Publicação
Hybrid cobalt ferrite/carbon catalysts: synthesis, characterization and applications in water treatment
| Resumo: | This work deals with the development of carbon-coated magnetic cobalt ferrite nanoparticles as catalysts for the treatment of water containing Contaminants of Emerging Concern (CEC) by Catalytic Wet Peroxide Oxidation (CWPO), using paracetamol (PCM) as model pollutant. For this purpose, a magnetic core (CoFe2O4) is developed by the sol-gel method, the core is subsequently coated with a resin prepared from formaldehyde, resorcinol and tetraethyl orthosilicate (TEOS), and later carbonized by pyrolysis at 600 °C under a N2 atmosphere. Afterwards, the silica generated from TEOS is removed by etching with NaOH to create a void inside the particle, creating a yolk-shell shape denoted as CoFe2O4@void@C. XRD, TEM and FTIR analysis revealed that the uncoated core is composed by a CoFe2O4 cubic spinel structure with space group Fd-3m and a crystallite size of 53 nm, calculated using the W-H method, that matches very well with the average size observed by TEM equals to 53.51 4.2 nm. The average size of the nanoparticles for the hybrid coated ferrite increases to 58.7 8.1 nm. After the preparation of the catalysts, reaction runs were performed to assess its suitability for the degradation of PCM by CWPO. The concentration of paracetamol, hydrogen peroxide and Total Organic Carbon (TOC) were recorded against the reaction time. The performance of the CoFe2O4@void@C catalyst was compared to that of the uncoated ferrite, the CoFe2O4 and CoFe2O4@void@C materials allowing TOC values of 46 and 58% respectively at 24h. The hybrid coated ferrite succeeds in avoid iron leaching and to be a stable catalyst. The amount of leached iron at the end of the treatment was equal to 1.59 mg·L-1, which is within the limit concentration of 2 mg·L-1 of iron allowed in waters, as established EU regulations. A kinetic model was proposed describing the decomposition of hydrogen peroxide and the removals of the pollutant PCM and TOC with the CoFe2O4@void@C as catalyst, applying an empirical kinetic model composed of a second-order and an autocatalytic expression to describe the decomposition of H2O2 and PCM, respectively. The kinetic model for TOC can be well-described as a sum of the initial pollutant plus the oxidation intermediates from the PCM and the organic components that are refractory to the process. |
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| Autores principais: | Guari, Nathalia Maria Costa |
| Assunto: | Magnetic nanoparticles CWPO Paracetamol Yolk-shell |
| Ano: | 2020 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Instituto Politécnico de Bragança |
| Idioma: | inglês |
| Origem: | Biblioteca Digital do IPB |
| Resumo: | This work deals with the development of carbon-coated magnetic cobalt ferrite nanoparticles as catalysts for the treatment of water containing Contaminants of Emerging Concern (CEC) by Catalytic Wet Peroxide Oxidation (CWPO), using paracetamol (PCM) as model pollutant. For this purpose, a magnetic core (CoFe2O4) is developed by the sol-gel method, the core is subsequently coated with a resin prepared from formaldehyde, resorcinol and tetraethyl orthosilicate (TEOS), and later carbonized by pyrolysis at 600 °C under a N2 atmosphere. Afterwards, the silica generated from TEOS is removed by etching with NaOH to create a void inside the particle, creating a yolk-shell shape denoted as CoFe2O4@void@C. XRD, TEM and FTIR analysis revealed that the uncoated core is composed by a CoFe2O4 cubic spinel structure with space group Fd-3m and a crystallite size of 53 nm, calculated using the W-H method, that matches very well with the average size observed by TEM equals to 53.51 4.2 nm. The average size of the nanoparticles for the hybrid coated ferrite increases to 58.7 8.1 nm. After the preparation of the catalysts, reaction runs were performed to assess its suitability for the degradation of PCM by CWPO. The concentration of paracetamol, hydrogen peroxide and Total Organic Carbon (TOC) were recorded against the reaction time. The performance of the CoFe2O4@void@C catalyst was compared to that of the uncoated ferrite, the CoFe2O4 and CoFe2O4@void@C materials allowing TOC values of 46 and 58% respectively at 24h. The hybrid coated ferrite succeeds in avoid iron leaching and to be a stable catalyst. The amount of leached iron at the end of the treatment was equal to 1.59 mg·L-1, which is within the limit concentration of 2 mg·L-1 of iron allowed in waters, as established EU regulations. A kinetic model was proposed describing the decomposition of hydrogen peroxide and the removals of the pollutant PCM and TOC with the CoFe2O4@void@C as catalyst, applying an empirical kinetic model composed of a second-order and an autocatalytic expression to describe the decomposition of H2O2 and PCM, respectively. The kinetic model for TOC can be well-described as a sum of the initial pollutant plus the oxidation intermediates from the PCM and the organic components that are refractory to the process. |
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