Electrodialytic recovery of tungsten and cobalt from an industrial residue – preliminary assessment

• Autor(a) principal: Gaspar, David Emanuel Pinto
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/134286
• topic: Electrodialytic process; critical raw materials; recycling; tungsten carbide; tungsten; cobalt; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia do Ambiente

Critical raw materials (CRMs) have a significant importance for key sectors in the European economy. This importance will continue to grow due to the Green Deal, as the sustainable transition to carbon neutrality by 2050 is settled in modern technologies and renewable energies, which are closely linked to a need for many raw materials. Europe is very highly dependent on imports of most of the raw materials needed by European industries, with a set of CRMs presenting a high level of concentration in particular countries, some of them geopolitically unstable. For this reason, the supply chains security depends largely on efficient management of resources throughout the lifecycle and the commitment to recycling using secondary resources, such as industrial residues. Investing in CRMs' recycling processes and their sustainability is essential to maintain the supply chains. The present work is the first attempt to study the application of the electrodialytic (ED) process for recovery of two CRMs, tungsten (W) and cobalt (Co), from tungsten carbide (WC-Co) scrap powder resultant from end-of-life cutting tools. ED process consists of the application of a low-level electric current, in the presence of cation and/or anion exchange membranes, which promote the separation between compartments. In this specific work, acid desorption of W and Co from the matrix was carried out, followed by electromigration and electrodialysis. Eight experiments were carried out during 24h, using ED cells with three (3C) and two (2C) compartments to perform three assessments: the best electrolyte, the best solid:liquid ratio, and the best current intensity. The WC-Co matrix was placed in the central cell compartment in the 3C setup and directly in the anode in a 2C cell. The results show that the 2C cell setup with NaCl 0.02 M as catholyte and citric acid 0.4 M as anolyte, a solid:liquid ratio 1:25, and an initial current intensity of 200 mA presented the highest W (2194 mg; 99.6% of total W solubilized) and Co (558 mg; 81.3% of total Co solubilized) recovery. However, the current intensity was not completely optimized yet and needs further investigation. This dissertation will contribute to guide future experimental work to optimize the ED conditions for W and Co recovery.