Characterization of Tharsis mine tailings for ore reprocessing for potential critical materials recovery

This study characterizes and evaluates the potential recovery of metals from tailings of the Tharsis mine (Huelva, Spain), with a focus on critical raw materials (CRMs) essential for the energy transition. These tailings, generated during past sulfuric acid production from pyrite concentrates, are highly homogeneous, with over 40% of particles finer than 60 μm. Chemical analyses revealed a uniform distribution of elements such as Cu (0,35%), Zn (1,06%), Pb (0,10%), Co (244 ppm), and Ag (49 ppm), while Sb showed enrichment in finer fractions. Mineralogical results identified pyrite and quartz as the dominant phases across all size ranges. Quantitative mineralogy using the Advanced Mineral Identification and Characterization System (AMICS) and Mineral Liberation Analysis (MLA) confirmed that more than 90% pyrite is liberated under 60 μm, which suggests strong potential for recovery through gravity concentration using multi-method approaches, including multi-gravity separation (MGS), air jet concentrators, and centrifugal jigs. In addition to exploring fiscal-chemical concentration techniques, such as froth flotation, where grinding to +75 -200 μm was identified as the optimal size range for pyrite and quartz liberation, improving flotation performance. The results demonstrate that CRMs can be more sustainably recovered from secondary resources such as mine tailings. In contrast to previous studies, which have mainly focused on leaching, this work emphasizes the efficiency of pre-concentration methods for CRM recovery, thereby reducing the environmental risks associated with hazardous elements. Potential applications of recovered products include batteries, cement, paints, and ceramics, thereby supporting industrial supply chains while contributing to circular economy strategies. • Tharsis mine tailings were analyzed for potential CRMs recovery. • The tailings were homogeneous, with more than 40% of particles under 60 μm. • Cu, Zn, Co and Ag were detected, while Sb was concentrated in finer fractions. • Pyrite presents more than 90% liberation below 60 μm, supporting gravity separation. • Froth flotation is adequate after milling between +75 -200 μm.