Background: Dye removal from effluents is one of the major problems faced in the world. It is a very important environmental issue and it is crucial to solve this problem. In this sense, ZIFs are increasingly important in the environmental area. Objective: This work presents the synthesis of metal-organic framework Zeolitic Imidazolate Framework-8 (ZIF-8) nanoparticles, characterization and then determine the potential to remove Rhodamine B (RhB) from an aqueous solution. Methods: ZIF-8 was synthesized under solvothermal treatment at 25 °C and it was characterized by X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy, infrared spectroscopy. To evaluate the capacity of the RhB, a pHinfluence and kinetic studies were determined. The pseudo first- and second-order kinetic models were used to describe the kinetic data, and the rate constants were evaluated. Results: ZIF-8 had average particle size 47 ± 4.6 nm. The removal percentage increases significantly when pH was in the range of 7.0–9.0. A pseudo-second-order kinetic of 13.00 mg/g was found for the RhB removal. The adsorption capacity at equilibrium was found to be 11.8 mg/g. Conclusion: According to the characterization results, the ZIF-8 synthesis was effective and produced a crystalline material. The ZIF-8 presented an affinity to the RhB dye. A pseudo-second order kinetic model represented well the mechanism of interaction involved during RhB adsorption and ZIF-8.
Background: The oil removal from industrial effluents is one of the biggest problems faced in the world. It is a very important environmental issue and it is necessary to solve this problem. In this sense, ZIFs are increasingly important in the environmental area. Objective: This work reports a method for the synthesis of ZIF-zni nanocrystals, at room temperature in 1 h, and a performance of the ZIF-zni nanoadsorbent in the oil removal from oil-water emulsion. Methods: ZIF-zni was produced from the solvothermal method and it was characterized by X-ray diffraction, electron microscopy, contact angle, infrared spectroscopy and thermogravimetry. Oil-water emulsion was produced by lubricant oil and distilled water. Batch-type adsorption at 200 rpm for 2 h was used to evaluate the potential of ZIF-zni for the separation of the oil-water emulsion with initial oil concentration (100, 300 mg/L) and temperature (30, 60 °C). Results: The characterizations showed that the crystalline phase of ZIF-zni was successfully obtained. The ZIF-zni exhibit a very high removal percentage (above 95 %) and adsorption capacity. The predictions of multiple linear regression models determined based on the factorial design of experiments are excellent. Conclusion: The value up to 2879 mg/g of adsorption capacity was reached, thus indicating that the use of the nanoadsorbent ZIF-zni has great potential in the process of separating oil-water emulsion.
Esse trabalho tem como objetivo analisar como uma proposta didática baseada na resolução de uma situação-problema auxilia na abordagem do conteúdo polaridade das ligações químicas, considerando a água como tema gerador. Elaboramos um conjunto de atividades que que consistiam em texto de apoio, aula expositiva dialogada, jogo de palavras-cruzadas, atividades experimentais e uma hipermídia não interativa para apresentação do problema, realizamos a intervenção didática em sete etapas, para uma turma do 1º ano do Ensino Médio de uma escola da rede pública da Paraíba, localizada na cidade de Remígio, com a participação efetiva de 21 estudantes. Para análise, escolhemos avaliar o conhecimento das respostas dadas no primeiro momento, levantamento de concepções prévias, e no último, a resposta final da situação-problema, mediante construção de um texto. Os resultados apontam um desempenho satisfatório, ainda que apenas um grupo tenha dado uma resposta satisfatória segundo critérios de análise, podemos perceber indícios da construção de conhecimentos sobre polaridade em todos os grupos. Na avaliação da proposta pelos estudantes, o resultado foi positivo, com um argumento de 2,4 na aprovação do máximo de 3, o que valida a proposta apresentada.
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