Impact of mechanical activation and mechanochemical activation on natural pyrite dissolution

• Mechanochemical activation (MCA) was introduced as new pretreatment method.
• Mechanochemical activation can be more effectual than mechanical activation.
• Pyrite Fe extraction in 1 M H2SO4 leaching at ambient temperature was 87.2% by MCA.
• MCA increase amorphization degree of pyrite to 83% after 50 min intensive milling.

In this paper, a new pretreatment method was employed for the enhancement of pyrite mineral dissolution by using mechanochemical activation. The mechanochemical activation was carried out by co-milling of pyrite and iron powder for 20 and 50 min. The XRD analysis indicated that a fraction of pyrite and iron phase remained and troilite (FeS) was formed as a new phase after 50 min milling. In addition, the microstructural changes of mechanochemically and mechanically activated pyrite were investigated by Rietveld method. The results revealed that amorphization degree increased from 53% in mechanically activated pyrite for 50 min to 83% in mechanochemically activated pyrite for 50 min. The mechanochemical activation intensified crystallite size reduction of pyrite in comparison with mechanical activation. In spite of mechanical activation, the microstrain measures slightly reduced during mechanochemical activation due to mechanochemical reaction. Although, both the mechanochemical and mechanical activations of pyrite can enhance the dissolution of pyrite, total iron extractions in the 1 M sulfuric acid leaching tests at ambient temperature increase from 1.12% for the initial pyrite to 21.22% for 50 min mechanically activated pyrite leaching and then abruptly climb to 87.2% for 50 min mechanochemically activated pyrite leaching.