Pyrometallurgical reduction of manganese-rich black mass from discarded batteries using charcoal

Abstract

The recycling of heavy metals contained in alkaline batteries allows minimizing the environmental impact and gives an alternative use to this waste, which can be used in the pyrometallurgical industry. In the present research work, we evaluated the possibility of reducing the manganese oxide black mass from discarded alkaline batteries to produce metallic manganese, using charcoal as a reducing agent. The procedure begins with the characterization of the raw materials, the stoichiometric calculations and the preparation of a practical method to produce self-reducing pellets, composed of manganiferous material, charcoal and bentonite as agglomerant. Computer simulations were performed, to establish the appropriate thermodynamic conditions for reduction. The tests were carried out in a tubular-type furnace, and the results obtained were evaluated using optical microscopy, scanning electron microscopy coupled with microchemical analyses and X-ray diffraction techniques. It was verified that the agglomerates showed a self-reducing behavior, so an increase of the %Mn in the samples due to increasing the temperature of the reduction treatment was found, as well as the presence of a metallic manganese phase that was identified by X-ray diffraction analysis. Graphical Abstract Flow sheet for the production of self-reducing pellets containing eucalyptus charcoal for the recycling of manganese contained in spent alkaline batteries

Pyrometallurgical Approach to Extracting Valuable Metals from a Combination of Diverse Li-Ion Batteries’ Black Mass

“…Another point to mention is that, although XRD patterns do not show any further reduction after 800 °C, mass loss continues in the BM up to 1200 °C, the highest temperature reached in this study. Possible sources for the continuation of mass loss (based on the thermodynamic modeling and literature survey) include the following: (i) late devolatilization of organics in the BM; (ii) carbothermic reduction of MnO to metallic Mn; (iii) reaction of Li/Mn oxides with F, producing Li/Mn fluorides and O [based on thermodynamic modeling, with increasing temperature, MnO(MeO) decreases and Mn(FeLQ), MnO(slag), and MnF 2 (slag) form]; ,, (iv) reaction of produced O with the existing C, leading to CO production.…”