Magnetite nanoparticles enhanced glucose anaerobic fermentation for bio-hydrogen production using an expanded granular sludge bed (EGSB) reactor

The feasibility and efficiency of magnetite nanoparticles (Fe₃O₄NPs) enhanced bio-hydrogen production from glucose anaerobic fermentation were evaluated in this study. The results demonstrated that the maximum hydrogen yield (HY) of 12.97 mL H₂/g-VSS was obtained with 50 mg/L and 40–60 nm of Fe₃O₄NPs in batch experiments. Moreover, the optimum dosage of Fe₃O₄NPs produced hydrogen production (HP) of 4.95 L H₂/d in an expanded granular sludge bed (EGSB) reactor. Fe₃O₄NPs involved could promote ethanol and acetic acid accumulation. Fe²⁺ as by-product of iron corrosion could effectively promote the activity of key coenzymes and soluble microbial products (SMPs). Importantly, Fe₃O₄NPs addition resulted in the formation of electronic conductor chains to enhance the electron transport efficiency in the granular sludge. Microbial community analysis revealed that the relative abundance of butyrate-hydrogen-producing bacteria (Clostridium) decreased from 40.55% to 11.45%, while the relative abundance of ethanol-hydrogen-producing bacteria (Acetanaerobacterium and Ethanoligenens) increased from 19.62% to 35.35% with Fe₃O₄NPs involved, confirming that the fermentation type was transformed from butyrate-type to ethanol-type, which finally facilitated more hydrogen production.