SÍNTESE DE ÓXIDO DE GRAFENO DECORADO COM FERRITA PARA ADSORÇÃO DE CROMO HEXAVALENTE

• Autor(a) principal: Lopes, Bibiana Culau
• Data de Publicação: 2017
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional Universidade Franciscana
• Texto Completo: http://www.tede.universidadefranciscana.edu.br:8080/handle/UFN-BDTD/557
• topic: Óxido de grafeno, ferrita, adsorção de cromo, fotocatálise.; Graphene oxide, ferrite, chromium adsorption, photo catalysis.; Biociências e Nanomateriais

One of the most common methods applied to heavy metal removal from contaminated aqueous solutions is adsorption through materials like activated carbon, and silica. In general, those materials are efficient and possible to reuse, although after their lifespan they become an environment liability, especially if inappropriately discharged. So that, it is seeking for materials that show more efficiency, that are easily regenerated, reusable and that generate less environmental impact. It is promising the use of graphene oxide (GO) as an adsorbent for environmental pollutants. GO with metallic nanoparticles attached to it, they confer magnetic features to GO, which makes it separation from the aqueous solution easy. In this study it was synthesized graphene oxide through Hummers & Offeman (1958) adapted method. Synthesized GO as well as commercial graphene oxide (Sigma) were submitted to hydrothermal process for insertion of ferrite (NiFe3O4) in its structure, then forming a nanocomposite NiFe2O4/GO. Nanomaterials were characterized by DRX, FTIR, Raman spectroscopy, MEV, BET and magnetization test, which all prove the formation and magnetization of the material. A solution of 100 mg.L-1 concentration of potassium dichromate (K2Cr2O7), was used as Cr(VI) source, for adsorption tests. The results show great efficiency of adsorption, which was stable in 150 min of stirring for more concentrated solutions of Cr(VI). It was used 500 mg.L-1 concentration of potassium dichromate in the photocatalytic process, which resulted in significant decrease of Cr(VI) and release of Cr(III) in the solution. The results obtained show high efficiency in the adsorption and the removal mechanism defined was through electrostatic attraction, due to the difference between charges of adsorbent and pollutant. A solution with 0.03 g of commercial graphene oxide decorated with ferrite and potassium dichromate in a concentration of 80 mg.L-1, adsorption reaction achieved the equilibrium, approximately, 20 minutes after the reaction started. When tested concentrations of 100, 80 and 40 mg.L-1 of potassium dichromate, the reaction achieved the equilibrium in 30 minutes. Adsorption reactions in concentrations of 300, 250 and 150 mg.L-1 of potassium dichromate stabilized 150 minutes after the reaction started. All tests were done with a fixed mass of 0.30 g of commercial graphene oxide decorated with ferrite. The results indicated that the major efficiency, when higher concentrations of Cr(VI) 9 source, depends on the adjustment of adsorbent added. Photocatalytic reaction promoted the reduction of Cr(VI) to Cr(III), which was proved through the difference in absorbance solution. The removal mechanism was through difference between charges, photocatalytic reaction also promoted the desorption of Cr(III) from the adsorbent surface, as it has negatively charged, they naturally repel.