A facile method to enhance the performance of soil bioelectrochemical systems using in situ reduced graphene oxide

Bioelectrochemical systems offer a potential solution for the treatment of a broad variety of environmental contaminants. Unfortunately, when applied to the remediation of soil and sediments, the low electrical and hydraulic conductivities of these media limit their effective applicability in full-scale installations. Interestingly, these drawbacks may be overcome by including conductive particles within the soil porosity in order to maximize the outreach of the electrode through the contaminated medium, thereby minimizing electron- and mass-transfer limitations. Herein, we increase the electrical conductivity of a model porous aquifer using amendments of graphene oxide (GO), followed by its reduction to produce reduced graphene oxide (rGO) by means of microbial or electrochemical reduction methods. Both approaches promoted the formation of rGO-sand composites with superior electrical features compared to controls not amended with GO, with conductivity being positively correlated to the GO application rates, within the applied range of 10e2000 mgGO kgsand 1 . The electrochemical reduction yielded significantly higher conductivity than the biological method. This result is putatively ascribed to a higher degree of reduction achieved by the former approach. When applied to laboratory scale soil bioelectrochemical systems fed with sodium acetate as a model contaminant, the GO-amended reactors delivered 32x higher anodic current compared to unamended controls. We conclude that GO amendments to porous soils improve the outreach of the electrochemical process to include microbial cells in distal soil locations.