645 Table 1 – Comparison of approaches to overcoming chalcopyrite passivation, interpreted within the resistance framework of Figure 3. Technology Resistances targeted Mixed potential effect Key operating conditions Representative metrics Status Thiocarbonyl catalysis (Jetti; Tu, ETu, TA, SDDC, ETC, TSCA) ↓Rj(E), ↓Rfilm, ↓Rct Raises id; lowers EM while increasing rate pH ~1.8–2; 25 °C; ~0.2–30 mM reagent; Fe(III) oxidant Columns: >70% Cu extraction; electrochem: ~6× rate with 10 mM Tu; Tu+Fe(III) ~30× vs Fe(III) alone Commercial deployments reported Thiocarbonyl + surfactants (Jetti extended family) ↓Rdiff (wetting, O₂ transfer, S⁰ hydrophobicity) plus catalytic depassivation As above; transport bottlenecks reduced to realize catalytic benefit pH ~1.5–2.5; ambient T Synergistic extraction improvements reported in patent Field status not publicly confirmed Chloride Eh-window control (BHP SaL/Full SaL family) Avoids growth of Rfilm and Rj(E) by operating in active potential window; ↓Rdiff via O₂ management Keeps EM below passive onset (~600 mV SHE) pH ~1–2; Cl⁻ ~5– 100 g/L; O₂ >1 ppm; Eh ~550– 600 mV SHE ~70% Cu at low potential vs ~7% at high potential (912 h); 73–79% at 550–600 mV vs 22.5% at 620 mV (1000 h); 88% at 550 mV (1240 h) Full SaL commercially deployed at Escondida (June 2025), primarily targeting secondary sulfides; primary sulfide application under study Nitrate/transpassive oxidation (BHP WO2024057216A1; Ceibo DOP) Bypasses passive regime entirely via transpassive potential; S⁰ oxidized to sulfate so ↓Rfilm; ↓Rct Sets EM above transpassive threshold via NO⁺ high oxidation potential High NO₃⁻ (~25– 80 g/L BHP; ~0.02–0.4 M Ceibo); ORP >770 mV SHE; covers/scrubbing required for NOx Metathesis to covellite and chalcocite possible under these conditions; full kinetic data not public Precommercial; NOx management is key barrier Elevatedtemperature bioheap leaching (Nuton, Rio Tinto) ↓Rct (temperature); ↓Rdiff (aeration, moisture management); sustained cathodic branch via Fe³⁺ regeneration Sustained oxidant supply strengthens cathodic branch; high T destabilizes passive regime Ambient to elevated T (selfheating via microbial oxidation); proprietary organisms; standard acidic heap conditions Up to ~84% Cu recovery from primary sulfides reported; column testing ~84% under Nuton conditions (NI 43101, 2025) First commercial production achieved (Johnson Camp, 2025)
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