Effect of blunging process on purification of halloysite ore from ferrous impurities by dry magnetic separation

The objective of this research is to study the effects of feed particle size, splitter angle, and washing process on Fe2O3 removal efficiency in the separation of ferrous impurities from halloysite ore by dry magnetic separation in order to increase the purity of halloysite sample after crushing and blunging processes separately. Firstly, after crushing ore in a jaw crusher and sizing to -2+1 mm, -1+0.5 mm, and -0.5+0.212 mm fractions, the sized materials were fed to REMS-type dry magnetic separator at a constant belt speed of 300 rpm with the splitter angles of 0, 15, 30° separately. Maximum Fe2O3 removal efficiency (FRE) (97.1%) was obtained in the nonmagnetic product at -0.5+0.212 mm size fraction and 0° splitter angle. The minimum Fe2O3 content (1.3%) was reached in the nonmagnetic product obtained in the experiment with the feed size of -2+1 mm and a splitter angle of 0°. Secondly, dry magnetic separation was applied to the washed -2+0.212 mm size fraction after drying at room temperature to evaluate the coarse particle-sized halloysite ore that was gained by mechanical dispersion in the aqueous medium towards sodium hexametaphosphate (SHMP), while a significant part of the clay minerals went into fine size after the dispersion process. In the experiment performed with a 0° splitter angle after washing, it was determined that halloysite concentrate of 0.4% Fe2O3 content could be obtained with 98.8% Fe2O3 removal efficiency. As a result of dry magnetic separation experiments, it was seen that Fe2O3 removal efficiency decreased as the splitter angle increased, while Fe2O3 content in magnetic and nonmagnetic products increased. It was determined that washing and cleaning of finesized minerals plastered on particle surfaces after mechanical dispersion and particle release of minerals with different magnetic properties increased the dry magnetic separation efficiency, and nonmagnetic products with very low Fe2O3 (0.4%) and high Al2O3 (31.9%) content was obtained. The blunging process in the presence of dispersant caused the dispersion of clay minerals and allowed to liberating of the ferrous minerals from the halloysite ore, hence the increase in the FRE for the magnetic separation.