Abstract
The flotation has been successfully applied to process the iron ore for the particle size (Ps) from 10 µm up to 150 µm. The presence of the slimes (Ps < 10 µm) is harmful on the reverse flotation of quartz, so they are usually prior removed by hydrocyclones. The main effects of the presence of slimes on the flotation are related to the increase on reagents consumption, the froth stability, and decrease on the selectivity. The lower floatability of coarse quartz particles (+74 µm) combined with the presence of slimes, even in small quantities, drastically affect the flotation response. This paper shows a study of characterization of a typical iron ore slime, aiming to create a better understanding of its role on the concentration by flotation. The main characteristics of typical slimes from the Iron Ore Quadrangle in Brazil are the presence of almost 70% of hematite, 25% of quartz, and 5% of kaolinite, as the main silicates gangue minerals. Furthermore, the particle size distribution revealed that 80% of the hematite and the kaolinite are below 20 µm. The affinity between the ultrafine kaolinite of the slimes with the corn starch is harmful to the reverse flotation of quartz, as the starch has an important depressing action over the hematite. The presence of 20% of hematite −20 µm decreased the recovery to the froth of quartz + 74 µm from 97% to 62%, where the slimes coating seems to be the main responsible.
Highlights
The flotation of iron ores is performed in circuits that consist of mechanical cells, columns, or a combination of both types of machine
The chemical analyses and size distribution of the iron ore slime, sample 1 are shown in Table 4 and Figure 1, respectively
More than 80% of the hematite and Typical slimes from the Iron Ore Quadrangle in Brazil present composition around 70% of the kaolinite are below 20 μm
Summary
The flotation of iron ores is performed in circuits that consist of mechanical cells, columns, or a combination of both types of machine. Studies that were conducted by Thella and coworkers with the iron slimes stored in slimes pond showed the possibility to obtain concentrates with 64.46% Fe, 2.66% Al2 O3 , and 2.05% SiO2 with the combination of two stages of hydrocyclones of 50 mm of diameter with vortex finders of 14.3 mm and 11 mm of diameters to remove the particles with high content of Al2 O3 and enhance the flotation selectivity while using amines and starch [8]. Bandini and coworkers analyzed the effect of colloidal iron ore slime on the flotation of galena and quartz particles by coatings [14]. Understanding the harmful effect of these slimes on the iron ore flotation is a challenging and it can be useful to develop alternatives to increase the Fe recovery on the beneficiation plants
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