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ELECTROCHEMICAL MECHANISMS OF INTERACTION OF ACIDOPHILIC MICRO-ORGANISMS WITH PYRITE-CONTAINING WASTES OF MINING INDUSTRY

Olga Kalashnikova

Abstract

The ability of acidophilic microorganisms to oxidize sulfide minerals is increasingly used in biohydrometallurgical technologies to produce non-ferrous and precious metals from sulfide ores. Strains of Acidithiobacillus ferrooxidans and Sulfobacillus thermotolerans often dominate heap bioleaching processes. Due to their high ability to catalyze redox processes, it has been suggested that they can be used in the technology of microbial fuel cells (MFCs). MFC allows using organic and inorganic waste as a substrate for microorganisms, rendering them harmless with parallel generation of electric current. The aim of this work was to study the electrochemical processes that occur in the cathode and anode spaces of MFCs under the action of acidophilic chemolithotrophic microorganisms on sulfur-containing and iron-containing mining wastes. As objects of study, strains of acidophilic chemolithotrophic microorganisms were used: 1) A. ferrooxidans 61, obtained from Dr. Sc. N. Vardanyan, Head of the Laboratory of Geomicrobiology of the Scientific and Production Center ?Armbiotechnology? of the National Academy of Sciences of Armenia; the strain was isolated in Tanzut (gold-polymetallic deposit), from acid drainage at ore deposits in the Lori region of Armenia; 2) S. thermotolerans Kr1 isolated from pulp of a gold-bearing sulfide concentrate treated at 40 ° C in a gold mining factory (Siberia). The substrates for microorganisms were molecular sulfur, iron (II) sulfate, and pyrite tailings from one of the mining and processing plants in Russia. Voltammograms were recorded using a potentiostat and «IPC Pro» software. The concentration of ferrous and oxide iron was determined by complexometric titration with trilon B. Using the method of cyclic voltammetry, data were obtained that testify to the intensification of redox processes using these systems. So, when utilizing elemental sulfur by A. ferrooxidans 61 strain, redox signals in the cathode and anode regions were recorded on the polarization curves. During utilization of iron sulfate in the voltammogram, significant peaks were noted in the reduction area. The voltammogram in the presence of the S. thermotolerans Kr1 strain in media with all tested substrates also showed significant redox signals in the field of oxidation and reduction. The intensification of the MF? operation was shown when using S. thermotolerans Kr1 and A. ferrooxidans 61 strains as cathode bioagents in them. The obtained materials suggest the possibility of using this biochemical system as catholyte in biofuel elements to reduce overvoltage at the cathode.

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