A green production process of electrolytic manganese metal based on solvent extraction

Abstract

A green method for producing electrolytic manganese metal using solvent extraction was developed to address the challenges of impurity magnesium contained in the electrolyte and ammonia nitrogen carried by electrolytic manganese residue, involving leaching, heavy metal removal, solvent extraction, stripping, and electrolysis. The extraction process used neodecanoic acid as an extractant to separate impurity Mg from the electrolyte, which had a Mn/Mg separation coefficient of 105.24. The removal of Mg from the electrolyte was 88.87% and the number of electrolyte cycles was increased by a factor of 9. DFT calculations show that neodecanoic acid has good electron donor capacity and chemical reactivity, it binds better to Mn than to Mg. The loaded organic phase was stripped through the anodic liquid, enabling the anodic liquid containing ammonia nitrogen to be closed-circulated between the stripping and electrolysis processes. The manganese content of the electrolytic manganese metal produced by this process is 99.81%, which meets the requirements of the Chinese national standard for DJMnD grade products. The separated impurity magnesium provides raw material for the preparation of high purity magnesium oxide, and the use of two stages of water circulation makes the electrolytic manganese residue completely free of ammonia nitrogen, which has the advantage of high resource utilization and clean production.