G. M. Mokrousov

Catalytic Ozonation of Oxalic Acid Using SrTiO3 Catalyst

A new catalyst, strontium titanate (SrTiO3), has been successfully employed to degrade oxalic acid in catalytic ozonation process. About 4.5%, 9.3% and 45.8% of oxalic acid removal efficiencies were noted in adsorption, ozonation, and catalytic ozonation processes, respectively, which demonstrates the catalytic activity of SrTiO3 towards ozone. The optimum amount of catalyst loading on decomposing oxalic acid was found to be 1.25 g/L. The catalytic stability was investigated up to four successive cycles and found that the catalyst was still stable and efficient.

Catalytic oxidation of phenol in the presence of iron-containing composites based on silicon and boron nitrides

Sorption and catalytic activities of iron-containing composites based on silicon and boron nitrides in purification of aqueous solutions to remove phenol under ozonation and UV irradiation in the presence of oxalic acid and hydrogen peroxide additives was studied.

Cadmium sulfide photoluminescence in poly(methyl methacrylate)-matrix composites

Poly(methyl methacrylate)-matrix composites containing cadmium, lead, and zinc sulfides and also mixed (cadmium lead and cadmium zinc) sulfides were prepared by reacting metal salts with thioacetamide. The transmission of the composites in the range λ > 500 nm is 92% at absorbing layer thicknesses of ≤5 mm. The photoluminescence (PL) of the composites in the wavelength range 500–820 nm is due to the cadmium sulfide, and that in the wavelength range 300–550 nm arises from the zinc sulfide. It results from radiative recombination at levels of extrinsic structural defects in CdS and ZnS, respectively. The PL excitation spectra contain excitonic absorption bands of cadmium sulfide and zinc sulfide quantum dots. The PL of the cadmium sulfide in the composites is influenced by the presence of lead(II) and zinc(II) ions and the complexation of cations on the surface of the particles.

Use of Si-N-Fe and B-N-Fe Compositions for Formaldehyde Degradation in Combined Heterogeneous and Homogeneous Catalytic Processes

The catalytic activity of B-N-Fe and Si-N-Fe compositions toward formaldehyde degradation in aqueous solutions by ozonation and UV irradiation was examined in relation to the time of exposure, phase composition and weight of the catalyst, and amount of oxalic acid added. The conditions for complete degradation of formaldehyde were determined, and high workability of the composites was demonstrated. The application of the catalysts in drinking water treatment to remove formaldehyde was tested.

Analysis of the sorption and catalytic activity of a B-N-Fe composite in water purification to remove oxalic acid

Sorption and catalytic activity of composites based on nitrogenized ferroalloys of boron in purification of aqueous solutions to remove oxalic acid in separate and joint exposure to UV radiation and ozone with and without addition of hydrogen peroxide was studied. The materials were produced by self-propagating high-temperature synthesis. X-ray diffraction analysis and IR spectroscopy were used to determine the presence of hydrated iron oxalate in a composite material upon its contact with a contaminant. The conditions in which the organic contaminant is completely degraded were found.

Synthesis of red phosphors based on borosilicate glass and NaMgSc0.5Lu0.5(MoO4)3:Eu3+ and Na0.5Mg0.5ScLu0.5(MoO4)3:Eu3+ NASICON phases of variable composition

Glass-ceramic materials based on NaMgSc0.5Lu0.5(MoO4)3:Eu3+ and Na0.5Mg0.5ScLu0.5(MoO4)3:Eu3+ NASICON phases of variable composition and borosilicate glass have been produced by solid-state reactions. The materials have been characterized by X-ray diffraction and differential thermal analysis, and their photoluminescence (excitation and emission) spectra have been measured. Their spectral characteristics have been analyzed with the aim of identifying materials potentially attractive as red phosphors.

