Immobilization of soil mercury by colloidal sulphur in the laboratory experiment

The results of the laboratory pot experiments on soil mercury (Hg) immobilisation with a non-toxic and price-reasonable agent — colloidal sulphur (S) water suspension, are presented. It was shown that fertilisation with small agrochemical doses of colloidal S reduces excess Hg effectively as follows: in interstitial waters by a factor 2 – 12 times for total Hg, and 22– 680 times for “reactive” Hg; in stems and leaves of oats – 7 – 22 times; and in moss bags, reflecting soil Hg degassing, 7 – 15 times, for the most heavily Hg-spiked soils. The results obtained allowed to conclude that the immobilization of Hg occurs through Hg binding to the newly formed S-bearing functional groups in humic acids and/or sulphides.      

An analysis of SCF and geometry convergence for diatomic molecules

A geometry and SCF convergence study of Hartree-Fock calculations using the 6-31G* basis set is carried out on the set of all possible diatomic molecules formed from atoms with Z≤36. The utility of Hartree-Fock calculations using the smaller STO-3G basis set to improve the convergence behavior is demonstrated.      

Crystallographic and structural characterisation of heterometallic platinum compounds: Part I. Heterobinuclear Pt compounds

This review covers almost 290 heterobinuclear Pt derivatives. When the heterometals (M) are non transition and the binuclear are found both with and without a metal to metal bond. Where M is a transition metal or actinide, only those with a metal-metal bond have been included here. There are thirteen non-transition metals (Sn, Hg, Ge, Sb, Tl, Zn, Pb, Cd, Na, K, Ga, Ca and In). The shortest Pt-M bond distance is 235.2(1) (Pt-Ge). There are eighteen transition metals (Fe, W, Rh, Re, Pd, Ag, Ir, Mo, Mn, Re, Co, Cu, Cr, Au, Ni, Ti, Ta and V). The shortest Pt-M bond distance is 249.5(2) pm (Pt-Cr). There is one example of an actinide, Pt-Th at 298.4(1) pm. The Pt atom has oxidation numbers 0, +2 and +4. The Pt coordination geometries include square planar (most common), trigonal bipyramidal, pseudo octahedral (Pt(IV)) and a few prevalently capped trigonal prismatic seven coordinate species. There are at least two types of isomerism distortion and polymerisation. Factors affecting bond lengths and angles are discussed and some ambiguities in coordination polyhedra are outlined.      

A direct method for the decontamination of a fly ash amended wet soil,artificially polluted with dioxins

We report hereby the first method of direct treatment of a wet soil containing toxic polychloroderivatives. Using a system with metallic Ca and 5% Rh fixed on charcoal in methanol, soil samples artificially polluted with fly ash containing polychloro-dibenzodioxins (PCDDs), polychloro-dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (co-PCBs), and having 69.2% to 84.6% moisture content, were successfully treated and decontaminated. This treatment afforded excellent hydrodechlorination yields for the 29 most toxic congeners of PCDDs, PCDFs and PCBs (98.3% degradation yield based on toxic equivalent quotient — or TEQ) after a 24 h treatment, at room temperature.      

Sequential extraction and thermal desorption of mercury from contaminated soil and tailings from Mongolia

Mercury forms in contaminated environmental samples were studied by means of sequential extraction and thermal desorption from the solid phase. The sequential extraction procedure involved the following fractions: water soluble mercury, mercury extracted in acidic conditions, mercury bound to humic substances, elemental Hg and mercury bound to complexes, HgS, and residual mercury. In addition to sequential extraction, the distribution of mercury species as a function of soil particles size was studied. The thermal desorption method is based on the thermal decomposition or desorption of Hg compounds at different temperatures. The following four species were observed: Hg⁰, HgCl₂, HgS and Hg^(II) bound to humic acids. The Hg release curves from artificial soils and real samples were obtained and their applicability to the speciation analysis was considered.      

