meios aquosos, a imobilização dessas nanopartículas em filmes de celulose, o biopolímero mais abundante na natureza, é uma vantagem, pois evita a agregação dessas partículas durante o uso, facilita o processo de remoção do meio reacional e o reuso.
Nesse contexto, na primeira parte desta tese foi desenvolvido um novo método de preparação de filmes de celulose contendo nanopartículas de prata (AgNP) (CAPÍTULO 1) que foram utilizados como catalisadores heterogêneos frente a redução química do poluente 4-nitrofenol (4-NF). O filme resultou na conversão total do 4-NF em 4 -AF, o filme pode ser utilizado por 5 ciclos sem perda da atividade catalítica. O valor da frequência de turnover (turnover frequency - TOF) para o primeiro ciclo foi de cerca de 290 h-1, que é comparável ou mesmo superior a valores reportados na literatura.
Na segunda frente de estudo, filmes de celulose contendo nanopartículas de dióxido de titânio puras (Cel_TiO2NP) sintetizada e comercial (Cel_P25) (CAPÍTULO 2) foram preparados. No teste fotocatalítico de descoloração do Índigo de Carmin (IC), o filme Cel_TiO2NP apresentou efeito duas vezes mais rápido do que o filme cel_P25 sob a luz ultravioleta, ambos os filmes podem ser usados por pelo menos 3 ciclos sem perder a atividade.
Por fim, nanocompósitos de dióxido de titânio e prata (TiO2NP/AgNP) contendo a razão molar 0,15, 0,5 e 1,0% (mol/mol) Ag/Ti foram preparadas por um procedimento inédito (CAPÍTULO 3). A adição de AgNP diminuiu o bandgap do TiO2, o que possibilitou o seu efeito fotocatalítico na luz visível. No teste fotocatalítico da descoloração do IC em região do visível, a amostra contendo 0,15% de Ag foi a mais eficiente apresentando um tempo de na descoloração da solução de IC de apenas 30 minutos. Quando o TiO2NP/AgNP foi imobilizado em um filme de celulose, a atividade catalítica foi reduzida, descolorindo totalmente em 150 min. Esse filme pode ser utilizado por pelo menos 3 vezes sem perda significativa do efeito fotocatalítico na região do visível. Comparando os filmes contendo apenas TiO2NP, os nanocompósitos de TiO2NP/AgNP apresentaram efeito fotocatalítico na região do visível.
Aiming at the use of these nanomaterials as heterogeneous nanocatalysts in reactions that involve the degradation of pollutants in aqueous media, the immobilization of these nanoparticles in cellulose films, the most abundant biopolymer in nature, is an advantage, as it prevents the aggregation of these particles during use and facilitates the removing from reaction medium and reuse. In this context, in the first part of this thesis, a new method was developed for the preparation of cellulose films containing silver nanoparticles (AgNP) (CHAPTER 1) that were used as heterogeneous catalysts in the chemical reduction of 4-nitrophenol (4-NF). The film resulted in the complete conversion of 4-NF and it could be used for 5 cycles without losing activity. The turnover frequency (TOF) value for the first cycle was around 290 h-1, which is comparable to or even higher than values reported in the literature. In the second study front, cellulose films containing pure titanium dioxide nanoparticles (Cel_TiO2NP) synthesized and commercial (Cel_P25) (CHAPTER 2) were prepared. In the Carmine Indigo (IC) decolorization photocatalytic test, the Cel_TiO2NP film showed effect twice as fast as the cel_P25 film under ultraviolet light, both films can be used for at least 3 cycles without losing activity. Finally, titanium dioxide and silver nanocomposites (TiO2NP/AgNP) containing the molar ratio of 0.15, 0.5 and 1.0% (mol/mol) Ag/Ti were prepared by an unprecedented procedure (CHAPTER 3). The addition of AgNP decreased the bandgap of TiO2, which enabled its photocatalytic effect in visible light. In the photocatalytic test of IC decolorization in the visible region, the sample containing 0.15% of Ag was the most efficient, presenting a decolorization time of the IC solution of only 30 minutes. When TiO2NP/AgNP was immobilized on a cellulose film, the catalytic activity was reduced, completely decolorizing in 150 min. This film can be used for at least 3 times without significant loss of photocatalytic effect in the visible region. Comparing the films containing only TiO2NP, the TiO2NP/AgNP nanocomposites showed a photocatalytic effect in the visible region. All films presented were applied as heterogeneous catalysts in the degradation of aqueous pollutants, avoiding the process of filtration, centrifugation to separate the catalyst from the medium.
Aiming at the use of these nanomaterials as heterogeneous nanocatalysts in reactions that involve the degradation of pollutants in aqueous media, the immobilization of these nanoparticles in cellulose films, the most abundant biopolymer in nature, is an advantage, as it prevents the aggregation of these particles during use and facilitates the removing from reaction medium and reuse. In this context, in the first part of this thesis, a new method was developed for the preparation of cellulose films containing silver nanoparticles (AgNP) (CHAPTER 1) that were used as heterogeneous catalysts in the chemical reduction of 4-nitrophenol (4-NF). The film resulted in the complete conversion of 4-NF and it could be used for 5 cycles without losing activity. The turnover frequency (TOF) value for the first cycle was around 290 h-1, which is comparable to or even higher than values reported in the literature. In the second study front, cellulose films containing pure titanium dioxide nanoparticles (Cel_TiO2NP) synthesized and commercial (Cel_P25) (CHAPTER 2) were prepared. In the Carmine Indigo (IC) decolorization photocatalytic test, the Cel_TiO2NP film showed effect twice as fast as the cel_P25 film under ultraviolet light, both films can be used for at least 3 cycles without losing activity. Finally, titanium dioxide and silver nanocomposites (TiO2NP/AgNP) containing the molar ratio of 0.15, 0.5 and 1.0% (mol/mol) Ag/Ti were prepared by an unprecedented procedure (CHAPTER 3). The addition of AgNP decreased the bandgap of TiO2, which enabled its photocatalytic effect in visible light. In the photocatalytic test of IC decolorization in the visible region, the sample containing 0.15% of Ag was the most efficient, presenting a decolorization time of the IC solution of only 30 minutes. When TiO2NP/AgNP was immobilized on a cellulose film, the catalytic activity was reduced, completely decolorizing in 150 min. This film can be used for at least 3 times without significant loss of photocatalytic effect in the visible region. Comparing the films containing only TiO2NP, the TiO2NP/AgNP nanocomposites showed a photocatalytic effect in the visible region. All films presented were applied as heterogeneous catalysts in the degradation of aqueous pollutants, avoiding the process of filtration, centrifugation to separate the catalyst from the medium.