XIV Encontro de Catálise do Norte, Nordeste e Centro-Oeste
A comunidade catalítica das regiões Norte, Nordeste e Centro-Oeste tem encontro marcado no período de 17 a 19 de novembro em Fortaleza-CE, onde ocorrerá o XIV ENCAT – Encontro de Catálise do Norte, Nordeste e Centro-Oeste, que é realizado a cada dois anos e é organizado pela Secretaria Regional 1 da Sociedade Brasileira de Catálise. O Encontro deste ano traz como tema “o protagonismo da Química no desenvolvimento regional”, evidenciando o caráter basilar desta ciência nos diferentes setores da nossa sociedade. Palestrantes renomados de vários países compartilharão os mais recentes avanços nas diferentes linhas de pesquisa da catálise, em consonância com a apresentação de trabalhos orais e/ou em painéis e de toda a integração que um evento desse tipo pode proporcionar. Venha apresentar seu trabalho, rever amigos e fortalecer laços. Aguardamos vocês!
The magnetic fraction of coal fly ash: separation and Properties
Fly ash is an abundant byproduct of industrial waste that presents a huge environmental concern regarding its disposal. Given this, the sustainable use of ash as a renewable support material in the property of materials has been growing in recent years. In this context, the present work aims to extract magnetic particles from fly ash derived from coal combustion and modify them through different routes for future photocatalytic applications. The fly ash (FA) was preconditioned for the removal of magnetic particles (MF0) and then modifications were carried out with oleic acid and NaOH, obtaining samples MF1 and MF2, respectively. The materials obtained were characterized by X-ray fluorescence, X-ray diffraction, infrared spectroscopy, scanning electron microscopy, vibrating sample magnetometer and hyperthermia. The characterization of the particles allowed the understanding of their microstructural, morphological and magnetic characteristics, as well as the identification of the material composition. X-ray diffraction analyses of the samples indicated the presence of the crystalline phase of iron oxides, hematite and magnetite phases. The change with oleic acid allows for greater saturation magnetization (18 emu/g) compared to many samples, and consequently a greater response in the presence of a magnetic field. Thus, the results indicated that the removal and chemical treatment made it possible to obtain magnetic particles with optimized properties, thus contributing to future applications as photocatalysts.
Síntese e caracterização de catalisadores e adsorventes.
Copyright (c) 2024 Natália Porto Alexandre, Armando Diego Lima de Freitas, Sandra Aguiar Soares, Adonay Rodrigues Loiola (Autor) https://creativecommons.org/licenses/by/4.0
Development of silicon-cerium nanospheres through fast soft-template synthesis
The present work aimed to develop spherical silicon-cerium nanoparticles through a rapid synthesis via a soft-template method and to use them in preliminary tests of photodegradation of the Rhodamine B dye. For this purpose, CTAB was used as a template, and Tetraethyl Orthosilicate (TEOS) and cerium nitrate were used as silicon and cerium sources, respectively. The materials were synthesized with 1.5%, 2.0%, and 4.0% cerium concentrations and characterized by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD), X-ray Fluorescence (XRF), and N2 adsorption/desorption. SEM images showed the formation of well-defined spheres with average diameters of 410 nm and 150 nm for samples with the highest and lowest cerium content (1.5% and 4.0% Ce, respectively). CeO2 agglomerates outside the lattice were also observed, especially with higher cerium concentrations, indicating a possible insertion limit into the material structure. XRD identified CeO2 through the presence of three reflection peaks (111), (230), and (331), except for the 1.5% sample, which showed only a halo, indicating the amorphous nature of the nanosphere walls. EDS results demonstrated a uniform distribution of cerium atoms across all materials, which, together with other characterizations, suggests the incorporation of Ce into the nanosphere structure. XRF analysis revealed actual cerium incorporation values close to the theoretical ones, namely 1.4%, 1.8%, and 3.7%. The materials generally showed significant N2 adsorption at low pressures in their isotherms, indicating high surface area, absence of capillary condensation (suggesting a lack of mesoporosity), and considerable adsorption at high pressures, attributed to interparticle spaces. The proposed synthesis method proved highly efficient, enabling the direct synthesis of Si-Ce nanospheres in a short time. The Si-Ce nanospheres demonstrated photocatalytic activity in preliminary photodegradation tests of the commercial Rhodamine B dye, achieving up to 45.2% dye degradation when the material with 1.5% Ce was used.
Copyright (c) 2024 Fernando Rodrigo Dantas Fernandes, Adriana Paula Batista dos Santos, Jesyka Macêdo Guedes, Antonia Larissa Santos do Nascimento, Anne Gabriella Dias Santos, Sibele Berenice Castellã Pergher (Autor) https://creativecommons.org/licenses/by/4.0
Biocarvões, a partir de resíduos amazônicos, na esterificação do destilado de óleo de palma em biodiesel
The valorization of solid waste is fundamental for the development of new sustainable products in the area of biofuels and bioenergy (Rahul et al., 2024; Yogin Soodesh et al., 2024). In this work, Amazonian biochars were developed from murumuru husks and the alcoholic extraction residue of açaí seeds for biodiesel production, according to Laohapornchaiphan, Smith, and Smith (2017) method. The biomass was subjected to hydrothermal carbonization at 240 °C for 10 hours and functionalized with ρ-toluenesulfonic acid (PTSA) in a 1:2 ratio of residual biomass to PTSA for the synthesis of biocatalysts. Biodiesel was obtained by esterification of the deodorized palm oil distillate (DDOP) under conditions of 65 °C ± 5 °C for 2 and 4 hours. TGA and FT-IR analyses confirmed that PTSA functionalization was effective at 240 °C, highlighting aromatic C=C (~1573 and 1603 cm⁻¹) or NH2 (1590–1550 cm⁻¹) functional groups, characteristic of lignocellulosic biomass, and esters C–O (1300–1020 cm⁻¹) and S=O (1350–1040 cm⁻¹) indicative of PTSA, as described by Laohapornchaiphan et al. (2017) and Queiroz et al. (2020). The best biodiesel conversions with biocatalysts were 87.29% and 89.15%, with murumuru husk biochar at 2 hours and açaí seed residue biochar at 4 hours, respectively, while the control sample showed a conversion of 10.52%. Thus, the bioproducts show potential in esterification reactions and in promoting biorefinery by utilizing three residual raw materials derived from murumuru (Astrocaryum murumuru), açaí (Euterpe oleracea), and palm (Elaeis guineensis) for biofuel production.
Catálise aplicada na produção de combustíveis, biocombustíveis, produtos químicos e energia.
Copyright (c) 2024 Nathalia Lobato Moraes, Maitê Thaís Barros Campos, Luiz Augusto Barbosa Santos, Klayton Francisco Pereira Oliveira, Larissa Carla Pinheiro Gatti, Marcos Jhony Almeida Costa, Ana Alice Farias da Costa, Rafael Luque, Luiz Antônio Magalhães Pontes, Geraldo Narciso da Rocha Filho, Luís Adriano Santos do Nascimento (Autor) https://creativecommons.org/licenses/by/4.0
Catalisadores zeolíticos HZSM-5 e Ni/HZSM-5 aplicados a pirólise catalítica das biomassas residuais de óleo de fritura e sebo bovino
A demanda por energia tem crescido desenfreadamente nos últimos anos, onde as questões ambientais encaminham o cenário rumo à uma transição energética acentuada através da implementação de combustíveis alternativos sustentáveis [1]. A pirólise é um dos processos termoquímicos substantivamente explorados para a conversão de diversos tipos de biomassas e, quando catalisado, possibilita resultados aprimorados; e um catalisador amplamente empregado é a zeólita ZSM-5, devido sua alta estabilidade, seletividade e atividade pela superfície mesoporosa [2]. Neste trabalho foi explorada a síntese verde da zeólita ZSM-5 pelo método hidrotérmico assistido por micro-ondas, de acordo com o depósito de patente BR 10 2024 022914 2, na ausência de semente e direcionador. Posteriormente, o catalisador foi protonado e impregnado com Níquel, onde foi explorada sua aplicação na rota termoquímica de pirólise sobre as biomassas residuais de óleo de fritura e sebo bovino [3]. Técnicas de caracterização, incluindo DRX, SEM, EDS e FTIR confirmaram o carregamento bem-sucedido do metal e preservação da estrutura zeolítica. Os resultados obtidos através dos ensaios de pirólise catalítica mostraram que o emprego dos dois catalisadores em testes termoquímicos impactou significativamente no percentual de distribuição dos produtos e percentual de oxigenados. Por fim, análises de CG-MS permitiram revelar propriedades aprimoradas do bio-óleo obtido, bem como o conteúdo de C e redução de oxigenados. Assim, este estudo oferece resultados valiosos para a rota termoquímica de pirólise com catalisadores zeolíticos modificados, e seu papel fundamental na conversão das biomassas residuais.
