Deep insight into the reductive roasting treatment on iron removing from quartz.

[Display omitted] • Reductive roasting was ued to improve iron leaching from natural powder quartz. • The effect of ammonium sulphate on iron removal was systematically studied. • DFT calculations were used to investigate the activation mechanism of iron. • Si substituted by Al atoms were analyzed to illustrate the effect of iron valence. In the present work, Natural powder quartz (NPQ) ore was purified based on an integrated approach involving a reductive roasting pretreatment and acid leaching technology. The reductive thermal pretreatment was carried out through roasting in the presence of ammonium sulphate (AS). Compared with the conventional acid leaching technology, the content of iron remaining in concentrate could be reduced to below 0.3 μg·g−1 from 145.2 μg·g−1 after roasting in the presence of AS followed by acid leaching at room temperature. Thermogravimetric-mass spectrometry (TG-MS), colour responses of quartz and Density Functional Theory (DFT) were used to investigate the activation mechanism of iron by roasting with AS. It is inferred that SO 2 was acted as a reducing agent which promoted the reduction of Fe (III) to Fe (II), which would facilitate the removal of trace iron impurity from NPQ. This study gives a new insight into the activation and removal mechanism of iron impurity from NPQ by reductive action. [ABSTRACT FROM AUTHOR]