Elemental Speciation and Fractionation of Potentially Toxic Elements in Copper Mine Waste and its Implications for Metal Recovery

Copper (Cu) mine wastes contain complex, heterogeneous mineral phases that complicate the elemental speciation and fractionation analysis of potentially toxic elements (PTEs). Understanding elemental speciation and fractionation is essential for predicting metal mobility, bioavailability, and toxicity, and for guiding the recovery of Cu and other valuable metals from these wastes. Recovering metals from Cu mine waste promotes environmental sustainability and creates economic opportunities by extracting Cu and other critical elements for a circular economy. This review critically evaluates current analytical techniques for determining elemental speciation and fractionation in Cu mine wastes, including both solid-state and solution-based approaches. Solid-state techniques such as X-ray absorption near-edge structure (XANES) and advanced micro-analytical approaches, including micro-XAFS (µ-XAFS) and X-ray Fluorescence (µ-XRF), provide information on elemental associations and mineral distributions, although limitations related to sensitivity and accessibility remain. Sequential extraction procedures continue to play an important role in chemical fractionation analysis, particularly when key phases, such as water-soluble, Fe oxide and oxyhydroxide phases, are incorporated. However, these procedures remain time-consuming and operationally defined, which may introduce uncertainties in phase selectivity and interpretation. Emerging geochemical modelling and machine learning techniques may improve the interpretation and prediction of elemental binding forms in complex mine wastes. Importantly, elemental speciation and fractionation data can help select metal recovery technologies by identifying the major geochemical fractions that control metal recovery. Therefore, future research should integrate geochemical characterisation with hydrometallurgical recovery strategies to enhance metal recovery efficiency while reducing environmental risks associated with Cu mine wastes.