Abstract
This study evaluates the influence of metal and metal-oxide nanoparticles (NPs) on biogas production from green microalgae Enteromorpha. The concentration of metallic NPs (Ni, Co) was 1 mg/L and oxides NPs (Fe3O4, MgO) was 10 mg/L. An anaerobic digestion was carried out batch-wise with working volume, operating temperature, mixing rate and hydraulic retention time as 500 ml, 37 °C, 150 rpm and 170 h, respectively. The measurements of chemical oxygen demand (COD), volatile fatty acids (VFAs), reducing sugar and biogas production were observed to monitor effectivity of nanoparticles. The results showed that NPs has moderate positive influence in biogas production until 60 h of retention time but significantly improve afterward. The maximum total biogas yield of 624 ml was achieved by Fe3O4 NPs whereas highest biohydrogen, 51.42% (v/v) was achieved by Ni NPs. The cumulative increase in biogas production for Fe3O4, Ni, Co and MgO NPs was 28%, 26%, 9% and 8%, respectively. A modified Gompertz and Logistic function model were used to determine kinetic constants of the reaction. The logistic model has the better predicting ability for microalgae anaerobic digestion.
•NPs showed an incremental effect on biodegradability of microalgal biomass.•Fe3O4 and Ni NPs showed more than 25% cumulative increase in biogas yield.•Reaction kinetics is determined by modified Gompertz and Logistic model.•Logistic model has better predicting ability for microalgae anaerobic fermentation.