Effects of mechanical activation on the HCl leaching behavior of plagioclase, ilmenite and their mixtures

Plagioclase (NaAlSi3O8–CaAlSi2O8) is one of the dominant impurity minerals in the ilmenite concentrate from the Panxi area of China. The effects of mechanical activation on the structural changes of plagioclase and ilmenite single minerals from Panxi were investigated using X-ray diffraction (XRD), particle size analysis, and scanning electron microscope (SEM). Hydrochloric acid leaching behaviors of mechanically activated plagioclase and ilmenite single minerals and their mixtures were also studied. The results show that with increasing milling time, the crystallite size, lattice strain and the particle size changed continuously but differed between plagioclase and ilmenite. Mechanical activation enhanced the leaching reactivity of plagioclase and ilmenite with 20% HCl at 105 °C, consistent with the lattice disorder and decreased particle size. The leaching of plagioclase was hardly affected by the existence of ilmenite, but the leaching of ilmenite was inhibited when plagioclase co-existed in the sample which is attributed to silica gel produced from leached plagioclase blocking the surface of unleached ilmenite.