Reverse Column Flotation of Ultrafine Magnetite Mixture with Fine Glass Beads Enhanced by Fine Bubbles

Abstract

Magnetite ores are among the most important sources of iron, which is in high demand in the global economy. Metallurgical properties of the magnetite concentrate significantly depend on impurities of silicon- and aluminum-bearing minerals. These impurities have to be separated from ore by magnetic separation and flotation techniques. Reverse column flotation is one of the methods applied for reducing the content of impurities in magnetite concentrate. This method allows recovering impurities from ore in the froth product (flotation tailings). However, the efficiency of this method significantly decreases with the decrease in particle size. As previously demonstrated, the effectiveness of fine particle column flotation can be increased if, before feeding the pulp into a column, fine bubbles are introduced into the pulp and the pulp is then passed through a tubular reactor. The major purpose of this study was to define the effectiveness of the reverse column flotation performance of ultrafine magnetite from the mixture with fine glass beads (ballotini) when, before the pulp is fed into the flotation column, it is mixed with fine air-in-water dispersion, and the mixture is then passed through a tubular flotation reactor (TFR). The obtained experimental findings allowed the definition of the optimal conditions of the mixture treatment in TFR that ensured high concentrate grade and iron recovery for the initial iron content in the mixture of 63.76%. These conditions were defined as follows: treatment time of the mixture in the TFR—7.5 s; average flow shear rate inside the TFR—1000 s−1; volume dosage of fine bubbles per solid mass unit—0.032 or 0.21 mL/g. At the fine bubble dosage of 0.032 mL/g, the iron recovery and the concentrate grade were, respectively, 88.1% and 68.3% Fe, and at the dosage of 0.21 mL/g, the iron recovery reached 89.4% for the concentrate grade of 68.7% Fe.