Enhanced Degradation of Phenanthrene by Soil MFCs: Synergistic Interaction between Iron Minerals and Microorganisms

Abstract

The bioelectrochemical system can enhance the degradation of polycyclic aromatic hydrocarbons (PAHs) in soil by the enrichment and improved diversification of microbial communities, as well as the electroactive microbial extracellular electron transport (EET). Microbial fuel cells (MFCs) are an innovative bioelectrochemical technology that leverages added anodes to enrich microbes and utilize organic substrates for electricity generation. Iron minerals in soil MFCs can mediate EET through the dissolution of ions, influencing the system’s performance. In this study, phenanthrene was used as the pollutant to assess the impact of adding nanoscale hematite and magnetite to soil MFCs on electricity generation and pollutant degradation. The results indicated that the soil MFCs with magnetite added to degrade phenanthrene (C-Mag) resulted in the highest electricity output of 410.83±7.11 mV, while the soil MFCs with the addition of hematite (C-Hem) were most effective for the degradation of phenanthrene, achieving a 63.29% degradation rate. The study analyzed the crystalline structure of iron minerals, their dissolution state, and the microbial community structure in different soil MFC devices. It was observed that hematite promoted the soil MFCs’ performance by dissolving more Fe(II), and magnetite was more through microbial promotion to improve the system performance. The addition of iron minerals to the soil increased the abundance of various bacterial genera, including Geobacter, Trichococcus, Pseudarcobacter, Pseudomonas, Shewanella, and Petrimonas. Structural equation model (SEM) results showed that in the system with minerals, microorganisms directly improved the electricity production and indirectly affected the electricity production and phenanthrene degradation by influencing mineral dissolution. Moreover, a synergistic pathway between iron minerals and microorganisms to promote electricity generation and pollutant degradation of soil MFCs was proposed.