Suchergebnisse

AbstractNanoparticulate titanium dioxide (nTiO2) is frequently applied, raising concerns about potential side effects on the environment. While various studies have assessed structural effects in aquatic model ecosystems, its impact on ecosystem functions provided by microbial communities (biofilms) is not well understood. This is all the more the case when considering additional stressors, such as UV irradiation — a factor known to amplify nTiO2-induced toxicity. Using pairwise comparisons, we assessed the impact of UV (UV-A = 1.6 W/m2; UV-B = 0.7 W/m2) at 0, 20 or 2000 μg nTiO2/L on two ecosystem functions provided by leaf-associated biofilms: while leaf litter conditioning, important for detritivorous invertebrate nutrition, seems unaffected, microbial leaf decomposition was stimulated (up to 25%) by UV, with effect sizes being higher in the presence of nTiO2. Although stoichiometric and microbial analyses did not allow for uncovering the underlying mechanism, it seems plausible that the combination of a shift in biofilm community composition and activity together with photodegradation as well as the formation of reactive oxygen species triggered changes in leaf litter decomposition. The present study implies that the multiple functions a microbial community performs are not equally sensitive. Consequently, relying on one of the many functions realized by the same microbial community may be misleading for environmental management.

The features of sorption of gallium from aqueous solutions on mechanically activated TiO2(rutile) were studied. The dependence of the degree of sorption on the time of mechanical activation is obtained. The experimental sorption isotherms at temperatures from 20 to 50 ºСwere processed by adsorption models of Langmuir, Freindlich, Dubinin —Radushkevich. To achieve sorption equilibrium depending on temperature, 10–30 minutes are required. Dependence of sorption on time is better described by the kinetic model of the pseudo-second order. According to the Arrhenius equation, the activation energy is calculated —9,7 kJ / mol.

The article presents the results of the studies of the physicochemical and photocatalytic properties of titanium dioxide modified with manganese, by the example of decomposition of organic dyes — ferroin and methylene blue. The correlations between the specific surface area and phase composition of the composites with their photocatalytic activity are revealed.

The possibility of synthesis of highly photoactive nanosized titania employing ion exchange to exert control over polycondensation of titanium acid in aqueous medium has been demonstrated. The resultant spherical TiO2 nanoparticles exhibits extra high light-induced oxidation activity remaining for some time even after termination of UV illumination. The nanodispersed titania readily penetrate into the surface pores and can be used for deposition of photocatalytic coatings by impregnation technique.