Characterisation and magnetic concentrationof an iron ore tailings.

Abstract

The Quadrilátero Ferrífero mineral province is one of the most important sources of ironore in Brazil. Nowadays this region produces 65% of the Brazilian iron ore. However, sincethe 1970s, there has been a continuous depletion of high Fe grade ores, obliging the mineralcompanies to concentrate low Fe grade ores in order to reach the quality demand of thesteel mills. It is estimated that 400 kg of tailings is produced for each tonne of beneficiatediron ore. This means there is a very big volume of tailings dumped from industrial plantsover the years. Owing to the inefficiency of the industrial operations, the tailings depositedin tailings dam have Fe grades similar to or higher than the Fe grades of some iron oresexploited nowadays (30–45 wt%). Therefore, the reprocessing of this material can recovermillions of tonnes of discharged Fe and decrease the volume of the existent tailings, whichcan be interesting for the environmental and economic sustainability of this region. Herein,we present the characterisation of a tailings sample from a gravity concentration circuitof a mine located in northwest of Quadrilátero Ferrífero with the objective of proposing aconcentration route for this material. The main characteristics of this tailings sample were:d80= 4 mm; grades of 30.3 wt% Fe and 55.4 wt%SiO2, while the identified minerals by XDR,optical microscopy and thermal analyses were quartz, hematite (martitic, lamellar, granu-lar, sinuous, specularitic), goethite (alveolar, amphibolitic, botryoidal), magnetite, kaolinite(5.3 wt%) and apatite (0.7 wt%). Liberation of quartz for size fraction – 0.150 mm was of 80%.Bench magnetic concentration of this material increased the Fe grade up to 23 wt% anddecreased the SiO2grade up to 39.4 wt% in the obtained concentrates, which is satisfactoryfor the rougher concentration step.