Abstract
In this work, we proposed a method for biohydrometallurgical processing of mining (old pyritic flotation tailings) and metallurgical (slag) wastes to recover gold and other nonferrous metals. Since this processing allows the removal of toxic metals or at least decreases their content in the solids, this approach may reduce the negative environmental impacts of such waste. The proposed process was based on pyritic tailings’ bioleaching to recover metals and produce leach liquor containing a strong oxidizing agent (ferric sulfate) to dissolve nonferrous metal from slag. This approach also allows us to increase concentrations of nonferrous metals in the pregnant leach solution after pyritic waste bioleaching to allow efficient extraction. The old pyritic tailings were previously leached with 0.25% sulfuric acid for 10 min to remove soluble metal sulfates. As a result, 36% of copper and 35% of zinc were extracted. After 12 days of bioleaching with a microbial consortium containing Leptospirillum spp., Sulfobacillus spp., Ferroplasma spp., and Acidithiobacillus spp. at 35 °C, the total recovery of metals from pyritic tailings reached 68% for copper and 77% for zinc; and subsequent cyanidation allowed 92% recovery of gold. Ferric leaching of two types of slag at 70 °C with the leachate obtained during bioleaching of the tailings and containing 15 g/L of Fe3+ allowed 88.9 and 43.4% recovery of copper and zinc, respectively, from copper slag within 150 min. Meanwhile, 91.5% of copper, 84.1% of nickel, and 70.2% of cobalt were extracted from copper–nickel slag within 120 min under the same conditions.
Highlights
The main source of copper and zinc is concentrated sulfidic ores
This study aimed to develop a complex biohydrometallurgical technology for the joint processing of mining and metallurgical wastes containing gold and other nonferrous metals
Wastes from mining and metallurgical processes, produced at plants in Russia, were the objects of research. These were (i) old flotation tailings of copper–zinc sulfide ores of the Urals (Russia), (ii) current converter slag obtained during the processing of copper sulfidic concentrates (Urals, Russia), and (iii) old slag of pyrometallurgical processing of copper–nickel sulfidic concentrates (Norilsk, Russia)
Summary
The main source of copper and zinc is concentrated sulfidic ores. Sulfide concentrates of nonferrous metals are processed in mining plants, while the wastes from ore concentration (primarily froth flotation tailings) are stockpiled in tailing dumps [1]. The production of metals in pyrometallurgical plants is associated with slag waste formation [2]. Billions of tons of flotation tailings have been accumulated in Russia (and globally), mainly due to ore-processing plants’ operation. Estimates of average mine tailings production worldwide range from 5 to 7 billion tons per year [3]. The current flotation tailings produced at the Ural concentrators are characterized by copper and zinc content of 0.25–0.58 wt.% and 0.53–1.36 wt.%, respectively [5]
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