Estudo do uso do magstream na flotabilidade de alguns sistemas minerais

Abstract

present work consists of a series of studies involving the effect of the use of Magstream on mineral surface properties, specifically quartz and pyrite. The Magnetic fluidused by the equipment, a mixture of lignin sulphonate and iron salts, the Magfluid, is responsible for changes on mineral surfaces. The first change observed on quartz characteristics, after it was processed in Magstream, was a change of color fromtransparent to brownish. The studies in the electron microprobe showed that the contact between quartz and Magfluid produces two kinds of precipitates on the quartz surface. One of these precipitates presents a regular morphology and was considered in the present work as colloidal magnetite. It can be observed in particles from size as large as 7 µm to less than 1 µm, on quartz surface as a slime coating. The second one, with a very irregular morphology, was considered as a precipitate of iron lignin sulphonate. Both precipitates cause changes on minerals behavior in flotation. They increase quartz floatability with amine in the range of pH from 6 to 9 and from 11 to 12. This activating effect was attributed to an increase in the number of negative sites on the surface and immobilization of the collector on the surface. The precipitates also showed a stronger activating effect on quartz floatability with potassium amyl-xanthate. In this case the increase in floatability was attributed to a formation of a metallic xanthate complex with the precipitates formed on quartz surface. For pyrite the same mechanism was proposed to explain the increase of its floatability with the same collector. The activating effecton pyrite is more pronounced than on quartz. No activating effect was observed on quartz using anionic collectors. Changes in the operating variables of Magstream: fluid dilution and speed did not reduce the activating effect on quartz floatability with amine. However, Magstreams magnetic field showed to enhance precipitates formation on themineral surface. Floatability tests carried out with quartz contacted with the magnetic fluid outside the magnetic field of Magstream showed a decrease in the activating effect, although it was still present. The use of reagent to complex iron, such as oxalic acid, was not able to eliminate the activating effect. According to these results it was possible to conclude that the use of Magstream is not recommended when the intentionof mineral separation is to study surface properties, at least for quartz and pyrite.