Leaching of Silver from Mechanically Activated Naumannite

In this paper, the structure, morphology, chemical composition and leaching of naumannite (Ag2Se) were studied. Mechanical activation of Ag2Se in a planetary ball mill resulted in increasing its specific surface area. The influence of milling time on the particle size was studied by particle size distribution analysis and scanning electron microscopy. The leaching kinetics of non-activated and mechanically activated samples in 3.5-7.9 mol/L HNO3 solutions were examined. Subsequently, the effect of leaching temperature in the range of 25-50 degrees C on the recovery of silver from mechanically activated naumannite was documented. The maximum yield of silver 94% was achieved after 120 min of leaching in 7.9 mol/L HNO3 at 50 degrees C for the sample mechanically activated for 30 min. Based on calculated activation energy values from the Arrhenius equation, a mixed leaching mechanism consisting of diffusion and surface chemical reaction as the rate-controlling steps of the solid-liquid reaction was assessed.