Building efficient biocathodes with Acidithiobacillus ferrooxidans for the high current generation

Abstract

The development of biocathodes is highly fascinating in microbial electrochemical technologies research. In this study, iron-oxidizing bacterium Acidithiobacillus ferrooxidans -based biocathodes were developed under the constant polarization of the electrochemical reactors at −0.2 V vs. Ag/AgCl with a pH of 2. On the 15 th day of the 21-day batch experiment, A. ferrooxidans -based biocathode produced a maximum current density of −38.61 ± 13.16 A m −2 when the reactors were supplemented with 125 mM Fe 2+ ions as an electron donor and 9 mM citrate as an iron chelator to buffer the iron-rich medium. Oxidation of Fe 2+ to Fe 3+ by A. ferrooxidans and its electrochemical regeneration at the cathode were mainly responsible for the high current generation. Furthermore, in the presence of iron, A. ferrooxidans develop a multi-layer biofilm on the cathode surface, which could potentially perform an indirect electron transfer mechanism. • Highly improved Acidithiobacillus ferrooxidans -based biocathodes were developed. • Biocathodes had shown the highest current density of −38.61 ± 13.16 A m −2 . • Fe 2+ /Fe 3+ redox transformation is mainly responsible for the highest current densities. • A. ferrooxidans develop a multi-layer biofilm in the presence of iron. • A. ferrooxidans could perform both direct and indirect electron transfer mechanisms.