Construction of conductive network using magnetite to enhance microflora interaction and petroleum hydrocarbons removal in plant-rhizosphere microbial electrochemical system

The combined bioremediation of microorganisms and plant roots is an environmentally friendly soil remediation technology with the application prospect. The inefficiency of electron transfer hinders the decomposition of reluctant petroleum hydrocarbons and the further absorption by plant roots in plant-rhizosphere microbial electrochemical system. A conductive network of extracellular electron transfer was constructed in this study by the combination of magnetite and external electrode, committed to strengthening the process of Direct interspecific electron transfer (DIET), Dissimilation iron reduction (DIR), and long-distance electron transport. The microbial conversions of C, N, and Fe related to the hydrocarbon removal were investigated in the compound remediation system (Fe + MEC). Compared with the control group (PCK), an increased 174-232% of Total petroleum hydrocarbons (TPHs) was removed from Fe + MEC, accompanied by the generation of bio-current. Synchronously, the reduction of iron oxide (mainly DIR) and nitrogen (mainly denitrification) was promoted due to the rapid transfer of extracellular electrons. A reinforced synergistic network of the potential degradation, denitrification, and iron-reducing/exoelectrogenic bacteria was constructed in the compound system, which may be connected through the magnetite-mediated electron transport chain. The results in this study provide an insight into the impasse overcoming of inefficient electron transfer during the remediation of organic contaminated soil.