Examination of Precious Metal Flotation Performance at Aitik Plant, Sweden

The Aitik concentrator in northern Sweden is one of Europe’s largest copper operations, processing low-grade ore (≈0.2% Cu; ≈0.07 g/t Au) and producing gold and silver as by-products through conventional sulphide flotation. Gold recovery to the copper concentrate is consistently lower than copper recovery under these operating conditions. This study combined a plant-scale survey with laboratory separation testing to identify the dominant mechanisms controlling gold losses and to evaluate complementary physical separation routes under varying ore mineralogical characteristics. A reconciled metallurgical balance of the industrial flotation circuit was established and integrated with year-long (2024) size-by-size gold deportment data for the feed, scavenger tailings, and cleaner tailings. Scavenger tailings were identified as the principal stream carrying unrecovered gold, with losses dominated by the coarse fraction (>180 μm; ~35% of Au losses), whereas cleaner tailings exhibited predominantly fine gold losses (<63 μm; ~45% of Au losses; with ~33% reporting to -10 μm where measured). Scanning electron microscopy combined with Energy-Dispersive X-ray Spectroscopy (SEM–EDS) observations corroborated these trends, identifying (i) coarse electrum locked within silicate-rich composite particles and (ii) ultrafine liberated Au–Ag/Au–Te-bearing particles and inclusion-hosted gold in sulphides. Laboratory tests on three mineralogically distinct ores demonstrated that separation response is strongly controlled by ore mineralogy, with distinct dominant recovery routes identified. Magnetite-rich ore showed limited gravity recovery (20.7% Au) but high magnetic recovery from gravity tailings (48.7% Au), indicating magnetite-associated gold deportment. In contrast, sulphide-dominated ores achieved higher gravity recoveries (42.7% Au for pyritic ore and 35.8% Au for low-pyritic ore) and produced high-grade gravity concentrates (up to ~26 ppm Au), consistent with recoverable dense gold-bearing particles. Flotation of post-separation tailings remained effective for sulphide recovery (Cu recovery 74–89%), and SEM confirmed gold recovery largely as sulphide-associated inclusions and fine liberated particles. The results demonstrate that gold losses at Aitik are governed by a bimodal size effect coupled with ore-dependent mineralogical associations, requiring different dominant recovery routes. These findings support a mineralogy-driven, ore-specific processing strategy integrating gravity concentration and/or magnetic scavenging upstream of flotation to reduce coarse and magnetite-associated gold losse