Materiais à base de carvão ativado proveniente de resíduos lignocelulósicos para suporte de fotocatalisadores com aplicação em remediação ambiental
Data
2024-02-06
Autores
Meirelles, Mariana Rodrigues 
Orientadores
Gonçalves, Maraísa
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Este trabalho propôs o aproveitamento de resíduos lignocelulósicos para preparação de carvão ativado (CA) e posterior impregnação com TiO2 para avaliação na degradação do paracetamol. O CA foi preparado a partir de resíduos de casca de café (CACC), borra de café (CABCF) e bagaço de cana de açúcar (CABC). A caracterização por adsorção/dessorção de nitrogênio mostrou que o CA preparado com bagaço de cana apresentou a maior área superficial,1596 m2.g-1, seguido do CA de borra de café com área superficial de 1465 m2.g-1, e o CA preparado com casca de café apresentou área superficial de 990 m2.g-1. A preparação dos fotocatalisadores de TiO2 foi dividida em duas etapas: 1) via sol-gel sem a presença de peróxido de hidrogênio (H2O2) e 2) via sol gel com H2O2 (gel de peróxido). Na primeira etapa, os materiais obtidos via sol gel foram calcinados por 2 h em diferentes temperaturas. Os resultados evidenciaram a mudança de fase anatase para rutilo em temperaturas elevadas (a partir de 650 ºC). Verificou-se que há correlação entre temperatura de calcinação, área superficial e tamanho de cristalito. Os materiais calcinados a 350, 400 e 450 ºC apresentaram maior fotoatividade, apresentando constante de velocidade de 0,0084, 0,0071 e 0,0063 min-1, respectivamente. Na segunda etapa, foi acrescentado H2O2 na preparação, estes materiais foram calcinados em 350 e 450 ºC. Para a temperatura de 350 ºC, variou-se o tempo de calcinação em 2, 4 e 6 h. Todos os TiO2-H2O2 preparados apresentaram eficiência fotocatalítica na degradação do paracetamol com remoção de 92 a 98%. O TiO2 calcinado a 350 ºC durante 4 h (TiO2-H2O2-350_4) demonstrou a maior eficiência fotocatalítica, com 98% de degradação do PCT e constante de velocidade igual a 0,0109 min-1. As caracterizações evidenciaram mudanças estruturais e morfológicas ao comparar a preparação com e sem a presença de H2O2. As heteroestrutras de Nb2O5-TiO2 foram preparadas com Nb2O5 comercial. O TiO2 foi sintetizado na superfície do Nb2O5 pelo método de gel de peróxido. Os materiais de Nb2O5-TiO2 não apresentaram bons resultados quando comparadas com o TiO2 preparado pelo método de gel de peróxido. Já as heteroestruturas preparas de CAs-TiO2 demonstraram melhores resultados quando comparadas com o fotocatalisador puro (TiO2-H2O2). Os materiais CABC-85TiO2, CABCF-85TiO2, CACC-85TiO2 apresentaram valores de constante de velocidade de 0,0045, 0,0053 e 0,0052 min-1, representando acréscimo na taxa de degradação do paracetamol de 7, 26 e 26%, respectivamente, quando comparadas ao TiO2. Todas as heteroestruturas de CAs-TiO2 evidenciaram capacidade de reaproveitamento até o sexto ciclo fotocatalítico. Sendo assim, as heteroestruturas de CAs-TiO2 apresentaram eficiência na degradação do paracetamol e foram preparados por meio de rota econômica e sustentável. O trabalho mostrou a viabilidade de produção de CAs proveniente de diferentes resíduos para utilização de suporte de fotocatalisadores.
