Dimitar Todorovsky

• Prof., PhD, DSc
• Sofia University "St. Kliment Ohridski"

The solvothermal synthesis of LnCl3.nH2O with terephthalic acid (benzene-1,4-dicarboxylic acid, H2BDC) produced metal–organic frameworks (LnBDC), [Ln2(BDC)3(H2O)4]∞, where Ln = Sm, Eu, Tb, and Dy. The materials obtained were characterized by a number of physico-chemical techniques. The influence of the ionic radius of the lanthanides on the microst...

The paper presents the effects of the mechanochemical activation of ThO2-UO3 and ThO2-CeO2 mixtures in air and (for ThO2-UO3) in suspension in H2O or CHCl3. Planetary ball mill (Pulverisette 5, Fritch) with stainless steel triboreactors and milling balls from the same materials are used. Milling for 5 h of the ThO2-UO3 mixture does not affect signi...

Depleted U3O8 was mechanically activated in suspension with tributyl phosphate (TBP), trioctylamine (TOA) and ethylenglycolmonomethylether (EGME) in planetary ball mill with stainless steel vessels and balls. X-ray diffractograms and IR spectra of the activated solid samples were taken. The radioactivities of 238U and 234Th in the leaching solution...

Depleted U3O8 was mechanically activated in suspension with tributyl phosphate (TBP), trioctylamine (TOA) and ethylenglycolmonomethylether (EGME) in planetary ball mill with stainless steel vessels and balls. X-ray diffractograms and IR spectra of the activated solid samples were taken. The radioactivities of 238U and 234Th in the leaching solution...

Depleted U 3 O 8 was mechanically activated in suspension with tributyl phosphate (TBP), trioctylamine (TOA) and ethylenglycolmonomethylether (EGME) in planetary ball mill with stainless steel vessels and balls. X-ray diffractograms and IR spectra of the activated solid samples were taken. The radioactivities of 238 U and 234 Th in the leaching sol...

Results from self-observation of the working time distribution of a university teacher for a period of 45 years (starting from the very beginning of his carrier till two years after retirement) are reported classified in (i) teaching; (ii) scientific; (iii) administrative, organizational, technical; (iv) social/other activities. For the whole perio...

The structural complexity of the 3D surface of poly(methylmethacrylate) films with immobilized europium β-diketonates is studied by atomic force microscopy and fractal analysis. Fractal analysis of surface roughness revealed that the 3D surface has fractal geometry at nanometer scale. The poly(methylmethacrylate), PMMA, as immobilization matrix is...

For the first time, data on the effect of TiO2 modification by N-doping or by carbon nanotubes on the photocatalytic destruction of endocrine disrupting compounds 17α-ethynylestradiol (EE2) and 17β-estradiol (E2) in aqueous solutions are reported. A possibility to accomplish photocatalytic process under halogen lamp irradiation is shown. The cataly...

Ru(II)-tris (4,7-diphenyl-1,10-phenanthroline) dichloride immobilized in matrices from sol-gel produced SiO2, SiO2-citric acid/ethylene glycol polyester hybrid or poly (methylmetacrylate) is explored as a sensor for determination of dissolved oxygen in white and red wines. The significant overlapping of the 612 nm spectral bands of the oxygensensit...

The paper presents a review of literature data on the occurrence of endocrine disruption compounds in the effluents from wastewaters treatment plants, surface, underground and drinking waters and sediments. General data concerning their action on the living organisms (mainly fish) are given. The peculiarities of the methods for removal/degradation...

Microcomposites consisting of TiO2 and ThF4 or UO3 (0.5–2% of the TiO2 mass) are produced by sol-gel synthesis of TiO2 in presence of the respective additives. X-ray diffraction study reveals small effect of the latter on TiO2 phase composition and cell parameters and significant influence on the crystallite size and UV/Vis reflectance spectra. The...

The paper considers the possibilities for mechanochemical synthesis of rare earth complexes. The complex Eu(TTA)3·phen (HTTA — 2-thenoyltrifluoroacetone, phen — 1,10-phenanthroline) is synthesized by mechanical treatment of a mixture of EuCl3.6H2O, HTTA, phen and NaOH in planetary ball mill Pulverisette 7 for 30 min at 800 min−1. The non reacted st...

The purpose of this article is to study the influence of gamma irradiation on the sorption capacity and photocatalytic activity of commercially available TiO2 Degussa P25. The photocatalyst was gamma-irradiated at ambient temperature with doses 8–60 kGy (137Cs, dose rate 2 kGy/24 h) and then stored until analysis/tests in liquid N2. X-ray diffracti...

