Estudos da decomposição direta do monóxido de nitrogênio sobre zeólitas ZSM-5 modificadas /

Dissertação (Mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico

Preparação e caracterização de bentonitas modificadas e sua utilização na clarificação de óleos vegetais

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia QuímicaDuas amostras de argilas bentoníticas argentinas de composições mineralógicas diferentes foram ativadas com ácidos clorídrico e sulfúrico, em diferentes concentrações e tempos, com o intuito de se avaliar a influência de suas propriedades estruturais, decorrentes do tratamento ácido, sobre a clarificação de óleos vegetais. Inicialmente foi realizado um conjunto de ensaios de caracterização nas amostras em seu estado natural, o que permitiu constatar que as argilas em questão eram constituídas principalmente de argilominerais esmectíticos, contendo impurezas tais como quartzo, feldspato, caulinita e gesso. Para o estudo dos efeitos do ataque ácido nas estruturas das argilas, as amostras naturais e depois de ativadas foram caracterizadas através de análise química, difração de raios-X, análise térmica diferencial e termogravimétrica, e espectroscopia de infravermelho. Dos ensaios de clarificação de óleo, observou-se uma influência das propriedades estruturais dos produtos (argilas ativadas) sobre seu desempenho para a clarificação de óleos. As argilas ativadas apresentaram um poder de clarificação de óleos vegetais comparável ou superior ao de argilas comerciais utilizadas como referência. As argilas foram também avaliadas para outras aplicações de interesse: a) verificar seu potencial para uso como fluidos de perfuração de poços de petróleo; (b) determinar suas propriedades catalíticas para a reação de isomerização do b-pineno

Enhanced catalytic performance of CuFeS2 chalcogenide prepared by microwave-assisted route for photo-Fenton oxidation of emerging pollutant in water

In this work, CuFeS2 chalcogenide powders were easily produced by conventional and microwave methods, and for the first time, the influence of synthesis route on their properties and consequent catalytic activity in the photo-Fenton reaction was investigated. X-ray diffraction, N2 adsorption–desorption isotherms, Fourier-transform infrared spectroscopy, transmission and scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were employed to characterize and point out the main properties and differences among samples. The CuFeS2 particles were used as catalysts for tartrazine dye degradation by the photo-Fenton reaction under visible irradiation. The results showed that the CuFeS2 prepared by microwave-assisted method (CuFeS2–MW) present higher crystallinity, higher concentration of Fe2+ on its surface and remarkable catalytic activity, reaching 99.1% of tartrazine decolorization and 87.3% of mineralization, at a rate twice as fast as CuFeS2 prepared by the conventional method. The catalyst showed high catalytic efficiency and stability during the reaction after five recycles. The hydroxyl radical was revealed to be the reactive species responsible for tartrazine degradation. A mechanism was proposed to elucidate how these free radicals are generated from the catalytic decomposition of H2O2 by CuFeS2–MW

Representation of phase equilibria and densities for complex systems using a van der waals volume translated equation of state with a unifac mixing rule

This work investigated the applicability of the van der Waals cubic equation of state (EoS) with volume translation (vdWt), using the modified Huron-Vidal (MHV2) mixing rule with the UNIFAC (UNIQUAC Functional Activity Coefficients) model for describing phase equi-librium and density data for a series of complex systems over wide ranges of temperature (T) and pressure (P). Some limitations were identified in the prediction of the experimental data collected, e.g., systems with highly associating components, but in general, the EoS vdWt+MHV was able to satisfactorily represent both phase equilibrium and volumetric behavior.En este trabajo se investigó la aplicabilidad de la ecuación de estado cúbica, de Van der Waals, con translación en volumen (vdWt). Para la regla de mezcla, se aplicó el método de Huron-Vidal modificado (MHV2), con el modelo UNIFAC (UNIQUAC funcional coefi-ciente de actividad) para describir datos del equilibrio de fases y la densidad para una serie de sistemas complejos; en amplias gamas de temperatura (T) y presión (P). Se encontraron algunas limitaciones en la predicción de los datos experimentales recogidos, por ejemplo, en los sistemas con componentes altamente asociativos, la ecuación vdWt+MHV demostró capacidad para representar de manera satisfactoria, tanto el equilibrio de fases como el comportamiento volumétrico

