Effect of Slime and Impurity Removal as a Pre-Treatment Stage Using a Low-Grade Zinc-Oxide Sample

Abstract

A low-grade zinc-oxide sample (6–8% Zn) from Mehdiabad mine in Iran, with a high amount of slime and iron (17–19% Fe) and manganese (5–7% Mn) impurities was studied. Pre-treatment processes, such as desliming and wet high-intensity magnetic separation were applied for impurity removal. Petrographic studies showed that the zinc minerals were hemimorphite, hetaerolite, smithsonite, sphalerite and a low amount of zincite; lead was present in galena and manganese was in hetaerolite and pyrolusite. The gangue minerals were dolomite, calcite, hematite, goethite, pyrite and quartz. From a processing perspective, the sample can be characterized as a low-grade zinc-oxide sample. Experimental data and scanning electron microscopy/energy-dispersive X-ray spectroscopy analysis showed that desliming prior to magnetic separation is required, and the optimum concentration ratio and recovery in the absorbed part can be determined by applying one stage of wet high-intensity magnetic separation with grinding and a magnetic field intensity for 16 min and 14 000 G. By considering the abovementioned conditions, the concentration ratio and recovery of iron and manganese in the absorbed part have been obtained as 1.42 and 1.54 and 73.28% and 79.79%, respectively, and the non-absorbed part of the pre-treatment stage with 10.56% Fe, 3.29% Mn and 6.83% Zn can be considered as flotation feed.