Síntese e aplicação de hexacianoferrato de zinco e seus nanocompósitos à base de nanoestruturas de carbono na degradação de contaminantes emergentes

Abstract

This work involves the synthesis and characterization of zinc hexacyanoferrate (HCFZn) and their respective composites, zinc hexacyanoferrate/graphene oxide (HCFZn/OG) and zinc hexacyanoferrate/carbon natotubes (HCFZn/NTC) aiming the application of these materials as photocatalysts in the degradation of paracetamol and ranitidine. The results obtained by X-ray diffraction revealed that all samples have the same rhombohedral crystal structure indexed to the ZnII3[FeIII(CN)6]2 formula. From the results obtained by IR spectroscopy, the characteristic bands of hexacyanoferrate can be observed in the regions of 2187/2101 cm-1 (νC≡N), 553 cm- 1, (δFe-CN) and 439 cm-1 (δFe-C). In addition, using Raman spectroscopy confirmed the presence of carbon materials, by observation of the characteristic D and G bands. In the images obtained by scanning electron microscopy (SEM) it was possible to observe HCFZn microparticles (~2.0 µm), which decrease in size in the presence of carbon nanomaterials. The degradation of the pollutants was monitored by high performance liquid chromatography, and the pH value and mass of the catalysts were evaluated using a triplicate central point factorial design 22 for each compound. The best degradation condition obtained for pure HCFZn led to a degradation of 78% of paracetamol and 66% of ranitidine, employing the mass of 5.0 mg and pH= 6.0. However, for HCFZn/OG and HCFZn/NTC nanocomposites results superior than 90% of degradation for both drugs were achieved under the same conditions, except for HCFZn/NTC in ranitidine degradation, where the lowest pH value (2.0) was the most appropriate condition. The excellent degradation results obtained may originate from the high surface area presented by HCFZn (896 m2 g-1) and the respective HCFZn/OG (692 m2 g-1) and HCFZn/NTC (473 m2 g- 1) nanocomposites. The better performance presented by nanocomposites may be due to the high adsorption capacity of the carbon materials and also to an increase of the electronic transfer rate, with consequent favoring of the redox process and higher efficiency in the electron/hole pair separation.