Mechanism of Tungsten Recovery from Spent Cemented Carbide by Molten Salt Electrodeposition

Abstract

The accumulation of spent carbide (YG8), not only pollutes the environment but also causes waste of tungsten, cobalt and other rare metal resources. To better address this issue, we proposed a combined electrochemical separation process of lowtemperature aqueous solution and high-temperature molten salt for tungsten and cobalt. H 2 WO 4 was obtained from spent carbide in an aqueous solution, and we calcined it to obtain WO 3 , which was used as a raw material to obtain tungsten by using molten salt electrodeposition. The influence of the current efficiency and the electrochemical behavior of the discharge precipitation of W(VI) were also studied. The calcination results showed that the morphology of WO 3 was regular and there were no other impurities. The maximum current efficiency of 82.91% was achieved in a series of electrodeposition experiments. According to XRD and SEM analysis, the recovered product was high purity tungsten, which belongs to the simple cubic crystal system. In the W(VI) reduction mechanism experiments, the electrochemical process of W(VI) in NaCl-Na 2 WO 4 -WO 3 molten salt was investigated using linear scanning voltammetry (LSV) and chronoamperometry in a three-electrode system. The LSV showed that W(VI) was reduced at the cathode in two steps and the electrode reaction was controlled by diffusion. The fitting results of chronoamperometry showed that the nucleation mechanism of W(VI) was an instantaneous nucleation mode, and the diffusion coefficient was 7.379×10 -10 cm 2 •s -1 .

Repair of soft magnetic properties of wasted silicon steel and Co7Fe3 alloy deposition mechanism

“…After that, the current decreases with time from the moment of energization due to the migration effect of ions to the cathode and finally slows down to reach the steady state current value, which indicates that the crystal growth and nucleation process occurs at this stage. 17 In an aqueous solution, the ion concentration is much larger than the cathode surface, at this time the electrode surface concentration polarization dominates. Due to the difference in ion concentration, eventually, the two regions reach an ideal equilibrium and the current no longer changes.…”

Facile Preparation of Porous Diamond Films via Microwave Plasma Based on Metal Particles Heterogeneous Catalysis Etching

“…As long as the carbon in the nickel film is not saturated, the movement of diamond carbon diffusing into nickel to form graphite will not stop. 33 However, cracks appear at the grain boundary of the diamond film during this process mainly because there are more electric fields at the edge of the substrate due to the small area of the substrate during etching the diamond film, which makes the temperature distribution of the silicon substrate and diamond film uneven, resulting in a certain stress between the two.…”