Commercial product Degussa TiO2 P25, sol-gel produced TiO2 and TiO2 modified by carbon nanotubes addition (5% of the TiO2 mass) are tested as photocatalysts for the degradation of endocrine disrupting compound 17α-ethynylestradiol (1 µM aqueous solution). The molecular and crystal structure, phase composition, crystallite size, specific surface are...

TiO2-based photocatalysts doped with 10 wt.% Nd3+ or 1.8 wt.% nitrogen are synthesized by a sol–gel method using Ti-butoxide and Nd(NO3)3 or aqueous ammonia as starting materials. The resulting powder crystal structure, textural properties, morphology, IR, UV/Vis and X-ray photoelectron spectra are studied. The photocatalytic activity was tested fo...

Sol-gel produced TiO2 is gamma-irradiated at ambient temperature (Cs-137, dose rate 2 kGy/24 h) with doses 8-60 kGy and stored up to the analysis/tests in liquid N-2. Phase composition, crystal cell parameters, crystallites size, textural properties (morphological grains size, specific surface area), EPR behaviour and UV-vis. reflectance spectra of...

Microcomposites consisting of TiO2 (or Ce-doped TiO2) and ThO2 (0.5–2% of the TiO2 mass) are produced by sol-gel synthesis of TiO2 in presence of ThO2. X-ray diffraction study reveals the effects of ThO2 (compared to the ThO2-free TiO2, obtained by the same method) on the anatase interplanar distances, crystallites size and phase composition. The p...

The structure changes and the degree of reduction of U3O8 after mechanoactivation in agate and stainless steel vessels in different media are studied. Clearly expressed reduction of U(IV, VI) oxide, accompanied by oxygen release as a result of mechanochemical activation is observed. The highest degree of reduction is reached when mechanoactivation...

Thin films of ferrites of the type MIIFe2O4 (M = Cu, Mg, Zn) are prepared by spray-pyrolysis using ethylene glycol solutions of mixed-metal citric complexes of the respective metals at substrate temperature between 350 °C and 450 °C and post-deposition annealing at 480–750 °C in air. Phase composition, crystal structure, morphology and adhesion of...

Microcomposites are produced consisting of optically active Ru (II)-tris(4,7-diphenyl-1,10-phenanthroline)dichloride (Rudpp) immobilized in poly(methylmethacrylate) prepared by polymerization of the monomer or by using chlorophorm solution of the polymer. The morphology of films and membranes (up to 1.5 mm in thickness) is studied in dependence of...

The properties of composites prepared by the immobilization of Eu(III) complexes with dibenzoylmethane and thenoyltrifluoracetone in poly(methylmethacrylate) are studied. The matrices are produced by polymerization of the monomer or by using chloroform solution of the polymer. The films produced from polymerized monomer by dip-coating or spray-pyro...

Organic–inorganic hybrid materials produced from tetraethoxysilane, citric acid and ethylene glycol in different mole ratios and consisting of Si–O–Si and Si–O–C nets are prepared and their molecular structure (IR and NMR spectroscopy), morphology (fluorescent microscopy, SEM and AFM), thermochemical behavior and fluorescence properties (excitation...

Results on the influence of mechanoactivation (3–30 min) in a planetary ball mill on the composition, crystal structure, IR spectra and morphology of EuCl3·6H2O, dibenzoylmethane (HDBM) and mixtures of EuCl3·6H2O — HDBM and EuCl3·6H2O — HDBM — 1,10-phenathroline (phen) are presented. Mechanoactivation leads to a decrease of interplanar distances of...

Method for synthesis of UO2+x and uranium–thorium mixed oxides by using sol–gel method and mechanochemical activation is proposed. The synthesis of UO2+x and solid solutions with equal amount of metals or enriched to one of them is performed by external gelation process, thermal decomposition of the sol–gel products in air and subsequent mechanoche...

The X-ray powder diffractogram of the europium complex Eu(DBM) 3 (DBM - dibenzoylmethane) is reported for the first time. It is shown that the mixed-ligand complex Eu(DBM)3.dpp (dpp - 1,4-diphenyl-1,10-phenanthroline) is X-ray amorphous. The 1H and 13C NMR spectra of Eu(DBM) 3, Eu(DBM) 3.phen (phen - 1,10-phenanthroline) and Eu(DBM) 3.dpp are inter...

