Development and Characterization of Nanoparticles for Industrial application : biohydrogen Production via Dark Fermentation

Abstract

Biohydrogen production through dark fermentation represents a sustainable and eco-friendly pathway for renewable energy generation, particularly from industrial waste as low-cost fermentable substrates. In recent years, a burgeoning interest in the application of nanomaterials to address thermodynamic limitations of dark fermentative hydrogen production has emerged. This thesis explores the development, characterization, and application of a series of iron-based nanomaterials as catalysts in dark fermentation process to achieve efficient hydrogen production. Two types of organic waste derived from the food industry, namely sugarcane molasses and cheese whey, were employed as substrates, while activated sludge and anaerobic sludge sourced from wastewater treatment plants served as microbial inocula. The study findings revealed the synergistic role of iron and cobalt in hydrogen production via dark fermentation of sugarcane molasses, achieved by doping magnetite nanoparticles by cobalt (Co-Fe3O4 NPs). The optimal Co-Fe3O4 NPs concentrations of 300 mg/L resulted in a maximum hydrogen yield of 2612.4 mL H2/L and production rate of 84.25 mL H2/L.h. Cobalt enhanced hydrogen yield by 13.43% compared to the undoped Fe3O4 NPs and a 41.78% compared to the control (avoid of NPs). The results also demonstrate that using activated carbon as a matrix support of Co-Fe3O4 NPs further enhance dark fermentation performance by increasing production rate, stimulating microbial growth and reducing the lag phase period. Additionally, employing both strategies, cobalt doping and activated carbon loading, showed positive effects on biomass yield, COD removal efficiency, and hydrogen production kinetics. As for the metabolic pathways of hydrogen production, a mixed route of acetate- butyrate was observed in all fermentation batch tests, with a notable shift towards the butyrate pathway upon the inclusion of the synthesized nanomaterials, thereby contributing to process stability. Moreover, magnetic materials, based on metal ferrite nanoparticles (MFNPs) were also evaluated for dark fermentative hydrogen production using cheese whey. From the results, hydrogen production results demonstrated dependency to MFNPs dosage. The inclusion of MFNPs at optimal concentrations led to significant hydrogen yield, whereas exceeding the Bioptimal levels led to inhibition of hydrogen production. Optimal concentrations of 2 mg/L CuFe2O4, 0.5 mg/L NiFe2O4, and 0.5 mg/L CoFe2O4 NPs improved hydrogen yield by 2.71, 2.58, and 2 folds, respectively, compared to the control. The highest hydrogen yield, 2432.8 mL/L, was achieved with 2 mg/L CuFe2O4 NPs, while the maximum production rate, 447.76 mL/L.day, occurred with 0.5 mg/L CoFe2O4 NPs. These results underscore the stimulatory impact of nanomaterials on the biochemical reactions and enzymatic activities underpinning dark fermentative hydrogen production, advancing the field's understanding of nanomaterial applications in sustainable energy processes.