Investigation of the reduction of ZnWO4 by hydrogen gas

• The reduction of zinc tungstate by hydrogen gas was studied using a thermogravimetric method in the temperature range 823 to 1073 K. The experiments were carried out isothermally. A new W to Zn binary phase was found in the samples reduced at 873 K. This discovery is in disagreement with the earlier information on Zn-W phase equilibria that Zn and W do not form alloys. The favorable kinetic conditions would be of help for the formation of this phase. On the other hand, this phase was not observed in the sample reduced at 1073 K. The evaporation of zinc during the reduction was found to play an important role. The apparent activation energy for the reduction of ZnWO4 by hydrogen was evaluated to be 90 kJ/mole using the initial reaction rates.

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