Photodynamics and surface characterization of TiO2 and Fe2O3 photocatalysts immobilized on modified polyethylene films

Polyethylene block-copolymer films containing negative anhydride groups wer e used to immobilize TiO2, Fe2O3, and Fe3+ photocatalysts. The kinetics of the mineralization of azo-dye Orange II and chlorophenols on copolymer-TiO2 , copolymer-Fe2O3, and copolymer-Fe3+ have been tested under optimized expe rimental conditions. In the case of copolymer-TiO2, the degradation kinetic s for the model organic compounds were about the same as those observed wit h TiO2 Suspensions containing about a 27 times higher amount of TiO2 per un it volume. The surface of the derivatized copolymer semiconductor catalysts was studied by infrared attenuated total reflection spectroscopy. The spec troscopic data provided evidence for a TiO2 interaction with the negatively charged conjugated carboxylic groups of the copolymer, leading to an asymm etric-stretching band of -COO-Ti4+ at the position expected for metal carbo xylates. In the case of FC2O3 and Fe3+, the asymmetric-stretching carboxyla te bands are ascribed to the carboxylate bands of -COO-Fe2O3 arid -COOO-Fe3 +. Evidence is presented by X-ray photoelectron spectroscopy for the existe nce of two oxidation states of Ti and Fe after the photocatalytic degradati on of Orange II. This observation is consistent with light-induced interfac ial charge transfer (redox processes) taking place at the metal-oxide copol ymer surface. The nature of the latter processes is presented in detail dur ing this study.