Magnetite-contained biochar derived from fenton sludge modulated electron transfer of microorganisms in anaerobic digestion

Biochar, with redox moieties or conjugated pi-bond, can act as electron shuttle or conductor to facilitate electron transfer of syntrophic metabolism to enhance anaerobic digestion. High pyrolysis temperature (>500 degrees C) is usually required to prepare conductive biochar, which however may cause biochar to loss redox moieties such as quinone/hydroquinone that are capable of serving as electron shuttle. Considering that magnetite is an excellent conductor which has been applied in improving syntrophic metabolism of anaerobic digestion, a novel magnetite-contained biochar was prepared using iron-rich Fenton sludge as raw material in this study. Amorphous iron oxides of Fenton sludge were transformed into magnetite at 400 degrees C of pyrolysis, while redox quinone/hydroquinone moieties of biochar were preserved well. Correspondingly, this magnetic biochar owned both high capacitance and excellent conductivity. When supplementing the biochar into an anaerobic digestion system, methane production was significantly enhanced. This study also offered a new approach to recycle Fenton sludge that is regarded as hazardous material.

Automated summary

A new magnetite-contained biochar was prepared using iron-rich Fenton sludge as raw material, with the transformation of amorphous iron oxides into magnetite at 400 degrees C of pyrolysis and preservation of redox quinone/hydroquinone moieties of biochar. This magnetic biochar exhibited high capacitance and excellent conductivity, leading to significantly enhanced methane production when supplemented into anaerobic digestion system, offering a new approach to recycle hazardous Fenton sludge.