Rodrigo Brackmann - Academia.edu (original) (raw)

Papers by Rodrigo Brackmann

Journal of Photochemistry and Photobiology A: Chemistry, 2022

A Diversidade de Debates na Pesquisa em Química 2, 2020

Journal of Environmental Science and Health, Part B, 2021

Abstract This study describes the experimental design and optimization of application TiO2 cataly... more Abstract This study describes the experimental design and optimization of application TiO2 catalysts doped with 0.5, 1, 1.5, 2.0% of Fe. The catalysts were prepared using the impregnation method applied in Paraquat herbicide degradation. The catalysts were characterized by the following techniques: specific surface area and volume, mean pore diameter (BET method), scanning electron microscopy and photoacoustic spectroscopy. The characterization presented results indicating that both calcination temperature and the increase nominal metallic load affected by the structure of catalysts, changing the textural properties, as well as the band gap. The catalyst that presented the best herbicide removal percentage was TiO2 calcined at 773 K with removal of 90.2%. However, according to the experimental design and optimization, both variables (calcination temperature and Fe percentage) are significant in the process. In addition, a positive effect was found in the interaction between the two variables. The values show that a third order kinetic model better described the Paraquat photocatalytic degradation.

Journal of Water Process Engineering, 2021

Abstract Selenium contamination in water bodies is a concerning issue due to the harmful effects ... more Abstract Selenium contamination in water bodies is a concerning issue due to the harmful effects of the excessive selenium intake to human health. Heterogeneous photocatalysis can be successfully applied to remove selenium ions from water, but the photocatalyst recovery in the end of the process still needs improvement. The application of a magnetic photocatalyst (TiO2/CoFe2O4) in the Se(IV) photoreduction was investigated, with emphasis in the catalyst magnetic separation. The photocatalyst was synthetized via a simple sol-gel method and a central composite design was considered to evaluate the effects of titanium isopropoxide mass ratio used in the synthesis, calcination temperature and pH on Se(IV) reduction. Calcination temperature showed a strong influence in the photocatalytic activity, and the catalyst calcined at 381 °C presented the best performance. In the bests test, at pH 2.61, it was possible to remove >99% selenium after 2 min of exposure to radiation. Photocatalysts containing great amounts of rutile phase produced the lowest removal results. The TiO2/CoFe2O4 photocatalyst was magnetically separable, however its saturation magnetization (2.7 emu g−1) was considerably smaller than pure CoFe2O4 (84.6 emu g−1) and the photocatalyst magnetic separation from the aqueous medium was about 11 times slower in comparison to pure cobalt ferrite. The synthetized photocatalyst was able to satisfactorily photoreduce Se(IV) (96.5%) even after five cycles of photocatalysis.

Applied Catalysis A: General, 2020

Abstract Gold nanoparticles were synthesized by a colloidal method and deposited on a Ce0.8Fe0.2O... more Abstract Gold nanoparticles were synthesized by a colloidal method and deposited on a Ce0.8Fe0.2O2-δ mixed oxide. The resulting material was characterized by High-Resolution Scanning Transmission Electron Microscopy, Temperature-Programmed Reduction, Mossbauer Spectroscopy, Oxygen Storage Capacity, Adsorption and Temperature-Programmed Desorption (NO and CO) and DRIFT Spectroscopy in order to elucidate the influence of gold nanoparticles and oxygen vacancies of Ce0.8Fe0.2O2-δ support on the selective catalytic reduction of NO by CO. Ce0.8Fe0.2O2-δ support presented a higher NO conversion (95% at 250 °C; and 99% at 350 °C) than Au/Ce0.8Fe0.2O2-δ catalyst (48% at 250 °C). We propose that gold deposition changed the support surface sites by blocking oxygen vacancies, which are the dissociation centers of NO molecules, decreasing thereby the catalytic activity of the gold-based catalyst. On the other hand, gold nanoparticles improved the reducibility and the oxygen storage capacity of the mixed oxide because isolated Fe3+ (in OFeCe3 sites) become more reducible, which could be evidenced by the increased oxidation of CO to CO2 at room temperature. On Au/Ce0.8Fe0.2O2-δ, the oxygen needed for CO oxidation can be supplied by the mixed oxide crystalline lattice, possibly from interface sites between gold nanoparticles and the mixed oxide, once the oxygen from NO dissociation becomes less abundant.

Applied Biochemistry and Biotechnology, 2019

This work aims to study the immobilization of Candida rugosa lipase (CRL) onto corn straw residue... more This work aims to study the immobilization of Candida rugosa lipase (CRL) onto corn straw residue. For this purpose, chemical, morphological, and textural characteristics of the corn straw; immobilization process by adsorption; and immobilized enzyme activity and storage stability were evaluated. The corn straw presented isoelectric point of 7.0, surface with hydroxyl bands being favorable to the immobilization process. An irregular surface was also observed with fibers and pores, which are mesoporous and macroporous, characteristics that demonstrate efficiency in mass transfer mechanisms. Upon immobilization, it was observed that adsorption velocity is proportional to the square of the available adsorption sites (pseudosecond-order), and that the immobilization occurs in monolayers (Langmuir isotherm). The adsorption process was favorable and considered as a chemical adsorption mechanism. After immobilization, the optimum temperature increased, the optimum pH reduced, and the affinity of the biocatalyst for the substrate decreased. Corn straw derivative demonstrated good thermal stability. Regarding storage stability, there was approximately 12% loss of activity after 60 days of storage at 4°C. Considering that no treatment was applied to the corn straw, this result is satisfactory and shows good affinity between this support and CRL.

