Projeto de um reator CSTR de bancada automatizado com uso de arduino e aplicado na degradação catalítica de corantes têxteis

Abstract

This study aimed to optimize cobalt recovery from spent lithium-ion batteries for the production of a catalyst applied in the degradation of the Reactive Blue 5G dye, as well as to develop a laboratory-scale Continuous Stirred Tank Reactor (CSTR) automated with Arduino. The cathode material, extracted from smartphone batteries, was used in the synthesis of cobalt oxide-based catalysts (Co-Ox), which were characterized by analyses such as X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), and nitrogen physisorption. The optimization of operational conditions for the catalytic degradation of Reactive Blue 5G dye using the Co-Ox catalyst produced from the base methodology was carried out through a 2² Central Composite Rotational Design (CCRD), evaluating the effects of the initial pH of the dye solution and the catalyst dosage on degradation efficiency. Kinetic tests were conducted under optimized conditions using 200 mL of dye solution (C₀ = 100 mg/L). Process efficiency was monitored by UV-Vis spectrophotometry at 614 nm over 3 hours. In a second 2² CCRD, the catalyst synthesis was optimized. Acid leaching for cobalt recovery was evaluated focusing on the optimization of both mass yield and catalytic degradation performance, using H₂SO₄ and H₂O₂ concentrations as independent variables. The resulting catalyst was applied in catalytic degradation tests in batch reactors, with a catalyst dosage of 0.6 g/L and dye solution (C₀ = 100 mg/L) at pH 1.85, with stirring maintained for 3 hours. The results of the study identified catalyst characteristics such as a porous and irregular structure, bands in the 543–643 cm⁻¹ region related to Co–O bonds, and diffraction peaks corresponding to Co₃O₄, suggesting the formation of this compound. Additionally, no significant mass loss was observed above 150°C, indicating the absence of further material decomposition. The specific surface area was determined as 5.06 m²/g, with an average pore size of 339.4 Å, indicating a predominance of mesopores in the catalyst. From appropriate statistical analysis, the optimal point for catalytic degradation was determined as an initial solution pH of 1.85 and a catalyst dosage of 0.6 g/L. For the second experimental design, the global desirability analysis indicated optimal conditions at a concentration of 0.26 mol/L H₂SO₄ and 1.13% v/v H₂O₂, optimizing both catalyst mass yield (70%) and catalytic degradation efficiency of Reactive Blue 5G dye (89%).The pseudo-first-order kinetic model fitted well to the kinetic data collected with the catalysts obtained under both the optimal point and base methodology conditions (R² = 0.9881 and 0.9904, respectively), with kinetic rate constants of 0.29 ± 0.03 min⁻¹ and 0.038 ± 0.004 min⁻¹, respectively. With the catalyst obtained under optimized conditions, the designed CSTR reactor was evaluated, yielding promising results in dye degradation. Thus, this study proposes a sustainable environmental impact minimization approach by valorizing lithium-ion battery waste, contributing to the development of alternative catalysts applicable to industrial effluent treatment.