Enhanced biohydrogen production from thermally hydrolysed pulp and paper sludge via Al2O3 and Fe3O4 nanoparticles

Abstract

The growing demand for sustainable and green energy sources has led to increasing interest in biohydrogen production from renewable biomass feedstocks. In this study, pulp and paper sludge (PPS), a widely available waste residue, was thermally treated at different temperatures (90^°C, 130^°C, and 165^°C) for varying durations (15, 30, and 60 min). Thermal hydrolysis of PPS increased the chemical oxygen demand (COD) solubilization from 11 % to 24.7 %, and volatile suspended solids (VSS) solubilization up to 15 % with increasing both hydrolysis temperature and reaction time. The resulting thermally treated samples were then evaluated for biohydrogen production through a batch assay. Among the different thermal treatment conditions, the sample treated at 165^°C for 60 min exhibited the highest biohydrogen production potential and yield (1287 mL-H₂ and 201 mL-H₂/g volatile solids (VS)), which is 72 % higher the control untreated PPS (747 mL-H₂ and 117 mL-H₂/gVS). To further enhance the biohydrogen yield, this optimal sample was mixed with two types of chemically synthesized nanoparticles, namely aluminium oxide (Al₂O₃) and magnetite (Fe₃O₄), at various concentrations (50, 100, and 200 mg/g VS). The addition of nanoparticles significantly influenced the biohydrogen production from the thermal-treated PPS. Remarkably, the batch assay mixed with 200 mg of Fe₃O₄ nanoparticles per gram of VS demonstrated the highest biohydrogen production potential, compared to the thermally treated PPS (1577 vs. 1226 mL-H₂). This finding suggests that the presence of Fe₃O₄ nanoparticles enhances the biohydrogen production process, possibly through improved microbial activity and substrate accessibility. The results of this study highlight the potential of utilizing PPS, an abundant waste product, as a valuable feedstock for biohydrogen production. Overall, this study contributes to the advancement of green energy technologies and underscores the potential of biohydrogen as a renewable and sustainable energy source.