The thermal decomposition of the 5,7-dihalo-8-quinolinol rare earth metal chelates

The thermal decomposition of the 5,7-dichloro-, 5,7-dibromo- and 5,7-duodo-8-quinohnol chelates of lanthanum, cerium, praseodymium, neodymium, samarium and yttrium was investigated on the thermobalance. The chelates decomposed in the temperature range from 65 to 125°C while the oxide levels were obtained from 395 to 805°C Although the chelate thermal stability temperatures varied little with the chelating agent, the minimum oxide level temperatures were largely dependent on the halogen substitution on the 8-quinolinol molecule. Results of this study were correlated with previous studies on the rare earth metal chclatcs with 8-quinolinol and 2-methyl-8-quinolinol.     

O-TOF-ICP-MS analysis of rare earth elements,noble elements,uranium and thorium in river-relating species

The determination of rare earth elements (REEs), Au, Pt, Ir, Pd, Th and U in various river species was performed by the orthogonal time-of-flight inductively coupled plasma mass spectrometry (o-TOF-ICP-MS). The method working conditions were optimised in order to minimise the presence and possible spectral interferences of oxides. Ratios MO⁺/M⁺ as well as interference of light REE and Ba oxides/hydroxides with high REEs were evaluated and confirmed to be insignificant. Using the internal standard Re, non-spectral matrix effects (originally decreasing of intensities up to 15%) were overcome and recoveries were found from 92 to 105% for all matrices analysed. For solutions, limits of detection (3σ) were 0.14–0.82 for REEs, Th, U and Y, 1.18 for La, 4.3–5.6 for Au, Pt, Ir and Pd 11 for Sc (all in ng L^?1). The Principal component analysis was used for classification of samples according to their places of origin successfully. The o-TOF-ICP-MS was proved to be a very sensitive and suitable technique for bio-monitoring purposes and was employed in the analysis of biota samples (fish, insect, profiles, benthal growths) originated from five different places in the river Elbe (Czech Republic).     

Thin-layer chromatographic separation of scandium, yttrium, the rare earths, thorium and uraniuin(VI)

The Chromatographic behaviour of scandium, yttrium, the rare earths, thorium and uranium(VI) in dioxan-hydrochloric acid and dioxan-nitric acid media on a plain cellulose thin layer has been investigated. The following separations are possible: scandium-yttrium-lanthanum, scandium-samarium-thorium, scandium-lanthanum-lutetium, yttrium-lanthanum-thorium, and lutetium-thorium-uranium(VI) with dioxan-12M hydrochloric acid (7:3) and scandium-samarium-thorium, scandium-yttrium-uranium(VI), lutetium-thorium, and scandium-lanthanum-thorium with dioxan-14M nitric acid (7:3). A single chromogenic spray (Arsenazo III) has been used for the detection of all the metal ions studied.     

Rare earth elements,thorium and uranium in ores of the North-Latium (Italy)

In geochemistry, the distribution of the Rare Earth Elements (REEs) in earth crust and mantle allows to understand geochemical cycles and origin and age of igneous rocks. In this article REEs (Ce, Dy, Eu, La, Nd, Sm, Tb, and Yb), Th and U in ores of the North-Latium (Bracciano area, Ceriti Mt., Fate Mt., Sabatini Mt., Vulsini Mt., Acqua Rossa basin), have been investigated for evaluating the extraction feasibility for industrial applications. 107 samples were irradiated in the rotating rack of the TRIGA Mark II reactor of the R.C. Casaccia (ENEA) at neutron flux of 2.6 × 10¹² n × cm⁻² × s⁻¹ for 12 h together with primary and secondary standards. The gamma spectrometry measurements were performed after 8 h, 3 and 30 days of decay by means of HPGe detector (FWHM 1.75 keV at 1332.5 keV, peak/Compton ratio 55.1, relative efficiency of 22%) connected to a multi-channel analyzer. The total REE mean content is 105 μg g⁻¹, ranging widely between 2.23 and 410.5 μg g⁻¹ (average coefficient of variation 112%). A similar behavior is found for Th and U: their average levels are 13.5 and 6.0 μg g⁻¹, respectively. A quite good correlation between REEs and Th (and U) is found for Ceriti Mt. (r ² > 0.8) whereas for the other areas the correlation is <0.7. The results obtained evidence the low U content in the investigated locations.     

