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Abstract <p>Copper-leaching residues generated from secondary resources, such as waste printed circuit boards, contain precious metals and other elements such as Sb and Sn. Conventional HCl-based leaching requires high acid input, leading to elevated HCl consumption and insufficient selectivity. This study investigates chloride-salt-assisted “brine leaching” as an alternative for reducing HCl consumption while enhancing the recovery of Au, Pd, Pt, Sn, and Sb. Leaching tests were conducted using NaCl, CaCl<sub>2</sub>, and KCl under controlled potential and pH conditions. The results showed that when utilizing HCl concentrations above 2&#xa0;mol/L, leaching rates exceeding 90% were achieved for Au, Pd, Pt, and Sn. However, at concentrations below 2&#xa0;mol/L, the dissolution of Au, Pd, Pt, and Sn was suppressed, and only a small fraction of Sb was leached. For NaCl, the leaching rates of Au, Pd, Pt, and Sn exceeded 90% at acid concentrations below 2&#xa0;mol/L, with Sb dissolution limited to less than 1%. Equilibrium analysis and speciation modeling indicated that Sn dissolved predominantly as Sn(IV) chloro-complexes, whereas Sb formed sparingly soluble Sb(V) complex oxide (Na,H)<sub>14</sub>Sb<sub>14</sub>O<sub>21</sub>(OH)<sub>42</sub>, confirmed by X-ray diffraction observations. For the total Cl<sup>−</sup> ions in the 3–5&#xa0;mol/L range, the consumption of HCl was very low or almost nonexistent, demonstrating that chloride salts can provide the necessary Cl<sup>−</sup> for the formation of stable chloro complexes while minimizing HCl consumption. These findings demonstrate the potential of brine leaching as a new environmentally friendly processing method to effectively leach precious metals while reducing the consumption of HCl using chloride salts.</p> Graphical Abstract <p></p>

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Chloride Salt-Based Brine Leaching of Precious Metals and Other Valuable Metals from Secondary Resources for Reduced Hydrochloric Acid Consumption

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  • 发表日期：

    2026年6月3日

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  • Kazuya Arakawa,
  • Labone Lorraine Godirilwe,
  • Satoshi Nakagawara,
  • Atsushi Shibayama

摘要

Abstract

Copper-leaching residues generated from secondary resources, such as waste printed circuit boards, contain precious metals and other elements such as Sb and Sn. Conventional HCl-based leaching requires high acid input, leading to elevated HCl consumption and insufficient selectivity. This study investigates chloride-salt-assisted “brine leaching” as an alternative for reducing HCl consumption while enhancing the recovery of Au, Pd, Pt, Sn, and Sb. Leaching tests were conducted using NaCl, CaCl2, and KCl under controlled potential and pH conditions. The results showed that when utilizing HCl concentrations above 2 mol/L, leaching rates exceeding 90% were achieved for Au, Pd, Pt, and Sn. However, at concentrations below 2 mol/L, the dissolution of Au, Pd, Pt, and Sn was suppressed, and only a small fraction of Sb was leached. For NaCl, the leaching rates of Au, Pd, Pt, and Sn exceeded 90% at acid concentrations below 2 mol/L, with Sb dissolution limited to less than 1%. Equilibrium analysis and speciation modeling indicated that Sn dissolved predominantly as Sn(IV) chloro-complexes, whereas Sb formed sparingly soluble Sb(V) complex oxide (Na,H)14Sb14O21(OH)42, confirmed by X-ray diffraction observations. For the total Cl− ions in the 3–5 mol/L range, the consumption of HCl was very low or almost nonexistent, demonstrating that chloride salts can provide the necessary Cl− for the formation of stable chloro complexes while minimizing HCl consumption. These findings demonstrate the potential of brine leaching as a new environmentally friendly processing method to effectively leach precious metals while reducing the consumption of HCl using chloride salts.

Graphical Abstract