Topics in Catalysis, 2018

CeFex (x = 0, 1, 3, 5, 10, 15 and 20 at.%) mixed oxides synthesized by an adapted Pechini method ... more CeFex (x = 0, 1, 3, 5, 10, 15 and 20 at.%) mixed oxides synthesized by an adapted Pechini method were characterized by Raman spectroscopy, high-resolution transmission electron microscopy, electron paramagnetic resonance, magnetization and 57 Fe Mössbauer spectroscopy (57 Fe-MS) measurements in order to evaluate the oxygen vacancies formation and the chemical environment of Fe +3 inserted into the CeO 2 crystalline lattice. Fe +3 introduction into the CeO 2 structure resulted in an increase of the oxygen vacancies concentration, which indicates that this is the predominant charge compensation mechanism in the formation of CeFex solid solutions by the Pechini method. Fe +3 insertion in CeO 2 led to the formation of substitutional solid solutions, in which Fe +3 replaced octahedral Ce +4 sites in the crystalline lattice. Fe +3 could be found in the form of isolated sites with orthorhombic distortion or Fe +3 species in pairs or clusters coupled by strong spin-spin interactions. No evidence of Fe +3 insertion into tetrahedral interstitial sites was found. Isolated Fe +3 species showed a less distorted chemical environment and greater ionic character of the Fe-O bonds than the clusters, being the concentration of both type sites approximately equal for all the Fe +3 doped contents. It was found that pure CeO 2 and all the CeFex mixed oxides presented ferromagnetic properties even at room temperature possibly due to their small crystallite size and the presence of oxygen vacancies. At high Fe +3 concentrations (above 10 at.%), probably super-exchange interactions (Fe +3-O −2-Fe +3), with an antiferromagnetic character, also took place, reducing the ferromagnetism of the CeFex mixed oxides.

Catalysts, 2019

This study describes the experimental design and optimization of the photocatalytic reaction usin... more This study describes the experimental design and optimization of the photocatalytic reaction using the immobilized catalyst Fe/Nb2O5 in the degradation of Triclosan and 2.8-DCDD. The techniques employed to characterize the photocatalysts were: specific surface area, average pore volume, average pore diameter, photo-acoustic spectroscopy (PAS), X-ray diffraction (XRD), and scanning electron microscopy (SEM/EDS). The reaction parameters studied were pH, catalyst concentration, catalyst calcination temperature, and nominal metallic charge. The results indicated that the immobilized Fe/Nb2O5 catalysts were efficient in the degradation of Triclosan and 2.8-dichlorodibenzene-p-dioxin. The catalysts with nominal metal loading of 1.5% Fe calcined at 873 K showed the highest constant reaction rate and the lowest half-life 0.069 min−1 and 10.04 min. Tests in different matrices indicated that the photocatalytic reaction using aqueous solution containing Cl− is faster when compared with the ult...

Blucher Chemical Engineering Proceedings, 2018

RESUMO-Óxidos mistos de cério e nióbio (CeO 2-Nb 2 O 5) com diferentes proporções mássicas CeO 2 ... more RESUMO-Óxidos mistos de cério e nióbio (CeO 2-Nb 2 O 5) com diferentes proporções mássicas CeO 2 :Nb 2 O 5 foram sintetizados pelo método de Pechini e calcinados em duas etapas de aquecimento (300 e 550 ºC). Os óxidos foram caracterizados por microscopia eletrônica de varredura (MEV), análise termogravimétrica (TG), difratometria de raios X (DRX) e refinamento de Rietveld. Foram obtidas soluções sólidas para a proporção de Nb 2 O 5 de até 50% e, com o aumento da proporção para 75%, houve a formação de uma fase segregada de Nb 2 O 5. As soluções sólidas CeNb 25 e CeNb 50 apresentaram tamanhos de cristalitos de 6,5 e 2,7 nm, respectivamente, enquanto que, para o óxido CeNb 75 , por este apresentar duas fases, foram obtidos cristalitos de tamanho 11,2 e 28 nm, para as fases CeO 2 e Nb 2 O 5 , respectivamente. O óxido simples Nb 2 O 5 apresentou tamanho de cristalito de 30,5 nm. Através do refinamento do difratograma do CeNb 25 , obteve-se um fator de ocupação de oxigênio de 83,70%, o que é desejável para reações do tipo redox. Inserido neste contexto, o presente trabalho tem como objetivo a obtenção de materiais com possíveis aplicações em catálise heterogênea, especialmente reações do tipo redox.

