Impact of Fe3O4 Nanoparticles on Methane Production from Anaerobic Digestion and Kinetic Analysis

Anaerobic digestion (AD) is one of the most widely used processes to stabilize waste sewage sludge and produce biogas as renewable energy. This study investigated the effects of Fe3O4 NPs at different concentrations (0,100 and 300 mg/L) on AD. 100mg/L Fe3O4 NPs could increase gas production by 21.9% and reach the highest methane content of 66.75%. In addition, 100 mg/L Fe3O4 kept pH at an appropriate level. Scanning electron microscope (SEM) was used to study the changes in surface morphology in sludge. The dynamics of cumulative biogas production and daily biogas production were studied by using the Logistic model and modified Gompertz model respectively. Other indices also had changed in the whole process, which in the end lead to the variation of biogas production. These results suggested that Fe3O4 NPs could increase microbial activity and relevant enzyme activities, caused changes and transitions between different phases in the system.