Search Results
Abstract
Extraction of Mo(VI) by 4-(5-nonyl)pyridine (NPy) in benzene from mineral acid solutions containing thiocyanate ions has been investigated at room temperature (23±2°C). From mineral acid (HCl, HNO3, and H2SO4) solutions alone Mo(VI) is not extracted quantitatively while the presence of small amounts of KSCN in the system augments the extraction by a large factor. Stoichiometric studies indicate that ion-pair type complexes (NPyH)2·[MoO2(SCN)4] are responsible for the extraction. Separation factors determined at fixed extraction conditions (0.1M Npy/C6H6–0.1M acid +0.2M KSCN) reveal that Ag(I), Cu(II), Co(II), Zn(II), Hg(II) and U(VI) are co-extracted while a clean separation from alkali metals, alkaline earths and some transition metals like Ln(III), Zr(IV), Hf(IV), Cr(III), Cr(VI) and Ir(III) is possible. Some of the complexing anions like oxalate, citrate, acetate, thiosulfate or ascorbate do not affect the degree of extraction of Mo(VI) allowing it to be recovered from diverse matrices.
Abstract
The extraction order of Th(IV), U(VI) and Mo(VI) based on pH0.5 values is Mo(VI)>U(VI)>Th(IV). Quantitative extraction has been observed for U(VI) by mixture of 10% (v/v) LIX 84 and 0.1M dibenzoylmethane at pH 4.2 and by mixture of 10% LIX 84 and 0.05M HTTA in the pH range 5.5–7.3 and for Mo(VI) by 10% LIX 84 from chloride media at pH 1.5. The order of extraction of Mo(VI) from 1N acid solutions is HCl>H2SO4>HNO3>HClO4 and extraction decreases very rapidly with increase in the concentration of HCl as compared to that from H2SO4, HNO3 and HClO4 acid solutions. The diluents C6H6, CCl4 and CHCl2 are found to be superior ton-butyl alcohol and isoamyl alcohol for extraction of Mo(VI). Influence of concentration of different anions on the extraction of U(VI) and Mo(VI) has been studied. Very little extraction has been observed in case of Th(IV) by LIX 84 or its mixtures with other chelating extractants or neutral donors.
Abstract
We have investigated the behaviour of109Cd, in two-phase systems: (HDEHP–C6 H6/ H3 PO4–HClO4–LiOH, 
=0.2), as a function of the independent equilibrium parameters which define the system: pH, equilibrium concentration of H3 PO4 and total concentration of HDEHP in the organic phase. The data have been interpreted in terms of the existence of phosphoric complexes characterized by their order 1 with regard to H3 PO4 and their charge z. The l and z. values are: 0<1<2, z=–2, 0, 1, 2 for the following ranges: 0.7<pH<2.7 and CH3 PO4<4M. Stability constants of the predominant complexes have been obtained. Finally, a formulation of these complexes has been proposed on the basis of partial charge of the atoms. Some complexes, could be formulated as hydroxy-phosphoric species, resulting from competition between hydroxy and dihydrogenophosphate anions. In concentrated phosphoric acid (CH3 PO4=4M), complexation of cadmium is not more than 25%.
Abstract
Human, animal (cow, buffalo and goat) and commercial milk powders (for infants and adults) have been analyzed for 5 minor (Na, K, Mg, Cl and P) and 13 trace elements (Cr, Mn, Fe, Co, Cu, Zn, Cd, Hg, As, Se, Sb, Cs and Br) by instrumental and radiochemical neutron activation. Milk standards NIST SRM 1549 and IAEA A-11 along with diet standards RM 8431 a and IAEA H-9 were also analyzed for quality assurance. The method involves thermal neutron irradiation for 10 m, 1 h, 6 h and 1 week in a reactor followed by high resolution 
-spectrometry. Concentrations of Fe, Co, Zn, Sb, and Se were also determined by radiochemical solvent extraction. Mean concentrations of Na, K, Mg, P, Cl, Fe, Mn and Cu in human milk (colostrum) are comparable with that of a WHO/IAEA study. It has, however, lower contents of toxic trace elements (Cr, Cd, Hg, Br, Se, Sb and As) compared to breast tissue from the same area. Cow milk is richer in Na, K, Cl, Mn and Se but it has comparable amounts of Mg, Zn, Br, Fe and Sb with respect to breast milk. Significant differences have been observed for elemental concentrations of Na, K, P and Fe in commercial formula milk powders for infants and adults. Infant's milk powders contain all the nutrient elements in balanced amounts required for the higher growth rate of a child.
