Distinctive effects of graphene oxide and reduced graphene oxide on methane production kinetics and pharmaceuticals removal in anaerobic reactors

Graphene oxide (GO) addition to anaerobic digestion has been suggested to enhance direct electron transfer. The impact of GO (0.075 g GO g−1 VS) and biologically and hydrothermally reduced GO (bio-rGO and h-rGO, respectively) on the methane production kinetics and removal of 12 pharmaceuticals was assessed in Fed-batch reactors. A decrease of 15 % in methane production was observed in the tests with GO addition compared with the control and the h-rGO. However, bio-rGO and h-rGO substantially increased the methane production rate compared to the control tests (+40 %), in the third fed-batch test. Removal of pharmaceuticals was enhanced only during the bio-reduction of GO (1st fed-batch test), whereas once the GO was bio-reduced, it followed a similar trend in the control and h-rGO tests. The addition of GO can enhance the methane production rate and, therefore, reduce the anaerobic treatment time ; This research is funded by AEI (Agencia Estatal de Investigación, Spanish Government) through project ANTARES (PID2019-110346RB-C22). O. Casabella-Font acknowledges funding from Secretariat of Universities and Research from Generalitat de Catalunya and European Social Fund for his FI fellowship (2023 FI-3 00122). The authors acknowledge the support from the Economy and Knowledge Department of the Catalan Government through a Consolidated Research Group (ICRA-TECH - 2021 SGR 01283). We also acknowledge the support from Fundació I-CERCA through the CERCAGINYS program, funded by the Ministerio de Ciencia e Innovación (MICINN, Spanish Government) ; Open Access funding provided thanks to the CRUE-CSIC agreement with Elsevier ; 6