Supercritical carbon dioxide extraction equilibrium of gallium(III) with 2-methyl-8-quinolinol and 2-methyl-5-butyloxymethyl-8-quinolinol

This work performed fundamental studies for the extraction of gallium(III) with 2-methyl-8-quinolinol (HMQ) and 2-methyl-5-butyloxymethyl-8-quinolinol (HMO(4)Q) into supercritical carbon dioxide (SF-CO(2)) from a weakly acidic solution. The distribution constants of HMO(4)Q between aqueous and SF-CO(2) phases were determined at 45 degrees C, 8.6-20.4 MPa and I=0.1 M (H, Na)NO(3) (M=mol dm(-3)). At 45 degrees C and 15.7 MPa, gallium(III) was hardly extracted with HMQ into SF-CO(2), but was quantitatively extracted with HMO(4)Q in the pH range of 2.20-2.84. The extraction constant, K(ex, SF-CO(2)) (=[Ga(OH)(MO(4)Q)(2)](SF-CO(2))[H(+)](3)[Ga(3+)](-1)[HMO(4)Q](SF-CO(2))(-2)), of gallium(III) with HMO(4)Q was determined to be 10(-2.6+/-0.1) at 45 degrees C, 15.7 MPa and I=0.1 M (H, Na)NO(3), which was 63 times larger than that in heptane at 45 degrees C and 0.10 MPa. It was also found that the addition of 3,5-dichlorophenol as a synergist enhanced the extractability of gallium(III) with HMO(4)Q into SF-CO(2).     

Thermal decomposition of cellulose hyphan and its complexes with rare earth elements and scandium

Thermal decomposition of cellulose hyphan (CH) and its complexes with Lu, Gd, Nd and Sc under an atmosphere of air has been studied using thermogravimetry (TG), differential thermogravimetry (DTG) and differential thermal analysis (DTA). The results showed that, a different stages are accompanying the decomposition of (CH) and its complexes. These stages are affected by the presence of the metal ions. On the basis of the applicability of a non-isothermal kinetic equation, it was demonstrated that three main stages are involved in the decomposition processes. The activation energies of the different stages are calculated.

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Zusammenfassung Mittels TG, DTG und DTA wurde die thermische Zersetzung von Cellulosehyphan (CH) und seiner komplexe mit Lu, Gd, Nd und Sc an Luft untersucht. Es zeigte sich, da\ die Zersetzung von (CH) und seiner Komplexe von verschiedenen Schritten begleitet werden. Diese Schritte werden durch die Gegenwart der Metallionen beeinflu\t. Unter der Annahme der Anwendbarkeit einer nichtisothermen kinetischen Gleichung wurde gezeigt, da\ im Zersetzungsproze\ drei Hauptschritte inbegriffen sind. Die Aktivierungsenergie der verschiedenen Schritte wurde berechnet.

     

Molybdenum (V) oxo-complexes of 2-methyl-8-quinolinol

The synthesis and structure elucidation of the dimeric or monomeric nature of several molybdenum (V) oxo-complexes of 2-methyl-8-quinolinol (2-methyloxine) have been described, and we have compared these complexes with the molybdenum (V) oxo-complexes of 8-quinolinol (oxine). These complexes, were identified by IR and electronic spectra, magnetic susceptibility, differential scanning calorimetry, thermogravimetric analysis and the analytical data. The results permit us to assign the formulae: (C₁₀H₈NO)₄Mo₂O₃, (C₁₀H₈NO)₂Mo₂O₄ and (C₁₀H₈NO)₂MoO(OH). We suggest that the low magnetic moments observed for the dimeric complexes (C₁₀H₈NO)₄Mo₂O₃ and (C₁₀H₈NO)₂Mo₂O₄ are due, at least in part to intramolecular metal-metal interactions. Monomeric molybdenum (V) species (C₁₀H₈NO)₂MoO(OH), exhibits a magnetic moment ca. 1.75 Bohr magnetons.     