Use of composites based on boron nitride in combined photocatalytic process for generation of hydrogen and degradation of soluble organic substances

Possibility of using composites based on boron nitride in combined photocatalytic processes for degradation of soluble organic substances and generation of hydrogen was examined. The hydrogen evolution rate and output capacity of the composites under study in release of hydrogen from aqueous solutions of formic and oxalic acids and hydrazine under irradiation with visible and UV light were evaluated. It is shown that the highest efficiency of generation of molecular hydrogen is achieved in photodecomposition of hydrazine and oxalic acid with a composite whose phase composition includes iron and a set of semiconductor carbides (Fe3C, MgC2, Al4C3, SiC).

Synthesis of Nitrogen-Doped ZnS with Camellia Brushfield Yellow Nanostructures for Enhanced Photocatalytic Activity under Visible Light Irradiation

Nitrogen modified zinc sulfide photocatalysts were successfully prepared and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), and surface area analysis. Thermal decomposition of the semisolid was carried out under nitrogen conditions at 500°C for 2 hours, and a series of nitrogen-doped ZnS photocatalysts were produced by controlling inflow flow rate of nitrogen at 15–140 mL/min. Optical characterizations of the synthesized N-doping ZnS substantially show the shifted photoabsorption properties from ultraviolet (UV) region to visible light. The band gaps of nitrogen-doped ZnS composite catalysts were calculated to be in the range of 2.58~2.74 eV from the absorptions edge position. The 15N/ZnS catalyst shows the highest photocatalytic activity, which results in 75.7% degradation of Orange II dye in 5 hrs by visible light irradiation, compared with pristine ZnS and higher percentage N-doping ZnS photocatalysts.

Interfacial Reactions in the System of MnTe-H2O

The thermodynamically possible reactions in MnTe-H2O system at room temperature have been studied. The potential–pH diagram has been plotted assuming quasi-equilibrium on interfacial boundary. The possible mechanism of formation and the composition of a surface in dependence on electrode potential and pH have been discussed and the stable conditions for manganese telluride, i.e. the specific area in the diagram (pH from −2 to 14 and potential from −1.5…− 1.1 to −0.9…−0.6 V) have been found. The obtained results may help optimize the conditions for electodeposition of manganese telluride thin films and for liquid chemical etching for the formation of interfacial boundaries.

Red and Green Phosphors Glow on the Basis of Oxide Glass-Ceramics Doped with Eu3+ and Tb3+

Glass-ceramics phosphors were obtained by the introduction of the crystalline phase NaMg3Sc (MoO4)5:Eu3+,Tb3+ in the glass composition 8SiO2-20B2O3-5Lu2O3-31Bi2O3-36ZnO. The properties were characterized by X-ray diffraction (XRD), photoluminescence (PL) and photoluminescent excitation spectra (PLE). The XRD patterns were indicated NaMg3Sc (MoO4)5:Eu3+,Tb3+ crystallize well with the novel structure type and were assigned to the triclinic phase (space group PĪ, Z = 6). Glass-ceramic phosphors are well-known and promising as solid electrolytes, laser, luminescent and other inorganic materials. Luminescent properties of the phosphors are performed at room temperature. The excitation spectra of Eu-doped phosphor present strong absorption at 300 nm and the sharp peaks in the 350-500 nm range. Under the 394 nm excitation, intense red emission peak at 616 nm corresponding to 5D0→7F2 transition of Eu3+ is observed in the emission spectrum. The luminescence property indicates that the local symmetry of Eu3+ ion has no inversion center. The excitation spectra of Tb-doped phosphor by monitoring wavelength at 546 nm shows the intense broad band from 260 to 420 nm and the line at 234 nm, which is mainly attributed to charge-transfer band transition in MoO42- group, indicating the existence of energy transfer from MoO42- to Tb3+ in the Tb3+:glass-ceramic. The measured emission spectrum of Tb-doped phosphor has intense green emission at 546 nm corresponding to 5D4→7F5 transition of Tb3+, with λex=368 nm. The as-prepared phosphors may find potential applications in the field such as color displays, light-emitting diodes (LEDs) and optoelectronic devices.