Comparison of calcium magnesium ferrite nanoparticles for boosting biohydrogen production

Dark fermentation (DF) is an eco-friendly process that simultaneously achieves organic matter degradation and obtains hydrogen (H₂). Nonetheless, low H₂ yield mainly caused by poor activity of key microbes, is still a problem that requires being resolved. In this work, MgFe₂O₄ and Ca_0.5Mg_0.5Fe₂O₄ nanoparticles (NPs) were synthetized and served as additives to boost H₂ form from DF. H₂ productivity gradually increased with the rise of NPs, and declined when NPs exceeded their optimal dosages. The highest H₂ yield was 183.6 ± 3.2 mL/g glucose at 100 mg/L of MgFe₂O₄ NPs, being 35.2 % higher than that of the control yield (135.8 ± 3.1 mL/g glucose). However, the highest H₂ yield of 171.9 ± 2.5 mL/g glucose occurred at 400 mg/L of Ca_0.5Mg_0.5Fe₂O₄ NPs, increasing by 26.6 % over the control. Interestingly, the two NPs favored the butyric acid pathway for H₂ synthesis. This provides guidance for multi-element oxide NPs used in DF.