D. S. Todorovsky

Thermal decomposition of yttrium–iron citrates prepared in ethylene glycol medium

Thermal decomposition of yttrium–iron citric complexes, prepared in ethylene glycol medium, with mole ratio Y/Fe=1 or 3:5 (intermediates in the production of YFeO3 and Y3Fe5O12 by the polymerized complex method) is studied. A scheme of the thermally induced processes is proposed.

Thermal decomposition of lanthanum-titanium citric complexes prepared from ethylene glycol medium

The paper addresses the thermal decomposition of La-, Ti- and bimetallic La-Ti-non-crystalline citric complexes, prepared in ethylene glycol medium. The latter complex is the starting material for the effective ferroelectric La2Ti2O7 preparation by the polymerized complex method. Based on thermogravimetric analysis (DTG, DTA and TG) and identification of some of the intermediates (by elemental analysis, NMR and IR spectroscopy and X-ray diffractometry), it is established that the thermal destruction proceeds step-wise, starting with dehydration above 50–60°C, partial transformation of the citrate to aconitate up to 200°C, followed by releasing of the ethylene glycol bonded as adduct and ester (200–280°C) and decarboxilation (280–335°C). The complete destruction of the organic components results in mixed-metal oxocarbonate. The process is completed at ∼750°C giving poorly crystalline La2Ti2O7. The results obtained are compared with those for a water-prepared NH4-La-Ti-citric complex.

Effect of the application of superphosphate on rare earths' content in the soil

Abstract The total rare earth content in superphosphate produced by the sulphuric acid treatment of Kola apatites is ∼ 2.6 mg/g. The amount of rare earths (in forms usable by plants) transferred into the soil solution when 300 kg fertilizer/ha per year is applied has been evaluated to be 30–170 g/ha per year. A long-term use of such a superphosphate leads to a statistically significant increase of the content of the rare earths in the cultivated soils.

Preparation and Characterization of Yttrium–Titanium Citrate Complexes

Yttrium, titanium, and yttrium-titanium citrate complexes are synthesized in ethylene glycol medium at conditions similar to those used when the polymerized complex method (a version of the sol-gel technology) is applied. The composition and IR, 1H and 13C NMR spectral characteristics of the isolated solid state complexes are studied. Proofs of the mixed metal nature of the bimetallic complexes are reported. The conditions of deprotonation of the alcoholic OH group of the citrate ligands are considered. Darstellung und Charakterisierung von Yttrium–Titan-Citratkomplexen Yttrium-, Titan- und Yttrium–Titan-Citratkomplexe wurden in Ethylenglykol unter ahnlichen Bedingungen wie bei der Komplexpolymerisation (Sol-Gel-Technik) synthetisiert. Die Zusammensetzung sowie IR-, 1H- und 13C-NMR spektroskopischen Charakteristika der isolierten festen Komplexe wurden bestimmt bzw. untersucht. Hinweise auf die gemischtmetallische Natur der Bimetallkomplexe werden angegeben. Die Bedingungen der Deprotonierung der alkoholischen OH-Gruppe der Citratliganden werden diskutiert.

On the uranium content in some technogenic products potential environmental pollutants

The uranium contents in phosphorites from North Africa, products of their processing (H3PO4, superphosphates, phosphogypsum), lignites from South Bulgaria and products of their burning, copper ores and concentrates have been determined by instrumental and radiochemical NAA. An evaluation of the contribution of the phosphoric fertilizers to the uranium content of soil, plants, breeding stock and man has been done.

Lanthanide complexes with β-diketones and coumarin derivates:synthesis,thermal behaviour,optical and pharmacological properties and immobilisation

