Avaliação da aplicabilidade do processo de flotação com água sem coadjuvantes (processo de Kumara) na purificação da Grafite de Balama

Abstract

Graphite is a material of high technological interest, and Mozambique possesses important reserves of this resource in the provinces of Cabo Delgado and Niassa. Graphite is used in nuclear reactors, aerospace, advanced materials, battery manufacturing, conductive coatings, foundry coatings, friction materials, fuel cells, gaskets and seals, steel and iron production, glass industry materials production, refractory production, among others. Graphite ore is usually accompanied by gangue minerals, which does not allow its direct use without prior treatment. The study explored the possibility of using water as a means of concentrating graphite, to reduce the use of aggressive chemicals that contaminate the environment. The process consisted of suspending the ore in water, stirring, letting the suspension rest, and then decanting to collect the (pure) graphite in the supernatant. The materials, ore, concentrated graphite, residue, and wastewater were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF), and inductively coupled plasma optical emission spectroscopy (ICP-OES).

The results showed that the ore is composed essentially of graphite and quartz. The XRF results showed high levels of Si, Al, Fe, K, S, and Zn, in addition to other elements in smaller and trace amounts. Graphite concentrated under optimal conditions, solid:liquid ratio of 0.01 g/mL, stirring time of 180 minutes at 4000 rpm, using ore with a size < 88 μm and a suspension resting time of 48 hours, produced a concentrate with a fixed carbon content of 88.9%, slightly lower than the comparison standard used (90.8%), concentrated graphite at the factory. However, the quantification of graphite by the XRD method showed that the graphite content in the sample produced in this work was higher than that of the standard, suggesting that the method can be used for industrial purposes. The presence of Al, Fe, K, S, Ca and Zn after graphite concentration suggests that it may be necessary to slightly acidify the water of the suspension to aid in the dissolution of the gangue metals.