Photochemistry of hexachloroosmate(IV) in ethanol.

The photochemistry of the OsIVCl62- complex in ethanol was studied by means of stationary photolysis, nanosecond laser flash photolysis, ultrafast pump-probe spectroscopy and quantum chemistry. The direction of the photochemical process was found to be wavelength-dependent. Irradiation in the region of the d-d and LMCT bands results in the photosolvation (with the wavelength-dependent quantum yield) and photoreduction of Os(iv) to Os(iii), correspondingly. The characteristic time of photosolvation is ca. 40 ps. Photoreduction occurs in the micro- and millisecond time domains via several Os(iii) intermediates. The nature of intermediates and the possible mechanisms of photoreduction are discussed. We believe that the lability of the photochemically produced Os(iv) and Os(iii) intermediates determines the synthetic potential of OsIVCl62- photochemistry.

Reactions of [Ru(NO)Cl5]2- with pseudotrilacunary {XW9O33}9- (X = AsIII, SbIII) anions.

Reactions of [Ru(NO)Cl5]2- with pseudotrivacant B-α-[XW9O33]9- (X = AsIII, SbIII) at 160 °C result in the rearrangement of polyoxometalate backbones into {XM18} structures. In the case of arsenic, oxidation of AsIII to AsV takes place with the formation of a mixture of plenary and monosubstituted Dawson [As2W18O62]6- and [As2W17Ru(NO)O61]7- anions, of which the latter was isolated as Me2NH2+ (DMA-1a and DMA-1b) and Bu4N+ (Bu4N-1) salts and fully characterized. Both α1 and α2 isomers of [As2W17Ru(NO)O61]7- were present in the reaction mixture; pure [α2-As2W17Ru(NO)O61]7- was isolated as the Bu4N+ salt. In the case of antimony, [SbW9O33]9- is converted into a mixture of [SbW18O60]9- and [SbW17{Ru(NO)}O59]10-. The formation of trisubstituted [SbW15{Ru(NO)}3O57]12- as a minor byproduct was detected by HPLC-ICP-AES. The monosubstituted [SbW17{Ru(NO)}O59]10- anion was isolated as DMAH+ (DMA-2) and mixed inorganic cation (CsKNa-2) salts and characterized by XRD, HPLC-ICP-AES, EA and TGA techniques. X-ray analysis shows the presence of the {Ru(NO)}-group in the 6-membered ("equatorial") belt of the Sb-free hemisphere. The experimental findings were confirmed and interpreted by means of quantum chemical calculations.

Near-UV photooxidation of As(III) by iron species in the presence of fulvic acid.

Photooxidation of As(III) in ternary As(III) - Fe(III) - Fulvic acid system at pH 4 was investigated by optical spectroscopy, steady-state photolysis (365 nm) and atomic-emission spectrometry with inductively coupled plasma techniques. It was found that at all values of [FA]/[Fe] ratio the main photoactive species is OH radical formed by photolysis of Fe(III) hydroxocomplexes. Addition of fulvic acid leads to mainly negative effect on As(III) photooxidation due to the following reasons: (i) slow dark reduction of photoactive Fe(III) species with formation of scattering particles and photoinert Fe(II) species; (ii) formation of photoreductive Fe(III)-FA complexes incapable to oxidize As(III), (iii) competition of both FA and Fe(III)-FA complexes for UVA quanta with FeOH2+ complex and for OH radicals with As(III). Aging of ternary system is also very important parameter leading to one order decrease of quantum yields of both Fe(II) formation and As(III) photooxidation.

Phytoextraction of trace elements by water hyacinth in contaminated area of gold mine tailing.

The ability of water hyacinth (Eichhornia crassipes) to uptake Ag, Ba, Cd, Mo, and Pb from waters in gold mine tailing area was studied. All experiments were carried out in the field conditions without using of model system. Bioconcentration (BCF) and translocation factors (TF) as well as elements accumulation by plant in different points of tailings-impacted area were evaluated. It has been shown that water hyacinth demonstrates high ability to accumulate Mo, Pb, and Ba with BCF values 24,360 ± 3600, 18,800 ± 2800 and 10,040 ± 1400, respectively and is efficient in translocation of Mo and Cd. The general trend of the plant accumulation ability in relation to the studied elements corresponds to their concentration in the medium. As the distance from tailings increases, concentration of Ag, Ba and Pb in plant decreases more clearly than that of Cd, while the amount of Mo accumulated by plant doesn't drop significantly in accordance with its concentration in water. Under the conditions of the confluence of river Ur and drainage stream Ba and Ag can be considered as potential candidates for phytomining.

Studies on cadmium accumulation by some selected floating macrophytes.

The results of investigation of the process of cadmium accumulation by floating plants of Eichhornia crassipes and Pistia stratiotes are discussed. The main specialty of this study is that it puts more emphasis on the mechanism of penetration of pollutant within the plant and its fate during accumulation act. As a result it was shown that at the first stage of cadmium uptake the sorption of the metal on the surface of the roots due to the presence of carboxylic groups takes place. At the root of the plant cadmium mainly localized in the cortex and rhizodermis, then the pollutant penetrates into the tissues of the stem according to its translocation factor. It has been also assumed that flavonoids perform an intermediate role in the accumulation of cadmium by the plant, taking part in the transport and combat an oxidative stress.