Electrodialytic recovery of tungsten and cobalt from tungsten carbide scrap

Critical raw materials (CRMs) are essential for a wide range of European industrial ecosystems. Access to critical resources is necessary for Europe’s ambition to achieve climate neutrality and deliver the Green Deal. However, supply of material from primary sources is putting extreme pressure on the planet through greenhouse gas emissions, biodiversity loss and water stress. In this scenario, promoting circular economy by obtaining resources from secondary sources is therefore essential to reduce the environmental burden posed by raw material primary extraction and to secure the supply chain of CRMs. This work is a preliminary assessment on the potential of the electrodialytic (ED) treatment in alkaline condition on a tungsten carbide scrap powder obtained from end-of-life cutting tools industry for the recovery of two CRMs: Tungsten (W) and Cobalt (Co). Modular ED reactors with 2 or 3 cell compartments have been used to perform eleven ED experiments (each lasting 24 h), with either NaOH or NH4OH and at 100, 150 or 200 mA to individuate the best reactor configuration, alkaline reagent, and current intensity. The alkaline reagents were placed at different concentrations in the anode compartment (in case of 2-compartments reactor) or in the central compartment (in case of a 3-compartments reactor) along with 450 mL of deionized water and the solid matrix with a solid:liquid ratio of 1/50. Inductively coupled plasma-atomic emission spectroscopy was used to quantify the amount of W and Co obtained in solution at the end of the experiments. The experiments showed that the 2-compartments ED cell setup at 100 mA and with NaOH 0.1 M resulted in the highest W dissolution ( 651 mg), and that the 3-compartments ED cell setup at 100 mA and with NaOH 0.01 M resulted in the highest Co dissolution ( 372 mg) and electromigration (85%). Further investigation is needed to optimize the operational parameters.