Mining Institute of the Far Eastern Branch of RAS (Khabarovsk, Russia)

Rasskazova A. V., Leading Researcher, PhD in Engineering Sciences, annbot87@mail.ru
Sekisov A. G., Chief Researcher, Doctor of Engineering Sciences, sekisovag@mail.ru

In response to declining cut-off grades in mined ores, there is increasing interest in the recovery of valuable metals from manmade mineral formations such as beneficiation tailings. Polymetallic ore tailings represent complex secondary mineral resources with potential economic value. This study evaluates the hydrometallurgical recovery of zinc from aged lead-zinc flotation tailings, where the initial zinc content is approximately 0.6 wt.% and primarily occurs as sphalerite. Silver, at about 30 g/t, also presents potential by-product value. The process consists of two stages: initially, the tailings were impregnated with activated leaching solutions and allowed to undergo diffusion intrapore leaching. Subsequently, atmospheric agitation leaching was performed at room temperature. Sodium hypochlorite served as the primary zinc solvent, applied either directly or following diffusion pre-oxidation using sodium hypochlorite or sulfuric acid solutions, with or without supplementary ozone saturation. Direct chloride leaching achieved a zinc extraction of 28.7 %. Optimization of process parameters, including solid-to-liquid (S : L) ratio and leaching duration, increased extraction to 47 % via diffusion pore leaching. The active sodium hypochlorite solution was synthesized electrochemically. Zinc extraction during hypochlorite leaching with sulfuric acid pre-oxidation averaged 19 %, while ozonation of sulfuric acid solution followed by hypochlorite leaching increased extraction to 22.4 %. For low-grade mineral residues such as beneficiation tailings, heap leaching preceded by pelletizing emerges as a costeffective technological option for zinc recovery.

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