Lixiviação dos metais lítio e manganês presentes em baterias do tipo botão (LiMn2O4)

Abstract

The increasing consumption of electronic devices has intensified the generation of waste from lithium-ion batteries (LIBs), which contain potentially toxic metals such as Li, Co, Ni, and Mn, posing risks to the environment and human health. In this context, the development of more sustainable recycling routes have become essential. Among commercial systems, the spinel LiMn₂O₄ (LMO) has been widely applied due to its low cost and good stability, with manganese being a key component in these batteries. Hydrometallurgy has emerged as a promising alternative for LIB recycling, particularly through the use of organic acids such as malic acid and ascorbic acid, which present a lower environmental impact. However, leaching kinetics may be limited, and the use of reducing agents, such as hydrogen peroxide, is commonly employed to enhance the process. This study aimed to recover lithium and manganese from button-type batteries (CR2032) using leaching with DL-malic acid combined with reducing agents. Preliminary tests with inorganic and organic acids indicated that malic acid achieved lithium extraction efficiencies close to 100%, while manganese showed good extraction efficiency, although still higher than those obtained with sulfiric acid, hydrochloric acid, propionic acid, and acetic acid. Following the preliminary tests, a central composite design was applied to evaluate the influence of malic acid concentration and the solid-to-liquid ratio. The highest efficiencies were obtained at lower solid-to-liquid ratios and intermediate acid concentrations. Subsequently, experiments were conducted using malic acid in combination with ascorbic acid and hydrogen peroxide as reducing agents. These experiments were carried out over 10 minutes at temperatures of 28, 40, 50, and 60 °C. The results demonstrated that malic acid alone showed low efficiency for manganese and high efficiency for lithium. The addition of ascorbic acid promoted moderate improvements, whereas the use of hydrogen peroxide resulted in a expressive synergistic effect, achieving extraction efficiencies of approximately 95% for Mn and 96% for Li in only 10 minutes, even at low temperatures (28 °C). Kinetic analysis revealed that, in the absence of hydrogen peroxide, manganese leaching is predominantly controlled by chemical reaction, with an activation energy of 62.7 kJ•mol⁻¹, while lithium exhibits a lower energy barrier (10.55 kJ•mol⁻¹). The addition of ascorbic acid reduces the activation energy of Mn, indicating a mixed control regime. In systems containing H₂O₂, low activation energy values were observed, characteristic of diffusion-controlled processes, highlighting a shift in the rate-limiting mechanism and enhanced manganese dissolution associated with the reduction of Mn(IV) to Mn(II). Therefore, the results demonstrate that the malic acid–H₂O₂ system presents high potential as an efficient and sustainable alternative for lithium-ion battery recycling, enabling high extraction efficiencies under mild operating conditions.