Enhanced photo-H2 production by Rhodopseudomonas faecalis RLD-53 immobilization on activated carbon fibers

Activated carbon fibers (ACFs) were firstly applied as fluidized solid carrier to immobilize photo-fermentative bacteria (PFB) for H2 production in batch culture. The observations by scanning electronic microscopy (SEM) demonstrated the close interaction between ACFs and PFB. The amount of immobilized bacteria and the performance of H2 production were strongly affected by specific surface area, length and amount of ACFs, respectively. Large specific surface area provided more surface attachment sites and more PFB were immobilized. ACFs with proper length avoided intertwining with each other and better fluidized during reactor operation. Excessive amount of ACFs not only limited the light conversion efficiency, but also increased biofilm detachment, resulting in low H2 yield. The maximum yield (3.08 mol H2 mol−1 acetate) and rate (32.85 ml l−1 h−1) of H2 production were obtained, using specific surface area (1500 m2 g−1), length (1 mm) and amount (0.8 g l−1) of ACFs. Compared with the conventional solid carriers, ACFs were effective solid carriers to immobilize PFB for improving H2 production, due to bacteria immobilized on the external surface of fluidized ACFs and formed a layer of dense biofilm.