Trace elements determination in tungsten ores by neutron activation analysis

The kinetics approach of the leaching of industrial scheelite (CaWO4) concentrates in hydrochloric acid media investigated under controlled acid concentration in leachates, reaction atmospheres and temperature conditions. Experiments show that the scheelite decomposition rate increases as the acid concentration in the leaching solution and temperature increase. The apparent activation energy for the scheelite acid decomposition process is estimated in the present study to be equal to 10.43 Kcal(mol)-1. On the basis of the experimental results, it is proposed an equilibria competition mechanism as a function of the acid concentration which explains the peculiar behavior of the experimental systems at low temperatures. (Author)