This work proposed the utilization of lignocellulosic waste for the preparation of activated carbon (AC) and subsequent impregnation with TiO2 for the evaluation of paracetamol degradation. AC was prepared using residues from coffee husk (ACCH), coffee grounds (ACCG), and sugarcane bagasse (ACSG). Nitrogen adsorption/desorption characterization revealed that AC prepared with sugarcane bagasse exhibited the highest surface area, equivalent to 1596 m².g⁻¹, followed by AC prepared with coffee grounds with a surface area of 1465 m².g⁻¹, and AC prepared with coffee husk with a surface area of 990 m².g⁻¹. TiO2 photocatalysts were prepared via the sol-gel method. The evaluation of the photocatalysts was divided into two stages: 1) without the presence of hydrogen peroxide (H2O2) and 2) with the presence of H₂O₂ during synthesis. In the first stage, sol-gel-derived materials were calcined for 2 hours at different temperatures. Results revealed a phase transition from anatase to rutile at elevated temperatures (starting from 650 ºC). The correlation between calcination temperature, surface area, and crystallite size was observed. Materials calcined at 350, 400, and 450 ºC exhibited higher photocatalytic efficiency, with degradation rates of 0.0084, 0.0071, and 0.0063 min⁻¹, respectively. In the second stage, H2O2 was added during synthesis, and these materials were calcined at 350 and 450 ºC. For the 350 ºC temperature, the thermal treatment time varied from 2, 4, and 6 hours. All TiO2-H2O2 samples demonstrated photocatalytic efficiency in paracetamol degradation, with removal ranging from 92 to 98%. The TiO2 calcined at 350 °C for 4 h (TiO2-H2O2-350_4) exhibited the highest photocatalytic efficiency with 98% degradation of PCT and a degradation rate constant of 0.0109 min⁻¹. Structural and morphological changes were evident when comparing the synthesis with and without H2O2. Nb2O5-TiO2 heterostructures were prepared using commercial Nb2O5. TiO2 was synthesized on its surface via the peroxide gel method. The Nb2O5-TiO2 samples did not perform well compared to TiO2 prepared by the peroxide gel method. Conversely, heterostructures designed with AC-TiO2 showed superior results to the pure photocatalyst. The ACSB-85TiO2, ACCG-85TiO2, and ACCH-85TiO2 samples exhibited rate constants of 0.0045, 0.0053, and 0.0052 min⁻¹, representing an increase in the PCT degradation rate of 7, 26, and 26%, respectively, compared to the TiO2 sample. All AC-TiO2 heterostructures demonstrated recyclability. Therefore, AC-TiO2 materials showed efficiency in PCT degradation and were prepared economically and environmentally sustainable. The study demonstrated the feasibility of producing ACs from different waste sources to support photocatalysts.
This work proposed the utilization of lignocellulosic waste for the preparation of activated carbon (AC) and subsequent impregnation with TiO2 for the evaluation of paracetamol degradation. AC was prepared using residues from coffee husk (ACCH), coffee grounds (ACCG), and sugarcane bagasse (ACSG). Nitrogen adsorption/desorption characterization revealed that AC prepared with sugarcane bagasse exhibited the highest surface area, equivalent to 1596 m².g⁻¹, followed by AC prepared with coffee grounds with a surface area of 1465 m².g⁻¹, and AC prepared with coffee husk with a surface area of 990 m².g⁻¹. TiO2 photocatalysts were prepared via the sol-gel method. The evaluation of the photocatalysts was divided into two stages: 1) without the presence of hydrogen peroxide (H2O2) and 2) with the presence of H₂O₂ during synthesis. In the first stage, sol-gel-derived materials were calcined for 2 hours at different temperatures. Results revealed a phase transition from anatase to rutile at elevated temperatures (starting from 650 ºC). The correlation between calcination temperature, surface area, and crystallite size was observed. Materials calcined at 350, 400, and 450 ºC exhibited higher photocatalytic efficiency, with degradation rates of 0.0084, 0.0071, and 0.0063 min⁻¹, respectively. In the second stage, H2O2 was added during synthesis, and these materials were calcined at 350 and 450 ºC. For the 350 ºC temperature, the thermal treatment time varied from 2, 4, and 6 hours. All TiO2-H2O2 samples demonstrated photocatalytic efficiency in paracetamol degradation, with removal ranging from 92 to 98%. The TiO2 calcined at 350 °C for 4 h (TiO2-H2O2-350_4) exhibited the highest photocatalytic efficiency with 98% degradation of PCT and a degradation rate constant of 0.0109 min⁻¹. Structural and morphological changes were evident when comparing the synthesis with and without H2O2. Nb2O5-TiO2 heterostructures were prepared using commercial Nb2O5. TiO2 was synthesized on its surface via the peroxide gel method. The Nb2O5-TiO2 samples did not perform well compared to TiO2 prepared by the peroxide gel method. Conversely, heterostructures designed with AC-TiO2 showed superior results to the pure photocatalyst. The ACSB-85TiO2, ACCG-85TiO2, and ACCH-85TiO2 samples exhibited rate constants of 0.0045, 0.0053, and 0.0052 min⁻¹, representing an increase in the PCT degradation rate of 7, 26, and 26%, respectively, compared to the TiO2 sample. All AC-TiO2 heterostructures demonstrated recyclability. Therefore, AC-TiO2 materials showed efficiency in PCT degradation and were prepared economically and environmentally sustainable. The study demonstrated the feasibility of producing ACs from different waste sources to support photocatalysts.