Thermal decomposition of the magnesium, zinc, lead and niobium chelates derived from 8-quinolinol

Solid M-Ox compounds, whereM represents Mg(II), Zn(II), Pb(II) and NbO(III), and Ox is 8-quinolinol, have been prepared. Thermogravimetry, derivative thermogravimetry (TG, DTG), differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR) and infrared absorption spectra (IR) have been used to characterize and to study the thermal stability and thermal decomposition of these compounds.The authors acknowledge the FAPESP (Proc. 90/2932-4), CAPES and CNPq for financial support.     

The thermolysis of the neocupferron chelates of yttrium and the rare earth elements

The thermolosis curves of the neocupferron chelates of yttnum, lanthanum, cerium(III), cerium(IV). praseodymium, neodymium, samarium and gadolinuim were determined. It was found that the ehelates were stable up to 8o°, with the oxide levels being reached at 460–750°.     

Solvent extraction of the lanthanide elements,scandium, uranium and thorium using tetracycline as complexing agent

Hydrogen ion dependence and extractant dependence of the extraction of the lanthanide elements, scandium, uranium and thorium into a solution of tetracycline in benzyl alcohol have been determined. Possiblity of using the tetracycline-benzyl alcohol system for separation of the lanthanide elements present in a mixture, as well as for the separation of uranium from those elements was tested. In the first case discontinuous countercurrent technique was used. In the second case a single step solvent extraction procedure was applied.     

Spectrophotometric determination of rare earth elements and thorium with arsenazo

The simultaneous spectrophotometric determination of rare earth elements (lanthanum and gadolinium) and thorium with arsenuzo is described. In 0.05 N nitric acid, thorium alone forms a colored complex with the reagent; at PH 7.2 both thorium and the rare carths form colored complexes. Satisfactory results were obtained with weight ratios of Th/rare earths ranging from 0.2 to 10.     

Determination of aluminium, scandium and rare earth elements by emission flame spectrometry

Summary Emission spectrometry in nitrous oxide-acetylene flames in combination with a highly resolving double monochromator and sensitive detecting system enables simple, sensitive and selective determinations of aluminium, scandium and all rare earth elements with exception of cerium in complicated matrices. Calibration plots are linear for a large concentration interval ( 100 g·ml^–1), detection limits are in ng · ml^–1 level and RSD does not exceed 3% on the optimal concentration level of the particular element. The determination of Al, Sc, Eu and Yb showed particular advantages as to methods using ICP-spectrometry.

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Bestimmung von Aluminium, Scandium und Seltenen Erden durch Emissions-Flammenspektrometrie

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Dedicated to Prof. Dr. G. Tölg on the occasion of his 60th birthday     

Spectral,thermal and magnetic studies of 2-chloro-5-nitrobenzoates of rare earth elements(iii)

The conditions of the formation of yttrium(III) and lanthanide(III) 2-chloro-5-nitrobenzoates were studied and their quantitative composition and solubilities in water at 298 K were determined. The compounds are dihydrates and their solubilities are of the order of 10^-3 mol dm^-3. The FTIR, FIR and X-ray spectra for the complexes were recorded. All complexes are crystalline compounds. Their thermal decomposition was studied only in the range 293-523 K since on heating above 523 K the complexes decompose explosively. Hydrated 2-chloro-5-nitrobenzoates of rare earth elements lose two crystallization water molecules in one step. The enthalpy of dehydration process was established and the magnetic moments of the complexes were determined in the range 77-300 K. The compounds obey the Curie-Weiss law. The 4f electrons do not participate in the formation of the Ln-O bonds. This revised version was published online in August 2006 with corrections to the Cover Date.     

