화학공학소재연구정보센터
Chemical Engineering Journal, Vol.361, 1487-1496, 2019
Self-assembled thin films of PAA/PAH/TiO2 for the photooxidation of ibuprofen. Part II: Characterization, sensitization, kinetics and reutilization
The photodegradation of emergent pollutants, such as ibuprofen, from streams and wastewaters by photocatalysis with TiO2 and solar energy is an important branch of environmental technology. In the Part II of the present study, we focused on the characterization of novel nanostructured self-assembled thin films (SATFs) for the immobilization of TiO2, aiming to prevent the leaching of this photocatalyst in the environment. The SATFs were composed of poly (acrylic acid), poly(allylamine hydrochloride), TiO2, copper and/or copper chlorophyllin and obtained by the layer-by-layer technique. The sensitization of the SATFs, the kinetics of their photodegradation of ibuprofen and their recyclability were all assessed. The cohesion of the films was shown to derive from electrostatic interactions, with no low-polarity bond formation. Through this mechanism, the films incorporated TiO2, which constituted 16% of the film mass. In addition, the SATFs exhibited high stability in aqueous medium. The photocatalytic activity was maintained for at least three photodegradation cycles of 150 min and leaching a total of less than 0.4% of its TiO2 content out into the reaction medium during the combined cycles, which demonstrates that the SATFs can be reused with minimum material or activity loss. In addition, the SATFs absorbed 9 times their own mass in water, which allowed easy-to-achieve photosensitization, by simple immersion of the SATFs in a solution containing the sensitizer. In the case of SATFs containing copper, an increase in photocatalytic activity of up to 52% over that of unsensitized SATFs was observed, with degradation rates of 76% after 150 min of irradiation. The kinetics of all films are consistent with pseudo-first-order models. In summary, the SATFs show both high efficiency and chemical/physical stability.