FLOATABLE FILTER MEDIUM AND ITS PRODUCTION

摘要

PROBLEM TO BE SOLVED: To provide a floatable filter medium filled in a biological filter apparatus and having high voids high specific surface area, high treatment efficiency and hydrophobicity. SOLUTION: This floatable filter medium has porosity and density of 1.0 g/cm<3> or less in an inorg. org. hybrid wherein a skeleton of an inorg. polymer composed of an M-O-M bond (M is a metal or semimetal atom) is substituted by one kind or two kinds of an Si(R)m(O-)(4-m)/2 group and an -O-[Si(R)2 -O-]n - group (R is an org. group). The inorg. org. hybrid contains the org. group R constituting the hybrid within a range of 0.5-2 times with respect to M and Si in a mol ratio and has hydrophobicity. This floatable filter medium is produced by dissolving one or more kind of metal alkoxide, organoalkoxysilane or polysiloxane of which the terminal is a hydroxyl group in an org. solvent and adding water containing an acid catalyst to the resulting soln. within a range of 2-10 mol times with respect to an alkoxy group to hydrolyze and gelatinize the obtained soln.