Influence of Fe2+ and Fe3+ on the Performance and Microbial Community Composition of a MFC Inoculated with Sulfate-Reducing Sludge and Acetate as Electron Donor

Abstract

A sulfidogenic sludge supplemented with acetate was evaluated in the anodic chamber of microbial fuel cells (MFCs) in the presence of sulfate (SO4-2)/Fe3+ and sulfate (SO4-2)/Fe2+ to investigate the MFC performance and the effect of the iron ions on the composition of the microbial community since sulfate and iron ions are frequently present in wastewater derived from several anthropogenic activities. The current densities were up to 0.025 mA/cm2 and 0.017 mA/cm2 for MFCs with Fe2+ and Fe3+, respectively. Accordingly, the redox activity was slightly higher in the presence of Fe2+ than Fe3+. In general, the metabolic activity of the MFC supplemented with Fe2+ was higher than the system with Fe3+ reaching a percentage of sulfate reduction (% SR), sulfide concentration (mg/L HS-), and removal of chemical oxygen demand (% COD removal) of 35.2 ± 0.75 , 450.3 ± 3.6 , and 50.05 ± 0.24 for % SR, HS-, and % COD, respectively, whereas in the MFC with Fe3+, the percentages were of 30.1 ± 1.076 , 220.6 ± 2.0 , and 11.78 ± 10.81 for % SR, HS-, and % COD, respectively. The microbial population determined in each system was also correlated to the metabolic activity. Rhodospirillales, Caulobacterales, and Burkholderiales were the most abundant orders of bacteria in the MFC with Fe3+, whereas with Fe2+, Rhodobacterales, Sphingomonadales, and Rhizobiales. Desulfohalobiaceae and Desulfovibrionaceae were identified in the presence of Fe2+. Unexpected interactions and combinations of microorganisms were observed in a relatively short culturing time, demonstrating the importance of characterizing the anode biofilm prior to shifts in iron ion concentrations on a long-term basis.

Unveiling the bioleaching versatility of Acidithiobacillus ferrooxidans

“…Microorganisms instead utilize Fe 2+ and sulfur for metabolic processes, leading to the formation of Fe 3+ and sulfate ions. This metabolic activity results in a higher concentration of these ions subsequently intensifying the dissolution of sulfide minerals and augmenting the volume of acidic water (González-Paz et al, 2022). A quintessential illustration of this bioleaching phenomenon is the process involving chalcopyrite (CuFeS 2 ) microbial-mediated dissolution (Eq.…”

Sulfate as an Alternative Electron Acceptor: A Potential Strategy to Mitigate N2O Emissions in Upland Arable Soils

“…AKYG1722, known for utilizing SO4 2 ⁻ in N-depleted environments, was notably more abundant under MS treatments 43 . The presence of Herminiimonas, Cyclobacteriaceae, Rhodospirillales, and Gemmatimonadaceae, which can utilize both NO3⁻ and SO4 2 ⁻, indicates a complex interplay within the microbial ecosystem [44][45][46][47] .…”

High-rate Biohydrogen Production in Single-Chamber Microbial Electrolysis Cell Using Iron-Sulfide Modified Biocathode

“…Hence, various technologies have been investigated, for instance, water electrolysis, biomass gasification, and biological hydrogen production, to achieve more sustainable hydrogen production (Noori et al 2024a). Among them, the process of using renewable electricity for water electrolysis is considered a promising technology (Godula-Jopek 2015). However, precious metal catalysts such as platinum and iridium are often required to be used on the electrodes, which potentially can increase the fabrication cost of the electrolyzers (Wang et al 2021).…”

“…Similarly, FexMnOy complexes provided a highly active surface area for the microbes to colonize the carbon cloth (CC) cathode in an MES for CO2 reduction into volatile fatty acids (VFAs), and the improved cathodic current response was about 1.2 times higher than the value using pristine CC cathode (Tabish Noori and Min 2019). While the precise mechanism of iron-based catalytic enhancement in the biocathode remains unclear, it can be postulated that iron facilitates direct extracellular electron transfer, owing to its dual redox states (Fe 2+ /Fe 3+ ) like those observed in microbial c-type cytochromes (González-Paz et al 2022). In an earlier study, the FeS nanosheet demonstrated high catalytic activity and fast electron transfer in abiotic HER with a significantly lower overpotential loss of 142 mV, owing to their intrinsic electron-transferring properties (Zhou et al 2019).…”