Figure 3 – Conceptual model illustrating chalcopyrite passivation as the result of multiple resistances to electron transfer and mass transport at the mineral–solution interface. The diagram shows two complementary perspectives. On the left, the processes occurring within a local surface patch are represented as resistances in series that collectively limit the dissolution current along a single reaction pathway ℎ. These include the charge-transfer resistance at the mineral surface ( ), the potential-dependent junction resistance ( ) associated with the formation of a semiconductor p–n junction at the chalcopyrite surface, the resistance of surface films ( ) formed by products such as CuS, elemental sulfur, or iron oxyhydroxides, and the diffusion resistance ( ) associated with mass transport through the boundary layer. The total current through an individual pathway is therefore governed by the sum of these resistances and the applied potential drop Δ . 4. APPROACHES TO OVERCOMING CHALCOPYRITE PASSIVATION 4.1 Thiocarbonyl catalytic systems – the Jetti approach The Jetti catalytic leaching approach, developed at the University of British Columbia in partnership with Jetti Resources, is based on the discovery that reagents bearing a thiocarbonyl functional group, when added in small concentrations to acidic ferric sulfate leach solutions, dramatically accelerate chalcopyrite dissolution at ambient temperature and pressure. The foundational IP covering this technology discloses leaching of chalcopyrite and related copper sulfides using a range of thiocarbonyl reagents, including thiourea (Tu), ethylene thiourea (ETu), thioacetamide (TA), sodium dimethyldithiocarbamate (SDDC), ethylene trithiocarbonate (ETC), and thiosemicarbazide (TSCA), at typical initial concentrations in the ~0.2–30 mM range, in combination with ferric sulfate as the primary oxidant (Dixon et al., 2018; Dixon et al., 2024). Standard operating conditions in the Jetti approach include ferric sulfate at 40 mM (2.2 g/L Fe), pH ~2 for column operation or pH ~1.8 for stirred reactors, at 25 °C. Importantly, the process
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