Copyright (c) 2024 Amanda Menezes Caldas, Aruzza M. M. Araújo, Amanda D. Gondim, Dulce M. A. Melo (Autor) https://creativecommons.org/licenses/by/4.0
Synthesis and characterization of NiAlMg mixed oxide catalysts aimed at application in the deoxygenation reactions of triglycerides
The production of advanced fuels via catalytic deoxygenation from renewable sources, such as vegetable oils, is essential for the transition of the energy matrix [1]. The use of catalysts in this process aims for high efficiency in converting vegetable oils into advanced fuels, such as green diesel and sustainable aviation kerosene. Depending on its composition, the catalyst can exhibit properties that enhance deoxygenation, resulting in products with higher energy value and lower environmental impact [2]. This work considers the synthesis and characterization of mixed NiAlMgOx catalysts derived from layered double hydroxides (LDH), varying the Mg/Al ratio. The precursors with the composition Ni0,2MgYAl(0,8-Y)(OH)2(TA)(0,8-Y)/2·mH2O (with TA = terephthalic acid, Y = 0,1 and 0,2) were synthesized by the slow addition of aqueous solutions of metal nitrates and terephthalic acid in NaOH (1 mol/L) to deionized water (65 °C), under stirring and constant pH. The precipitate was aged under stirring for 4 hours at 65 °C and subsequently at room temperature for 16 hours. After filtration and washing, the material was dried in an oven at 100 °C (overnight) and calcined at 600 °C for 3 hours with a heating rate of 10 °C min⁻¹, forming the mixed oxide catalysts NiAlMg(0,1) and NiAlMg(0,2). The characterization of the materials was performed using X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Energy-dispersive X-ray spectroscopy (EDX), Nitrogen physisorption at -196 °C, Hydrogen temperature-programmed reduction (H2-TPR), and Ammonia temperature-programmed desorption (NH3-TPD). The XRD patterns confirmed the formation of the NiAlMg layered double hydroxides (LDHs) and the mixed oxides (with the dominant phase being NiAl2O4) after calcination. TGA established 550 °C as the minimum calcination temperature required to completely decompose the LDH structure. The composition of the materials (EDX) shows the proportionality between the fractions (Yi), the differences in aluminum content across the formulations, and a constant nickel content. The catalysts are of the mesoporous type, with SNiAlMg(0,1) = 258 m²/g, SNiAlMg(0,2) = 275 m²/g, Vp-NiAlMg(0,1) = 0,8 cm³/g, and Vp-NiAlMg(0,2) = 1,0 cm³/g. The increase in magnesium content resulted in a slight decrease in nickel reducibility (VTPR- NiAlMg(0,1) = 34,5 mL H2/g and VTPR- NiAlMg(0,2) = 33,8 mL H2/g). NH3-TPD analysis indicated a slight decrease in the acidity of the catalysts with increasing magnesium content: 9,56 µmol NH₃/m² (Y=0,1) and 9,22 µmol NH₃/m² (Y=0,2), primarily attributed to the reduction of acidic sites on the alumina. Given the results obtained, the proposed catalysts exhibit promising characteristics for evaluating the effect of acidity in NiAlMg oxides on the catalytic deoxygenation of vegetable oils aimed at the production of advanced fuels
Copyright (c) 2024 Juan Felipe González Alba, Celmy M.B.M. Barbosa, José Geraldo A. Pacheco, Santiago Arias Henao, Roger Frèty, Luiz Stragevitch, Florival Rodrigues de Carvalho (Autor) https://creativecommons.org/licenses/by/4.0
Synthesis and optical characterization of Lippia grata leaf extract for the production of carbon quantum dots for heterogeneous photocatalysis applications
In recent years, there has been growing concern about the high toxicity of reagents, solvents and other chemical agents present in industrial or household processes. It is known that the processes resulting from these effluents being discharged into the environment pose major risks to society as a whole. In order to minimize these processes, new methodologies for their treatment must be developed, among them, Advanced Oxidative Processes (AOP) have been widely used, especially photocatalysis, based on the oxidative activity of a semiconductor material on the harmful compounds present in the effluent. Photocatalysts are generally produced via a synthesis route involving solvents and environmentally unfriendly processes. Green synthesis methodology, which uses organic compounds present in nature to produce nanomaterials, has been outstanding in obtaining new photocatalysts based on carbon quantum dots (CQDs) [1]. CQDs are carbon nanomaterials that have absorption and photoluminescence properties (in the UV, visible or NIR), their properties include photochemical stability and biodegradation [2]. Lippia grata is a highly aromatic plant, endemic to northeastern Brazil, has remarkable pharmacological properties associated with its chemical composition. This study aims to use Lippia grata leaf extract to produce CQDs. The plants were collected on the campus of the State University of Rio Grande do Norte/Mossoró/RN. After collection, the leaf were prepared, separated, cleaned and dried on absorbent paper at room temperature in a sheltered place for 48 hours. The leaves were then added to Kraft paper and dried in an oven with forced air circulation at 40°C for 120 hours. After drying, the leaves were macerated until a powder was obtained. Two extracts were prepared using 40 g of these leaves: the first (aqueous) used 200 mL of ultrapure water, and the second (hydroalcoholic) used a mixture of 100 mL of ultrapure water and 100 mL of ethyl alcohol. The extracts were left to stand in the hood for 72 hours, then filtered using a simple filtration system, kept in amber bottles covered with aluminum foil and refrigerated at 4°C. The characterizations were carried out in liquid and solid state, using the techniques of Photoluminescence Spectroscopy, UV-Vis Absorption and Thermogravimetric Analysis. The UV-Vis Absorption tests showed similarities between the spectra, with absorption bands being observed between 250-400 nm and 500-700 nm. In the hydroalcoholic extract, bands near 650 nm characterize the presence of chlorophyll, which was also observed in the aqueous extract with less intensity. In the 250-400 nm region, a shoulder with two distinct variations was observed, related to the presence of flavonoids and phenolic compounds in the extracts, with greater intensity in the hydroalcoholic extract. Photoluminescence analysis showed results with high emission intensities between 580-600 nm and 350-400 nm for both extracts, characterizing the presence of aromatic compounds, flavonoids and chlorophyll. The TG curves showed that the plant powder has a more pronounced loss of mass from 300°C onwards. The compounds present in the extracts are rich in carbon, important structures for the production of CQDs. Based on the results obtained, the CQDs were synthesized using the microwave-assisted bottom-up method, which will later be used for photocatalysis.
Copyright (c) 2024 Ruth Batista de Andrade, Alessandra Raiany de Oliveira, Keurison Figueredo Magalhães, Suely Souza Leal de Castro (Autor) https://creativecommons.org/licenses/by/4.0
Síntese da zeólita LTA empregando um resíduo industrial gerado na produção de silício para a fabricação de placas solares: estudo de temperatura de dissolução
Com a crescente demanda por energia renovável, a indústria de placas solares tem crescido muito, demandando um maior consumo de dióxido de Silício (SiO2). Para a produção deste, numa pureza desejada para o emprego em placas solares, se gera uma quantidade significativa de resíduos, especialmente um pó que contém aproximadamente 93,3% de SiO2. Este resíduo é produzido em grandes quantidades e ainda não tem um destino definido [1]. O estudo se propõe a investigar a viabilidade da síntese da zeólita LTA a partir desse resíduo, explorando variáveis críticas, mais especificamente, o estudo de tempo e temperatura de dissolução deste resíduo. Para tal, seguiu-se o modelo padrão de síntese da IZA (International Zeolite Association), adotando o tempo de cristalização de 1 hora, e variando o tempo de dissolução do resíduo em 30 minutos, 1 hora e 2 horas, sob as temperaturas de 60 °C e 80°C. Os materiais sintetizados foram denominados da seguinte forma: LTARL_XTYG, onde LTA se refere a estrutura da zeólita LTA, RL se refere ao resíduo industrial empregado, “X” faz referência ao tempo de dissolução, T = M para minutos e H para horas, “Y” corresponde à temperatura adotada e G a graus. Por meio da caracterização por Difração de Raios X (DRX) da zeólita LTA sintetizada a partir do resíduo, é possível observar a presença de picos de difração característicos da zeólita LTA, com posições angulares correspondentes aos planos cristalográficos conhecidos dessa estrutura para a amostra LTARL_30M60G, confirmando que a síntese foi bem-sucedida na formação da fase desejada. Quando analisados em conjunto com a micrografia (MEV) da amostra, pode-se observar a presença significativa de aglomerados e cristais deformados. A presença de aglomerados pode ser atribuída à inadequada dispersão do material precursor durante a síntese ou à insuficiente homogeneização do gel de síntese. Esse fenômeno pode resultar na formação de regiões onde os cristais de zeólita tendem a se aglomerar, o que pode impactar negativamente a distribuição uniforme dos poros e, consequentemente, as propriedades adsortivas e catalíticas da zeólita. Pode-se concluir portanto que foi possível sintetizar a zeólita LTA a partir do resíduo em temperaturas de síntese relativamente baixas e menores tempos de dissolução com boa cristalinidade e elevada intensidade de picos. Ainda assim, estudos para melhor dispersar e disponibilizar o resíduo de partida no meio reacional ainda mostram-se necessários.
Síntese; zeólitas; resíduos industriais; placas solares.
Copyright (c) 2024 Mikael Breno, Manuela Silva M. de Oliveira, Sibele B. C. Pergher (Autor) https://creativecommons.org/licenses/by/4.0
Structural characteristics of CoAl materials Obtained by coprecipitation at high and low supersaturation, with application in the glycolysis of bottle-grade PET
The massive consumption of poly(ethylene terephthalate) (PET) polymers, especially in single-use packaging, requires waste management policies that are sometimes absent and therefore cause environmental problems. The depolymerization of PET by glycolysis with ethylene glycol (EG) in the presence of a catalyst leads to the production of the monomer bis-(2-hydroxyethyl) terephthalate (BHET), which can reduce the demand for fossil resources for the production of PET. In this work, CoAl materials were synthesized by co-precipitation at high supersaturation (a.s.) and low supersaturation (b.s.) using carbonate or terephthalate as interlamellar anions, identified as CoAl or CoAl-T, respectively. These catalysts were calcined at 400°C and identified as CoAl (a.s.)c, CoAl (b.s.)c, CoAl-T(a.s.)c, CoAl-T(b.s.)c., then they were applied in the glycolysis of PET (bottle grade post-consumer) in the presence of EG to obtain its monomer. The reaction conditions used were 0.5% catalyst: PET, EG: PET 5, at ~200°C for 60 min, as described in previous work (Arcanjo et. al. 2023). The XRD results show that a low crystallinity hydrotalcite phase was the main diffractogram pattern observed for all the materials, except for CoAl a.s.T which shows characteristics of an amorphous material, without a well-defined crystalline structure. N2 adsorption/desorption results indicate that all CoAl and CoAl-T calcined materials are mesoporous. CoAl-T materials present an H2(b) type hysteresis loop, characteristic of materials with complex porosity, which undergo the strong influence of network effects; on the other hand, CoAl materials present H5 type loop, whose main characteristic is associated with a porosity composed of open or partially blocked pores. Textural analysis shows CoAl-T(a.s.), CoAl-T(b.s.) and CoAl a.s. presented smaller surface areas like 106 m2.g-1, 105 m2.g-1 and 103 m2.g-1, respectivelly, while CoAl b.s. presented a greater surface area of ​​125 m2.g-1. The application of these materials in the glycolysis of bottle-grade PET shows that the best PET conversion performances were observed as follows: CoAl-T (b.s.) (68.2%) > CoAl-T (a.s.) (62.6%) > CoAl (b.s.) (58.6%) > CoAl (a.s.) (41.2%). BHET yield and selectivity of BHET (sel. of monomer) also followed this order. These results observed in Figure 1 may be associated with the larger average pore diameter size of CoAl-T (b.s.), ~170 Å, which was higher than that observed for the other materials with pore diameters between 104 and 149 Å. Characterization of the products demonstrated that BHET was the main product obtained. 1H-NMR analysis shows the main protons of BHET. DSC analysis shows a characteristic BHET melting point around 110 °C, which coincides with all the products and differs from the melting point observed for the PET at 250 °C. Future tests to improve the efficiency of PET conversion can be carried out with the inclusion of other metals in these catalysts.
