Ferrous iron oxidation microflora from rust deposits improve the performance of bioelectrochemical system

Ferric iron (Fe(III)) ions are efficient electron acceptor in bioelectrochemical systems (BESs). For the first time, this study applied the enriched Fe(II)-oxidizing microflora individually from rust deposits, aerobic sludge, or topsoil to catholyte to regenerate Fe(III) ions to boost BES operation. Among three microflora, the rust-microflora had the highest Fe²⁺ oxidation rate and the lowest Fe ion loss rate since Acidithiobacillus sp., Ferrovum sp., Rhodobacter sp., Sphingomonas sp., and others enriched it. The rust-seeded BES generated the maximum power density of 77.15 ± 1.62 Wm^-3 at 15 ℃, 38.9 %, and 31.4 % higher than those in sludge and topsoil-seeded BES, respectively. The rust-microflora with enriched Fe(II)-oxidizing bacteria could enhance the performance of BES, reaching coulombic efficiencies of 98.2 ± 2.6 at reduced internal resistance (5.14 Ω), with 1.59 Ω by activation resistance and 0.77 Ω by diffusion resistance.