Abstract
Hard Metals (HM) production plays a fundamental role in economy and technological development. Due to the criticality of its main raw materials, W and Co, a sustainable HM waste recycling is hence desirable for both environmental and economic reasons and strongly encouraged by European waste management directives. This work describes a new solvometallurgical leaching method based on diluted maleic acid (H2Mal) ethanolic solutions, which demonstrated to couple effectiveness in materials enhancement from HM waste, with mildness and sustainability of operative conditions. Specifically, H2Mal (0.5 M, EtOH) selectively and quantitatively leached Co trapped within WC-Co powders, to afford [Co(HMal)2(H2O)4] complex within 4 h at room temperature and leaving WC unreacted and ready for re-employment in HM manufacturing. Characterization of the resultant materials i.e. treated powders (SEM-EDS, p-XRD, ICP-OES) and Co-leaching solutions (ICP-OES), confirmed the near quantitative Co removal as well as the possibility to finely tune the composition of WC-Co mixtures. Parameters for best leaching conditions, i.e. time and liquid-to-solid ratio, were obtained. A scale-up experiment addressed to test the leaching conditions and the quality of the recycled material is also described. The quality of the recycled material for direct re-employment in HM manufacturing was validated by Metallurgical Quality Control, to good effect. Finally, preliminary experiments on cobalt metal recovery from the metal complex by electrowinning and by quantitative precipitation as CoCO3 were performed with encouraging results: a step forward resources circularity.
| Original language | English |
|---|---|
| Article number | 105534 |
| Number of pages | 9 |
| Journal | International Journal of Refractory Metals and Hard Materials |
| Volume | 98 |
| Early online date | 31 Mar 2021 |
| DOIs | |
| Publication status | Published - 1 Aug 2021 |
Bibliographical note
Funding Information:This work was supported by the Italian Ministry of University and Research [Dottorati innovativi con caratterizzazione industriale - PON R&I 2014-2020, scholarship N. DOT1304527-3 ] and ERASMUS+ Placedoc 2018-19 action [AOA's felloship]; the Italian Ministry for the Environment, Land and Sea Protection [CoW_aste project, 2019]; Fondazione di Sardegna [“Precious metal-free complexes for catalytic CO 2 reduction” project, 2017]; the FILMS corp. [“The selective extraction of excess cobalt from the recovery powders of the ‘hard metal’ production process” project, 2018; “The selective extraction of excess cobalt from the powders produced by carbothermal regeneration of ‘hard metal’ scrap” project, 2019]. The authors gratefully acknowledge Prof. Luciano Marchiò, University of Parma, for the always fruitful scientific collaboration and his valued contribution in the single-crystal X-ray characterization of the [Co(HMal) 2 (H 2 O) 4 ] complex.
Funding Information:
This work was supported by the Italian Ministry of University and Research [Dottorati innovativi con caratterizzazione industriale - PON R&I 2014-2020, scholarship N. DOT1304527-3] and ERASMUS+ Placedoc 2018-19 action [AOA's felloship]; the Italian Ministry for the Environment, Land and Sea Protection [CoW_aste project, 2019]; Fondazione di Sardegna [?Precious metal-free complexes for catalytic CO2 reduction? project, 2017]; the FILMS corp. [?The selective extraction of excess cobalt from the recovery powders of the ?hard metal? production process? project, 2018; ?The selective extraction of excess cobalt from the powders produced by carbothermal regeneration of ?hard metal? scrap? project, 2019]. The authors gratefully acknowledge Prof. Luciano Marchi?, University of Parma, for the always fruitful scientific collaboration and his valued contribution in the single-crystal X-ray characterization of the [Co(HMal)2(H2O)4] complex.
Publisher Copyright:
© 2021 Elsevier Ltd
Keywords
- Carbides
- Cobalt
- Green chemistry
- Maleic acid
- Waste prevention