Integration of external magnetic field on flotation system and depression of iron minerals in magnetic flotation

In this study, the effect of an external magnetic field on the depression of iron minerals was investigated by using a magnetic flotation column. For this purpose, a micro-flotation column jacketed with three solenoid coils was fabricated to create a funnel-shaped axially magnetic field.Effect of the magnetic system parameters, such as magnetic field strength and magnetic force, were analyzed using the theoretical approaches and experimental measurements. Additionally, other forces taking place in flotation (e.g. gravity, hydrodynamic and surface forces) were also determined. The results of the analysis showed that magnetic force was considerably higher than other forces. However, the successful depression of iron minerals depend not only on the magnetic field but also various flotation parameters and position of magnetic field placed on the flotation column are highly effective in magnetic flotation.Initially, magnetic flotation experiments were carried out on pure minerals. Flotation of binary mixtures of quartz-magnetite with 6×10-5 M dodecylamine as collector was carried out at pH 6.5 in the absence and presence of magnetic field and it was found that separation efficiency increased from 0% to 90% in the presence of the magnetic field. The significant enhancement in separation efficiency between magnetite and quartz was evident that magnetite could be successfully depressed by magnetic field.In order to obtain a phosphate concentrate containing low iron, magnetic flotation was subsequently conducted on the high-iron phosphate ore. The flotation results showed that magnetic field was more effective on the depressing of magnetite than corn starch in terms of Fe2O3 grades of the concentrates. A phosphate concentrate having about 27.78% P2O5 and 2.42% Fe2O3 grade was obtained with a 86% recovery from the ore containing 8.53% P2O5 and 14.69% Fe2O3.This research showed that external magnetic field can be used as selective depressant for magnetic iron minerals in the flotation of iron bearing ores.KEYWORDS: Flotation, magnetic flotation, external magnetic field, magnetic force, quartz, magnetite, phosphate