The complexes of europium with dibenzoylmethane (= HDBM) and mixed-ligand complexes containing 1,10-phenanthroline (= phen) or 4,7-diphenyl-1,10-phenanthroline (= dpp) are synthesized by different methods (already proposed in the literature) and their elemental composition, I.R., 1H and 13C NMR, and fluorescence excitation and emission spectra, as...

A short review of recent investigations of the authors on the Ru(II)-based optical oxygen sensors is presented focused on the influence of: (i) type of the supporting matrix (SiO2 or polymethylmetacrylate based), (ii) precursors used (tetraethoxysilane, ormosil-type alkoxosilanes, methylmetacrylate, polymethylmetacrylate), (iii) method applied for...

The complex of europium with dibenzoylmethane and mixed-ligand complex containing 1,4-diphenyl-1,10-phenantroline is entrapped in SiO2-based sol-gel produced immobilization matrices. The IR spectra, thermochemical behavior, photoluminescence properties of the obtained composites and the influence of the synthetic conditions (composition of the sol,...

A short review is presented on the authors, investigations on the influence of the crystal structure and the morphology on the sorption ability and photocatalytic activity under UV-irradiation of thin TiO2 films produced by spray-deposition process. Commercially available TiO2 (Degussa P25 and Tronox), titania modified by mechanoactivation as well...

On the admission exams in chemistry at the Sofia University "St. Kliment Ohridski" this year appeared fewer candidates than in 2008. Although the average grade of this year's exam is higher than last year, in the subjects of Chemical Faculty enrolled fewer students - there was a lack of interest. One reason for the higher marks is the easier test a...

The photocatalytic activity of TiO2 films deposited on different substrates by the spray-drying method using suspensions of commercially available TiO2 (Degussa P25 or Tronox) as starting material was studied. The influence of the type of the initial TiO2, preparation conditions (temperature of the substrate during the film deposition, temperature...

Samples of pure aluminium and aluminium alloy were heated at 150 kPa and 130 °C in ethylene glycol (EG)–water mixture (volume ratio 1:1) for 172 h (8–12 h heating, 12–16 h pause). The corrosion of the metals was characterised by the transfer of Al into solution, changes in the surface morphology of the samples and their electrochemical behaviour. F...

Films are deposited by dip- or spin-coating in gels produced from tetraethoxysilane (TEOS), octyltriethoxysilane (OtEOS) or mixtures of TEOS and OtEOS (mole ratio1:1) as well as TEOS and methyltriethoxysilane (MtEOS) (mole ratio 1:3). The Stern–Volmer constants and the response to oxygen of Ru(II)-tris(4,7-diphenyl-1,10-phenathroline) dichloride im...

Films (∼0.5 mg/cm2) from TiO2 doped with 1–10 mol% Ln3+ (Ln = La or Gd) are deposited on different types of substrates by spray-pyrolysis using ethylene glycol solutions of Ti4+–Ln3+ citric complexes as starting material and O2 as a carrier gas. The films are post-deposition heated at 500 °C. Their phase composition, crystal structure, morphology,...

The purpose of the present article is to make clearer the possibilities of the non-destructive method for neutron activation determination of lithium without the use of apparatus or measurement of gamma-gamma coincidences. The most important sources of error has been investigated and it was shown how these could be eliminated. The sensitivity of th...

The changes in crystallites size, phase composition, morphology, sorption and photocatalytic properties of TiO2 (Degussa P-25) as a result of mechanoactivation in planetary ball mill Pulverisette 5 are reported. These alterations are investigated as a function of the times of milling and storage before the photochemical test, the nature of triborea...

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, 13C and 1H NMR, X-ray photoelectron and Mössbauer spectra were studied, and formulae describing their composition were proposed. The complexes contained EG bon...

The possibility to use the photoluminescence of Ru(II) tris(4,7-diphenyl-1,10-phenathroline) dichloride, immobilized in sol-gel produced SiO2-based matrix for the determination of dissolved oxygen concentration in beer is studied. Organically-modified silane (octyltriethoxysilane) and mixtures from tetraethoxysilane and octyltriethoxysilane are use...

Cerium citric and tartaric complexes have been synthesized in ethylene glycol solutions under conditions similar to those used at polymerized complex method (PCM) application. The composition, IR, 13C and 1H NMR spectral characteristics, morphology and thermal decomposition of the isolated complexes have been studied. The influences of the anionic...

The results reported concern the characterization of thin layer SiO2-based matrices with an oxygen sensing component Ru(II)-tris(4,7-diphenyl-1,10-phenanthroline) immobilized, when a sol–gel process along with dip- and spin-coating deposition methods are used.SEM, TEM and AFM study, assisted by X-ray energy dispersive microanalysis reveals the infl...

