is fully compatible with conventional downstream copper recovery: thiocarbonyl reagents present in the pregnant leach solution do not interfere with SX–EW and may in fact act as leveling agents in electrowinning. This is a meaningful integration advantage relative to halide- or nitrate-based catalytic systems. A second patent family extends the technology by combining thiocarbonyl reagents with wetting agents and surfactants (e.g., Tween™ series, Triton™ X-100, PEG) at pH ~1.5–2.5, with optional iron-oxidizing bacteria, and is explicitly applicable to heap, dump, and column percolation leaching (Dixon et al., 2018). This surfactant plus thiocarbonyl combination simultaneously targets interfacial depassivation at the mineral surface and bed-scale wetting and gas–liquid–solid mass transfer, making it particularly suited to the practical challenges of heap operation. The performance improvements achieved under laboratory-scale column conditions are substantial. In three separate chalcopyrite-bearing ores (A–C), the addition of 10 mM thiourea increased final copper extractions from 21.2% to 37.9% (Ore A; 198 days), 12.4% to 32.0% (Ore B; 50 days), and 40.6% to 72.3% (Ore C; 322 days), corresponding to leaching rate increases averaging ~1.5–2.4× across the three ores (Dixon et al., 2024). At the electrochemical scale, 10 mM Tu alone produced a ~6× increase in chalcopyrite dissolution rate relative to the reagent-free control at pH 2 and 25 °C, and the combination of 10 mM Tu with 40 mM Fe(III) yielded a dissolution rate approximately 30× higher than 40 mM Fe(III) alone. The mechanistic basis for the Jetti approach is supported by various publications. Ren et al. (2020) demonstrated that ETu enhances chalcopyrite dissolution in acidic ferric sulfate bioleaching media and, critically, that ETu can reactivate chalcopyrite that has already been passivated under non-catalytic leaching conditions. This is a particularly important result for heap applications where passivation builds progressively over months of operation. Column tests in that study confirmed enhanced copper recovery from low-grade ore at industrially relevant conditions. The underlying mechanism was subsequently elucidated by (Ren et al., 2023), who showed using TOF-SIMS and ex-situ current-voltage analysis that ETu suppresses the formation of the copper polysulfide passivation phase and dissolves the p-type covellite-like surface product layer that constitutes the p–n junction barrier described in (Ren et al., 2022). By removing this layer, ETu reverses the resistor-to-diode transition and restores the chalcopyrite surface to its native, electrochemically active state. Interpreted within the resistance framework of Figure 3, the Jetti approach primarily reduces Rj(E), the semiconductor junction resistance, by chemically dissolving the p-type surface product responsible for the electronic barrier. It additionally reduces Rfilm by suppressing polysulfide accumulation. The net effect is a reduction in total series resistance across active surface domains and a shift of passivated surface area back toward active domains, increasing the weighted dissolution current isurface = Σθ_k×i_k. This is consistent with the electrochemical observation that thiourea-containing solutions operate at ~75–100 mV lower ORP vs Ag/AgCl than controls while simultaneously delivering higher copper extraction: the catalyst may shift the mixed-potential intersection to higher current density at lower potential, as predicted by the mixedpotential framework of Figure 2. Independently of these film-related effects, Olvera et al. (2018) demonstrated that TU and FDS directly reduce both the anodic and cathodic charge-transfer
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