Síntese e avaliação de heteroestruturas de Fe2O3/CeO2 e Fe2O3/V2O5 como catalisadores no processo foto-Fenton heterogêneo para a degradação de venlafaxina
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Data
2022-04-29
Autores
Ayala Durán, Saidy Cristina [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Neste trabalho foram estudados materiais heteroestruturados compostos de hematita (Fe2O3) modificada com óxido de cério (CeO2) e com óxido de vanádio (V2O5, sintetizados pelo método de co-precipitação a partir da síntese das ferrihidritas em porcentagens atômicas de ferro de 70%, 50% e 30%, sendo definido por Fe(%at)Ce(Ttratamento) como por exemplo Fe70Ce600. Foi avaliada a atividade catalitica com a degradação do antidepressivo venlafaxina (VEN) pelo processo Fenton e foto-Fenton usando lampadas LED UV e Vis. Os catalisadores obtidos foram caracterizados pelas técnicas: Difração de Raios- X (DRX), Espectroscopia de Reflectância Difusa (ERD), área específica (BET), Microscopia Eletrônica de Varredura (MEV), Microscopia Eletrônica de Trasmissão (TEM), Fotoluminescência (FL) e Potencial Zeta (Pζ). O estudo está dividido em duas partes: a primeira contempla as Fe2O3/CeO2 num estudo comparatativo de duas temperaturas (600 e 800 °C). Os resultados mostraram a formação do material heteroestruturado a partir das interações na interface pela presença dos picos de reflexão característicos dos óxidos puros, assim como, o entrecruzamento de planos cristalinos e a as distâncias interplanares. A 800 °C promoveu maior cristalinidade, aumento de tamanho de cristalito, melhor definição de morfologia, diminuição da área especifica, aumento da área e volume do microporo, alta absorção da radiação entre 200 – 600 nm mostrando energia de banda proibida (Eg) entre 1,7 e 3,0 eV. Foi observado aumento de defeitos de superficie, com perfis de emissão em comprimentos de onda diferentes associados com as mudanças de mecanismo para as heteroestruturas classificadas como tipo I e Z direto. A atividade catalítica dos materiais frente à degradação da VEN foi avalida nos valores de pH 3,0 e 5,6 (pH natural), com concentração de H2O2 1,0 mmol L-1, 0,5 g L-1 de catalisador. Foi observado que no processo foto-Fenton (UV) o Fe70Ce800 e Fe50Ce800 apresentaram melhor eficiência com total degradação de VEN em 90 e 120 min, respectivamente. Em pH 5,6, a atividade catalítica foi fortemente comprometida, porém resultou em até 50% de degradação da VEN sob radiação UV, com baixo consumo de H2O2 e baixa lixiviação de ferro. O reuso de Fe70Ce800 mostrou perda consecutiva após segundo uso. Quanto aos materiais Fe2O3/V2O5 tratados a 600 °C, estes foram caracterizados usando as mesmas técnicas e avaliados nos mesmos processos e condições de experimento. Foram observados os picos de reflexão, intensidades que variam de acordo com a % molar de vanádio na sua composição, entrecruzamento de planos cristalinos, porém com mais dificultade devido à formação de particulas de maior tamanho, com uma menor área específica. Estes materiais mostraram uma maior faixa de absorção da radiação (200 – 800 nm) com Eg 1,4 a 2,1 eV. A FL mostrou geração de defeitos de superficie, sendo proposto um mecanismo de hetereoestrutura tipo p-n. Estes catalisadores mostraram alta degradação no processo Fenton e foto-Fenton em pH 3,0 e a maior geração de HO• com Fe30V600 e Fe50V600. No entanto, apresentaram baixa estabilidade com lixiviação de V em solução. Em pH 5,6 80% de degradação de VEN após 120 min sob irradiação UV (Fe50V600) foi atingida com maior estabilidade do que em pH 3,0. Com Fe30V600 sob irradiação Vis, o processo foi altamente favorecido atingindo total degradação de VEM em 60 min. Foi observado que as heteroestruturas no processo foto-Fenton (UV-Vis) permitem uma rápida transferência de cargas, maior participação dos pares e-/h+ favorecidos pela irradiação LED, possibilidade de uso em ampla faixa de pH e alta geração de radicais hidroxila. A informação obtida das caracterizações e o processo demonstraram ser materiais promissores e versáteis para serem aplicados em processos Fenton heterogêneo na degradação de micropoluentes emergentes.