The effect of the mechanical treatment of UO 2(NO 3) 2·6H 2O in a planetary ball mill in air and as a suspension in toluene has been studied. The X-ray diffractometry results strongly suggest that part of the mechanoactivated material is transformed in nitrosyl uranyl nitrate.

The effect of the mechanical treatment of UO2(CH3COO)2·2H2O in a planetary ball mill in air or as a suspension in toluene or benzene on its crystal structure and coordination mode has been studied. No significant changes in the crystal structure are observed. IR-spectroscopy results suggest that in the part of the mechanoactivated material the bide...

The results from DSC and thermogravimetric analysis of gels produced from a mixture of tetraethoxysilane (TEOS) and octyltriethoxysilane (OtEOS) both with and without immobilized Ru(II) tris(4,7-diphenyl-1,10-phenanthroline) dichloride as well as DSC and TG data for films deposited by deep-or spin-coating from the same gels, are reported. The initi...

Cerium(III/IV) and Ce(IV)–Ti(IV) citric complexes were synthesized in ethylene glycol medium under conditions similar to those of the polymerized complex method (PCM). Solution phase 1H, 13C NMR, solid state 13C CP MAS NMR and IR spectroscopy, and X-ray powder diffractometry were used to characterize the composition and structure of the synthesized...

Composite La2O3–TiO2 and plain TiO2 photocatalytic coatings were prepared by a dip-coating technique on stainless steel substrates (SS) and tested as photoelectrodes in the electrically enhanced UV-photooxidation of organics. Electrode specimens were characterised by photovoltammetry under UV light in 0.1M K2SO4 solutions in the absence and presenc...

Thin films of La2Ti2O7 have been deposited on fused silica and Si substrates by a spray pyrolysis method using ethylene glycol solution of La(III)-Ti(IV)-citrate complexes as starting material and O2 as a carrier gas. The composition, crystal structure and morphology of the films are studied.

The cocrystallization of Ce2(SO4)3 and La2(SO4)3 is studied in aqueous and H2SO4 (150 g/dm3) solutions at 25 °C and 64 °C. The effect of the formation of inner sphere sulfate complexes of the type LnSO 4+ in determining the composition of the equilibrium phases is revealed.

The effect of the mechanical treatment of UO 2 (CH 3 COO) 2. 2H 2 O in a planetary ball mill in air or as a suspension in toluene or benzene on its crystal structure and coordination mode has been studied. No significant changes in the crystal structure are observed. IR-spectroscopy results suggest that in the part of the mechanoactivated material...

Al-and Y-Al-citric complexes have been synthesized in ethylene glycol medium at conditions close to the ones used in polymerized complex method and their composition and spectral characteristics have been studied. Proofs have been found for the formation in the bimetallic system of a mixed-metal Al-Y-complex. Doubly ionized and esterified ligands t...

The commercially available TiO2-catalyst (Degussa P25) was supported by spray pyrolysis deposition method on the outer surface of the quartz tubes, incorporated in photocatalytic reactor. The crystal structure and the morphology of the films were studied. The immobilized TiO2 is modified with nanosized gold particles by the photoreduction method to...

The effect of the mechanoactivation on UO3 and U3O8 in agate or stainless steel vessels in air or in toluene is studied. UO2(OH)2 is the main product of UO3.H2O activation in steel vessel in air. The presence of toluene leads to strong amorphization and dispersity increase and, probably, to the formation of U2O5. The activation of U3O8 leads to its...

Ethylene glycol solutions of La–Mn(II) and La–Ca–Mn(II) citric complexes has been used as a starting material for spray-pyrolysis deposition of LaMnO3 and La1−xCaxMnO3 thin films on β-quartz, fused quartz, Si(0 0 1) and SrTiO3(1 0 0) substrates heated during the deposition at 380 °C. At suitable post-deposition heating conditions highly uniform fil...

The thermal decomposition of Y–Zr citric complexes prepared in ethylene glycol or in water medium is studied. The compositions of “aqueous” Y-, Zr- and YZr complexes are determined and the corresponding IR spectra are analyzed. Proofs are put in concerning the mixed-metal nature of the complexes. Based on TG, DTG and DTA analyses as well as on some...