Copyright (c) 2024 Hezrom Saulo Nascimento, Ana P. Arcanjo, Celmy Maria Bezerra Menezes Barbosa, Roger Frety, José Geraldo Andrade Pacheco (Autor) https://creativecommons.org/licenses/by/4.0
Desidratação do glicerol catalisada por hexaniobato de potássio lamelar
O hexaniobato de potássio lamelar é um sólido cuja estrutura das lamelas é formada por unidades octaédricas de [NbO6] ligadas pelos vértices e arestas¹. Este material se destaca por possuir dois espaços interlamelares distintos e por ser amplamente estudado em processos de fotocatálise. Neste trabalho, o hexaniobato de potássio foi avaliado como catalisador na desidratação do glicerol. O resultado mostrou alta seletividade à acroleína, o que é atribuído a sua estrutura que facilita a protonação do glicerol. Em suma, o hexaniobato de potássio se mostrou um material com grande potencial para reações que necessitam de acidez de Brønsted.
Sólido lamelar, hexaniobato de potássio, desidratação do glicerol, acroleína
Copyright (c) 2024 Vitoria Santos, Marcos A. S. Araújo, Tiago P. Braga, Sibele B. C. Pergher (Autor) https://creativecommons.org/licenses/by/4.0
Activated carbon obtained from Tucum (Astrocaryum vulgare Mart.): an alternative bioadsorbent for dye removal in aqueous media
With the increase in environmental law enforcement regarding industrial effluent contamination, such as synthetic dyes, methods and technologies to treat and control them have been increasingly sought. In this context, adsorption is an effective method for removing contaminants, with the advantage of using alternative materials such as activated biochar. The objective of this study was to investigate the capacity of the adsorption of activated carbon produced from the endocarp of tucum (Astrocaryum vulgare Mart.) (ATC) in the removal of rhodamine B dye in aqueous media. The ATC was characterized using the following methods: ash and moisture content, FTIR (Fig.1), pH at the point of zero charge (Fig.2) and Scanning Electron Microscopy (Fig.3). The experimental data were fitted to the Langmuir and Freundlich isothermal models from their linear mathematical equations (Fig.4). The ash content of ATC was 1.13%, while the moisture content was 1.62%. These values are consistent with the values found in the literature for materials similar to ATC (Haryanti, 2024). Unactivated carbon is poor in functional groups on its surface. The bands between 1475-1600 cm-1 (C=O and C=C) are attributed to the increase in aromatic structures due to the activation and pyrolysis process. The bands between 1220-1180 cm-1 can be attributed to the stretching of hydrogen bonded to the P=O group and O-C stretching vibrations in P-O-C coupled to aromatic rings, proving the activation of H3PO4. A band between 1360-1250 cm-1 (C-N) shows the adsorption of the dye on the ATC surface. The pHpzc value equal to 5.2. Micrographs (a) and (b) show the morphology of non-activated carbon, showing a homogeneous and regular surface. Micrographs (c) and (d) show the morphology of ATC, showing more irregular surfaces with the presence of pores of varying sizes. The experimental data of the adsorptive process showed a better fit to the Langmuir model (R2 = 0.967). Wei (2022) investigating the use of activated carbon in the removal of rhodamine B, obtained a good fit of the experimental data with the Langmuir model. The maximum adsorption amount was 1467.01 mg.g-1, with 93.21% dye removal. ATC is a promising adsorbent for dye removal in aqueous media.
Copyright (c) 2024 Walinson Martins, Leonardo Cantanhede, Denize Maria Silva (Autor) https://creativecommons.org/licenses/by/4.0
Síntese e caracterização de materiais híbridos, microporosos e mesoporosos H-Y/MCM-41
The use of sustainable fuels, aims to reduce the environmental impacts caused by dependence on fossil sources, but it still presents challenges. Production from fossil sources generates greenhouse gas emissions and causes environmental damage, such as the excessive use of natural resources. Furthermore, there is a risk of negative impacts on ecosystems and biodiversity, necessitating chemical and technological solutions that minimize these effects. In this context, the work focuses on the synthesis of catalysts such as microporous zeolite H-Y (FAU), the mesoporous material [Al]-MCM-41, and the hybrid H-Y/MCM-41, which play a crucial role. These catalysts offer unique properties that optimize chemical reactions, increasing efficiency and sustainability. These materials were characterized by X-Ray Diffraction (XRD) showing similarity with patterns, Thermogravimetric analysis (TGA) to determine the thermal stability and calcination temperature of each material. The SiO2/AlO3 ratio was determined by Wavelength Dispersive X-Ray Fluorescence (WDXRF) to be 4.55, 32.20 and 58 respectively. The morphology of the materials was well defined by Scanning Electron Microscope (SEM), the N2 adsorption and desorption analysis showed that the surface area of the materials determined by the NLDFT method were 506 m2/g, 1527 m2/g and 978 m2/g respectively. The significantly higher surface area of [Al]-MCM-41 suggests its potential for enhanced catalytic activity, while the properties of the hybrid material indicate a balance between the microporous and mesoporous characteristics. In conclusion, the synthesis and characterization of these catalysts demonstrate their promising potential. By leveraging the unique properties of zeolite H-Y, [Al]-MCM-41, and H-Y/MCM-41, it is possible to enhance catalytic processes that contribute to the development of high-value-added products. This work not only supports the transition towards more sustainable energy solutions but also highlights the importance of innovative materials in addressing the challenges faced by different sectors dependent on fossil fuels.
Copyright (c) 2024 Jorge Arce Castro, Gabrielle Silva de Aquino, Ana Beatriz Moraes Bastos, Raildo Alves Fiuza Junior, Delano Mendes de Santana, Mauricio Brandão dos Santos, Fernanda Teixeira Cruz, Silvio Alexandre Beisl Vieira de Melo, Artur José Santos Mascarenhas (Autor) https://creativecommons.org/licenses/by/4.0
Zeolite growth over fiberglass for biogas enrichment
Biogas, produced during anaerobic digestion processes of organic substrates from industrial, agricultural and sewage waste, is considered a promising alternative source of renewable energy [1]. It is mainly composed of CH₄ (50–70%), CO₂ (30–50%) and other gases in smaller quantities. The removal of CO₂ is a key stage for biogas to be commercially used. In this context, the adsorption of molecules on solid surfaces combined with the PSA method has been efficient in applications with several selective grade materials, such as membranes, titanosilicates, carbon molecular sieves, and silica gels. Zeolites, which are part of the tectosilicate subgroup, are well-known as efficient CO₂ adsorbents. This work aims to promote the growth of zeolite A on fiberglass by using nanozeolite A as seed to induce the controlled growth of zeolite crystals over the fiber surface giving rise to materials suitable to form cartridges to be used as columns for biogas enrichment. The fiberglass underwent an activation process that consisted of contact with NaOH solution for 72 h, under orbital stirring. Next, the fibers were impregnated were molded as cylinders and impregnated with nanozeolite which were dispersed in water. The seeded fiber was then submitted to zeolite growth by a hydrothermal treatment for 4h in. The gel composition used in the synthesis was 3.165 Na₂O: Al₂O₃ : 1.926 SiO₂ : 128 H₂O. The activation of the fiberglass by alkaline treatment was efficient in favoring the growth of zeolite type A crystals due to the increase of the roughness on the fiber surface, combined with the increase of silanol groups present in its filamentous structure, therefore compatible with the species present in the synthesis gel that give rise to the grown zeolite A. The X-ray diffractogram shows peaks consistent with zeolite A as well as the baseline distortion related to the amorphous nature of the fiberglass [2]. The scanning electron microcopy images allow the visualization of cubic crystals of zeolite A grown on the glass fiber, indicating the effectiveness of the experimental approach and shedding light to a possibly potential material to be applied in the removal of CO₂ in the enrichment process of biogas.
