Abstract
Aurubis AG, Europe’s leading Copper producer and multi-metal recycler, has been developing a Hydrometallurgical process to recycle Li-ion Battery Black Mass (BM) since 2020. This process, comprising of leaching, precipitation, crystallisation processes, and flotation for recovery of Graphite was developed by Aurubis’ R&D Department and piloted at our Hamburg site until end of 2023 with results openly presented in 2024.
Aurubis’ process uses Ozone as an oxidant for Lithium-first leaching of BM and for the separation of Cobalt and Manganese from Nickel out of a subsequent reductive leach filtrate. The ability of a strong oxidant to de-lithiate a layered Lithium Cobalt Oxide (e.g., a cathode active material) was investigated in the 1990’s. The oxidative precipitation of Mn and Co with Ozone selectively from Ni has also been both well researched and practised.
Using a gaseous, strong oxidant like Ozone has numerous advantages such as, high oxidative potential and water balance considerations (e.g., vs. H2O2) or lack of salt addition (e.g., vs. Na2S2O8). However, unlike the commonly used oxidant, Chlorine gas in Chloride-based processes, Ozone has a similar solubility in water than Oxygen and cannot be produced as a pure gas (e.g., only ~10 wt.% in O2 carrier gas at low pressures). Therefore, gas-liquid mass transfer and utilisation becomes a serious application challenge and ultimately decides cost competitiveness.
The industrial application of Ozone in hydrometallurgical, solid-liquid-gas systems is not commercially developed or widely practised. Therefore, there is little existing knowledge to aid process and reactor design. Aurubis believed that High-shear-mixing technologies were the best chance to achieve high mass transfer rates and enable high utilisation of poorly soluble Ozone gas. Scale-up from overhead Lab stirrer design to Pilot plant circulating in-line mixer design (~1 kW) and industrial scale (~100 kW) mixers in a Demonstration plant have been completed. We will present on the process chemistry related to Li-first leaching from real BM samples and Cobalt Manganese separation from real leach liquors and the operational results from our Pilot and Demo Plants using Ozone gas injection into High-shear mixing reactor systems.