Thin films of CeO2 were deposited by spray-pyrolysis on β-quartz or optical grade silica glass substrates heated at 350–500 °C. Ethylene glycol solutions of Ce(NO3)3 and cerium citrates or tartrates (prepared using Ce(NO3)3 or CeCl3 as cerium sources) were used as starting materials. Crystalline films may be obtained “in situ”. Post deposition anne...

In the present paper procedures are described for spray pyrolysis deposition of YSZ films (0.1–30 μm in thickness) with 8 or 15 mole % of YO1.5 on different substrates. Aqueous or ethylene glycol solutions of Y–Zr-citrates were used as starting material and O2 as carrier gas. The crystal structure and the morphology of the films were studied.The op...

For Abstract see ChemInform Abstract in Full Text.

Mn-, LaMn- and LaCaMn-citrates were synthesized at 60–120°C in ethylene glycol medium using chlorides or nitrates as metal sources. Their composition, IR spectra and thermal decomposition were studied. Equimolar La/Mn ratio has been established in the complex, prepared from chloride solution with the same initial composition of the metals. In the i...

The effect of the mechanical treatment of U3O8 in a planetary ball mill in air or as a suspension in benzene solution of thyolilthreefluoroacetone (TTA) on the nature of the oxide and on the leaching of U and 234Th into diluted aqueous solutions of HCl, Na2EDTA and NaCl has been studied. Transformation of U3O8 to UO2, is much stronger expressed whe...

La-, Ti-and La–Ti-citrates, prepared in ethylene glycol medium (at conditions similar to those used in the polymerized complex method) and isolated as solid substances, have been studied by 13 C-solid state NMR analysis, XPS, SEM and EDAX. The obtained results, together with data from elemental, thermogravimetric, IR, 13 C-and 1 H-NMR (in solution)...

Yttrium-zirconium citric complexes prepared in ethylene glycol (EG) medium are used for preparation of yttria-stabilized zirconia (YSZ). The composition and some spectral characteristics of the complexes are studied and their formulae are derived. Most probably, they are of a mixed-metal nature. The utilization of the complexes for YSZ production a...

The effect of the mechanical treatment of U3O8 in a planetary ball mill in air or as a suspension in benzene solution of thyolilthreefluoroacetone (TTA) on the nature of the oxide and on the leaching of U and 234Th into diluted aqueous solutions of HCl, Na2EDTA and NaCl has been studied. Transformation of U3O8 to UO2, is much stronger expressed whe...

The composition, IR, C and H NMR spectral characteristics and thermochemical behavior of La‐, Ti‐ and bimetallic La‐Ti‐tartrates (potential precursors of La2Ti2O7), obtained in ethylene glycol, were studied. The comparison of their main characteristics with those of the analogous citric complexes contributes to the elucidation of the processes invo...

Thin films of α-Fe2O3 have been deposited on fused silica substrates (heated at 500 °C) by an in situ spray pyrolysis method using ethylene glycol solution of Fe(III)-citric complexes and O2 as a carrier gas. The monophase composition of the films was confirmed by the X-ray diffractometry. Their morphology and roughness have been estimated by means...

Ethylene glycol solution of mixed-metal Y(III)-Fe(III) citric complexes has been used as a starting material for a spray pyrolysis deposition of Y3Fe5O12 (YIG) thin films on silica and on single crystal Y3Al5O12 (YAG) substrates heated up to 500°C. O2 was used as a carrier gas. A post-deposition thermal annealing at 800–1100°C was applied. Films of...

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.

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 identificat...

Solid state La-Ti-citrate complexes are isolated from ethylene glycol and water solutions. The elemental composition of the compounds is determined, the 13C- and 1H-NMR and IR spectra are analysed, and their thermochemical behaviour is studied. It is found out that the ethylene glycol is present in the complex, prepared at 40°C, mainly as an adduct...

The changes in the solubility and in the phase composition of yttrium-aluminum garnet (YAG) as a result of its mechanochemical treatment for 2 h in a planetary ball mill together with H3BO3 and Na2CO3 (mole ratio H2BO3/Na2CO3=4) in ratios (H3BO3+Na2CO3)/YAG=2,4, and 9 are studied. At a ratio of 9, the yield of yttrium in the water solution obtained...

The influence of mechanoactivation on the overall solubility of CaSO4 · 2H2O and of phosphogypsum in water and in diluted acids (10% HCl, 7% H2SO4) as well as on the leaching of rare earths from phosphogypsum have been studied. The mechanoactivation is performed in a centrifugal ball mill in air and in suspension with the acids mentioned above. Par...