Transforming shrub waste into a high-efficiency adsorbent: Application of Physalis peruvian chalice treated with strong acid to remove the 2,4-dichlorophenoxyacetic acid herbicide

In this study, the chalice generated from the production of the Physalis peruviana fruit was subjected to a treatment with sulfuric acid and applied in the adsorption of 2,4-Dichlorophenoxyacetic acid (2,4-D). The precursor, and the treated material before and after the adsorption, were analyzed by different techniques. After the acid treatment, it was found that the surface was changed from a smooth to an irregular surface with the presence of cavities with irregular size. The adsorption was favored at pH = 2 and with a dosage of 0.8 g L−1. The pseudo-second-order model was the best to represent kinetic data. The isothermal experiments were well represented by the Langmuir and Tóth models, reaching a high capacity of 244 and 320 mg g−1, respectively. The computed thermodynamic values show that the 2,4-D adsorption was spontaneous and exothermic. Overall, this study indicates that the Physalis peruviana chalice treated with strong acid presents great potential as an alternative material for the adsorption/removal of 2,4-D herbicide from liquid effluents

Synthesis of citrate–modified cufes2 catalyst with significant effect on the photo–fenton degradation efficiency of bisphenol a under visible light and near–neutral PH

In this study, for the first time, citric acid was employed as a chelating agent in CuFeS2 synthesis in order to accelerate the regeneration of Fe2+ during the photo–Fenton reaction, promoting a faster production of •OH radicals. The novel CuFeS2 material showed remarkable catalytic efficiency for bisphenol A (BPA) degradation during the photo–Fenton process under visible light and near–natural pH, with a rate 10 times faster than that of CuFeS2 prepared without citrate. Furthermore, CuFeS2 promoted rapid generation of •OH radicals and showed efficient H2O2 consumption, sustaining the catalytic efficiency and stability even after 4 consecutive cycles of use. CuFeS2 was also efficient for BPA degradation from a municipal wastewater treatment plant effluent. BPA by–products were identified and a mechanism for BPA degradation was proposed. After the photo–Fenton process, no Fe3+ species were identified on the catalyst surface by X–ray photoelectron spectroscopy (XPS), indicating that citric acid accelerated the conversion of Fe3+/Fe2+, thus increasing the generation of •OH and the process efficiency

Highly effective adsorption of synthetic phenol effluent by a novel activated carbon prepared from fruit wastes of the Ceiba speciosa forest species

Fruit wastes of the Ceiba speciosa forest species were employed as raw material for preparing activated carbon towards removing phenol from water. Concave cavities spread over the entire material surface were observed from characterization results, resulting in a high surface area, 842 m2 g−1. Adsorption isotherm and kinetic studies were performed under the best conditions of pH (7) and adsorbent dosage (0.83 g L−1). An increase in temperature from 298 K to 328 K disfavored the phenol adsorption, decreasing from 156.7 to 145 mg g−1 for the best-fit model, Langmuir. The thermodynamic results indicated that the phenol adsorption was spontaneous, favorable, and exothermic. The phenol concentration decay shows that the equilibrium is reached at 120 min. The pore volume and surface diffusion model (PVSDM) was employed satisfactorily to describe the phenol decay behavior. The surface diffusion coefficient values were in the range of 10−9 cm2 s−1. The external and the internal mass transfer were the rate-controlling mechanisms. Therefore, the application of fruit wastes from Ceiba speciosa as raw material for preparing activated carbon proved very efficient towards removing phenol from an aqueous medium. The activated carbon is an alternative material to suppress water contamination due to phenol-derived species