International Journal of Hydrogen Energy, 2016

The effect of substitution of cobalt by iron in LaCo 1Àx Fe x O 3 (x ¼ 0.0, 0.5 and 1.0) perovski... more The effect of substitution of cobalt by iron in LaCo 1Àx Fe x O 3 (x ¼ 0.0, 0.5 and 1.0) perovskitetype oxides on its physical properties and catalytic performance in the partial oxidation of methane (POM) reforming was investigated. The perovskites were characterized by X-Ray Diffraction (XRD) and the diffractograms were refined by the Rietveld method, X-Ray Fluorescence (XRF), Thermal analysis, BET (Brunauer-Emmett-Teller) specific area, Temperature Programmed Reduction (TPR) and Scanning Electron Microscopy (SEM). Remarkable is the product distribution varying with space time and with perovskite-type catalyst employed. For lower W/F values, the major product was H 2 for the LaCoO 3 (55.8%) and LaCo 0.5 Fe 0.5 O 3 (59.2%), with similar ratios H 2 /CO (1.8e1.9) and low CO 2 formation. On the other hand, the commercial catalyst (REF-11) was relatively more active (conversion of 75.2%), and the H 2 production was 60.7%. Differently was the LaFeO 3 perovskite that showed lower H 2 and CO formation or ratio of H 2 /CO, but a significant increasing of CO 2 formation. According to the catalytic and characterization results before and after reaction, we proposed reaction routes that showed different paths on the LaCoO 3 , LaFeO 3 and mixed perovskite-type oxides.

Topics in Catalysis, 2016

We prepared Ce1−xFexO2−δ mixed oxides (x = 0; 0.05; 0.1; 0.15 and 0.2) by Pechini method and we c... more We prepared Ce1−xFexO2−δ mixed oxides (x = 0; 0.05; 0.1; 0.15 and 0.2) by Pechini method and we characterized the materials by X-ray fluorescence, X-ray diffraction, N2 physisorption, UV–Vis diffuse reflectance spectroscopy and scanning electron microscopy. The mixed oxides were evaluated in the selective catalytic reduction of NO by CO. The characterization showed that the synthesis method is suitable for obtaining oxides with desired stoichiometry and single phase solid solution for all Fe contents. The catalytic tests allowed to conclude that Ce1−xFexO2−δ are promising for NO abatement by CO due to the improvement of the physicochemical properties of the synthesized solid solutions by Fe incorporation, such as decreasing crystallite sizes and increasing oxygen vacancies. Ce1−xFexO2−δ mixed oxides were able to dissociate NO even at room temperature due to the presence of the anionic vacancies. The increase of iron content in the mixed oxides enhanced the catalytic activity and selectivity to N2.

A radiação solar quando penetra na atmosfera, sofre complexas interações com os elementos atmosfé... more A radiação solar quando penetra na atmosfera, sofre complexas interações com os elementos atmosféricos, tais como nuvens e aerossóis. As nuvens representam o principal fator modulador da radiação que chega à superfície terrestre. Dessa forma, a compreensão dessas interações é de fundamental importância para o estudo da disponibilidade dos recursos de energia solar no Território Brasileiro. O trabalho apresenta o desenvolvimento de modelos empíricos que relacionam a radiação solar com fatores de nebulosidade. Os dados de radiação solar global e difusa foram coletados por piranômetros instalados na estação de referência do Projeto SONDA (Sistema de Organização Nacional de Dados Ambientais do CPTEC/INPE-MCT, Brasil) no Observatório Espacial do Sul OES/CRS/INPE MCT. Imagens do céu foram registradas pelo Imageador Total Sky Imager TSI-440 e avaliadas pelo TSI Manager Software, que classifica as nuvens em finas e opacas. Os parâmetros I/I0, ID/I0 e K, onde I representa a irradiância solar...

.Durante as queimadas, são emitidas partículas de aerossóis para a atmosfera, que ao interagir co... more .Durante as queimadas, são emitidas partículas de aerossóis para a atmosfera, que ao interagir com a radiação solar modifica o balanço radiativo terrestre. O trabalho analisa a relação existente entre a ocorrência de queimadas e o déficit de radiação solar que atinge a superfície terrestre em dias de céu claro. Os dados de radiação solar global foram coletados por piranômetros instalados nas estações do Projeto SONDA (Sistema de Organização Nacional de Dados Ambientais do CPTEC/INPE-MCT do Brasil para o setor de energia ) em Petrolina PE, Cuiabá MT, Campo Grande MS e Alta Floresta MT, sendo que os dados de espessura ótica dos aerossóis (AOT) foram obtidos pela rede AERONET. Os dias selecionados como de céu claro tiveram calculados seus respectivos índices de nebulosidade (Kt), razão entre a irradiância solar global na superfície terrestre com a irradiância no topo da atmosfera. Gráficos de Kt em função das médias diárias de AOT para λ = 500, 675, 870 e 1020 nm foram efetuados para a...