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<p>As a strategic critical metal, indium is mainly used in indium tin oxide (ITO) targets. Given the scarcity of natural indium minerals, recovering spent ITO targets is significant for sustainable indium utilization. This study systematically investigated sulfuric acid leaching of spent ITO targets. Thermodynamic analysis confirmed that indium and tin could be selectively separated in sulfuric acid systems. Three schemes (leaching, curing-leaching, roasting-leaching) were proposed, and their effects on leaching rates and separation efficiency were explored. Comparative experiments showed curing-leaching had optimal separation and the highest indium leaching rate. Optimizing its key parameters revealed optimal conditions: self-curing (no external heating) for 1&#xa0;h, 1.2-fold stoichiometric sulfuric acid dosage, liquid–solid ratio (L/S) 6:1&#xa0;mL/g, 60&#xa0;°C, 1.5&#xa0;h. Under these, indium leaching rate reached 98.98%, while tin extraction was only 0.2%, yielding a separation factor (SF) of 48,900.29; leachate contained 62.38&#xa0;g/L indium and 13.62&#xa0;mg/L tin. Sulfuric acid curing mechanism involves concentrated sulfuric acid breaking indium-oxygen double bonds to form indium hydrogen sulfate tetrahydrate (InH(SO<sub>4</sub>)<sub>2</sub>·4H<sub>2</sub>O). Both leaching and curing-leaching follow the unreacted shrinking core model. The former is governed by solid-product-layer diffusion (activation energy 22.96&#xa0;kJ/mol, pre-exponential factor 4.39), whereas the latter proceeds under mixed control (activation energy 21.40&#xa0;kJ/mol, pre-exponential factor 26.05).</p> Graphical Abstract <p></p>

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Selective Recovery of Indium and Tin from Spent Indium Tin Oxide Targets via Enhanced Sulfuric Acid Leaching

  • 期刊论文

  • 发表日期：

    2026年3月31日

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  • Kang Yan,
  • Yihang Shu,
  • Feng Wu,
  • Lianghong Duan,
  • Siyu Duan,
  • Zhipeng Xu,
  • Yuntao Xin,
  • Qinghua Tian

摘要

As a strategic critical metal, indium is mainly used in indium tin oxide (ITO) targets. Given the scarcity of natural indium minerals, recovering spent ITO targets is significant for sustainable indium utilization. This study systematically investigated sulfuric acid leaching of spent ITO targets. Thermodynamic analysis confirmed that indium and tin could be selectively separated in sulfuric acid systems. Three schemes (leaching, curing-leaching, roasting-leaching) were proposed, and their effects on leaching rates and separation efficiency were explored. Comparative experiments showed curing-leaching had optimal separation and the highest indium leaching rate. Optimizing its key parameters revealed optimal conditions: self-curing (no external heating) for 1 h, 1.2-fold stoichiometric sulfuric acid dosage, liquid–solid ratio (L/S) 6:1 mL/g, 60 °C, 1.5 h. Under these, indium leaching rate reached 98.98%, while tin extraction was only 0.2%, yielding a separation factor (SF) of 48,900.29; leachate contained 62.38 g/L indium and 13.62 mg/L tin. Sulfuric acid curing mechanism involves concentrated sulfuric acid breaking indium-oxygen double bonds to form indium hydrogen sulfate tetrahydrate (InH(SO4)2·4H2O). Both leaching and curing-leaching follow the unreacted shrinking core model. The former is governed by solid-product-layer diffusion (activation energy 22.96 kJ/mol, pre-exponential factor 4.39), whereas the latter proceeds under mixed control (activation energy 21.40 kJ/mol, pre-exponential factor 26.05).

Graphical Abstract