Enhanced fermentative biohydrogen production from milk processing wastewater by magnetic spinel ferrites nanoparticles

In the present study, metal ferrites nanoparticles (MFNPs), comprising nickel ferrite (NiFe2O4), cobalt ferrite (CoFe2O4), and copper ferrite (CuFe2O4) nanoparticles (NPs), were synthesized and characterized for investigating their effect on biohydrogen production by thermophilic dark fermentation of milk processing wastewater (MPWW). The MFNPs were synthesized using the chemical coprecipitation method and were characterized using XRD, SEM-EDS, and VSM analysis. According to the characterization results, the average nanocrystallite sizes of NiFe2O4, CoFe2O4 and CuFe2O4 spinels were 25.8 nm, 33 nm, and 20.7 nm, respectively. The NPs prepared were pure and showed a ferromagnetic behavior. Dark fermentation tests revealed that the MFNPs had a promoting effect on biohydrogen production. In comparison with the control assay, biohydrogen yield was enhanced by 2.71, 2.58, and 2 folds higher for optimal concentrations of CuFe2O4, NiFe2O4, and CoFe2O4, respectively. The maximum biohydrogen yield of 246.13 ± 3.69 mL/g VS was obtained by adding 2 mg/L of CuFe2O4 NPs. The experimental data of MFNPs-assisted dark fermentation were well predicted by the Gompertz kinetic model.