Copyright (c) 2024 Lucas Medrado, Loiola, A.R. (Autor) https://creativecommons.org/licenses/by/4.0
Application of bismuth vanadate in the photodegradation of brewing industry effluents
The brewing industry is one of the largest industrial consumers of water, generating effluents with a high pollutant load due to waste arising from the processing and cleaning of equipment. Inadequate disposal of these effluents can lead to contamination of water bodies, resulting in significant environmental impacts [1]. Despite technological advances, challenges in treating these effluents remain, highlighting the need to optimize and implement advanced treatment methods that are effective in degrading the organic matter present. In this study, the efficiency of bismuth vanadate (BiVO4) as a photocatalyst in the degradation of effluents from the brewing industry under UV-visible irradiation was evaluated. The experiment was carried out in a bench system, containing a jacketed cell with a maximum capacity of 100 mL, where the brewery effluent was placed together with photocatalyst (BiVO4) dispersed in the solution plus the addition of hydrogen peroxide (H2O2) in some tests under agitation. A mercury vapor lamp (80 W) was used, shining light at 5 cm from the solution, and controlled temperature. The tests last 4 hours for photolysis and 4 hours and 30 minutes for photocatalysis; aliquots were withdrawn at times from 0 to 240 min. where 30 minutes of photocatalysis is reserved for the adsorption of the material in solution. Samples are analyzed pH; UV-Vis absorption spectra; total organic carbon;. Two studies were carried out: study of catalyst concentration and study of pH of the effluent in photodegradation. The results for the study of the two concentrations were carried out at pH 4.0 and 10, in photocatalysis with catalyst concentrations of 500 and 1000 ppm, the samples at pH 4.0 present the same behavior profile at different times of irradiation of light .For pH 10, the effluent presented two distinct groups in terms of its behavior, samples added with H2O2 showed greater degradation compared to samples without added H2O2, all tests were monitored at a wavelength of 330 nm. There is a difference in samples with pH 10 added with H2O2 with those with pH 4.0, in photolysis this difference was 33.91% while in photocatalysis it was 8.46%, demonstrating that there was greater degradation of effluent with pH 10 with the addition of hydrogen peroxide, in the photocatalytic tests the greatest TOC removal occurred in the photocatalysis of 1000 ppm BiVO4 with 18.93%. Heterogeneous photocatalysis showed satisfactory results.
Catálise ambiental, fotocatálise e eletrocatálise.
Copyright (c) 2024 Maiara Cristina de Araújo, Alessandra Raiany Oliveira, Keurison Magalhães, Suely Souza Leal de Castro (Autor) https://creativecommons.org/licenses/by/4.0
Thermocatalytic conversion of plastic waste over catalysts synthesized by interzeolitic transformation
Plastics are polymeric materials with a wide variety of properties and are very present in everyday life. Although, as useful as they can be, their waste can take centuries to be completely degraded, with the accumulation of plastics in nature causing serious environmental problems such as contamination of the water, the food chain, and even the air, due to microplastic particles (WWF, 2019). A way to reduce this excessive amount of plastics in the environment is through chemical recycling to generate other products, such as chemicals and fuels. This work aimed to study the pyrolysis and the hydrothermal conversion of high density polyethylene (HDPE) waste using zeolites synthetized through interzeolitic conversion, in order to obtain higher economic valuable chemical products, focusing on fuels. The pyrolysis system consisted on a vertical tubular furnace, the triturated plastic waste was deposited over a quartz wool bed inside a small vertical quartz reactor, which was then heated under a 10°C/min heating rate and a 100mL min-1 N2 flow. The temperature was varied, with each product phase’s mass being quantified after the tests, to study its influence on the HDPE pyrolysis. That way, it was perceived that increasing the temperature from 400 to 500°C, the amount of gaseous products increased, from 18.1% to 54.2%, as expected since the temperature is a parameter that controls the cracking of the polymeric chains and its degradation rate (Sharuddin et al, 2016). But, at temperatures like 600 and 700°C, an inversion was observed, with a high amount of solid phases being formed, 27.2% and 32.6%, respectively, while the percentage of gases masses decreased to 39.5% for the 600°C test and 34.8 for the 700°C test. It was also noted a difference between the solids below and above 600°C, with that last ones presenting a yellowish color. The pyrolysis products were characterized through ATR, where there was identified the presence of long aliphatic chains and olefin unsaturation related bands. No liquid phases were observed in this system until the test with the zeolite catalyst, where 10% of the plastic mass was of the zeolite gmelinite (GME). It was observed that a higher amount of gases were produced when compared to the test without catalyst at the same temperature. Eventually, other zeolites such as ZSM-5 (MFI), Y (FAU) and Chabazite (CHA) will be added to the thermocatalytic test to study how their properties may alter the proportions of product’s phase formation and how to use them to direct to a higher production of a certain phase, since some properties like pore size, pore structure and acidity can have different effects on plastic pyrolysis reaction mechanism.
Copyright (c) 2024 João Gabriel Vaz dos Santos Rios, Kim Costa Vianna, Maurício Brandão dos Santos, Fernanda Teixeira Cruz, Artur José Santos Mascarenhas (Autor) https://creativecommons.org/licenses/by/4.0
Síntese de biodiesel a partir do óleo de girassol utilizando CaO residual da indústria ceramista
O setor ceramista gera grandes quantidades de resíduos, constituído por materiais metálicos e não metálicos, impactando o meio ambiente. No entanto, esses resíduos podem ser reutilizados se transformados em catalisadores para produção de biocombustíveis. Este estudo visou utilizar os resíduos da indústria ceramista com e sem tratamento térmico para obtenção do biodiesel através da transesterificação do óleo de girassol. O resíduo foi purificado por tratamento ácido, ativado termicamente à 800 °C e analisado por difração de raios-X, para comprovação da obtenção do óxido de cálcio. A reação de transesterificação usou a proporção óleo/álcool de 1:12, com 4% para o resíduo sem tratamento e 8% para resíduo com tratamento, em refluxo a 65 °C por 3h. Os produtos gerados nas sínteses foram analisados por termogravimetria. O difratograma de raios X do material purificado e ativado apresentou picos característicos do óxido de cálcio, comprovando a eficiência do processo utilizado. Na avaliação das curvas de DTG, utilizando o resíduo sem tratamento e analisando as temperaturas máximas (Tmáx), o produto do resíduo calcinado (PRORCAL) teve Tmáx de 413,79 °C, similar ao produto do resíduo in natura (PRORNAT), 413,14 °C, indicando que o resíduo in natura e o calcinado não alterou a estabilidade térmica e a atividade catalítica, estando próxima da Tmáx da amostra de óleo, 416,64 °C. As amostras do biodiesel utilizando o resíduo purificado e ativado (BIORPA) como catalisador e do biodiesel utilizando o óxido de cálcio comercial (BIOOC) como catalisador, para comparar o efeito da fonte de cálcio, mostraram Tmáx inferiores e próximas, 252,88°C e 251,80 °C, respectivamente, comparáveis ao biodiesel utilizando KOH (BIOKOH) como catalisador, no qual sua Tmáx é de 254,38 °C. Nas curvas TG, a amostra do óleo de girassol apresentou três eventos, com perdas de massa de 67,6% (294,69 – 422,57 °C), 23,96% (422,57 – 456,16 °C), e 5,8% (456,16 – 510,07 °C). A decomposição em múltiplos estágios sugere uma composição típica de triglicerídeos em óleos vegetais. As curvas TG das amostras utilizando o resíduo in natura (PRORNAT) e resíduo calcinado (PRORCAL) não indicaram conversão, mesmo apresentando uma perda de massa de 96,5% e 97,22% com uma massa residual de 0,27% e 2,07%, respectivamente. Estes apresentaram o mesmo perfil da volatilização/degradação do óleo. Nas curvas TG das amostras BIORPA e BIOOC, os resultados foram promissores, pois os perfis de degradação apresentam perdas de massa de 84,99% e 82,06%, respectivamente, em temperaturas mais baixas (125 °C à 254 °C) tendo uma redução de 60.69% da temperatura máxima do BIORPA para o óleo. Esses valores estão próximos ao biodiesel obtido com KOH (BIOKOH), usado como referência, com perda de massa de 92,03% em temperaturas mais baixas. Indicando que o BIORPA obteve uma melhor conversão do óleo. Esses resultados sugerem que o uso do catalisador CaO, independentemente de sua origem, possui um comportamento estável e semelhante ao KOH em relação à reação de transesterificação empregada. Em suma, esse estudo mostrou que o resíduo purificado e tratado termicamente apresentou conversão do óleo de girassol em biodiesel superior em 3% comparada ao óxido de cálcio comercial, mostrando uma alternativa para o destino dos resíduos gerados pela indústria ceramista com maior valorização econômica e destinação ambientalmente atrativa.
Copyright (c) 2024 Ronildo Ribeiro de souza, Alrivan Gomes do Rego Junior, Antony Jeová Teixeira da Silva, Anne Gabriella Dias Santos, Adriana Paula Batista dos Santos, Vinicius Patricio Santos Caldeira (Autor) https://creativecommons.org/licenses/by/4.0
Transforming kaolin byproduct into a superior catalyst for acetal formation
In this study, kaolin waste was enhanced with sulfonic groups to improve its textural and chemical properties, resulting in a high-efficiency heterogeneous catalyst. The functionalized material was characterized using techniques such as FTIR and EDX. The addition of sulfonic groups created active sites that significantly increased the ion exchange capacity, enhancing catalytic performance and the analyses confirmed that the catalyst functionalization occurred efficiently. The acetalization of benzaldehyde was carried out at room temperature, with different reaction times tested. A remarkable conversion rate of 98% was achieved after 30 minutes, although significant conversion was already observed from 15 minutes onward. In contrast, the reaction without the catalyst resulted in only 6.1% conversion. The successful transformation of kaolin waste into a highly effective catalyst demonstrates its potential for broader applications in green chemistry, especially in sustainable synthesis. Acetals, the target products, are crucial intermediates in organic synthesis and the pharmaceutical industry. The catalytic process proposed in this study offers an efficient and eco-friendly approach to acetal formation, advancing the field of heterogeneous catalysis. Additionally, applying this functionalized material to other challenging reactions could further highlight its versatility and potential as a sustainable catalyst in various industrial processes.
