Electrochemical reduction of tungsten disulfide to tungsten in molten salts

Date

2025-1-10

Author

Yılmaz, Olgun

Metadata

Show full item record

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Item Usage Stats

46
views

0
downloads

Cite This

Electrochemical reduction of tungsten disulfide (WS2) was investigated under constant voltage. The cell and anode designs were successfully developed. The effects of key process parameters including temperature, the composition of salt mixtures containing four different salts such as KCl, NaCl, CaCl2 and BaCl2, the type of starting material and applied voltage were evaluated on reduction time and energy consumption. Temperature had a dominant factor on reducing reduction time while increasing energy consumption. Linear sweep voltammetry (LSV) was used to determine the necessary reduction potential as 2.05 V and the electrochemical mechanism of cell. Based on the Design of Experiment (DOE), reduction times and energy consumption was found to decrease when the composition of CaCl2 and NaCl were increased. The energy consumption changes between 1.1 and 1.6 kWh/kg, while reduction times varied from 2 to 14 hours for reduction of two grams of WS2. From the ranges studied, optimal process parameters were identified as; working temperature of 750°C, applied potential of 2.8 V and salt composition of 75% CaCl2-NaCl molten salt. Treating produced powder with dilute HCl solution effectively removed all calcium-based impurities and significantly decreased Fe, Cr and Ni-based impurities. Moreover, when unsintered pellets were used, faster reduction rates were achieved compared to their sintered counterparts. An analytical model was developed based on sulfur diffusion to predict current-time graph closely fit the experimental data. In addition, increasing CaCl2 content led to larger crystallite and particle sizes due to changes in the physical and electrical properties of the salt mixture.

Subject Keywords

Electrochemical Reduction, Molten Salts, Tungsten Recovery

URI

https://hdl.handle.net/11511/113354

Collections

Graduate School of Natural and Applied Sciences, Thesis