Application of cathode modified by reduced graphene oxide/polypyrrole to enhance anammox activity

Abstract

In this paper, a modified carbon felt (serving as the cathode) prepared by coating reduced graphene oxide (RGO) with polypyrrole (PPy) was applied in an electrode-anammox reactor. Compared with an anammox reactor with RGO addition directly, the anammox reactor with the RGO/PPy electrode applied had a higher nitrogen removal rate. Under the optimal voltage of 1.0 V, the nitrogen removal rate of reactor 3 (R3, RGO/PPy modified cathode applied) reached 1524 g-N m⁻³ d⁻¹ on day 198, which was about 37.5% and 13.7% higher than those of reactor 1 (R1, the control) and reactor 2 (R2, RGO addition). Moreover, transmission electron microscope observation indicated that RGO could cross into the anammox cells and lead to a morphological change of anammox biomass cells. In addition, the high affinity of the RGO electrode could make a biofilm of anammox biomass gather onto the surface of the RGO/PPy electrode as observed by scanning electron microscope images. Besides, it was demonstrated that RGO/PPy cathode application increased the crude enzyme activities and the cell quantities of the anammox reactor.