Facultatea de Chimie şi Tehnologie Chimică / Faculty of Chemistry and Chemical Technology

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    Preparation and characterization of biochar-iron oxide-palygorskite composites for uranium(VI) removal from aqueous solutions [Articol]
    (2025) Pylypenko, Ihor; Kovalchuk, Iryna; Tsyba, Mykola; Lytvynenko, Yurii; Shyrokov, Oleksandr
    This paper details the synthesis of palygorskite/biochar/iron oxide composites and their utilization for the remediation of water solutions contaminated with uranium(VI). The synthesis procedure involved the combination of iron chloride, starch, and palygorskite with subsequent pH adjustment, drying of the formed precipitate, and pyrolysis at 600°C. The synthesis of mesoporous materials, primarily composed of iron oxides, including magnetite and hematite, was confirmed using various characterization techniques, including FTIR, SEM, and XRD. It was shown that the adsorption of uranium(VI) reached a maximum of 100.2 μmol/g, exhibiting the highest affinity, which is associated with significant magnetite involvement, which facilitates the reduction processes of uranium(VI) to uranium(IV). The findings demonstrated that the uranium removal process was enhanced by a rise in pH, with significant adsorption and possible precipitation occurring under neutral conditions, so using these composite materials is suitable for in situ remediation of water solutions contaminated by uranium(VI).
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    Synthesis and study of heterometallic Co-Bi compounds based on ethylenediaminetetraacetic acid. Crystal and molecular structures of [Co(DH)2(o-NH2C6H4CH3)2]2[Bi2(μ-Edta)2(H2O)2]• 10H2O (DH 2 is dimethylglyoxime) [Articol]
    (2002) Stăvilă, Vitalie; Gulea, Aurelian; Șova, Sergiu; Gdanec, M.; Simonov, Iurie
    Compounds of the [Co(DH)2A2](BiEdta)·6H 2O type (where DH is the monodeprotonated dimethylglyoxime -ON=C(CH3)-(CH3)C=NOH; A is the o-, m-, or p-toluidine; and Edta is the ethylenediaminetetraacetate(4-) ion) were synthesized and studied. The composition and structures of the complexes were determined from their UV and 1H NMR spectra and from X-ray diffraction data. The isomer [Co(DH)2(o-NH2C 6H4CH3)2]2[Bi 2(μ-Edta)2(H2O)2]·10H 2O was structurally characterized using X-ray diffraction analysis. The crystals are triclinic: a = 12.153(2) Å, b = 12.824(3) Å, c = 16.215(3) Å, α = 67.73(3)°, β = 86.18(3)°, γ = 66.96(3)°, space group P1̄ , ρ(calcd) = 1.719 g/cm3, Z = 4. The structure is composed of complex binuclear [Bi2(μ-Edta) 2(H2O)2]2- anions, [Co(DH) 2(o-NH2C6H4CH3) 2]+ cations, and molecules of crystallization water. The Edta4- anion chelates with the Bi atom in a hexadentate manner (N2O4); the fifth O atom functions as a bridging ligand. The bismuth coordination polyhedron can be regarded as a strongly distorted antiprism. In the octahedral cation, the Co(III) atom coordinates four N atoms of two DH ligands (average Co-N 1.897 Å) and two N atoms of two o-toluidine molecules (Co-N 2.023 Å). Thermolysis of the complexes studied was found to proceed in several successive steps, namely, the deaquation, deamination, and pyrolysis of the ligands.
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    Synthesis and structure of {μ-oxalato-bis[ethylenediaminetetraacetatobismuthato(III)]}pentaamminethio cyanatocobalt(III)dodecahydrate, [Co(NH3)5NCS]2[(Edta)Bi(μ-C2O4)Bi(Edta)] • 12H2O [Articol]
    (2000) Stăvilă, Vitalie; Gdanec, M.; Șova, Sergiu; Simonov, Iurie; Gulea, Aurelian; Vignacourt, Jean-Pierre
    A heterometallic complex of cobalt(III) and bismuth(III), [Co(NH3)5NCS]2[(Edta)Bi(μ-C2O4)Bi(Edta)] · 12H2O, was synthesized and studied by X-ray diffraction analysis. The crystals are monoclinic, a = 12.792(3) Å, b = 9.792(2) Å, c = 22.945(5) Å, β = 92.92(3)°, P(calcd) = 1.970 g/cm3, space group P21/c, Z = 4. The complex has an isle structure composed of [(Edta)Bi(μ-C2O4)Bi(Edta)]4- and [Co(NH3)5NCS]2+ complex ions and molecules of crystallization water. The Edta4- ligand functions as a hexadentate chelating (2N + 40) agent, while the oxalate ion acts as a bridging ligand. The thiocyanate ion is coordinated to cobalt(III) through the N atom, while the cation interacts with the anion via the Bi-S contact (3.571 Å). Hence, the coordination polyhedron of Bi can be regarded as a tricapped trigonal prism. It was shown that thermolysis of the complex proceeds in several stages, viz., the deaquation, deamination, and pyrolysis of its ligands.