Studies on thermal decomposition of 3-chlorobenzoates of rare earth elements in air atmosphere

The conditions of thermal decomposition of the 3-chlorobenzoates of Y, La and the lanthanides from Ce(III) to Lu have been studied. The complexes of La, Pr(III), Sm, Eu, Gd, Tb(III) and Dy were prepared as heptahydrates, those of Ce(III) and Y as pentahydrates, that of Nd as the tetrahydrate, that of Ho as the dihydrate and those of Er, Tm, Yb and Lu as anhydrous salts. On heating, these complexes decompose in three or two stages. They first lose some water molecules and then decompose to oxides through the intermediate formation of LnOCl. Cerium(III) 3-chlorobenzoate loses its crystallization water in two stages and yields the anhydrous salt, which is then transformed directly into CeO₂. All these complexes melt before decomposition in the temperature range 441–513 K.     

Thermal decomposition kinetics of thorium(IV) chelates of two naphthol dyes

The thermal decomposition of thorium(IV) chelates of 1-(2-fluorenylazo)-2-naphthol ando-carboxyphenylazo-2-naphthol was studied by TG. Thermoanalytical data (TG and DTG) of these chelates are presented in this communication. Interpretation and mathematical analysis of these data and evaluation of order of reaction, the energy and entropy of activation based on the differential method employing the Freeman-Carroll equation, the integral method using Coats-Redfern equation and the approximation method using the Horowitz-Metzger equation are also given. On the basis of experimental findings in the present course of studies the relative thermal stabilities of the thorium chelates can be given as [Th(FAN)₂(NO₃)₂]>[Th(CPAN)₂(H₂O)₂]2H₂O.

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Zusammenfassung Die thermische Zersetzung von Thorium(IV)-Chelaten von 1-(2-Fluorenylazo)-2-naphthol undo-Carboxyphenylazo-2-naphthol wurde thermogravimetrisch untersucht. Thermoanalytische Daten (TG und DTG) dieser Chelate werden angegeben und interpretiert. Reaktionsordnung sowie Aktivierungsenergie und -entropie wurden nach der differentiellen Methode unter Anwendung der Freeman-Carroll-Gleichung, nach der integralen Methode unter Verwendung der Coats-Redfern-Gleichung und nach der Näherungsmethode von Horowitz-Metzger bestimmt. Für die relative thermische Stabilität wird die Reihenfolge [Th(FAN)₂(NO₃)₂]>[Th(CPAN)₂(H₂O)₂]2H₂O angegeben.

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1(2- )-2- 1(2-)-2- --2-, . , . -, , - -. .

     

Thermal decomposition of pentacoordinate uranium(VI) complexes

The thermal decomposition of some mixed uranyl complexes with Schiff bases and DMSO, EtOH or (Ph)₃PO as neutral ligand, were investigated and the corresponding activation energy, E*_a, and enthalpy of dissociation, ΔH_d, values were calculated.

The results obtained indicate that for the same neutral ligand, the thermal stability of the uranyl complexes is influenced by the Schiff base used; for the same Schiff base, the presence of (Ph)₃PO results in a greater thermal stability of the mixed complexes than when the other two neutral ligands are present.     

Extraction studies of uranium(VI) and thorium(IV) with tributylphosphine oxide

Clay minerals occur widely in nature and play a very important role in agriculture, mineral recovery and chemical manufacturing. Among the many properties which affect clay behaviour, water binding and ion exchanging appear to be the most important. The study of the cation exchange capacity of soils is of great theoretical and practical importance since the CEC determines in many ways the behavior of nutrients, chemical amendments, and many toxic compounds entering the sols. Sorption interactions with montmorillonite and other clay minerals in soils are potantially important mechanisms for attenuating the mobility of heavy metal cations through the subsurface environment. In this work the cation exchange capacity (CEC) of montmorillonite from west Anatolia, and sorptions with montmorillonite for attenuating the mobility of uranium were studied. The CEC value was found to be 77 meq/100 g montmorillonite. The relative importance of test parameters e.g., contact time, particle size, pH and U(+6) aqueous speciation was determined. The results show that sorption on montmorillonite is a funtion of pH depending strongly on the aqueous U(+6) species. It reaches a maximum at near neutral pH(pH}7). At low and at high pH solutions the sorption values of uranium are poor. These sorption values were attributed to the formation of aqueous U(+6) carbonate complexes in alkaline conditions and the ionexchange process between UO₂ ⁺² species and interlayer cations on montmorillonite in acidic solutions.