Copyright (c) 2024 Marcos Costa, Maitê Campos, Viviana Bressi, Larissa Gatti, Thomas Len, Rafael Luque, Fabíola Costa, Luís Nascimento (Autor) https://creativecommons.org/licenses/by/4.0
Obtenção de materiais mesoporosos do tipo Al-SBA-16 impregnados com metais de transição para degradação do Óleo de Dendê
Com a necessidade em desenvolver energias renováveis, diversas pesquisas buscam a produção de combustíveis oriundos de fontes verdes. Uma rota viável para produção de biocombustíveis é a utilização de óleos vegetais como matéria-prima, dentre as possibilidades o óleo de dendê possui destaque devido as suas propriedades energéticas e de cultura. Ademais, a utilização de catalisadores mesoporosos do tipo SBA-16 no processo de craqueamento de óleos tem sido de interesse, uma vez que possuem uma estrutura tridimensional facilitando a passagem de moléculas sem haver bloqueio de poros. Contudo, apesar do SBA-16 possuir boa atividade catalítica, estudos buscam modificações a fim de aprimorar este material no âmbito da catálise, sendo uma delas a necessidade de maior acidez nos materiais, podendo ampliar a utilização em diferentes processos. Entretanto, a inserção de óxidos metálicos pode proporcionar mudanças positivas nas estruturas dos materiais e na atividade catalítica, dentre os metais o La e Zr são celebres na indústria catalítica devido a sua versatilidade. Dessa forma, esse trabalho tem por objetivo desenvolver catalisadores do tipo SBA-16, com inserção de Al, impregná-los separadamente com La e Zr e avaliar suas atividades catalíticas frente a degradação do óleo de dendê por análise térmica. Para a síntese do SBA-16 e Al-SBA-16, foi utilizado o método hidrotérmico. Contudo, foi realizado controle de pH para o aluminossilicato, através de uma solução de ajuste. A impregnação do La e Zr ocorreu pós síntese pelo método de excesso de solvente. Os materiais sintetizados foram caracterizados por DRX e FRX. O teste catalítico foi realizado através da análise térmica (TG/DTG e DSC). Os difratogramas obtidos confirmaram a estrutura mesoscópica dos materiais mesoporosos, uma vez que apresentaram os índices de Miller (110), (200) e (211) e indicaram a formação de La2O3 e ZrO2 nos materiais impregnados. O FRX realizado semi-quantificou as porcentagens referentes aos metais presentes na composição química dos materiais, comprovando que a inserção do Al e impregnação do La e Zr, foram realizados com sucesso. Portanto, através do teste catalítico, foi possível perceber que os materiais modificados possuíram maior diminuição na temperatura máxima para degradação e/ou volatilização do óleo de dendê, indicando que a inserção de Al e impregnação de La e Zr contribuem para maior atividade catalítica destes materiais SBA-16. As curvas de DSC apresentam fluxo de calor semelhante, ressaltando que as amostras catalisadas não alteraram o fluxo típico do óleo de dendê in natura. Por fim, a aplicação de catalisadores no craqueamento de óleos vegetais é uma das chaves para transformar recursos renováveis ​​em biocombustíveis eficientes, impulsionando uma transição energética sustentável.
Copyright (c) 2024 Jefferson Filho, Alexandro Hígor de Azevedo Costa, Profa. Dra. Anne Gabriella Dias Santos Caldeira, Prof. Dr. Vinícius Patrício da Silva Caldeira (Autor) https://creativecommons.org/licenses/by/4.0
Use of Murumuru seed shells as precursors for sulfonated biochar in vanillin synthesis
The Amazon region has a vast diversity of trees and plants, offering valuable biological resources. Among them, murumuru stands out, especially for the cosmetic industry, due to its excellent active ingredients. The industry uses the pulp and kernels of murumuru, but the seed shells are generally discarded as waste. To explore a new application for this agro-industrial waste, murumuru shells were utilized as biomass for the production of biochars, which served as support for heterogeneous catalysts. The biochars from murumuru shells (BCM) were sulfonated using 3-mercaptopropyltrimethoxysilane (MTPS) and concentrated sulfuric acid to produce two catalysts with sulfonic groups: BCM-MTPS and BCM-SULF. These catalysts were tested in reactions for the synthesis of vanillin, a flavoring widely used in various industries. The acid-base titration to evaluate the acidic sites revealed that the BCM-MTPS catalyst had a surface acidity of 0.97 mmol H⁺ g⁻¹, while BCM-SULF had 2.29 mmol H⁺ g⁻¹. These data suggest that the functionalization of BCM-MTPS may not have been efficient, as its surface acidity index is lower than that of the original biochar, which had 1.24 mmol H⁺ g⁻¹. EDS analysis indicated that both catalysts have a typical composition of carbonaceous materials. However, no sulfur traces were detected in BCM-MTPS, suggesting the absence of sulfonic groups. In contrast, BCM-SULF showed a sulfur concentration of 5%. Catalytic tests, involving the oxidation of vanillyl alcohol to vanillin, were conducted for 1 hour under reflux at 80°C. The GC-MS results of the reaction without the catalyst showed a 34.5% conversion of vanillyl alcohol, the precursor reagent. For the BCM-MTPS and BCM-SULF catalysts, this conversion was 18.7% and 100%, respectively. Due to its high efficiency, BCM-SULF was subjected to 3 reuse reactions, and in the last reaction, it achieved approximately 80% conversion of the precursor. The vanillin conversion, the desired product, for BCM-MTPS and BCM-SULF was 8.8% and 11.9%, respectively. However, it was observed that in subsequent reactions with BCM-SULF, despite the loss of catalyst efficiency, vanillin conversion increased, reaching a maximum of 46.8% in the second reuse and 31.1% in the final cycle. This effect may be due to vanillin overoxidation, a phenomenon described in the literature as the further conversion of vanillin into other compounds. It is concluded that BCM-SULF showed better catalytic performance compared to BCM-MTPS. Therefore, the synthesis steps of BCM-MTPS should be reevaluated, and further characterizations and catalytic tests with BCM-SULF are recommended to improve vanillin conversion. This demonstrates that BCM-SULF is a promising catalyst for vanillin synthesis and other reactions requiring acid catalysis.
Murumuru seed shells; Heterogeneous catalyst; Biochar; Sulfonation
Copyright (c) 2024 Larissa Gatti, Maitê Campos, Ana Alice Costa, Marcos Costa, Nathalia Moraes, Carlos Costa, Geraldo Rocha Filho, Renata Noronha, Luis Nascimento (Autor) https://creativecommons.org/licenses/by/4.0
Transformação de resíduos ceramistas em estruturas cúbicas de CaO para aplicações industriais
A geração de resíduos pela indústria ceramista, especificamente cinzas ricas em cálcio, representa um desafio ambiental significativo. A reutilização desses resíduos traz diversos benefícios, pois, além de minimizar o impacto ambiental, gera valor agregado ao transformá-los em uma fonte de óxido de cálcio (CaO). Estudos mostram que o resíduo ceramista tem sido amplamente utilizado em aplicações industriais, sendo um potencial precursor para a síntese de materiais estruturados de óxido de cálcio, o que torna todo o processo mais econômico e ambientalmente amigável. O CaO estruturado possui uma ampla gama de aplicações, podendo ser utilizado como catalisadores heterogêneos na produção de biodiesel e como adsorventes. Nesse estudo, explorou-se a reutilização do resíduo ceramista como fonte de óxido de cálcio para a produção de catalisadores estruturados. Para a síntese do CaO o resíduo foi submetido a um processo de purificação, no qual foi utilizada uma solução de ácido clorídrico (HCl) 1:1 para promover a formação de CaCl₂, seguida da adição de uma solução de carbonato de sódio (Na₂CO₃) 1M, resultando em um precipitado mais puro de carbonato de cálcio (CaCO₃). Esse precipitado foi analisado por termogravimetria (TG/DTG), difração de raios-X (DRX) e fluorescência de raios-X (FRX). Com base nos resultados de TG, a temperatura de 800 °C foi escolhida para a calcinação em forno mufla, com uma taxa de aquecimento de 10 °C.min⁻¹. Após purificação e tratamento térmico, o resíduo foi submetido a um tratamento hidrotérmico em meio alcalino a 180 °C, durante 36 horas. O material obtido foi caracterizado por microscopia eletrônica de varredura (MEV). De acordo com os dados obtidos pelo FRX observou-se a eficiência do tratamento onde o estado in natura, o resíduo apresentava um teor de cálcio de 80% e com o tratamento de purificação, foi alcançando teores de 92%. A análise termogravimétrica para o resíduo purificado indicou a degradação do CaCO₃ entre 590 e 700 °C, justificando a escolha de 800 °C para a calcinação. Os resultados de difração de raios X confirmou a transformação do CaCO₃ em CaO após o tratamento térmico, com picos bem definidos e característicos do CaCO₃ na fase romboédrica para o material purificado e do CaO na fase cúbica para o material tratado termicamente com a ausência de fases carbonáticas tendo como referência as cartas JCPDS 85-1108 e JCPDS 75-0264 respectivamente. As imagens de MEV revelaram uma morfologia cúbica, com tamanho variando entre 119 e 288 μm, o que potencializa suas aplicações catalíticas. Dessa forma, esse trabalho mostrou uma alternativa viável de reutilização de resíduos industriais da atividade ceramista, agregando valor ao subproduto e oferecendo um material promissor para diversas aplicações industriais.