Adsorption of ibuprofen, ketoprofen, and paracetamol onto activated carbon prepared from effluent treatment plant sludge of the beverage industry

The presence of emerging contaminants such as pharmaceuticals in aquatic means presents as a serious threat, since their real consequences for the environment and human health are not well known. Therefore, this work consisted of preparing and characterize sludge-derived activated carbons (beverage sludge activated carbon – BSAC and acid-treated beverage sludge activated carbon - ABSAC) to investigate their use in the pharmaceuticals adsorption in aqueous media. The morphology study has demonstrated that ABSAC, unlike BSAC, exhibited an abundant porous structure, with smaller particles and bigger roughness. Adsorption results indicated that the ABSAC was more effective that BSAC, since it presented superior surface area (642 m2 g-1) and total pore volume (0.485 cm3 g-1) values. Pseudo-second-order kinetic model was more suitable to predict experimental data. Sips model best described the equilibrium data, with maximum adsorption capacities of 145, 105, and 57 mg g-1 for paracetamol, ibuprofen, and ketoprofen, respectively. Besides, the sludge-derived adsorbent was highly efficient in the treatment of a simulated drug effluent, removing 85.16% of the pharmaceutical compounds. Therefore, the material prepared in this work possesses intrinsic characteristics that make it a remarkable adsorbent to be applied in the treatment of pharmaceutical contaminants contained in industrial wastewater

Investigation of the reaction pathway for degradation of emerging contaminant in water by photo-Fenton oxidation using fly ash as low-cost raw catalyst

In this work, fly ash from a Brazilian thermal power plant was employed as a low-cost raw catalyst for Procion red degradation by photo-Fenton process. The ash was characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), nitrogen adsorption/desorption isotherms (BET), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectrometry (EDX). The material had an iron content of 4.10 wt%, distributed homogeneously on the solid surface. The ash particles showed mainly spherical morphology between 0.5 and 20 µm. The catalyst presented promising activity, reaching 93% of dye decolorization at 60 min of reaction, and 85% of organic load removal at 240 min. The predominant oxidizing species involved on the degradation of dye molecules during the photo-Fenton reaction were the hydroxyl radicals (HO·). The material showed remarkable stability and reusability after five successive cycles of reuse. The reaction intermediates were identified by LC/MS analysis and a reaction pathway was proposed

Síntese de CoFe2O4 sobre os suportes MgAl2O4 e ZSM-5 para uso na degradação de poluente orgânico pelo processo foto-Fenton heterogêneo sob irradiação visível e solar

Neste trabalho, ferrita de cobalto (CoFe2O4) foi sintetizada sobre aluminato de magnésio (MgAl2O4) e zeólitaZSM-5 e a atividade catalítica desses materiais na reação foto-Fenton visando a decomposição de umpoluente orgânico em solução aquosa foi avaliada. Ferrita de cobalto foi sintetizada sobre os suportes pelarota solvotérmica. Os materiais magnéticos foram caracterizados por difração de raios-X, isotermas deadsorção/dessorção de nitrogênio, microscopia eletrônica de varredura e espectroscopia de energia dispersivade raios-X. Os catalisadores foram avaliados na degradação de corante amaranto sob irradiações visívelartificial e solar. Os sistemas produzidos CoFe2O4/MgAl2O4 e CoFe2O4/ZSM-5 apresentaram satisfatóriasatividades catalíticas, sendo superior comparado a ferrita de cobalto pura. As atividades catalíticas paraambos os sistemas foram superiores quando do uso de irradiação solar, atingindo 95 % de descoloração e80 % de mineralização em 30 e 240 min de reação, respectivamente. Portanto, MgAl2O4 e ZSM-5 comosuportes para a ferrita de cobalto apresentam-se como materiais promissores para a degradação de poluentesorgânicos em soluções aquosas através da reação foto-Fenton heterogênea.Palavras-chave: ferrita de cobalto, decomposição de poluente orgânico, foto-Fenton, propagação da energiasolar