Enhancing the performance of soil microbial fuel cells by using a bentonite-Fe and Fe₃O₄ modified anode

To improve the performance of soil microbial fuel cells (SMFCs), Fe₃O₄ and bentonite-Fe were selected as anode modifiers, and correspondingly, graphite felt (GF), GF + Fe₃O₄ (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^-2 to 18.28 mW·m^-2 (GFF) and 29.98 mW·m^-2 (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 Fe₃O₄ and bentonite-Fe could enhance the potential of SMFCs in soil remediation, and bentonite-Fe outperformed Fe₃O₄.