Reduction of lead from MnO2 anodic waste by thermal decomposition and leaching with ammonium acetate

Avalo Cortez O.; Martínez Coronel M.J.; Martínez Aguilar D.P.; Yoplac Castromonte E.; Uza Teruya J. · European Public and Social Innovation Review (2025) · DOI: 10.31637/epsir-2025-1900

Resumen

Introduction: Manganese dioxide (MnO2) is a by-product generated in the electrolysis process during the production of cathodic zinc. This adheres to the Pb-Ag anodes, forming crusts that can make their reuse difficult. To solve this, a washing cycle is carried out by brushing and ironing, generating MnO2 residues with Pb. Methodology: The pre-treatment consisted of thermal decomposition of MnO2 alpha, which caused phase changes and increased crystallinity and particle size. Leaching tests were performed using ammonium acetate to leach PbSO4 at room temperature, applying magnetic stirring and ultrasonic bath at different temperatures (300, 500 and 900°C). Results: Thermal decomposition of α-MnO2 changed its structure to Mn2O3 and Mn3O4, increasing its crystallite size from 14.82 nm to 256.9 nm. In the leaching tests, the amount of Pb in the anodic residue was reduced by 61%, from 4.84% to 1.89% Pb. Discussion: Significant changes in the morphology and particle size of MnO2 were observed before and after thermal decomposition, facilitating the removal of Pb and reducing the Mn content in the leached solution. Conclusions: Lead reduction in the anode residue was achieved by 61%, generating almost pure PbO as a by-product, and an effluent with Pb and Mn contents within environmental regulations.

Instituciones: Universidad Nacional de Ingeniería