This study is carried out to obtain basic data regarding oxidation and reduction reactions, originated on the recycling of waste tungsten hard scraps by oxidation and reduction processes. First, it is estimated that the theoretical Gibbs free energy for the formation reaction of WO₂ and WO₃ are calculated as ΔG_1,000K= -407.335 kJ/mol and ΔG_1,000K = -585.679 kJ/mol, from the thermodynamics data reported by Ihsan Barin. In the experiments, the oxidation of pure tungsten rod by oxygen is carried out over a temperature range of 700-1,000°C for 1 h, and it is possible to conclude that the oxidation reaction can be represented by a relatively linear relationship. Second, the reduction of WO₂ and WO₃ powder by hydrogen is also calculated from the same thermodynamics data, and it can be found that it was difficult for the reduction reaction to occur at 1,027°C, in the case of WO₂, but it can happen for temperatures higher than 1127°C. On the other hand, WO₃ reduction reaction occurs at the relatively low temperature of 827oC. Based on these results, the reduction experiments are carried out at a temperature range of 500-1,000°C for 15 min to 4 h, in the case of WO₃ powder, and it is possible to conclude that the reduction at 900°C for 2h is needed for a perfect reduction reaction.

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• A Basic Study on the Recycling of Wasted Cemented Carbide by the Zn Bath Process(Ⅰ)
  Kyung-Sik Kim, In-Ho Kim, Chan-Gi Lee, Chang-Bin Song
  Journal of the Korean Institute of Resources Recycling.2020; 29(6): 35.     CrossRef