Copyright (c) 2024 Alrivan Gomes do Rego Júnior, Ronildo Ribeiro de Souza, Antony Jeová Teixeira da Silva, Adriana Paula Batista dos Santos, Vinícius Patrício da Silva Caldeira (Autor) https://creativecommons.org/licenses/by/4.0
Evaluation of barium removal by zeolite natural Clinoptilolite
The contamination of water bodies by toxic metals has been one of the main problems faced today (1). Among the techniques capable of treating water bodies contaminated by these metals, natural adsorbents such as zeolites stand out due to their good ion exchange capacity and low cost (2,3). Depending on their origin, natural waters may also have different metallic ions in their composition, so it is important to consider the influence of these ions on the removal of heavy metals (4). Thus, the aims to investigate the interference of alkali metals (Ca2+, Mg2+ and Na+) in barium removal through adsorption tests with the natural clinoptilolite zeolite. The raw material used to carry out this work was the clinoptilolite zeolite granted by the Celta Brasil company. Initially, the material was ground in Retsch model PM 100 equipment and was separated by sieving on a 400 mesh sieve. Then, the material was characterized using X-ray diffraction with the aid of the Bruker model D2 Phaser analyzer. Subsequently, two solutions were prepared with chloride salts with analytical purity. Solution A was adjusted to have a concentration of 40 mg.L-1 of barium and solution B was prepared containing 40 mg.L-1 of barium, 500 mg.L-1 of sodium, 1,000 mg.L-1 of calcium and magnesium. After that, the pH of both solutions was adjusted between 2 and 3 with concentrated nitric acid. Adsorption tests involved batch system with 300 mg of zeolite in contact with 50 ml of solution A and B, under agitation of 150 rpm for 4 hours at room temperature. The concentration of metal in solutions was evaluated through the ICP-OES ICAP 6300 duo. The X-ray diffractions presented a characteristic clinoptilolite pattern, which has intense reflections in 9.83, 22.33 and 25.74 at 2θ degrees. The outcome of the adsorption test in a solution A (barium cations) showed high efficiency regarding the barium removal, approximately 98.2%. However by performing the test in a solution B (Ca2+, Mg2+ and Na+ cations) under the same conditions, the effectiveness of barium removal fell to 61.3%. This behavior is due to the competitiveness of ions by occupying the active sites of the zeolite and this process depends on several factors such as: zeolite selectivity, hydration energy, ionic radius and concentration of the species involved (4.6). Therefore, it is evident that clinoptilolite zeolite was able to barium removal and although its effectiveness is affected by the presence of other metal ions, the values show their potential as an adsorbent and/or ion exchanger for treatment of industrial effluents.
water contamination, toxic metals, treatment, adsorption.
Copyright (c) 2024 Weslen Ismael de Miranda da Silva, Ana Laura Fernandes Pereira, Alrivan Gomes do Rêgo Júnior, Anne Gabriella Dias Santos, Vinicius Patrício Santos Caldeira (Autor) https://creativecommons.org/licenses/by/4.0
Synthesis of graphene oxide via electrochemical exfoliation of graphite from batteries
In recent years, there has been a significant increase in the amount of solid waste, including dry cell batteries. Although many countries have adopted regulations for recycling these materials, in many regions, batteries continue to be discarded in household waste, which can cause environmental problems. During battery dismantling, the graphite rods inside are not reused and end up being disposed of in landfills or incinerated. If incinerated, they are converted to CO2, further damaging the environment. Graphene obtained from graphite exfoliation demonstrates exceptional properties, presenting high electrical conductivity and thermal resistance. However, graphene synthesis faces technical difficulties and high costs, and electrochemical exfoliation is a promising technique for minimizing these problems. This study evaluated the use of graphite rods from new and used dry batteries to produce graphene oxide (GO) by electrochemical exfoliation, with the aim of reducing the disposal of solid waste. (Ferella; Michelis; Vegliò, 2008). The study began with the removal and preparation of graphite rods from new and used AA batteries (1.5 V). First, the rods were sanded and immersed in a 5% H2SO4 solution to remove the remaining electrolytic paste and were then used as electrodes in the manufacture of graphene oxide (GO). The synthesis optimization was carried out with new rods, and the optimized experimental condition was applied for the tests with the used rods. For the synthesis, the rods were immersed in 50 mL of H2SO4 solution, at different concentrations (0.1, 0.2 and 0.3 mol L−1). Exfoliation was performed in direct current and different voltages and times were evaluated. The produced material was filtered, washed until reaching neutral pH and dried in an oven. For characterization, the samples were dispersed in ultrapure water and analyzed by UV-Visible spectrophotometry. To evaluate the applicability of GO, a cyclic voltammetry study at 50 mV/s was carried out, in which a glassy carbon electrode (GCE) modified with the produced GO (GCE/GO) was used as the working electrode. The absorption spectra revealed bands between 220 and 230 nm, characteristic of GO, attributed to the π-π* transitions of the C=C bonds of the aromatic rings in the material, and a soft band between 350 and 450 nm, indicating n-p* transitions attributed to the presence of carbonyl groups in the GO nanosheets (Protopapa et al., 2022). The results showed that the synthesis in H2SO4 0.1 mol L−1 was more efficient and the produced GO was used to modify the surface of an GCE, which was tested in a 7.0 x 10−4 mol L−1 solution of potassium ferrocyanide in 0.10 mol L−1 of KCl. The cyclic voltammograms showed a significant increase in the redox peak currents of the ferro/ferricyanide pair, as well as a decrease in ΔEp, when compared to the results obtained using the GCE without modification. This behavior highlights the effectiveness of GCE/GO as an electrochemical sensor platform, which is attributed to the high electrocatalytic capacity, excellent support for electron transfer, and high surface area of ​​GO. This study demonstrates the potential of the electrochemical approach for both the production of GO and the use of ECV/GO as a platform for the development of sensors; it also shows the relevance of continuing research aimed at improving work with graphite from used batteries and the use of solid waste as a form of environmental protection.
Copyright (c) 2024 Georgia Jully Bezerra Araújo, Camila da Costa de Morais, Livia Islanny Fernandes de Melo, Crislânia Carla Oliveira Morais, Keurison Figueiredo Magalhães (Autor); Suely Souza Leal Castro (Tradutor) https://creativecommons.org/licenses/by/4.0
Geopolymer/zeolite composite from fly ash
Steel mills generate a high volume of solid waste in their production chain. A large thermoelectric plant produces around 1 million tons of waste per year, with reuse rates usually very low, which generates strong environmental impacts. One of these residues is fly ash, which is obtained from the burning of coal. The use of this type of material in the synthesis of compounds can represent an alternative that offers significant economic and environmental benefits. The conversion of these residues into materials such as geopolymers and zeolites, known for their adsorptive capacities, has proven to be a viable recycling route. This is due to the fact that fly ash has high levels of silica and alumina, which are fundamental components of both geopolymers and zeolites. This work aims to produce composites of geopolymer with zeolites, in the form of cartridges, using fly ash as the primary source of Si and Al. First, zeolite Y was synthesized via hydrothermal route employing colloidal silica (LUDOX 40) and sodium aluminate as Si and Al sources, respectively, and sodium hydroxide solution. Next, the obtained zeolite was added the geopolymer reaction mixture, which was prepared by mixing fly ash with kaolin, the latter as a supplementary source of alumina and silica, and NaOH solution as the mineralizing agent, and the transferring of the reaction mixture to cylindrical PTFE molds (30 mm base × 50 mm height) for subsequent hydrothermal treatment, giving rise to cylindrical monoliths with good mechanical stability. The resulting material was characterized by a set of techniques including X-ray diffraction, infrared absorption spectroscopy (FTIR), and scanning electron microscopy (SEM). X-ray analyses showed the presence of the zeolite Y, that was added during the preparation of the composite, and the appearance of other zeolitic phases, mainly sodalite, accompanied by an amorphous structure, which is expected for a geopolymer. This dual nature of the geopolymer, as well as the presence of the added zeolite Y, is highlighted in the images obtained by SEM and complemented by FTIR. These preliminary results suggest that the use of low-cost materials can be used to prepare porous materials with potential to be applied as efficient adsorbents for multipurpose uses.
Copyright (c) 2024 Thaiamis do Nascimento Lopes, Adonay Rodrigues Loiola, Ronaldo Ferreira do Nascimento (Autor) https://creativecommons.org/licenses/by/4.0
Desenvolvimento do catalisador core-shell NbOPO4 /H-ZSM-5
As zeólitas podem sofrer modificações para melhorar o caminho difusional, acessibilidade aos centros ativos, seletividade catalítica e vida útil, o que as torna ainda mais promissoras para aplicações. Outra abordagem para melhorar as propriedades das zeólitas é a criação de compósitos core-shell que combina as características de dois ou mais materiais. Dessa forma, este trabalho visou desenvolver um catalisador micro e mesoporoso combinando as propriedades da zeólita H-ZSM-5 e do NbOPO4. A sínteses da ZSM-5 e hierarquização ocorreram pelo método hidrotérmico. A obtenção da estrutura NbOPO4/H-ZSM-5 foi realizada por precipitação controlada. Os materiais foram caracterizados por difração de raios-X (DRX), adsorção/dessorção de nitrogênio (N2) a 77 K e microscopia eletrônica de varredura (MEV). De acordo com o resultado de DRX, a ZSM-5 apresentou fases cristalinas referentes a tipologia MFI, de acordo com o banco de dados International Zeolite Association – IZA. Após a hierarquização, a ZSM-5 manteve seus picos característicos. Por sua vez, o compósito apresentou o desaparecimento de alguns picos, que pode estar relacionado com a obstrução dos poros da ZSM-5 após a inserção do fosfato de nióbio. De acordo com a carta ICSD 0,1-0731609 nos ângulos 19,55, 25,78, e 27,9 apresentou a formação do fosfato de nióbio. A adsorção e dessorção de N2 a 77K para a zeólita ZSM-5 mostrou uma isoterma do tipo I, característica de sólidos microporosos. Enquanto a HZSM-5 apresentou uma combinação de isotermas do tipo I e IVa, indicando características micro-mesoporosas. As isotermas do tipo IV são típicas de materiais mesoporosos, exibindo uma condensação capilar com histerese. Por sua vez, a isoterma do compósito é a combinação do tipo I com o tipo II indicando a presença de espaços interparticulares. As imagens de MEV do compósito mostrou que ambos os materiais mantiveram suas estruturas. A ZSM-5 demonstrou uma morfologia de partículas esféricas formadas por um aglomerado de pequenos cristais corroborando com a literatura, e o fosfato de nióbio um aglomerado de partículas laminares, sendo possível observar um indício de estrutura core-shell tendo a ZSM-5 como núcleo e NbOPO4 a casca revestindo/cobrindo a zeólita. De acordo com os resultados, conclui-se, que ocorreu a formação da ZSM-5 como também o processo de hierarquização e formação do compósito. Tais materiais demostraram ser promissores para serem aplicados em diferentes tipos de reações.
