Photocatalytic degradation of organic dyes in aqueous solution with TiO 2 nanoparticles immobilized on foamed polyethylene sheet

Abstract

Degussa TiO 2 nanoparticles have been immobilized on a foamed polyethylene by thermal bonding to produce a stable catalyst sheet containing 0.7 mg TiO 2 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.