Fermentative production of hydrogen in presence of modified mesoporous silica SBA-15

Hydrogen production was studied in the series of batch tests at 310 K in the presence of digested sludge free from methanogenic bacteria, glucose as the source of organic carbon and mesoporous silica of SBA-15 type as the adhesion-like material. Although mesopores of SBA-15 are too small for accommodation of bacteria (in this study mainly Clostridium and Enterobacter) within the porous system of SBA-15, the obtained results showed that process efficiency and reaction rate were significantly improved in presence of modified SBA-15 in comparison with those results obtained in their absence. The amount of produced hydrogen in presence of small amounts of non-modified and surface modified (NH2, Al3+) SBA-15 was apparently higher of about 50% (20% for non-modified SBA-15) than in suspensions without silica. Experiments with SBA-15 modified with SO3H groups showed negative influence of acidic surface properties on hydrogen production. Appropriate surface properties (mainly basic) of silica are probably responsible for better adhesion and propagation of bacteria properties, biofilm formation and in consequence higher activity. Moreover, systems containing SBA-15 are more resistant to temperature changes of medium. Sequential adjustment of reaction pH with stabilization at 5.5 improved the efficiency of hydrogen production.