Petr Melnikov

Neodymium biosorption from acidic solutions in batch system

Abstract Biosorption of neodymium in batch experiments took ∼2 h to achieve the equilibrium biosorbent-metal for all microorganisms tested. The best biosorption coefficient at a constant pH value of 1.5 was obtained using the microalgae Monoraphidium sp. (1511 mg g −1 cell), followed by Bakers’ yeast (313 mg g −1 cell), Penicillium sp. (178 mg g −1 cell), and activated carbon (61 mg g −1 cell). When compared to the biosorption of other metals, these results pointed out to the application of biosorption in neodymium recovery from acidic solutions.

Er3+ and Eu3+ containing transparent glass ceramics in the system PbGeO3–PbF2–CdF2

Abstract Glasses with composition 60PbGeO 3 –10PbF 2 –30CdF 2 (mol%) have been obtained in the bulk form with a high stability against crystallization. After doping them with 0.5 mol% of Er 3+ or Eu 3+ and appropriate heat treatment transparent glass ceramics could be obtained. Electronic spectroscopy, X-ray diffraction and transmission electron microscopy measurements have been made. β-PbF 2 : Er 3+ /Eu 3+ single crystals, 5–10 nm in size, are detected in the otherwise transparent composite medium, the size of the particles and absence of clustering allowing for the increased transparency of the final materials.

Four new metal complexes with the amino acid deoxyalliin

The solid complexes [Co(C6H10NO2S)2], [Ni(C6H10NO2S)2], [Cu(C6H10NO2S)2] and [Fe(C6H10NO2S)2] were obtained from the reaction of cobalt(II), nickel(II), copper(II) and iron(II) salts with the potassium salt of the amino acid deoxyalliin (S-allyl-L-cysteine). Electronic absorption spectra of the complexes are typical of octahedral structures. Infrared spectroscopy confirms the ligand coordination to the metal ions through (COO-) and (NH2) groups. EPR spectrum of the Cu(II) complex indicates a slight distortion of its octahedral symmetry. Mossbauer parameters permitted to identify the presence of iron(II) and iron(III) species in the same sample, both of octahedral geometry. Thermal decomposition of the complexes lead to the formation of CoO, NiO, CuO and Fe2O3 as final products. The compounds show poor solubility in water and in the common organic solvents.

Synthesis and spectroscopic characterization of new metal(II) complexes with methionine sulfoxide

Methionine sulfoxide complexes of iron(II) and copper(II) were synthesized and characterized by chemical and spectroscopic techniques. Elemental and atomic absorption analyses fit the compositions K2[Fe(metSO)2]SO4·H2O and [Cu(metSO)2]·H2O. Electronic absorption spectra of the complexes are typical of octahedral geometries. Infrared spectroscopy suggests coordination of the ligand to the metal through the carboxylate and sulfoxide groups. An EPR spectrum of the Cu(II) complex indicates tetragonal distortion of its octahedral symmetry. 57Fe Mössbauer parameters are also consistent with octahedral stereochemistry for the iron(II) complex. The complexes are very soluble in water.

A solid nickel(II) complex with methionine sulfoxide

Abstract Solid Ni(C 5 H 10 NO 3 S) 2 ·2H 2 O complex was prepared and characterized. Electronic absorption spectrum shows an octahedral geometry for the complex. Infrared spectroscopy analysis shows that the metal atom is coordinated to the ligand through (COO − ) and (S=O) groups. Thermal analysis confirmed the composition of the complex and suggests that the water molecules are not coordinated to the metal ion. The complex shows extremely high solubility in water.

In(PO3)3 stabilised fluoroindate glasses

Abstract Results on thermal and optical characterization of new lanthanide containing fluoroindate glasses in the system InF 3 –BaF 2 –In(PO 3 ) 3 are presented. Good optical quality and very stable glasses presenting up to 5 mm in thickness could be prepared in this system. Thermal analysis, Raman scattering and Eu 3+ luminescence were the techniques utilized. A novel method for In(PO 3 ) 3 synthesis is proposed and the dependence of physical properties and structural features on the polyphosphate content is stressed.

Competition between humic substances and alpha-amino acids by metal species

The aim of the present work was to carry out experimental comparison between humic substances (HS) and representative a-amino acids (methionine, methionine sulfoxide and cysteine hydrochloride) in relation to the complexation of biologically active trace elements (Al, Cu, Pb, Mn, Zn, Cd and Ni). A mobile time-controlled tangential-flow UF technique was applied to differentiate between HS-metal and a-aminoacids-metal complexes. Metal determinations were conventionally carried out using a ICP-OES. The results showed that HS may be considered as a selective complexing agents with higher metal bonding capability in relation to Al, Cu and Pb, the fact that may be clinically important.

Iron(II) djenkolate: synthesis and properties

Abstract Djenkolate complex of iron, [Fe(C 7 H 12 N 2 O 4 S 2 )]·H 2 O, has been synthesized by the reaction of potassium djenkolate with Fe(SO 4 )·7H 2 O under nitrogen atmosphere. X-Ray diffraction pattern has been indexed in orthorhombic system with lattice parameters: a =11.24 A, b =7.50 A and c =6.96 A. According to IR spectroscopy, coordination is performed through COO − and NH 2 groups. An octahedral geometry for Fe ion is suggested by UV-Vis and Mossbauer spectroscopies. Thermal decomposition leads to the formation of Fe 2 O 3 (hematite). The compound shows poor solubility in water and in common organic solvents.

The substitution of cations by magnesium in the structure K3Ho(VO4)2

Abstract The cation substitutions in the crystal lattice of binary potassium–holmium vanadate (V) K 3 Ho(VO 4 ) 2 by magnesium have been studied using various types of chemical solid state reactions. It was shown that in the presence of the quasi-ternary system K 3 VO 4 –Mg 3 (VO 4 ) 2 –HoVO 4 at 700°C there a compound defined as K 3 Ho(VO 4 ) 2 with a narrow homogeneity range where K and Ho are partially substituted by Mg in accordance with various schemes.

Lithium-lanthanum double chromates

Abstract Synthesis and crystallographic data are reported for low and high temperature forms of LiLa(CrO4)2. The compounds are closely related to lamellar rare earth phosphates and arsenates of sodium and to RbLu(CrO4)2. Lattice parameters of the orthorhombic (low temperature) and monoclinic (high temperature) forms are given. The low temperature form is moisture sensitive and Li+ ions are easily displaced by protons. Thermal decomposition takes place at 250 °C and results in the formation of LiCrO2, LaCrO4, LaCrO3 and Cr2O3.