Acidophilic Microorganisms Leptospirillum sp., Acidithiobacillus sp., Ferroplasma sp. As a Cathodic Bioagents in a MFC

Abstract

Reducing fuel cells electrical losses is achieved by the use of a catalyst. Being inexpensive and renewable, biocathodes have an advantage over synthetic and chemical ones. Here the microbial fuel cell (MFC)-utilizing biocathode based on the acidophilic chemolythotrophic microorganisms (ACM) mixed culture has been studied. The Leptospirillum sp., Acidithiobacillus sp., Ferroplasma sp. consortium has been used as a cathode biocatalyst. Pyrite enrichment tails of a mining and processing enterprise served as the catholyte substrates. It is experimentally demonstrated that ACM mixed culture Leptospirillum sp., Acidithiobacillus sp., Ferroplasma sp. introduced into the catholyte leads to MFC electrical characteristics increase by approximately two times. With the selected external load (30 Ω) Cathodic bioagents increased the MFC electric power four-fold (from 137 to 579 µW). Catholyte redox potential increased from 431 to 581 mV during 11 d in the presence of acidophilic iron-oxidizing microorganisms. At 33 d, this value increased up to 695 mV. This is an indirect evidence for active processes of iron oxidation. The analysis results for the Fe3+ content in the medium also support this assumption. Thus, in a course of a 33-d experiment Fe3+ concentration increased from 0 to 1.5 g/l. The redox processes intensification in the studied systems also confirmed by the cyclic voltammetry (CV). Under pyrite utilization conditions in the presence of ACM mixed culture cyclic voltammograms show an increase in the reduction current at the cathodic potentials region. The results obtained herein suggest that the studied biochemical system is a perspective catholyte for MFC capable to reduce a cathodic overpotential.