Nosov Magnitogorsk State Technical University (Magnitogorsk, Russia):

Chizhevsky V. B., Doctor of Engineering Sciences, Professor
Fadeeva N. V., Associate Professor, Candidate of Engineering Sciences, Associate Professor, magtu_opi@mail.ru
Gmyzina N. V., Associate Professor, Candidate of Engineering Sciences, magtu_opi@mail.ru

The flotation rates for flake graphite ores are significantly reduced in the presence of oxidized graphite. Its proportion is constantly growing, which requires the development of effective flotation technologies. The recovery rates for easily floated and oxidized graphites in a frothless flotation cell are 55.6 and 4.7 %, respectively. When studying their surface properties, it was found that oxygen-containing groups were present on the surface of oxidized graphite. A quantitative assessment of the compounds on the graphite surfaces was performed using the differential thermal analysis (DTA). It has been established that, in the case of oxidized graphite, the DTA curve indicates an endothermic effect in addition to the exothermic effect. The mass loss increases from 0.68 to 3.84 %, and the wetting heat grows from 1.88 to 8.95 kJ/kg. The surface oxygen-containing groups were identified using the chemical methods based on acetate for the carboxyl groups and bisulfite for the carbonyl groups and using the acid-base analysis for the phenol and carboxyl groups. It has been established that the total surface content of oxygen-containing groups is 0.284 mg-equ/g for the easily floated graphite and 0.892 mg-equ/g for the oxidized graphite. Alkaline reagents were used to neutralize the oxygen-containing groups; optimal conditions and patterns for their action were determined. In industrial conditions, during the flotation of refractory ores, the carbon recovery was 87.9 % with and 4.2 % without the supply of Na₂CO₃. A floatability-based classification of graphite ores has been developed, taking into account the number of oxygen-containing groups along with the flake size.

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