Mechanisms of Fine Mud Covering and Enhanced Dispersion for a Rutile Middling

Electric separation is usually adopted to separate and purify rutile and zircon. However, fine mud covering over the target minerals either reduces the conductivity of rutile or improves the conductivity of zircon. Therefore, the conductivity difference between zircon and rutile becomes smaller, leading to the difficulty of separation and purification of both minerals. In this paper, the mechanisms of fine mud covering and enhanced dispersion for a rutile middling were illustrated by theoretical calculations of Derjaguin–Landau–Verwey–Overbeek (DLVO) and the extended DLVO (EDLVO), respectively. The fine mud was initially characterized by chemical multi-element analysis, X-ray diffractometer (XRD) analysis, electron probe micro analysis (EPMA), and laser particle size analyzer. The results showed that the gangue was mainly composed of goethite, quartz, calcite, and kaolinite and the average particle size of the fine mud reached 11.06 μm. The DLVO theoretical calculation revealed that the covering ability of fine-grained gangue ranked as follows: quartz < goethite < kaolinite < calcite. Compared with the zircon, the fine-grained gangue was more likely to cover the surface of rutile. The EDLVO theoretical calculation suggested that the addition of sodium silicate or sodium hexametaphosphate promoted detachment of the gangue from the surface of rutile and zircon and the shedding order was quartz > kaolinite > calcite > goethite. Moreover, the sodium hexametaphosphate had a better dispersion effect than the sodium silicate.