Structure and property of polyvinyl alcohol/precipitated silica composite hydrogels for microorganism immobilization

Polyvinyl alcohol (PVA) hydrogel filled with precipitated silica (PSi) was prepared by chemical crosslinking in the saturated boric acid solution. The structure and property of the composite hydrogel was studied. It was found that PSi could accelerate the crosslinking reaction of PVA, and the intermolecular bonding of PVA/PSi composite was confirmed. Effect of PSi on reactive kinetics of PVA hydrogel was investigated. The tensile strength of PVA hydrogel increased with PSi content. Proper content of PSi could also enhance the permeability and swelling property, resulting in the improvement of the capillary water absorption capacity of PVA hydrogel. By addition of PSi, many large pores formed in the hydrogel so as to provide channels for microbial metabolites. When being applied in waste water treatment, the value of oxygen uptake rate (OUR) and COD removal rate of the PVA composite hydrogel immobilized with activated sludge increased significantly, indicating that the microbial activity of PVA immobilized beads could be enhanced.