Hydrogen sorption characteristics of magnesium-based composites with addition of Mg<Subscript>2</Subscript>Ni<Subscript>0.7</Subscript>Co<Subscript>0.3</Subscript> and graphite

Magnesium-based composites of 75 wt% Mg — (10, 15, 20) wt% Mg2Ni0.7Co0.3 — (15, 10, 5) wt% C mechanically activated for 30 min under argon in a planetary mill, were obtained. Their absorption-desorption characteristics were investigated under a pressure P = 1 MPa and temperatures of 623, 573, 473, 423 and 373 K. Desorption was carried out at 623 K and 573 K and a pressure of 0.15 MPa. All the three composites showed improved hydriding kinetics as compared to pure magnesium. However, the desorption temperature was somewhat higher than needed for practical application.      

Physicochemical characteristics of 2-, 3- and 4-methylpyridinium tetrachloroferrates(III)

The crystal structure of 2-methylpyridinium tetrachloroferrate(III) was determined. The iron cation is tetracoordinated by chloride anions, and it adopts a slightly distorted tetrahedral coordination with three angles smaller, two almost equal and one larger than the tetrahedral. The compound is isostructural with its 3-, and 4-methylpyridinium analogues. The thermal properties of 2-, 3- and 4-methylpyridinium tetrachloroferrates(III) have been studied using TG and DSC techniques. The compounds exhibit a high stability in the melt.      

Protolytic properties of the structurally rigid analogs of 2,6-distyrylpyridine. Widening the pH sensitivity range by the photochemical E→Z isomerisation and introduction of substituents capable to protolytic interactions

Protolytic interactions in the series of prospective fluorescent ratiometric wide-range pH indicators — structurally rigid analogs of 2,6-distyrylpyridine — (3E,5E)-3,5-dibenzylidene-8-phenyl-1,2,3,5,6,7-hexahydrodicyclopentano[b,e]pyridine — were investigated. The pyridine nitrogen atom basicity in these compounds is significantly lower in comparison with that of unsubstituted heterocycle and 2,6-distyrylpyridine. The photochemical E→Z photoisomerization and the side benzene rings substituents influence on the acid-base equilibria were studied. The complex multi-stage mechanism of the acid-base interactions of the polysubstituted compounds was elucidated. The most significant spectral effects were typical to the N,N-dialkylamino substituted compounds of the investigated series. The widest pH sensitivity interval covering nearly the full range of 0–14 units was demonstrated for compounds with both proton donor and proton acceptor substituents.      

Indirect determination of lutetium by differential pulse anodic stripping voltammetry at a hanging mercury drop electrode

Lutetium has been determined by differential pulse anodic stripping voltammetry in an acidic solution containing Zn-EDTA. Lutetium (III) ions liberated zinc (II), which was preconcentrated on a hanging mercury drop electrode and stripped anodically, resulting in peak current linearly dependent on lutetium (III) concentration. Less than 0.4 ng mL⁻¹ lutetium could be detected after a 2 min deposition.      

Synthesis and structure of new 3,7,10-substituted-phenothiazine derivatives

The synthesis of new 3,7-dibromophenothiazine derivatives bearing bromoalkyl, mercaptoalkyl and alkylthioacetate groups on the N atom at position 10 is reported. The Suzuki coupling reaction of one of these derivatives via the bromine atoms at positions 3 and 7 with bromothiophene derivatives is also discussed.      

Uncertainty of nitrate and sulphate measured by ion chromatography in wastewater samples

This paper presents an evaluation of measurement uncertainty regarding the results of anion (nitrate and sulphate) concentrations in wastewater. Anions were determined by ion chromatography (EN ISO 10304-2, 1996). The major sources of uncertainty regarding the measurements’ results were identified as contributions to linear least — square or weighted regression lines, precision, trueness, storage conditions, and sampling. Determination of anions in wastewater is very important for the purification procedure, especially the amount of nitrate in waste and potable waters. The determined expanded uncertainty was 6.1 % for nitrate anions and 8.3 % for sulphate anions. The difference between measurement uncertainties determined by the two methods, the weighted and linear least — square methods, is negligible.      

Metathesis transformations of unsaturated derivatives of β-diketones

Selected β-diketones bearing unsaturated derivatives have been demonstrated to undergo homo-metathesis and cross-metathesis with selected olefins in the presence of Grubbs catalysts. The reactions led to respective homo- and cross-metathesis products mainly with good yields and selectivities.      

