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<p>A hybrid pyrometallurgical–hydrometallurgical route was developed for the selective recovery of cobalt oxide from spent WC–Co cutting tools using NaNO<sub>3</sub>-based oxidative fusion followed by hot water washing and mild acid leaching. Cemented carbide scraps (6–12 wt% Co) were treated at 650–900&#xa0;°C without prior comminution. Optimization of fusion temperature and holding time showed that 850&#xa0;°C for 10&#xa0;min provides the best compromise between phase separation and cobalt recovery: the solid residue contains 94.1 wt% Co and only 1.1 wt% W, corresponding to Σ<sub>Co</sub> ≈ 97.3%. Subsequent purification by combined hot water washing and treatment in 0.05&#xa0;M HNO<sub>3</sub> reduces Na from 3.3 to 0.1 wt% and yields a final product with 97.6 wt% Co and ~1.2 wt% W. X-ray diffraction (XRD) confirms that the purified residue consists predominantly of Co<sub>3</sub>O<sub>4</sub> (JCPDS 96-900-5889) with only trace WO<sub>3</sub> (JCPDS 96-210-7313). Scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy (STEM-EDS) mapping and transmission electron microscopy with energy-dispersive X-ray spectroscopy (TEM-EDS) analyses reveal a homogeneous distribution of Co and O within particle aggregates, and only sparsely distributed impurity elements, in agreement with bulk energy-dispersive X-ray fluorescence spectrometry (EDXRF) data. Semi-pilot tests at the “Uzbekistan Technological Metals Complex” JSC demonstrated that cobalt recovered via this route can be reduced to metallic Co and reused in WC–Co hardmetal production without deterioration of performance. The proposed process is technically feasible, reagent-efficient, and suitable for closing the cobalt loop in WC–Co manufacturing.</p> Graphical Abstract <p></p>

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Selective Recovery of High-Purity Cobalt Oxide from Spent WC–Co Cutting Tools via NaNO3 Oxidative Fusion and Combined Washing

  • 期刊论文

  • 发表日期：

    2026年5月28日

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  • O. E. Abdurakhmonov,
  • I. A. Bozorov,
  • A. B. Ibragimov,
  • Sh. E. Abdurakhmonov,
  • U. N. Ruziyev,
  • F. R. Abdullayev,
  • U. B. Sharopov,
  • F. O. Ma’rufov,
  • S. O. Ramazanov,
  • M. K. Kurbanov,
  • D. Sh. Saidov

摘要

A hybrid pyrometallurgical–hydrometallurgical route was developed for the selective recovery of cobalt oxide from spent WC–Co cutting tools using NaNO3-based oxidative fusion followed by hot water washing and mild acid leaching. Cemented carbide scraps (6–12 wt% Co) were treated at 650–900 °C without prior comminution. Optimization of fusion temperature and holding time showed that 850 °C for 10 min provides the best compromise between phase separation and cobalt recovery: the solid residue contains 94.1 wt% Co and only 1.1 wt% W, corresponding to ΣCo ≈ 97.3%. Subsequent purification by combined hot water washing and treatment in 0.05 M HNO3 reduces Na from 3.3 to 0.1 wt% and yields a final product with 97.6 wt% Co and ~1.2 wt% W. X-ray diffraction (XRD) confirms that the purified residue consists predominantly of Co3O4 (JCPDS 96-900-5889) with only trace WO3 (JCPDS 96-210-7313). Scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy (STEM-EDS) mapping and transmission electron microscopy with energy-dispersive X-ray spectroscopy (TEM-EDS) analyses reveal a homogeneous distribution of Co and O within particle aggregates, and only sparsely distributed impurity elements, in agreement with bulk energy-dispersive X-ray fluorescence spectrometry (EDXRF) data. Semi-pilot tests at the “Uzbekistan Technological Metals Complex” JSC demonstrated that cobalt recovered via this route can be reduced to metallic Co and reused in WC–Co hardmetal production without deterioration of performance. The proposed process is technically feasible, reagent-efficient, and suitable for closing the cobalt loop in WC–Co manufacturing.

Graphical Abstract