St. Petersburg Mining University (St. Petersburg, Russia):

Melnichuk M. S., Postgraduate Student, myguiero@gmail.com
Fokina S. B., Assistant, Candidate of Engineering Sciences, fokina_sb@mail.ru
Boduen A. Ya., Associate Professor, Candidate of Engineering Sciences, bodyen-anna@mail.ru
Petrov G. V., Professor, Doctor of Engineering Sciences, petroffg@yandex.ru

The paper presents the results of the Nizhny Tagil dunite massif lowgrade platiniferous chromite ore (0.21 g/t Pt; 0.08 g/t Rh) material composition and processing technology studies. Gravity-magnetic processing flow sheet permits to recover platinum-containing magnetic concentrate with high grades of magnetite and platinum-iron alloys. Platinum recovery into magnetic product (0.35 % yield) is at least 70 % with hundred-fold beneficiation relative to feed ore. The reductive sulfuric acid leaching has been considered as a method of platinum-containing magnetic concentrate final dressing, providing for selective dissolution of iron and noble metals concentration in undissolved leaching residue. To provide for hydrochemical reduction of iron (III) present in leach solution to iron (II), iron powder was chosen, permitting to obtain saturated sulfate ferriferrous solutions, suitable for separation of iron vitriol as a marketable product. The study of physical and chemical regularities of magnetite reductive sulfuric acid decomposition permitted to determine iron leaching process optimal parameters: solution acidity – 200 g/l, twofold excess of metallic iron from theoretically required, temperature +70 °С, duration — 1.5 hr, L : S = 10 : 1. Platinum content in cake was 0.59 %, rhodium — 130 g/t with practically complete recovery of iron and chrome into solution — 95.1 and 98.9 %, respectively. On the basis of the accomplished studies, the dunite massif chromite ores integrated machine-processing flow sheet is proposed, providing for production of high-grade platinum-containing concentrate and chromite concentrate, complying with the requirements of the chemical production.

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