Promoting biomethane production from propionate with Fe2O3@carbon nanotubes composites

Using a batch anaerobic system constructed with 60 mL serum bottles, potential of a composite material with Fe 2 O 3 nanoparticles decorated on carbon nanotubes (CNTs) to enhance biomethane production was investigated. The composites (Fe 2 O 3 @CNTs) with well dispersed Fe 2 O 3 nanoparticles (4.5 nm) were fabricated by a facile thermal decomposition method in a muffle furnace under nitrogen atmosphere. Compared with Fe 2 O 3 , Fe 2 O 3 @CNTs showed a large specific surface area and good electrical conductivity. Supplementation of Fe 2 O 3 @CNTs to the propionate-degrading enrichments enhanced the methane production rate, which was 10.4-fold higher than that in the control experiment without material addition. The addition of Fe 2 O 3 @CNTs also not only showed a clearly electrochemical response to flavin and cytochrome C, but also reduced the electron transfer resistance when compared to the control. Comparative analysis showed that Fe 2 O 3 in Fe 2 O 3 @CNTs played a key role in initiating electrochemical response and triggering rapid methane production, while CNTs functioned as rapid electron conduits to facilitate electron transfer from iron-reducing bacteria (e.g., Acinetobacter , Syntrophomonas , and Geobacter ) to methanogens (e.g. Methanosarcina ).