In this work, heterostructured materials composed of hematite (Fe2O3) modified with cerium oxide (CeO2) and vanadium oxide (V2O5) were studied, synthesized using the co-precipitation method from the synthesis of ferrihydrite in atomic percentages of iron of 70%, 50%, and 30%, being defined by Fe(%at)Ce(Ttreatment) such as Fe70Ce600. The catalytic activity was evaluated with the degradation of the antidepressant venlafaxine (VEN) by the Fenton process and photo-Fenton using UV and Vis LED lamps. The catalysts obtained were characterized by the following techniques: X-Ray diffraction (XRD), Diffuse Reflectance Spectroscopy (ERD), specific area (BET), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Photoluminescence (FL) and Zeta Potential (Pζ). The study is divided into two parts: the first includes Fe2O3/CeO2 in a comparative study of two temperatures (600 and 800 °C). The results showed the formation of the heterostructure material from the interactions at the interface by the presence of reflection peaks characteristic of pure oxides, as well as interplanar spacing and the determination of lattice fringes. At 800 °C promoted greater crystallinity, crystallite size increase, better morphology definition, a specific area decrease, micropore volume and area increase, high radiation absorption between 200 - 600 nm showing bandgap energy (Eg) between 1.7 and 3.0 eV. An increase in surface defects was observed, with emission profiles at different wavelengths associated with changes in mechanism for heterostructures classified as type I and direct Z. The catalytic activity of the materials against VEN degradation was evaluated at pH 3.0 and 5.6 (natural pH), with an H2O2 concentration of 1.0 mmol L-1, 0.5 g L-1 of catalyst. It was observed that in the photo-Fenton (UV) process, Fe70Ce800 and Fe50Ce800 showed better efficiency with total VEN degradation in 90 and 120 min, respectively. At pH 5.6, the catalytic activity was strongly compromised, but resulted in up to 50% degradation of VEN under UV radiation, with low H2O2 consumption and low iron leaching. The reuse of Fe70Ce800 showed consecutive losses after the second use. As for the Fe2O3/V2O5 materials treated at 600 °C, they were characterized using the same techniques and evaluated in the same processes and experimental conditions. Reflection peaks were observed, intensities that vary according to the %at of vanadium in its composition, determined interplanar spacing but with more difficulty due to the formation of larger particles, with a smaller specific area. These materials showed a greater radiation absorption range (200 – 800 nm) with Eg 1.4 to 2.1 eV. The FL showed surface defect generation, proposing a p-n heterostructure mechanism. These catalysts showed high degradation in the Fenton and photo-Fenton processes at pH 3.0. However, they showed low stability with leaching of V in solution. At pH 5.6 80% degradation of VEN after 120 min under UV irradiation (Fe50V600) was achieved with greater stability than that at pH 3.0. With Fe30V600 under Vis irradiation, the process was highly favored reaching full VEN degradation in 60 min. We observed that the heterostructures in the photo-Fenton process (UV-Vis) allow rapid charge transfer, greater participation of e-/h+ pairs favored by LED irradiation, the possibility of use in a wide pH range and high generation of hydroxyl radicals. The information obtained from the characterizations and the process proved to be promising and versatile materials to be applied in heterogeneous Fenton processes in the degradation of emerging micropollutants.
In this work, heterostructured materials composed of hematite (Fe2O3) modified with cerium oxide (CeO2) and vanadium oxide (V2O5) were studied, synthesized using the co-precipitation method from the synthesis of ferrihydrite in atomic percentages of iron of 70%, 50%, and 30%, being defined by Fe(%at)Ce(Ttreatment) such as Fe70Ce600. The catalytic activity was evaluated with the degradation of the antidepressant venlafaxine (VEN) by the Fenton process and photo-Fenton using UV and Vis LED lamps. The catalysts obtained were characterized by the following techniques: X-Ray diffraction (XRD), Diffuse Reflectance Spectroscopy (ERD), specific area (BET), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Photoluminescence (FL) and Zeta Potential (Pζ). The study is divided into two parts: the first includes Fe2O3/CeO2 in a comparative study of two temperatures (600 and 800 °C). The results showed the formation of the heterostructure material from the interactions at the interface by the presence of reflection peaks characteristic of pure oxides, as well as interplanar spacing and the determination of lattice fringes. At 800 °C promoted greater crystallinity, crystallite size increase, better morphology definition, a specific area decrease, micropore volume and area increase, high radiation absorption between 200 - 600 nm showing bandgap energy (Eg) between 1.7 and 3.0 eV. An increase in surface defects was observed, with emission profiles at different wavelengths associated with changes in mechanism for heterostructures classified as type I and direct Z. The catalytic activity of the materials against VEN degradation was evaluated at pH 3.0 and 5.6 (natural pH), with an H2O2 concentration of 1.0 mmol L-1, 0.5 g L-1 of catalyst. It was observed that in the photo-Fenton (UV) process, Fe70Ce800 and Fe50Ce800 showed better efficiency with total VEN degradation in 90 and 120 min, respectively. At pH 5.6, the catalytic activity was strongly compromised, but resulted in up to 50% degradation of VEN under UV radiation, with low H2O2 consumption and low iron leaching. The reuse of Fe70Ce800 showed consecutive losses after the second use. As for the Fe2O3/V2O5 materials treated at 600 °C, they were characterized using the same techniques and evaluated in the same processes and experimental conditions. Reflection peaks were observed, intensities that vary according to the %at of vanadium in its composition, determined interplanar spacing but with more difficulty due to the formation of larger particles, with a smaller specific area. These materials showed a greater radiation absorption range (200 – 800 nm) with Eg 1.4 to 2.1 eV. The FL showed surface defect generation, proposing a p-n heterostructure mechanism. These catalysts showed high degradation in the Fenton and photo-Fenton processes at pH 3.0. However, they showed low stability with leaching of V in solution. At pH 5.6 80% degradation of VEN after 120 min under UV irradiation (Fe50V600) was achieved with greater stability than that at pH 3.0. With Fe30V600 under Vis irradiation, the process was highly favored reaching full VEN degradation in 60 min. We observed that the heterostructures in the photo-Fenton process (UV-Vis) allow rapid charge transfer, greater participation of e-/h+ pairs favored by LED irradiation, the possibility of use in a wide pH range and high generation of hydroxyl radicals. The information obtained from the characterizations and the process proved to be promising and versatile materials to be applied in heterogeneous Fenton processes in the degradation of emerging micropollutants.
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Palavras-chave
Heterojunção, POA, Fotocatalisadores, Mecanismo, Micropoluente