Sequential microwave roasting and magnetic separation for removal of Fe and Ti impurities in low-grade pyrophyllite ore from Wando mine, South Korea

Abstract

The applications and price of pyrophyllite are highly dependent on its Al2O3 and impurity contents. Titanium as well as iron in pyrophyllite are impurities causing colorization of the final product. We investigated a method for removal of Fe and Ti impurities to improve the grade of pyrophyllite ore using sequential microwave roasting and magnetic separation. Pyrophyllite ore from the Wando mine (South Korea) contains Fe impurities, such as pyrite and hematite, and Ti impurities, such as rutile and Ti-oxides. This research demonstrate that the ore can be purified by the proposed sequential separation technique using microwave treatment and magnetic separation. The purification efficiency for the low-grade pyrophyllite ore was evaluated by conducting batch-scale sequential treatment tests. The microwave treatment magnetized Fe minerals in the ore due to mineral phase changes, and thus the magnetic impurities could be successfully separated by the subsequent magnetic separation. Iron and Ti were removed from the pyrophyllite ore with 86.3% and 68.3% efficiency, respectively, by 30 min of microwave irradiation and 2000 gauss of magnetic separation. The high removal efficiency of Ti impurity was resulted from association of rutile with Fe minerals, although weak. The efficiency of impurity removal was improved by lengthening the microwave irradiation time and increasing the magnetic field intensity. By applying a high magnetic intensity ( > 5000 gauss), it was possible to remove additional paramagnetic Ti impurities. The sequential separation technique using microwave roasting and magnetic separation may be a promising method for enhancing the grade of low-grade pyrophyllite ore.