Study of photocatalytic activity of ZnO nanoparticles comparatively to TiO2 applied on cementitious exterior surfaces of buildings

Abstract

The aim of the study is to compare the photo catalytic activity of NPs of ZnO and TiO2 P25, with known efficiency, on self-cleaning properties when applied on cementitious building envelopes to improve thermal comfort and energy savings inside of ambients. Both NPs are white and low solubility in water, are broadband semiconductors, and are used in photocatalytic processes. Commercial NPs, obtained by different chemical processes with different morphologies and nanostructures, and laboratory NPs produced in the Ceramics Processes Lab - Metallurgical and Materials Engineering Department - EPUSP will be selected for the study. The nanostructure, chemical and mineralogical composition of both types of NPs will be characterized using nano particle analyser (size and shape), zeta potential and surface area. The photo catalytic activity of both NPs will be determined using methylene blue, a stable bacteriological dye. The activity will tested under UV radiation with different times of exposure. The NPs with higher efficiency, according to this test will be select for further studies. The efficiency shall be tested by natural exposure in São Paulo city and by accelerated weathering in tropical chamber, coupled with UVA/B and IR radiation incidence. The nano particles will be added in a mixture of hybrid silane/siloxane emulsion (coupling and dispersion agent) and applied on cementicious panels and smaller test specimens for laboratory test. The leaching of both NPs on cimenticious surfaces will be estimated by accelerated method (Soxhlet) and a untreated surface will be used as reference. The maintenance of the properties along time will be estimated by visual inspection and color and reflectance determinations, after 18 months. (AU)