Enhancing the performance of soil microbial fuel cells by using a bentonite-Fe and FeO modified anode.

To improve the performance of soil microbial fuel cells (SMFCs), FeO and bentonite-Fe were selected as anode modifiers, and correspondingly, graphite felt (GF), GF + FeO (GFF), and GF + bentonite-Fe (GFB) anodes were created and applied to the SMFCs system. The stable voltages of SMFCs were 249 mV for GFF and 324 mV for GFB, thus representing an increase by 8.26% (GFF) and 40.87% (GFB) in comparison with those of GF. Moreover, the maximum power density in the modified treatment increased from 10.6 mW·m to 18.28 mW·m (GFF) and 29.98 mW·m (GFB), and the internal resistance was reduced to 395 Ω for GFF and 219 Ω for GFB. The degradation efficiency clearly improved after being modified, especially by bentonite-Fe, and the removal ratios of the total petroleum hydrocarbon (TPH), anthracene, phenanthrene and pyrene reached 31.42%, 36.62%, 32.48% and 26.24%, respectively, after the SMFCs had run for 45 days. Both modifications contributed to the enrichment of electricigens on the anodes; however, there was minimal difference between them, which resulted in a similar microbial community on the modified anodes. The results demonstrated that FeO and bentonite-Fe could enhance the potential of SMFCs in soil remediation, and bentonite-Fe outperformed FeO.