Navegando por Assunto "Pollutants"

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Acesso aberto (Open Access)
Produção de material zeolítico em escala semi piloto com o calor proveniente da dissolução de hidróxido de sódio
(Universidade Federal do Pará, 2025-02-05) LIMA, Haianny Beatriz Saraiva; COSTA, Deibson Silva da; http://lattes.cnpq.br/1521124351431087; HTTPS://ORCID.ORG/0000-0002-2165-2628; ESTUMANO, Diego Cardoso; http://lattes.cnpq.br/5521162828533153; https://orcid.org/0000-0003-4318-4455
The increasing demand for zeolitic materials, due to their high adsorption capacity, selectivity, and ion exchange, highlights the need for more efficient and sustainable production methods. Thus, the study aimed to produce zeolites on a semi pilot scale from kaolin waste, utilizing reactive heat for hydrothermal synthesis and applying these zeolites for copper ion adsorption. The methodology involved drying, disaggregation, and calcination of the kaolinitic waste, followed by the synthesis of the zeolitic material. Characterization of the materials was performed using X-ray Diffraction (XRD), X-ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), and Thermogravimetric Analysis (TGA), Differential Thermogravimetric Analysis (DTG), and Differential Scanning Calorimetry (DSC). Subsequently, equilibrium isotherms were conducted at temperatures of 25 ºC, 35 ºC, 45 ºC, 55 ºC, 65 ºC, 75 ºC, 85 ºC, and 95 ºC, along with parameter estimation to study the adsorption mechanisms and the adsorbate/adsorbent interface. Additionally, modeling of the adsorption process for hydrogen sulfide (H2S) and carbon dioxide (CO2) gases was carried out, using experimental data from the literature and employing analytical breakthrough curve models to describe the adsorption phenomenon in continuous flow. The results confirmed the predominant presence of kaolinite in the waste, the efficiency of the calcination process, and the formation of zeolitic material, evidenced by the mineralogical and chemical composition, as well as the cubic morphology characteristic of zeolite 4A and the spherical shapes of sodalite. Thermal analyses elucidated changes associated with water loss and phase transitions. Adsorption tests demonstrated that the produced material was effective in removing copper ions, with a maximum amount adsorbed of 782,76 mg/g at 95 ºC, indicating a good interaction between the adsorbent and the adsorbate. Furthermore, the use of Bayesian techniques for parameter estimation in isotherm and breakthrough curve models enabled a better understanding of the process dynamics. Finally, this study demonstrated the feasibility of producing zeolites from kaolin residue on a semi-pilot scale using reactional heat, offering an approach that is less harmful to the environment and reduces costs through the reuse of industrial waste and energy optimization of the process.
Acesso aberto (Open Access)
Simulação computacional da adsorção dos poluentes benzeno, tolueno e p-xileno sobre carvão ativado
(Universidade Federal do Pará, 2013-12-27) COSTA, Wanessa Almeida da; MARTELLI, Marlice Cruz; http://lattes.cnpq.br/1213009262936026; BRASIL, Davi do Socorro Barros; http://lattes.cnpq.br/0931007460545219
The greatest problems of groundwater and soil contamination are assigned to monoaromatic hydrocarbons which are the most soluble and the most mobile constituents of the fraction of certain substances, such as gasoline. To remove these contaminants, adsorption by activated carbon is the most widely used method, for it presents a significant ability to adsorb organic low molecular weight components, such as benzene, toluene and p-xylene. In this work, we verified the adsorption on activated carbon thereof via computer simulation. As base, we used the postulated model of charcoal prepared by Bourke et al. (2007). Several steps have been completed since the design of the structures of carbon and pollutants to the molecular dynamics phase. For the conformational analysis of the coal’s structure, it was used the semi-empirical method PM3 and for the molecular dynamics technique, the AMBER force field FF99SB. The structure went through a heating at constant pressure until it reaches a final temperature of 298K (25ºC), being its information collected every 50 ps. Subsequently, the structure was submited to equilibrium system at a constant temperature of 298K (25ºC) for 500ps for its information can be analyzed. Finally, the system was then submited to molecular dynamics during 30ns. After analyzing the results, it was found that the ether, lactone and carbonyl (ketone) groups present in the structure of activated carbon provide to it acid feature and because of this and its consequent negative surface charge, adsorption has become viable once the pollutants had positive surface charge, which supports the view that is already known about this type of phenomenon.