Processing of Alluvial Sand Wastes Using Thermal Hydrochemical and Biohydrometallurgical Technologies

The research focuses on processing of copper–nickel alluvial sand wastes at the Verkhnee deposit, Norilsk Industrial District. In the sand wastes, the size category of –100 $$\mu$$ m is chosen, with the nickel and copper contents of 0.32 and 0.22%, respectively. The material constitutions of the initial sand waste and experimental samples were examined, and the optimal mode of their processing by a combination of low-temperature roasting with ammonia sulfate and bio-leaching is selected. The sand samples were mixed with ammonia sulfate and roasted, then the roasted mix was leached in water for 40 min with continuous stirring at a rate of 230 min−1, and the remained was subjected to bio-leaching using iron-oxidizing bacteria. The maximal recovery of metals is achieved at the temperature of 400 °C and at a sand and ammonia sulfate mass ratio of 1:3: nickel recovery was 73.2% and copper recovery was 71.6%. Bio-leaching produced additional recovery of more than 20% of metals. Thus, through recovery of nickel and copper reached 95.4 and 88.0%, respectively.