METALOXIDE COMPOSITES FOR PHOTOCATALYTIC DISINTEGRATION OF TOXICANTS

Abstract

The processes of plasma-electrolytic formation of heteroxide coatings on titanium alloys for the photocatalytic disintegration of natural and technogenic toxicants are studied. Synthesis of coatings was carried out from aqueous diphosphate solutions in the galvanostatic mode. For a quantitative description of photocatalytic reactions, reaction rate constants were calculated from the linearized dependences lnCt/C0, where Ct is the current concentration of the azodye and C0 is the initial concentration of the reactant. The surface morphology of the coatings was studied by atomic force microscopy and visualized the results by reconstructing the relief in the form of 2D and 3D topographic maps. The morphological features of titanium (IV) oxide coatings and heteroxide composites containing zinc and / or copper oxides are analyzed. It has been shown that the specific surface remains an effective factor in controlling the photocatalytic activity of coatings; therefore, the establishment of the morphology of heteroxide composites, as well as methods for controlling this parameter of the target product, is an invariable component of a systematic study of such materials when establishing their functional properties. It is established that, in comparison with titanium oxide coatings, whose surface layers are characterized by toroidal mesostructures, heteroxide compositions have a more developed surface, which positively affects their functional properties. Subsequent heat treatment also has the same effect on coating properties. The rate constants of the photocatalytic decomposition of the methyl orange azodye, determined under similar conditions, were used to rank coatings of various compositions according to their functional properties. Thus, for the reaction on the surface of titanium oxide, the rate constant is 1.56∙10–3 min–1, while for the heterooxide layer TiO2·ZnO it increases to 5.8∙10–3 min–1. The coating of TiO2·ZnO is the most catalytically active, although the TiO2·ZnO·CuO system also accelerates the decomposition process with a degree of degradation of 25% for 60 minutes, further, the efficiency of the catalyst decreases.