Siberian Federal University (Krasnoyarsk, Russia):

Gilmanshina T. R., Associate Professor, Candidate of Engineering Sciences, gtr@mail.ru
Koroleva G. A., Associate Professor, Candidate of Chemical Sciences, lpiomd@bk.ru
Kovaleva A. A., Associate Professor, Candidate of Engineering Sciences
Lytkina S. I., Associate Professor, Candidate of Engineering Sciences, svetka-lisa@mail.ru

The objective of this work is to study the prospects of natural cryptocrystalline graphite microbiological beneficiation method. In the series of simulation experiments in cryptocrystalline graphite microbiological beneficiation technology development a simulated solution of A. niger microorganism culture medium was used. With that, graphite ash content decreased from 20–25 to 8–10 %. X-ray spectral analysis proved that as a result of microbiological beneficiation, iron and potassium are removed from graphite, while contents of titanium, calcium and sulfur practically do not change; quartz, finely disseminated in flake graphite, is not oxidized by microorganisms. Also, it was established, that in the course of beneficiation process a new phase — wavellite — is accumulated in graphite, which is due to release of gaseous products СО and СО₂ in atmospheric oxidation of graphite. With a view to further improve beneficiation efficiency, mechanically activated graphite and subjected to mechano-thermochemical modification graphite were processed by means of microbiological leaching. Graphite ash content, subjected to mechanical activation with subsequent microbiological beneficiation, decreased from 21 to 14 % (with activation in planetary centrifugal mill) and to 7 % (with activation in vibratory mill). This is due to the fact that in the mills of both types high-rate deformation of graphite becomes possible under high loads, resulting in liberation of graphite intergrowths with impurity minerals, permitting to decrease ash impurities content. With activation in vibratory mill, liberation of graphite from ash impurities becomes more intensive, leading to a more significant decrease of ash content. Ash content of beneficiated graphite, subjected to microbiological beneficiation, amounted to 3 %.

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