Polyoxometalate catalyzed ozonation of chemical pulps in organic solvent media

Polyoxometalate (POM) catalyzed ozonation of chemical pulps in organic solvent media was found to be particularly effective and selective environmentally benign bleaching approach providing a way for substantial increase in pulp brightness, viscosity and degree of delignification in comparison with other ozone-based bleaching techniques. A series of tested low-boiling polar aprotic and protic organic solvents showed a well-defined capacity for ozonation improvement in the presence of Keggin-type heteropolyanion [PMo₇V₅O₄₀]⁸⁻ (HPA-5). Even moderate solvent proportion of 6% (w/w) in the reaction solution caused additional gain in brightness up to 3.4% ISO with simultaneous increase in pulp viscosity up to 8.8% and lignin removal up to 18.9% after HPA-5 catalyzed ozonation (0.8% O₃; 0.5 mM HPA), as compared with the control solvent-free process. An aqueous acetone solution was found to be the preferred reaction medium in terms of pulp brightening and delignification. Under optimized conditions, the POM-catalyzed ozonation of eucalypt kraft pulp in acetone/water solution showed remarkable brightness improvement by 15.1% ISO with additional lignin removal by 39.4% and increase in intrinsic viscosity by 3% in comparison with pulp bleached in water media.     

On a Crack in Viscoelastic Isotropic Media Opened by a Rigid Growing Wedge

Wedging of an isotropic linear viscoelastic space with crack by a rigid semi-infinite indentor is studied. The wedge is assumed to have growing with time thickness. An analysis is done in the framework of generalised Dugdale model and COD criterion using Volterra's principle. The results for safe wedge growth law as well as for the crack growth are obtained.     

Alkynes Carbonylation Reactions in Solutions of Palladium Complexes as a New Class of Oscillatory Processes

This article dedicated to study of few oscillating reactions in homogeneous systems. The experimental data and preliminary mechanism are reported. The authors affirm they find new type of oscillating processes—the reactions of carbonylation.     

Towards the integration of dark and photo fermentative waste treatment. 1. Hydrogen photoproduction by purple bacterium Rhodobacter capsulatus using potential products of starch fermentation

In this study, the H₂-photoproduction capacity of Rhodobacter capsulatus B10 was measured as a function of variations in the nature and concentration of volatile fatty acids (VFAs) and other products of dark fermentation. When an equimolar mixture of VFAs was provided, C4 substrates (butyrate and isobutyrate) were not consumed until the C2–C3 substrates (acetate, propionate, and lactate) became unavailable, but in order for the cells to produce H₂ at high rates they could not be exposed to severe growth substrate depletion. Among other possible fermentation products, the highest inhibition was observed by the addition of butanol (50% inhibition at 50 mM). The influence of high concentrations of VFAs, phosphate (used to stabilize the pH during dark fermentation) and some heavy metals (known inhibitors of methanogenesis) was also shown. Based on the results, the conditions of fermentation can be manipulated to avoid the inhibition of subsequent H₂ photoproduction by photosynthetic bacteria.     

Positional‐Species Composition of Triacylglycerols from the Arils of Mature Euonymus Fruits

Positional‐species composition (PSC) of 1,2,3‐triacyl‐sn‐glycerols (TAG) from the arils of mature fruits of 13 species of Euonymus L. genus was established. The residues of six major fatty acids (FA), palmitic, stearic, hexadecenoic (H), octadecenoic (O), linoleic (L), and linolenic, were present in the TAG. PSC of TAG was determined by their partial lipase hydrolysis. By using hierarchical cluster and principal component analyses, it was definitely demonstrated that separate taxonomic units forming this genus were significantly distinguished as regards PSC of TAG. In particular, the Euonymus subgenus greatly exceeded the Kalonymus subgenus in both total content of L in TAG and in the rate of its incorporation into their mid‐position, while TAG of Kalonymus were marked by a prevalence of O‐TAG and sn‐2‐O isomers. Thus, these subgenera were significantly distinct in the rate of incorporation of O and L residues in the sn‐2 position of TAG molecules. Meanwhile, the TAG from the Euonymus section species were marked by an enhanced concentration of H and the incorporation of H in UUU TAG was much more active than in other TAG types. As for positional‐type composition of TAG, saturated FA were always virtually absent in the sn‐2 position of Euonymus aril TAG.     

Synthesis and characterization of a mesoporous hydrous zirconium oxide used for arsenic removal from drinking water

Powder (20-50 μm) mesoporous hydrous zirconium oxide was prepared from a zirconium salt granular precursor. The effect of some process parameters on product morphology, porous structure and adsorption performance has been studied. The use of hydrous zirconium oxide for selective arsenic removal from drinking water is discussed.     

Effect of competitive ions on the arsenic removal by mesoporous hydrous zirconium oxide from drinking water

Adsorption properties of 302-type commercially available hydrous zirconium oxide (302-HZO) towards arsenic and some competitive anions and cations have been studied under batch and column conditions. Due to amphoteric properties, anion exchange performance of hydrous zirconium oxide is pH dependent. Media exhibits high affinity towards arsenic in a broad pH range, with high adsorption capacity at pH < 8. It was shown that silicate and phosphate ions are arsenic's main competitors affecting media adsorption capacity. Presence of transition metal cations in <1 ppm does not affect 302-HZO capacity on arsenic, whereas alkaline-earth cations improve arsenic removal. The possibility for significant increase of 302-HZO adsorption capacity on arsenic at pH > 8 by using “solid acidifier” technique is discussed. Results of 302-HZO field trials are presented.     

Efficiency of naphthalene biodegradation by Pseudomonas putida G7 in soil

The efficiency of naphthalene degradation by Pseudomonas putida G7 in soil was assessed using a mathematical model. The number of microorganisms and the concentration of naphthalene in soil samples were monitored. The feasibility of a spectrofluorometric method for naphthalene assay in soil samples was compared with high pressure liquid chromatography. A proposed mathematical model described the growth of the naphthalene‐degrading strains and the consumption of substrates (naphthalene, naphthalene degradation intermediates and soil organic substances) in soil. To describe the growth kinetics of microorganisms having high affinity to substrates with low solubility, two differential equations with substrate exponent 2/3 were proposed. These equations were used to describe utilization of soil organic matter. The model parameters characterize the growth rates for different substrates and respective yield coefficients, specific bacterial death and adaptation rates, and also the rates of PAHs degradation and evaporation. These characteristics can be used in choosing the bacterial strains for biopreparations and efficient clean‐up biotechnology of polluted soils. Copyright © 2004 Society of Chemical Industry     

Monofrequency excitation of open resonator with inclined comb grating

The theoretical and experimental analysis of the open resonator with the reflection diffraction comb grating has been presented. This resonator has excitation where is close to the monofrequency mode. This results may be used for the elaboration of mm-wave quasi-optical devices such as generators, mixer, converter, wavemeters and others.