Photocatalytic degradation of organic dyes in aqueous solution with TiO2 nanoparticles immobilized on foamed polyethylene sheet

Degussa TiO2 nanoparticles have been immobilized on a foamed polyethylene by thermal bonding to produce a stable catalyst sheet containing 0.7 mg TiO2 cm(-2) and retaining 40-50% of active surface area of the particles. On such a catalyst sheet, exposed to radiation of a 125 W mercury vapour lamp, decomposition of about 0.3 mg of methylene blue (MB) is obtained per cm(2) in 1 h at ambient temperature from an aqueous solution of 200 ppm MB. The rate data fit well to classical Langmuir-Hinshelwood (L-H) rate form. This rate form also results from mechanisms based on the assumption of hydroxyl radical formation on the irradiated catalyst and a reaction between the hydroxyl radical and the organic dye molecule, either or none of them being adsorbed on the catalyst surface. An activation energy of 14.5 kcal mol(-1) is obtained for the photocatalytic decomposition of methylene blue following the L-H rate laws. (C) 1998 Elsevier Science S.A.