Preparation of needle-like Fe3O4/Fe2O3 nanorods on stainless steel plates to form inexpensive, high-performance bioanodes

Promotion of direct electron transfer between Shewanella putrefaciens CN32 and carbon fiber electrodes via in situ growth of α-Fe2O3 nanoarray

The iron transport system plays a crucial role in the extracellular electron transfer process of Shewanella sp. In this study, we fabricated a vertically oriented α-Fe2O3 nanoarray on carbon cloth to enhance interfacial electron transfer in Shewanella putrefaciens CN32 microbial fuel cells. The incorporation of the α-Fe2O3 nanoarray not only resulted in a slight increase in flavin content but also significantly enhanced biofilm loading, leading to an eight-fold higher maximum power density compared to plain carbon cloth. Through expression level analyses of electron transfer-related genes in the outer membrane and core genes in the iron transport system, we propose that the α-Fe2O3 nanoarray can serve as an electron mediator, facilitating direct electron transfer between the bacteria and electrodes. This finding provides important insights into the potential application of iron-containing oxide electrodes in the design of microbial fuel cells and other bioelectrochemical systems, highlighting the role of α-Fe2O3 in promoting direct electron transfer.

Efficient biodechlorination at the Fe3O4-based silicone powder modified chlorobenzene-affinity anode

The treatment of chlorinated volatile organic compounds faces challenges of secondary pollution and less-efficiency due to the substitution of chlorine. Microbial fuel cells (MFCs) provide a promising opportunity for its abatement. In this study, a novel Fe3O4 nanoparticles and silicone-based powder (SP) were integrated and immobilized on carbon felt (CF+Fe3O4@SP), which was further used as anode in the chlorobenzene (CB) powered MFC. Owing to the cooperation between SP and Fe3O4, the anode exhibited excellent performance for both biodechlorination and power generation. The results indicated that the CF+Fe3O4@SP anode loaded MFC achieved 98.5% removal of 200 mg/L CB within 28 h, and the maximum power density was 675.9 mW/m3, which was a 45.6% increase compared to that of the bare CF anode. Microbial community analysis indicated that the genera Comamonadaceae, Pandoraea, Obscuribacteraceae, and Truepera were dominated, especially, the Comamonadaceae and Obscuribacteraceae showed outstanding affinity for Fe3O4 and SP, respectively. Moreover, the proportion of live bacteria, secretion of extracellular polymer substances, and protein content in the extracellular polymer substances were significantly increased by modifying Fe3O4@SP onto the carbon-based anode. Thus, this study provides new insights into the development of MFCs for refractory and hydrophobic volatile organic compounds removal.

Preparation of AuNP-CQD/PDA/GO anode for MFC and its treatment of oily sewage from ships

Oily sewage discharged from ships has brought many harms to the marine environment, even endangered marine life and human life. As a new type of water treatment technology, microbial fuel cell (MFC) can efficiently treat pollutants and recover energy, which can be converted into electric energy. However, its large internal resistance restricts its development. In order to solve the problems of low power generation performance and poor biocompatibility of microbial fuel cell, a gold nanoparticle-carbon quantum dot/polydopamine/graphene oxide/bacterial cellulose (AuNP-CQD/PDA/GO/BC) electrode was prepared, and it was applied to the treatment of oily sewage from ships. Fourier transforms infrared spectroscopy, X-ray diffraction, scanning electron microscopy, gas chromatography-mass spectrometry, and contact angle measuring instrument were used to characterize the electrode. The results show that PDA bridges GO and AuNP-CQD particles through the electrostatic interaction/π-π bond/hydrogen bonding, respectively. This attracts a large number of microorganisms to attach to the surface of the porous anode material, which greatly improves the activity and quantity of microorganisms. Moreover, the maximum power density of AuNP-CQD/PDA/GO/BC electrode is 2624.91 mW/m², which obviously improves the electrochemical performance of MFC. The oil content of the treated water is ≤ 15 mg/L, reaching the discharge of MARPOL 73/78 convention. Therefore, the proposed approach has paved new dimensions in not only the preparation of a new composite electrode materials but also its applications as effective degradation of ship oily sewage in MFC.