The surface science of Itabirite iron ore

In this project, iron ore from Brazil, and laboratory model system such as pure hematite and quartz monocrystals are investigated by surface sensitive techniques. The main goal is to establish a clear physical and chemical understanding on the mineral chemical interaction with differents reagents, like a corn starch and amine, in a complex aqueous solution system. These both are greatly applied industrially as reagents and surfactants on a separation process called flotation. In short, the separation process is based on the adsorption of starch molecules onto iron oxide, which renders the surface hydrophilic, preventing, at the same time, the adsorption of hydrophobic amine molecules present in the solution. Despite this process importance, the rather complex physical and chemical mechanism is not well understood. This project involves several experimental techniques such as FTIR, Raman, SEM and Zeta Potential to correlated the chemical properties observed on the industrial process to the surface characteristics observed by AFM and XPS investigations. The mineral samples and well-defined model systems of iron oxide and silica will be investigated with respect to the adsorption characteristics of selected reagents. The results may impact basic and applied research in the field.

The loss of iron-bearing minerals in the tailings of the reverse cationic flotation of quartz, evidenced by the presence of levels above 10% in metallic content in the floated product, constitutes a problem to be faced by the mineral industry. The most common causes of loss of iron-bearing minerals in the flotation process are hydrodynamic drag and failure in the action of the depressant, which leads to loss by true flotation of hematite. These factors were confirmed in studies carried out in recent years in the flotation circuits of the Vale S.A. mines plants in the state of Minas Gerais. Within this context, an in-depth study of the action of the depressant (corn starch) on the hematite surface becomes necessary, as well as the hydrodynamic aspects of the operation. It is also intended to study the interactions of flotation reagents depending on the different crystallographic orientations present in typical hematite crystals and how the surface physical-chemical composition and the formation of iron oxyhydroxides in the different crystals influence the interactions. Thus, an in-depth study of these interactions, involving Fourier transform infrared spectroscopic (FTIR) and X-ray photoeletric spectroscopy (XPS) techniques, has been developed by ITV MI in collaboration with CBPF.