Ekaterina A. Kozlova

COMPARATIVE STUDY ON PHOTOCATALYTIC OXIDATION OF FOUR ORGANOPHOSPHORUS SIMULANTS OF CHEMICAL WARFARE AGENTS IN AQUEOUS SUSPENSION OF TITANIUM DIOXIDE

Abstract Photocatalytic oxidation by oxygen of air was carried out for dimethyl methyl phosphonate (DMMP), trimethyl phosphate (TMP), triethyl phosphate (TEP), and diethyl phosphoramidate (DEPA) in different concentration. The initial rate of organophosphorus compounds consumption increases with the initial concentration at relatively low concentrations but decreases at higher initial concentrations. If the concentration is higher than the concentration in maximum, the rate decreases because of the lack of adsorbed oxygen. These summit-like dependences are well approximated by one site Langmuir–Hinshelwood equation with competitive adsorption of oxygen and organophosphorus compound. Parameters of the Langmuir–Hinshelwood equation are reported. Complete mineralization of the organophosphorus compounds at the end of reaction was evidenced by the total organic carbon concentration profiles. These profiles have sigmoidal shape. GC–MS technique was used to identify intermediates of TEP and TMP oxidation. The main intermediates are dimethyl phosphate and methyl phosphate in the case of TMP and diethyl phosphate and ethyl phosphate in the case of TEP. The set of intermediates shows that photocatalytic oxidation proceeds primarily at α carbon atoms of TEP. The distribution of intermediates corroborates that photocatalytic oxidation is initiated by reaction with hydroxyl radicals.

Effect of Titania Regular Macroporosity on the Photocatalytic Hydrogen Evolution on Cd1−xZnxS/TiO2 Catalysts under Visible Light

Multiphase photocatalysts Cd1−xZnxS/TiO2 were synthesized through the deposition of solid solutions of cadmium and zinc sulfides on the surface of titania samples with different porous structures, including a 3D‐ordered meso/macroporous structure. The photocatalysts were characterized by a wide range of experimental techniques: X‐ray diffraction, high‐resolution transmission electron microscopy combined with energy‐dispersive X‐ray spectroscopy, N2 adsorption at 77 K, X‐ray photoelectron spectroscopy, and UV/VIS spectroscopy. The photocatalytic activity was tested in a batch reactor for the H2 evolution reaction from aqueous solutions of Na2S/Na2SO3 under visible‐light irradiation (λ=450 nm). The highest achieved photocatalytic activity was 1.8 mmol H2 per gram of photocatalyst per hour. The regular porous structure of titania was demonstrated to enhance the photocatalytic activity and stability of Cd0.4Zn0.6S/TiO2 samples.