Síntese de óxidos de ferro com nióbio ou lantânio como catalisadores de fenton na oxidação do composto modelo azul de metileno

Abstract

The present work aimed to synthesize pure magnetic iron oxides and iron oxides doped with niobium, lanthanum and niobium/lanthanum in order to verify how doped materials have their catalytic efficiency improved. The materials were synthesized by the inverse co-precipitation method according to the methodology proposed by Jolivet & Tronc (1987) and were named as MagPura, MagNb, MagLa and MagNb-La respectively. The following techniques were used for characterization: spectroscopy in the infrared region (FTIR/ATR); scanning electron microscopy (SEM); energy dispersive spectroscopy (EDS); electron backscattered diffraction (EBSD); X-ray diffraction (XRD). In order to evaluate the catalytic activity of the material for the oxidation of organic compounds, adsorption, degradation, photocatalysis and photo-Fenton reaction tests were performed using methylene blue dye (AM) as a model molecule of colored pollutant. In addition, a hydrogen peroxide (H2O2) evolution test was also carried out as a way of also evaluating the catalytic activity of the materials. The inverse co-precipitation method proved to be very efficient, resulting in a material with a dark color and a fine appearance, with a yield of around 80%. Regarding the catalytic tests, it can be observed that the material MagNb presented a maximum adsorption capacity of 40% while the other materials MagPura, MagLa and MagNb-La were 10, 10 and 15% respectively. As for the degradation and color removal tests, the maximum percentage reached was 40% for MagNb, that is, it reached the maximum adsorption capacity, which demonstrates that these materials are good adsorbents, not being efficient for these types of catalytic tests. Finally, in relation to the oxidation tests of the organic compound, it is observed that all the synthesized materials presented an efficiency above 75%, which makes them very favorable to be used for this type of reaction. However, MagNb presented the best rate, 92%, which can be justified by the strong connection that niobium makes with the active phase. While for the other materials, MagPura, MagLa and MagNb-La, the removal efficiency was 89, 76 and 81% respectively. Therefore, it is suggested for future works that other catalytic tests, other organic compounds, synthesis methods and characterizations be developed in order to evaluate the behavior and efficiency of the materials.