A mineral-centric framework for predicting arsenic behaviour in lithium mine wastes

The expansion of lithium mining in Europe is essential for securing strategic raw materials, but it raises increasing challenges for long-term tailings management. Arsenic (As), present at trace levels in lithium ores, can partition into mine wastes during beneficiation, yet its mineral hosts and solid-phase speciation remain poorly constrained due to low concentrations and diffuse distribution. This limits predictions of arsenic behaviour during processing, leaching, and storage, while current assessments often rely on bulk data that overlook key mineralogical controls. Here, we combine quantitative mineral deportment with As K-edge XANES to characterise arsenic distribution and speciation in ores and residues from three major European lithium projects. Arsenic occurs across sulfide, sulfarsenide, silicate, oxide, and phosphate phases, typically at trace levels but within abundant minerals. Sulfarsenides are dominated by As(–I), whereas other phases show mixed speciation (As(–I), As(III), As(V)). Linear combination fitting indicates overall dominance of As(–I) and As(V), with As(III) minor and sample-specific. XANES of leaching residues reveal the oxidation of arsenic released during arsenopyrite dissolution to As(V), followed by its immobilisation under specific pH conditions, demonstrating that arsenic leaching behaviour at disposal sites is strongly controlled by weathering conditions. Coupled with traditional leaching approaches, this mineral-centric framework quantifies the contribution of As-bearing phases and their control on release across environments, supporting more targeted tailings management and improved environmental strategies for lithium production.