Copyright (c) 2024 Manoel B. Lima Neto, Antony J. T. Silva , Antonia L. S. Nascimento, Daniele S. Oliveira , Anne G. D. Santos , Vinicius P. S. Caldeira (Autor) https://creativecommons.org/licenses/by/4.0
Copyright (c) 2024 Ruth Andrade, Alessandra Raiany de Oliveira, Keurison Figueredo Magalhães, Suely Souza Leal de Castro (Autor) https://creativecommons.org/licenses/by/4.0
Síntese e caracterização de nanotubos de CeO2 de paredes porosas
Os nanomateriais têm atraído grande interesse na comunidade científica principalmente por suas propriedades morfológicas e composição química. Em função dessas características, os nanotubos de cério destacam-se por suas características estruturais e funcionais, pois têm potencial para aplicação em catálise, sensores e remoção de poluentes ambientais. A síntese hidrotérmica alcalina tem sido utilizada para a obtenção de nanotubos de óxido de cério (CeNTs). Em virtude da sua baixa área específica, etapas subsequentes de síntese podem ser utilizadas para melhorar essas propriedades. O diferencial desse trabalho é a realização de síntese hidrotérmica em autoclave seguida por um tratamento realizado em temperatura ambiente para promover a formação de poros na superfície do material. Para isso, a síntese foi realizada utilizando uma solução de NaOH 10 M, que passou por um banho ultrassônico de 15 minutos, seguida pela adição da fonte de cério sob agitação por 30 minutos, e posteriormente submetida a banho ultrassônico por 15 minutos. Em continuidade, a mistura foi colocada em autoclave de teflon revestido de aço inoxidável e submetida a tratamento hidrotérmico a 125°C por 72 horas. O material foi lavado até atingir o pH neutro, e parte do material foi submetido a uma etapa adicional de tratamento alcalino estático em autoclave de Teflon revestido de aço inoxidável à temperatura ambiente por 30 dias, e denominado de CeO2-NW-NT. Parte do material obtido foi submetido a tratamento térmico 450°C, com rampa de aquecimento de 10 C/min, sem fluxo, e denominado de CeNW-NT-450. Os materiais obtidos foram caracterizados por Difração de Raios X (DRX), Análise Termogravimétrica (TG), Microscopia Eletrônica de Varredura (MEV) e Microscopia Eletrônica de Transmissão (MET). Os resultados de DRX mostraram que os materiais são constituídos de CeO2 com fase fluorita cúbica em ambas as amostras, com uma maior cristalinidade na amostra calcinada. A análise Termogravimétrica (TG) mostraram eventos de perda de massa a altas temperaturas relacionadas ao processo de desidratação. Os resultados de MEV e MET para o CeNTs revelaram a formação de alto rendimento da morfologia nanotubular, com a presença do oco no interior das nanoestruturas. A formação de nanotubos com paredes porosas na superfície foi observado para o CeO2-NW-NT, em que a morfologia foi mantida após o tratamento térmico. Ademais, o processo de calcinação não destruiu a morfologia de interesse, preservando os poros nas paredes dos tubos. Portanto, a formação dos nanotubos de CeO₂ de parede porosa foi alcançado com sucesso, através da rota de tratamento alcalino estático, proporcionado materiais com maior superfície de contato, e que a morfologia foi mantida após o tratamento térmico realizado, mostrando que os CeO2-NW-NT apresentam uma interessante estabilidade térmica.
Copyright (c) 2024 Maurício Nunes da Silva, Beatriz Ferreira Paulino, Vinícius Patrício da Silva Caldeira, Anne Gabriella Dias Santos , Adriana Paula Batista dos Santos (Autor) https://creativecommons.org/licenses/by/4.0
Influência da temperatura na síntese de nanoestruturas de CeO2 utilizando KOH como fonte alcalina
Nanomateriais têm ganhado destaque devido às suas propriedades físicas e químicas aprimoradas, comparadas com o material de origem. Dentre as estruturas dos meais de terras raras, as nanoestruturas de cério se destacam em virtude de suas propriedades eletrônicas, ópticas e capacidade de armazenamento e liberação de oxigênio. Este estudo investiga a síntese de nanoestruturas de CeO₂, por meio de uma metodologia hidrotérmica alcalina sem o uso de templates, utilizando diferentes temperatura e KOH como agente mineralizador. O objetivo deste estudo foi investigar a influência da temperatura no tipo e rendimento da morfologia e no tamanho das nanoestruturas formadas. O processo consistiu na dissolução da fonte de cério em uma solução de KOH a 10 mol·L⁻¹, que foi envelhecida em diferentes temperaturas na estufa (80, 125, 150 e 180°C). As amostras obtidas foram nominadas CeNTs-KOH-T e caracterizadas por difração de raios X (DRX), análise termogravimétrica (TG) e microscopia eletrônica de varredura (MEV). Os resultados de DRX mostraram que de acordo com a posição dos picos (111, 200, 220, 311, 222, 400, 331, 420, 422), o material é constituído de CeO2 com uma estrutura fluorita cúbica, e que há um aumento da intensidade dos picos dos materiais a medida em que a temperatura das sínteses aumenta. Isso ocorre por a temperatura tem forte influência sobre o crescimento do cristalito de CeO2 e consequentemente promove uma melhor formação da estrutura cristalina. As curvas TG dos materiais obtidos apresentaram quatro eventos de variações de massas para as amostras de 80 e 125 sendo: o evento I está relacionado a perda de água adsorvida no material; o evento II de perda de massa é atribuído a desidratação da superfície externa do nanomaterial; o evento III é devido a desidratação do diâmetro interno dos CeNTs; no último evento é observado um pequeno ganho de massa, observado para as amostras obtidas a 125, 150 e 180 °C, e que pode estar relacionado à oxidação de Ce3+ a Ce4+, que é devido ao processo de recristalização para formar as nanoestruturas, ocorrer a formação de defeitos estruturais ou vacâncias de oxigênio. Nas amostras de CeNTs-KOH-150 e CeNTs-KOH-180 é observado que no evento IV o ganho de massa é superior a das outras amostras, o que pode indicar que nelas a presença de espécies Ce3+ estão em maior quantidade. Na amostra de 150 C, o material se manteve estável até acima de 700 °C acima dessa temperatura apresentou um ganho de massa. Já a amostra obtida à 180 °C apresentou ganho de massa em temperaturas mais baixas o que pode ser devido uma maior deficiência de vacâncias e um alto rendimento na oxidação do Ce3+ ocasionado pela alta temperatura de envelhecimento na síntese. As imagens obtidas por MEV revelaram a formação de morfologias distintas nas amostras de CeO₂, a depender da temperatura de síntese utilizada. A presença de alto rendimento da morfologia fibrilar foi observada nas sínteses realizadas nas temperaturas de 80 e 125°C. Com o aumento da temperatura para 150°C e 180°C, verificou-se uma transição nas morfologias, com um rendimento crescente para morfologia cúbica. A presença majoritária dessas estruturas cúbicas nas amostras sintetizadas a temperaturas mais elevadas sugere que o aumento da temperatura acelerou a nucleação e o crescimento anisotrópico, promovendo uma reorganização estrutural do CeO2 para a formação de nanocubos. Assim, as sínteses de nanoestruturas de CeO₂ foi bem-sucedida utilizando o método hidrotérmico alcalino, e o controle da temperatura foi essencial para ajustar o tipo de morfologia, favorecendo a formação de morfologia fibrilar em temperaturas mais baixas e a formação de nanocubos em temperaturas mais elevadas, com estruturas mais cristalinas e possivelmente com maior quantidade de defeitos estruturais.
: Nanotubos, nanocubos, Síntese Hidrotérmica, KOH, Caracterização
Copyright (c) 2024 Beatriz Paulino, Mauricio Nunes, Adriana Santos, Anne Gabriella (Autor) https://creativecommons.org/licenses/by/4.0
Síntese via soft template de nanoesferas de Silício e Alumínio
A crescente demanda por processos eficientes e sustentáveis ​​tem impulsionado pesquisas voltadas à produção de materiais com propriedades físicas e químicas avançadas, como as nanopartículas de sílica mesoporosa (MSNs). Dentre esses materiais, destacam-se as nanoesferas de sílica, que oferecem vantagens como síntese rápida, baixa densidade, ordenamento estrutural e alta área específica. No entanto, a estrutura de suas redes possui ausência de sítios ativos, devido ser constituída unicamente por sílica, em que a incorporação de metais, como o alumínio, pode aprimorar suas propriedades ácido-base e catalíticas. Nesse sentido, este trabalho visa sintetizar e avaliar a morfologia e estrutura dessas esferas com inserção de alumínio. A produção das nanoesferas de sílica foi conduzida de acordo com o método soft-template, envolvendo a dissolução de CTAB como direcionador orgânico, etanol e água em meio alcalino, seguida da adição de TEOS como fonte de sílica. Para a produção do catalisador de sílicio/alumínio, o metal foi incorporado diretamente com a fonte de sílica na proporção Si/Al de 50. As amostras, denominadas NE Sí e NE Sí/Al, foram lavadas, calcinadas e submetidas a análises de Difração de Raios X (DRX) no equipamento Bruker D2 Phaser e Microscopia Eletrônica de Varredura (MEV) no equipamento Tescan Mira 3. As medições da distribuição do tamanho das partículas foram realizadas no programa ImageJ. Os resultados de DRX evidenciaram em ambas as amostras, um único pico em torno de 22° (100) característico de agregados de estrutura amorfa de óxido de silício, comum em materiais sintetizados com TEOS. Não foram identificados outros picos cristalográficos ou picos referentes à formação de óxido de alumínio na amostra NE Sí/Al, sendo esse um indício de que o metal pode estar presente na estrutura das esferas. Nas imagens de MEV da amostra NE Si, foi possível observar a formação de partículas esféricas bem definidas, com tamanhos em torno de 500 a 600 nm e formatos uniformes, devido à estrutura do material ser composto exclusivamente por ligações de silício e oxigênio. Nas imagens de NE Si/Al observou-se a formação de esferas definidas, porém com tamanhos menores de 300 a 400 nm e mais irregulares. Ao comparar as partículas da amostra NE Sí/Al com a amostra NE Si, foi possível evidenciar a diferença na uniformidade, que pode estar relacionada à diferença nos raios atômicos de Si e Al. Esse comportamento também pode ser um indicativo de que parte do alumínio possa estar inserida na rede das esferas. Assim, nanoesferas uniformes de silício foram sintetizadas com sucesso, através do método de soft template, e a síntese das nanoesferas de Si/Al com a inserção direta de alumínio também foi eficaz, resultando em morfologia esférica bem definida e, promovendo a variação de tamanhos de estruturas esféricas.
