Cold oxygen plasma induces changes on the surface of carbon materials enhancing methanogenesis and N₂O reduction in anaerobic sludge incubations

Abstract

BACKGROUND Conductive materials, such as activated carbon (AC), graphene and biochar, have recently been applied for enhancing methane (CH4) production in anaerobic digesters. However, few efforts have been made to develop engineered conductive materials for these purposes. The aim of this work was to synthesize carbon materials from pecan nut shells and peach stones to apply them in anaerobic sludge incubations for enhancing the methanogenic activity, as well as the reduction of nitrous oxide (N2O). RESULT Addition of conductive materials increased up to six‐fold the maximum CH4 production rate. Moreover, oxidation of these carbon materials with cold oxygen plasma enriched their surface with redox functional groups (e.g. quinones), so that their application further increased the methanogenic production rate up to 11‐fold as compared to controls lacking conductive materials. Furthermore, the reduction rate of N2O was increased several orders of magnitude in the presence of synthesized carbon materials, which constitutes the first demonstration that conductive materials can significantly increase the reduction rate of this greenhouse gas. CONCLUSION Results indicate that there is great potential to develop engineered conductive materials to enhance both the production of CH4 and the reduction of N2O from wastewater treatment plants (WWTP), which may contribute to achieve more efficient processes. © 2019 Society of Chemical Industry

Immobilized Nanomaterials for Environmental Applications

“…Certainly, it was shown that the lack of pili and other cellular structures involved in electron transfer in microbial consortia can be compensated by the presence of CM [ 7 , 8 ]. Nevertheless, additional studies have indicated that the input of CM on AD processes goes beyond the stimulation of DIET because electric conductivity is not the only relevant parameter [ 6 , 9 ]. In fact, several physical-chemical properties of NMs, such as particle size, functional group, and surface area, drive the interactions between these materials and anaerobic microorganisms, ultimately determining the performance of anaerobic bioreactors during the production of methane from wastewater and solid residues.…”

Methane production enhanced by reduced graphene oxide in an anaerobic consortium supplied with particulate and soluble substrates

“…More recently, activated carbon derived from organic wastes has been shown to effectively enhance the reduction of N 2 O by denitrifying microorganisms, in addition to improving methane production in anaerobic consortia. 9 Additionally, the conductivity of activated carbon favors direct interspecies electron transfer (DIET). 10 Carbon nanofibers have also been reported to enhance the anaerobic biotransformation of nitroaromatic compounds; moreover, chemical surface modification played a relevant role, indicating that functional groups, which are able to accept and donate electrons, such as quinone groups, take part as redox mediators.…”

“…Activated carbon increases methane production due to the porosity of its particles, which serve as a proper niche to support microbial growth. More recently, activated carbon derived from organic wastes has been shown to effectively enhance the reduction of N 2 O by denitrifying microorganisms, in addition to improving methane production in anaerobic consortia . Additionally, the conductivity of activated carbon favors direct interspecies electron transfer (DIET) .…”

Enhanced anaerobic treatment of synthetic protein-rich wastewater promoted by organic xerogels

“…Signals corresponding to the presence of C=C, C-O, O-H and C-H bonds were likewise present in the reference materials (GO and CC); however, the lower intensity obtained for these samples indicate the prominent functionality of the synthesized OX samples. Enriched surface functionality of organic xerogels can lead to an increase in the interspecies electron transfer since these groups can serve as redox mediators37 .…”