Reduction of Fe(III) from iron-rich sludge by Geobacter to reconstruct MIL-100(Fe)@Fe3O4 to accelerate electron transfer and organic pollutants mineralization in Fenton-like system.

Iron-rich sludge contains abundant iron resources, yet lacks high-value processing methods. Iron-based metal-organic frameworks (Fe-MOFs), such as MIL-100(Fe), are widely used but suffer from considerable attrition and hardly recycle. Integrating iron extraction from sludge with Fe-MOF modification is promising for solid waste management. The redox capabilities of Geobacter, along with its production of Extracellular polymeric substance (EPS), hold potential for enabling this process. Nevertheless, the underlying mechanisms remain unclear, and the performance of the resulting product needs evaluation. In this study, Geobacter successfully loaded reduced Fe3O4 from iron-rich sludge onto MIL-100(Fe), creating MIL-100(Fe)@Fe3O4 (MF), a mesoporous nanomaterial with magnetic recovery. MF demonstrated excellent catalytic performance and repeatability, with removal efficiencies 1.4-2.5 times than those of MIL-100(Fe) in terms of pollutants. After seven cycles, the catalytic performance of MF remained stable because of the exist of EPS produced by Geobacter. Density Functional Theory (DFT) calculations confirmed that Fe3O4 loading enhanced charge transfer, improving catalytic efficiency. This study offers important insights on Geobacter for the pivotal role between iron-rich sludge and Fe-MOFs, which achieve the sustainable recovery and efficient utilization of solid waste.