Modifying milling parameters: Impact on selective separation of lithium-rich phases in a thermodynamically designed battery slag

Abstract

Slag products resulting from the pyrometallurgical recycling of lithium-ion batteries (LIBs) exhibit considerable potential as a secondary source of raw materials, particularly regarding the critical element lithium. Similar to ore processing, comminution is the primary method for liberating lithium-bearing phases. This study examines the impact of milling parameters on the separation behavior of lithium-containing phases prior to hydrometallurgical treatments for recovery. The selection of grinding conditions is determined by the characteristics of the targeted particles. Consequently, a range of separation methods were investigated based on the mineralogical properties of the slag, with froth flotation proving the most promising approach. A roller mill was used for grinding. In order to determine the optimal particle size and milling settings, the milling parameters of the roller gap size, circumferential speed, and mass flow of the material fed (feeding rate of the mill) were varied across different feed particle ranges.

The results demonstrate that a recovery rate of 70% can be achieved for lithium-containing phases, notably lithium aluminate. However, the recovery rate was found to reach 82% through adjustments of the milling parameters of a roller mill implemented in the study. Thus, it can be concluded that the grinding parameters not only affect the comminution processes and their energy consumption, but also the particle morphology and flotation behavior. Therefore, an optimal mechanical pre-treatment of the slags enables an increase recovery of lithium in the recycling of LIBs and a decreasing the requirement of primary sources, both of which contribute to the circular economy.