Copyright (c) 2024 Joanna Gabrielly de Souza, Fernando R. D. Fernandes, Adriana P. B. Santos, Sibele B. C. Pergher, Anne G. D. Santos (Autor) https://creativecommons.org/licenses/by/4.0
Zeólita ZSM-5 hierarquizada aplicada na termodegradação de biomassa e PEAD por análise termogravimétrica
Os plásticos são amplamente utilizados no cotidiano pela sua versatilidade. Entretanto, o aumento na produção de materiais descartáveis de decomposição lenta gera problemas ambientais alarmantes. Nesse contexto, o tratamento termocatalítico de polímeros utilizando biomassa lignocelulósica sob a presença dezeólitas se destaca. As zeólitas são vantajosas por suas propriedades, incluindo alta capacidade de troca iônica, capacidade de adsorção, elevada área específica, seletividade de forma e estabilidade térmica. Além disso, o processo de hierarquização de zeólitas contribui para a formação de uma porosidade secundária que consiste em poros com diferentes diâmetros, aumentando sua acessibilidade. A adição da biomassa também pode influenciar na eficiência energética do processo e nos produtos finais. Diante disso, este trabalho estudou a degradação termocatalítica de uma mistura de PEAD com biomassa lignocelulósica utilizando zeólita ZSM-5 hierarquizada como catalisador. As zeólitas hierarquizadas possuem uma porosidade secundária adicional além dos microporos que proporciona maior acessibilidade. A zeólita ZSM-5 foi sintetizada utilizando template orgânico e uma razão molar Si/Al de 25. O material foi calcinado a 550°C por 6 h. Para obter a forma protônica, realizou-se troca iônica com solução de NH₄Cl 1,0 mol. L⁻¹ a 80 °Cpor 2 h, três vezes, seguido de calcinação a 400 °C por 3 h. O polietileno de alta densidade (PEAD) foi misturado com a biomassa (serragem de madeira) por quarteamento 10 vezes. Em seguida, adicionou-se a ZSM-5 e homogeneizou-se novamente essa mistura por quarteamento, de forma semelhante. Por fim, a degradação termocatalítica ocorreu em um uma termobalança. Os resultados confirmaram a síntese bem-sucedida das zeólitas ZSM-5 padrão e hierarquizada. O DRX revelou índices de Miller [(011), (200), (051), (033)] com picos estreitos e intensos a alto ângulo, indicando uma estrutura cristalina do tipo MFI. As curvas termogravimétricas indicaram a presença de dois eventos de perda de massa, onde a primeira etapa representa a decomposição da parte da biomassa, enquanto a segunda etapa representa a decomposição do polímeroPEAD. A zeólita ZSM-5, especialmente na forma hierarquizada, demonstrou eficiência notável na termodegradação. Essa eficiência foi observada na redução da temperatura necessária para a degradação do polímero. Isso se deve à porosidade secundária criada na estrutura hierarquizada, que facilita o acesso das moléculas do polímero aos sítios ativos do catalisador, reduzindo as limitações difusionais. A atuação da biomassa na termodegradaçãodeve ser melhor avaliada pela identificação dos produtos finais e sua seletividade, a fim de inferir uma possível sinergia com o catalisador. Diante disso, esse trabalho ressalta o potencial das zeólitas com estrutura hierarquizada empregadas como catalisadores em processos de reciclagem química de polímeros, e a positivapossibilidade da termodegradação combinada de polímeros e biomassa, contribuindo para a inovação na gestão de resíduos plásticos.
Copyright (c) 2024 Britney Eliza B. Cavalcante de Sena, Anne Layanne M. de Souza, Raissa N. Silva, Jefferson Lhankaster T. G. Filho, Vinicius Patricio S. Caldeira, Anne Gabriella Dias Santos (Autor) https://creativecommons.org/licenses/by/4.0
Evaluation of BiVO4 as a photocatalyst in the photocatalysis process of effluent generated in biodiesel production
In recent years, Brazil has excelled in the production of biodiesel, diversifying its energy matrix. Law No. 11.097/2005 establishes a gradual increase in the percentage of biodiesel in diesel, from 2% to 12%. Biodiesel is obtained by transesterifying triglycerides from vegetable oils or animal fats with methanol or ethanol, generating esters and glycerin. Purification involves washing, resulting in effluents that need to be treated and reused. With this, it is possible to reduce the amount of waste and minimize environmental impacts, making the process more sustainable and efficient [1]. To treat these effluents, advanced oxidative processes such as heterogeneous photocatalysis are highly effective, using solid catalysts activated by UV light to decompose organic and inorganic pollutants present. Bismuth vanadate (BiVO₄) stands out for its high photocatalytic efficiency, especially when activated by UV light, making it an effective and promising alternative for mitigating the negative impacts associated with environmental pollution. The aim of this study is to use heterogeneous photocatalysis with BiVO₄ and UV radiation to promote the efficient and sustainable degradation of contaminated effluents generated in biodiesel production, with a view to environmental protection. The photocatalyst was synthesized via the hydrothermal method using ammonium metavanadate and bismuth nitrate, after which the powder was calcined at 400oC. The biodiesel was obtained via methyl transesterification with sodium hydroxide (NaOH), and soybean oil heated to 60°C under stirring for 1 hour. After 24 hours, the glycerin was separated and the biodiesel washed until the residual water reached pH 7. The photolysis and photocatalysis experiments were conducted using an 80W mercury lamp in a jacketed reaction cell. The pH of the samples was kept neutral and the concentrations of BiVO₄ varied between 500 and 1000 ppm. Aliquots of 5 mL were taken throughout the experiment and centrifuged to determine pH, conductivity and temperature and UV-Vis in the 200 to 800 nm range, the analyses were carried out and quickly returned to the reaction medium. Representative samples from the initial and final times were preserved for Total Organic Carbon (TOC) analysis in order to gauge the efficiency of the degradation processes. The study compared the effectiveness of photocatalysis with BiVO₄ and photolysis in the treatment of biodiesel effluents. Photocatalysis with 500 ppm of BiVO₄ at neutral pH proved to be the most efficient, with a degradation rate of 30%, while the sample with 1000 ppm and photolysis performed less well. These results indicate that photocatalysis with 500 ppm is a promising solution for treating effluents, with the potential to be applied in industrial processes, helping to reduce environmental impacts.
Copyright (c) 2024 Maria Jessica Lima Barbosa, Maria Eduarda Araujo Vieira , Alesssandra Raiany de Oliveira, Keurison Figueredo Magalhães, Suely Leal de Castro (Autor) https://creativecommons.org/licenses/by/4.0
Evaluation of Bi25FeO40 obtained from mining waste as a photocatalyst in norfloxacin degradation
Norfloxacin (NOR) is a widely used antibiotic, frequently detected in water bodies, which raises significant environmental concerns, mainly due to its persistence and resistance to conventional wastewater treatment methods. This scenario highlights the need to develop and implement new approaches, such as Advanced Oxidative Processes (AOPs), which have the ability to effectively degrade these organic pollutants. Among the AOPs, heterogeneous photocatalysis stands out, a process that involves the use of a solid catalyst, which, when irradiated, promotes chemical reactions capable of decomposing contaminants [1]. Recently, research focusing on catalysts obtained from mineral waste has gained interest, with bismuth ferrite (Bi25FeO40) being one of these materials, presenting high photocatalytic activity due to its optical properties [2]. In this work, the efficiency of Bi25FeO40 as a photocatalyst in the degradation of NOR, under UV-visible irradiation, was investigated. Bi25FeO40 was synthesized via solid-state reaction and characterized by energy-dispersive X-ray fluorescence spectroscopy (EFRXF), diffuse reflectance spectroscopy (DRS) and X-ray diffraction (XRD). Photolysis and photocatalysis tests were performed in NOR solution (20 ppm), using a concentration of 500 ppm of Bi25FeO40, neutral pH and analyzed by UV-Vis absorption spectroscopy and ion chromatography. XRD analysis of Bi25FeO40 identified the formation of the silenite phase (COD ID 4030661), with cubic symmetry and space group 123, in addition to the presence of a spurious phase BiClO2Pb, with phase fractions of 95.05% and 4.95%, respectively. The band gap of the material was 3.01 eV. The results of the photolysis and photocatalysis tests indicated NOR degradation rates of 21.8% and 42.2%, respectively. The photolysis and photocatalysis processes followed pseudo-first order kinetics, with rate constants of 1.2 x 10-3 min-1 and 2.5 x 10-3 min-1, respectively. In the photocatalysis test, Ion chromatography studies revealed the formation of short-chain organic acids, such as acetate and formate, confirming the degradation of NOR. Thus, the results obtained demonstrate that Bi25FeO40 presents a promising performance in NOR removal under UV-visible irradiation.
Copyright (c) 2024 Alessandra Raiany Oliveira, Vitória C. S. Silva, Alan M. S. Silva, João M. Soares, Keurison F. Magalhães, Suely S. L. de Castro (Autor) https://creativecommons.org/licenses/by/4.0