Produção de catalisadores a base de cobalto oriundo de baterias exauridas para aplicação fotocatalítica

Abstract

In the present work, the recovery of cobalt, in the forms of oxide and cobalt hydroxide from exhausted lithium-ion batteries, was studied using two main routes, being these by evaporation and chemical precipitation. The recovered material was characterized by structural, morphological and elementary techniques, being applied in the photocatalysis process aiming at the degradation of the reactive blue dye 5G. The photocatalysis tests were conducted in a box with UV irradiation, where the mineralization potential of each catalyst produced (H1, O1, H2, O2, H3, O3, H4 and O4) was evaluated. The dosage of 0.1 g of catalyst and addition of 100 L of hydrogen peroxide (H2O2) was used for the degradation of 100mL of the dye solution (pH 2) with initial concentration of 50 mg L−1. The concentration variation over time was determined by reading the absorbance spectrophotometer (UV-Vis) at times of 0, 5, 10, 20, 40, 60, 80 and 100 minutes of reaction. All the catalysts presented excellent results, with emphasis on the O4 sample, which reached 99.4 % degradation of the reactive blue dye 5G and equilibrium close to 60 minutes of reaction. The influence of pH on the rate of degradation of the dye was also evaluated. For this, the cobalt oxide (O4) catalyst was used, which presented better performance at pH 2, and the pH values were used: 2, 3, 4, 6, 8 and 10. It was verified that the degradation of the reactive blue dye by the photocatalysis process can be conducted at any pH, the acid medium (pH 2) being the best scenario for the process, although the mineralization at pH 8 occurred rapidly (the first 10 minutes of reaction). , for some cases, to meet the concentrations of interest and to make the process even more feasible due to the short degradation time. The pseudo-first order model was suggested to try to describe the experimental data, where great adjustments were verified for catalysts H1, O1, H2 and O2. For catalysts H3, O3, H4 and O4, a slight divergence was observed, making it necessary to study another model that best describes the experimental data. Therefore, the work shows pathways of an environmentally and economically sustainable process, since it recycles a residue containing toxic materials and assigns it the possibility of a nobler application, such as the process of photocatalysis in the treatment of effluents.