Abstract The paper presents the results of the synthesis of complexes of the type Eu(DBM) 3 and Eu(DBM) 3 ·Q (DBM-dibenzoylmethane, Q-1,10-phenantroline or 4,7-diphenyl-1,10-phenantroline) and of Tb- and Nd-complexes with the newly-synthesised coumarin derivates 3,3′-[(4-chlorphenyl)methylene)bis(4-hydroxy-2H-chromen-2-one), 3,3′-[(3,5-dimethoxy-4-hydroxy)methylene)bis(4-hydroxy-2H-chromen- 2-one), etc. Elemental and thermogravimetric analysis, IR, UV, NMR and fluorescence spectroscopy and X-ray analysis were applied for characterisation of the complexes. Some peculiarities of the synthetic procedures for both types of complexes were discussed and the influence of the synthetic approach, pH of the reaction medium, temperature of synthesis and drying of the complexes on the composition, stability and optical properties was reported. The immobilisation of the complexes in thin films based on sol-gel produced SiO 2 and on polymethylmethacrylate was studied. The optimal conditions for preparation of the matrices (composition of the starting system, temperature and time of sol aging, etc.) were recommended. The film morphology was evaluated by fluorescence, scanning electron and atomic force microscopy. The interaction of the lanthanide ions with the matrices and the influence of their nature, the effect of the in-situ polymerisation and other factors on photoluminescent excitation and emission spectra and excited state life-times of the complexes were followed. The effect of the second ligand on the photoluminescence properties of the immobilised diketonates was further elucidated. Processes involved in the thermal decomposition of the complexes and microcomposites produced on their base were proposed. Preliminary results on the pharmacological properties of the coumarin complexes reported showed unambiguously higher cytotoxicity of the Nd complex in comparison with that of the respective ligand.

Solubility of some lanthanide sulfates in polycomponent systems containing H2SO4

SummaryThe paper presents data on the solubility of La, Ce, Pr, Nd sulfates in the polycomponent system La2(SO4)3·8H2O-Ce2(SO4)3·8H2O-Pr2(SO4)3·8H2O-Nd2(SO4)3· 8H2O-H2SO4-H2O (at 25°C and 64°C) as well as in the same polycomponent system but in the presence of CaSO4·2H2O. The solubility of the sulfates — ocathydrates of Pr at 25°C and 64°C and of La and Ce at 64°C in tricomponent systemLn2(SO4)3·8H2O-H2SO4-H2O are also reported.ZusammenfassungDie Arbeit präsentiert Daten für die Löslichkeit von La-, Ce-, Pr- und Nd-Sulfaten in den Vielkomponenten-Systemen La2(SO4)3·8H2O-Ce2(SO4)3·8H2O-Pr2(SO4)3·8H2O-Nd2(SO4)3· 8H2O-H2SO4-H2O (bei 25°C und 64°C) sowie in den gleichen Systemen, jedoch in Anwesenheit von CaSO4·2H2O. Über die Löslichkeit von Sulfatoctahydraten von Pr bei 25°C und 64°C und von La und Ce bei 64°C in den Dreikomponenten-SystemenLn2(SO4)3·8H2O-H2SO4-H2O wird auch berichtet.

An algorithm for data processing in neutron activation analysis

An algorithm for processing NAA data is described. Input data are the output data from a multichannel pulse-height analyzer with a microprocessor. This algorithm permits to calculate the concentrations of the analyzed elements (using a standard or a standard curve), the error of concentrations in the analysis of one or several parallel samples and the sensitivity of the analysis according to Curries criteria in counts, g and g/g. Some other intermediate data (e.g. corrected net area of the peaks, parameters of the standard curve) may have individual importance in differenct cases.

Synthesis and characterization of yttrium-aluminum-iron and yttrium-cerium-iron citric complexes

Abstract Fe-, Y-Fe-Al- and Y-Ce-Fe- citrates were synthesized in ethylene glycol (EG) medium under conditions similar to those used in the polymerized complex method. Their elemental composition, IR, 13 C and 1 H NMR, X-ray photoelectron and Mossbauer spectra were studied, and formulae describing their composition were proposed. The complexes contained EG bonded as adduct and ester with citric acid ligand and did not contain ligands with deprotonated alcoholic groups. The complexes consisted of agglomerated spheres, 0.7–3μm in diameter. The local composition of the products was established by energy dispersive X-ray microanalysis. The comparison of the number of the ligands, their average electrical charge and the esterification degree of mono-, di- and trimetallic complexes proved the mixed-metal nature of the species studied. The thermal decomposition of the complexes was studied and a general scheme of the processes taking place was proposed. Highly crystalline, phase homogeneous Y 3 Fe 4 AlO 12 was produced after heating the respective complex at 1000 °C. Ce-doped yttrium-iron garnet, similarly prepared, contained traces of CeO 2 .

The sulfuric acid processing of rare earth concentrate with high calcium content: an attempted simplified mathematical description

Abstract The sulfuric acid treatment of a rare earth concentrate with a high calcium content (produced from phosphogypsum) was studied. A simplified model of both the sulfatization process and the treatment of the sulfate precipitate produced is proposed to evaluate the material balance of the process.