“Priargunsky Industrial Mining and Chemical Union” JSC (Krasnokamensk, Russia):

Litvinenko V. G., Chief Technologist, Doctor of Engineering Sciences, e-mail: LitvinenkoVG@ppgho.ru

Sheludchenko V. G., Deputy Head of Central Research Laboratory, Candidate of Engineering Sciences

Filonenko V. S., Head of Chemical and Toxicological Laboratory (Central Research Laboratory)

Expensive manganese concentrate is used as an oxidant during the agitation uranium leaching. Decreasing of consumption of this concentrate or its replacement by another reagent is an urgent task. The following operations became the purpose of the carried out semi-industrial testings:
— stepwise decreasing of MnO₂ consumption with introduction of nitric acid, which has been earlier used for the equipment passivation into the process;
— decreasing of the range of agitation leaching of raw materials;
— increasing of uranium leaching into the solution.

Concentration of sulphuric acid was stepwisely increased from 40 to 80 g/dm³ with corresponding change of flows ratio and provision of pH of leached pulp within 1.2–1.8. This process was carried out for the following operations:
— choice of optimal and steady mode of sulphuric-nitric acid processing of raw materials during the first stage of uranium leaching;
— maintenance of redox process at the level of 700 mV.
During the experiments for raw materials opening with replacement of MnO₂ by nitric acid, there was substantiated, that steady redox process with application of HNO₃ and opened ore iron is maintained, taking into account the acidity of 65– 70 g/ dm³ and redox process, regulated by the acid dosage at the level of 690– 710 mV. In comparison with operating scheme of hydrometallurgical plant, the technology of sulphuric-nitric acid opening of raw materials during the processing of ores with ~0.12% of uranium content makes it possible to do the following operations:
— decreasing of MnO₂ consumption by 80–95% (from ~4.8 to 1.0–0.7 kg/t);
— increasing of uranium extraction into the solution from ~91.1 to 92–93.5% during the increasing of HNO₃ consumption from ~0.4 to 1.3–1.6 kg/t.