Efficient and solvent-free synthesis of 1-amidoalkyl-2-naphthols using <Emphasis Type="Italic">N,N,N’,N’</Emphasis>-tetrabromobenzene-1,3-disulfonamide

N,N,N,’N’-Tetrabromobenzene-1,3-disulfonamide [TBBDA] is found to be a reusable catalyst for efficient synthesis of various amidoalkyl naphthols from β-naphthol, aromatic aldehydes and urea in good to high yields under solvent-free conditions.      

Catalytic degradation of methylene blue in aqueous solutions over Ni- and Co- oxide systems

The oxidative catalytic degradation of the cationic dye methylene blue (MB) with NaOCl in aqueous solutions was studied using individual and iron modified Ni- and Co-oxide systems as catalysts. The adsorption extent and the contribution of the uncatalyzed oxidation on the overall degree of MB were determined. The results indicate that methylene blue—a representative of a class of dyestuffs resistant to biodegradation—could be successfully decolorized and degraded using nickel and cobalt oxide catalysts at room temperature. The highest catalytic activity manifests in the Co-oxide system which is consistent with the adsorption data. The oxidative degradation reaction proceeds via first-order kinetics. Temperature has a relatively small effect on the methylene blue degradation kinetics. The results obtained reveal that the catalysts investigated are suitable for oxidative destruction of methytlene blue dye in wastewaters.      

Characterization of sorption gels used for determination of mercury in aquatic environment by diffusive gradients in thin films technique

The influence of pH, ionic strength and selected natural ligands on the measurement of mercury by the diffusive gradients in thin films technique (DGT) using recently introduced sorption gels was determined. Sorption gels containing Chelex 100, Spheron-Thiol, Duolite GT73 and modified Iontosorb AV resins were investigated, with the sorption capacity determined for all used sorption gels. The minimum DGT measurable concentrations were calculated from 3 times the standard deviation of mercury amount in unexposed sorption gels.      

Diironcarbonyl-coumarin complex: preparation, intramolecular electron transfer, and electro-generation of hydrogen

A new organometallic complex coupling photoactive coumarin to a diironhexacarbonyl unit has been successfully prepared and its composition and electronic structure confirmed by elemental and spectroscopic analyses. Emission spectral analysis of the complex reveals photoinduced intramolecular electron transfer from coumarin to the iron-carbonyl moiety. The compound is electrochemically reduced at −1.24 V vs. Fc/Fc⁺. This reduction is irreversible, attesting to the instability of the complex. Electrochemical evolution of hydrogen in the presence of the complex has been studied and results are discussed.      

Consequence of hydrogen atom abstraction from 5’-hydroxyl group of 2’-deoxyadenosine. Theoretical quantum mechanics study

Reactive oxygen species (ROS) may generate different nucleoside/nucleotide radicals in a cell environment. In this study, the possibility of cyclic-2’-deoxyadenosines formation by a rearrangement of their free radicals was investigated. It seems that for cyclic-nucleosides formation, adoption of an O4’-exo conformation by the sugar moiety is necessary. However, this is the energetically unfavoured form of the 2-deoxyribose ring. Moreover, the creation of a O5’, C8 bond in purine deoxy-nucleosides/nucleotides leads to the termination of the DNA elongation process.      

Electrospinning of the hydrophilic poly (2-hydroxyethyl methacrylate) and its copolymers with 2-ethoxyethyl methacrylate

The goal was to electrospin 2-hydroxyethyl methacrylate — based biocompatible polymers and prepare submicron fibres (nanofibers) for biomedicinal applications. Syntheses of poly(2-hydroxyethyl methacrylate) (HEMA) and its copolymer with 2-ethoxyethyl methacrylate (EOEMA), and their characterization by viscometry and molecular weight are described. Their relation to electrospinning is discussed. Electrospinning of HEMA homopolymer from water-ethanol is successful for molecular weights 6.31 × 10⁵ and 1.80 × 10⁶ g/mol. Electrospinning of HEMA/EOEMA copolymers is feasible from ethanol.      

Ionic liquid promoted Diels-Alder Reaction between anthrone and maleimides

Ionic liquids (IL) are gaining importance as green solvents. Imidazolium ionic liquid [bmim]⁺[Cl]⁻, an environmentally benign solvent, was found to promote the Diels-Alder reaction between anthrone and maleimides at room temperature with excellent yields. The ionic liquid played a dual role as solvent and catalyst.