Results of a self-observation of the working time distribution of an university teacher for a period of 28 years are reported. Averaged over the whole period, the teaching activities take 18%, scientific work −20%, and the various kinds of administrative, organizational and technical activities −51% of the working time. The changes of the working t...

The changes of the dispersive and phase composition of a Cerox type polishing material as a result of its exploitation and mechanochemical treatment are studied. A slightly expressed destruction of the solid solution CeO2-Ln2O3 during the exploitation and mechanoactivation in water suspension (in centrifugal ball mill) is found out. The mechanoacti...

The influence of the mechanoactivation in air and in water suspension on the oxides and hydroxides of La and Nd is studied. The activation is carried out at ambient temperature in agate vessels of a Pulverisette 6 ball mill(Fritsch). La and Nd systems have similar behaviours during the activation with certain quantitative differences. The activatio...

The synthesis of a new type of complexes of Y, Nd and Er with mono-(2-ethylhexyl) phosphoric acid is reported. The elemental composition, IR-spectral data and thermogravimetric analysis prove the presence of both mono-and bivalent ions of the acid as ligands as well as of NO3-ions. The IR-spectrum is interpreted in comparison with those of other la...

The thermochemical behaviour of solid-state complexes of lanthanum with mono-(2-ethylhexyl) phosphoric acid (H2B) (La(HB)3·1.5H2O and La2B3·3H2O) was studied. The thermal decomposition of these complexes proceeds without melting to yield La(PO3)3 and a mixture of La(PO3)3 and LaPO4, respectively. La(HB)31.5H2O decomposes via dehydration (323–383 K)...

IR-spectra of the solid state lanthanum complexes with mono-and bis-(2-ethylhexyl) phosphoric acids (H2B, resp. HA) are studied. It is confirmed that La coordinates HA as LaO6-octahedra, connected through -La-O-P-O-La-bridging bonds. The so fixed polynucleous chains form the crystal structure of the complex. The obtained IR-spectral data as well as...

The elemental composition, IR spectrum and thermal decomposition of the precipitate obtained during interaction of a Ce(NO3)3-acetone solution and a partially neutralized mixture of bis- and mono-(2-ethylhexyl) phosphoric acid are studied. It is established that the precipitate represents CeA3NO3, whereas under the same experimental conditions Pr,...

The elemental composition, molecule, and crystal structure of precipitates obtained from an acetone solution of Ln(NO3)3 (Ln = Pr + Er or La + Nd) with a mixture of bis- and mono-(2-ethylhexyl) phosphoric acids and their sodium salts were studied. In this study we found enrichment of the precipitate with the heavier lanthanide. The separation facto...

The crystal structure of the complexes of some rare-earths (RE = La, Nd, Pr and Er) with bis- and mono-(2-ethylhexyl)phosphoric acids were studied by using the X-ray powder diffraction. The results show that for all RE investigated, the complexes of the diester crystrallize in orthorombic symmetry and cell parameters have been determined. The compl...

The thermal decomposition of LnA3 (Ln is Ce, Pr, Nd, Er; A is [CH3CH(CH2CH3)-(CH2)4O]2PO−2)2 has been studied. It is established that heating to 443–453 K leads to recrystallization of the LnA3 complexes accompanied by a partial annealing of the crystal defects. Their decompositions start above these temperatures and are complete at 583–608 K, prod...

The influence of thermal or mechanochemical treatment on the structural state of yttrium-aluminium garnet (YAG) is studied. The formation of tetragonal form of Y3AL5O12 is assumed by X-ray diffractometry. The effects of the temperature, pressure and cooling rate are discussed and a scheme explaining the transformation is proposed. The thermally and...

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 uran...

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.

The paper presents data on the solubility of La, Ce, Pr, Nd sulfates in the polycomponent system La2(SO4)38H2O-Ce2(SO4)38H2O-Pr2(SO4)38H2O-Nd2(SO4)3 8H2O-H2SO4-H2O (at 25C and 64C) as well as in the same polycomponent system but in the presence of CaSO42H2O. The solubility of the sulfates — ocathydrates of Pr at 25C and 64C and of La and Ce at 64C...

Comparison of liquid–liquid extraction and liquid–membrane extraction is made on the basis of some experimentally established parameters of the La and Nd separation process. The observed effects confirm the important role of surfactants in the LME process.

The possibility of purifying the rare earth concentrates produced as a by-product of sulphuric acid processing of apatite was investigated. Special attention was paid to the elimination of silicon. The precipitation of hydroxides and oxalates gave rare earth oxide mixtures with a rare earth content of about 99.6%.