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<p>Ammoniacal leaching is a recognized processing route for recovering metals from complex ores, in which the role of controlled gas-phase pressure in this environment has been less quantitatively assessed. This technical note investigates the effect of oxygen partial pressure on high-temperature, high-pressure ammoniacal leaching of a polymetallic (Au–Ag–Cu–Pb–Zn) oxide concentrate. Autoclave tests were conducted at 200&#xa0;°C for 3&#xa0;h using a solution containing 85&#xa0;g/L NH₃, 48&#xa0;g/L (NH₄)₂CO₃, 10&#xa0;g/L CuSO₄, and 13 wt% solids, under two conditions: (a) without O₂ injection and (b) with O₂ injected to pO₂ ≈ 14&#xa0;bar. The presence of O₂ markedly increased the recoveries of gold (from 43.6% to 71.7%) and silver (from 14.0% to 63.3%), while copper recovery decreased slightly (from 91.1% to 84.4%) and lead (from 12.6% to 8.7%) and zinc (from 61.0% to 56.5%) showed modest declines. XRD/XRF characterization of residues indicated an increased proportion of hematite and a reduction in carbonate phases under oxygenated conditions. Overall, the data reveal an opposing response of precious metals (Au, Ag) versus base metals (Cu, Pb, Zn) to elevated oxygen partial pressure, suggesting that pO₂ control can be leveraged to promote selective recovery of precious metals during ammoniacal pressure leaching.</p>

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Technical note: effect of oxygen partial pressure on the ammoniacal pressure leaching of gold and silver from a polymetallic (Au–Ag–Cu–Zn–Pb) concentrate

  • 期刊论文

  • 发表日期：

    2026年6月30日

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  • Sepideh Taheri,
  • Mohammad Reza Khalesi

摘要

Ammoniacal leaching is a recognized processing route for recovering metals from complex ores, in which the role of controlled gas-phase pressure in this environment has been less quantitatively assessed. This technical note investigates the effect of oxygen partial pressure on high-temperature, high-pressure ammoniacal leaching of a polymetallic (Au–Ag–Cu–Pb–Zn) oxide concentrate. Autoclave tests were conducted at 200 °C for 3 h using a solution containing 85 g/L NH₃, 48 g/L (NH₄)₂CO₃, 10 g/L CuSO₄, and 13 wt% solids, under two conditions: (a) without O₂ injection and (b) with O₂ injected to pO₂ ≈ 14 bar. The presence of O₂ markedly increased the recoveries of gold (from 43.6% to 71.7%) and silver (from 14.0% to 63.3%), while copper recovery decreased slightly (from 91.1% to 84.4%) and lead (from 12.6% to 8.7%) and zinc (from 61.0% to 56.5%) showed modest declines. XRD/XRF characterization of residues indicated an increased proportion of hematite and a reduction in carbonate phases under oxygenated conditions. Overall, the data reveal an opposing response of precious metals (Au, Ag) versus base metals (Cu, Pb, Zn) to elevated oxygen partial pressure, suggesting that pO₂ control can be leveraged to promote selective recovery of precious metals during ammoniacal pressure leaching.