Graphene functions as a conductive bridge to promote anaerobic ammonium oxidation coupled with iron reduction in mangrove sediment slurries

Graphene is a one-atom-thick sheet, possessing a high electron mobility, constructed from sp(2)-bonded carbon atoms. Here, we hypothesize that graphene functions as a conductive material to promote anaerobic ammonium oxidation coupled with Fe(III) reduction (Feammox) in mangrove sediments slurries. In this study, graphene and 9,10-anthraquinone-2-sulfonate (AQS) were both investigated using a nitrogen isotope tracing technique. Graphene and AQS addition increased the Feammox rates by 31% and 56%. Graphene also increased the Fe(III) reduction rate by 43%, but Feammox-associated Fe(III) reduction accounted for only 1.5-4.9% of the total Fe(III) reduction. Graphene may have behaved as a conductive bridge to promote electron transfer to the Fe(III) acceptor in the Feammox process; however, the mechanisms by which graphene and AQS stimulate Feammox are different.