Abstract
The paper presents the conditions under which compounds of the commercial herbicides, 2,4-dichlorophenoxyacetic acid (2,4D; C8H6O3Cl2) and 2-(2,4-dichlorophenoxy)-propionic acid (2,4DP; C9H8O3Cl2), with lead(II) and cadmium(II) are formed and the results of the examination of their properties.On the basis of the elemental analysis and Pb and Cd determination, the following molecular formulae for the obtained compounds were proposed: Pb(C8H5O3Cl2)2.H2O, Cd(C8H5O3Cl2)2.2H2O, Pb(C9H7O3Cl2)2·H2O and Cd(C9H7O3Cl2)2·H2O. Water solubility of the synthesized complexes at room temperature was examined. X-ray powder analysis was carried out. The discussion of IR spectra and conductivity data is presented. Thermal decomposition of these compounds in air was studied by TG/MS methods.
Novel Co(II) and Cd(II) complexes with non-steroidal anti-inflammatory drugs
Synthesis, properties and thermal investigation
Abstract
New metal(II) complexes with empirical formulae Co(ibup)2·4H2O, Cd(ibup)2·3H2O, Co(nap)2·H2O, Cd(nap)2·3H2O (where ibup=(CH3)2CHCH2C6H4CH(CH3COO−) and nap=CH3O(C10H6)CH(CH3COO−)) were isolated and investigated. The complexes were characterized by elemental analysis, molar conductance, IR spectroscopy and thermal decomposition. The thermal behavior was studied by TG, DTG, DTA methods under non-isothermal conditions in air atmosphere. The hydrated complexes lose water molecules in first step. All complexes decompose via intermediate products to corresponding metal oxides CoO and CdO. A coupled TG-MS system was used to detect the principal volatile products of thermolysis and fragmentation processes of Co(nap)2·H2O. The IR spectra of studied complexes revealed also absorption of the carboxylate group. Principal concern with the position of asymmetric, symmetric frequencies. The value of their separation allow to deduce about type of coordination these groups.
Abstract
This paper presents a study for the preparation of CoxFe3−xO4 (x = 0.02, 0.2, 0.5, 0.8, 1.0, 1.1, 1.5) nanoparticles, starting from metal nitrates: Co(NO3)2·6H2O, Fe(NO3)3·9H2O and ethylene glycol (C2H6O2). By heating the solutions metal nitrates-ethylene glycol, the redox reaction took place between the anion NO3 − and OH–(CH2)2–OH with formation of carboxylate anions. The resulted carboxylate anions reacted with Co(II) and Fe(III) cations to form coordinative compounds which are precursors for cobalt ferrite. XRD and magnetic measurements have evidenced the formation of cobalt ferrite for all studied molar ratios. The average diameter of the cobalt ferrite crystallites was estimated from XRD data and showed values in the range 10–20 nm. The crystallites size depends on the annealing temperature. The magnetization of the synthesized samples depends on the molar ratio Co/Fe and on the annealing temperature.
Abstract
It was observed that the addition of a very small quantity (5·10−3 M L−1) of an organic solvent, benzene (C6H6) in the aqueous growth medium (pH ∼5.9) of tristhioureazinc(II)sulphate (ZTS) markedly influences the SHG efficiency. The measurements using Nd:YAG laser source reveal that second harmonic generation (SHG) conversion efficiency which is one of the most important nonlinear optical (NLO) properties is enhanced by benzene dopant by a factor of nearly 1.5 times. The crystalline perfection of the grown crystals was evaluated by high-resolution X-ray diffractometry (HRXRD). The full width at half maximum (FWHM) of the diffraction curve (which gives an estimate for the degree of crystalline perfection) for undoped and benzene doped specimen crystals are 26 and 15 arc sec, respectively. The reduction in FWHM due to the benzene solvent indicates the significant improvement in crystalline perfection. This very much suggests that the dissolution of trace impurities in the presence of benzene prevents the entry of impurities into the crystal lattice and at the same time enhances the growth promoting effect (GPE). Not much variation is observed in XRD, FTIR and TG-DTA of ZTS in the presence and absence of benzene in the aqueous growth medium.
Abstract
A flow microcalorimeter has been used to determine excess enthanlpies (H E) at 298.15 K for binary mixtures of dimethylsulfoxide (1)+alkylbenzenes (benzene, methylbenzene, ethylbenzene, n-propylbenzene and sec-propylbenzene, n-butylbenzene, sec-butylbenzene and tert-butylbenzene) or tetrachloromethane, trichloromethane, tetrachloroethane, dichloromethane and monochloroalkanes (1-chloropropane, 1-chlorobutane, 1-chloropentane, 1-chlorohexane) (2). These data with the data available in the literature on the molar excess enthalpies (H E), molar excess Gibbs energies (G E), activity coefficients at infinite dilution, γi ∞, liquid-vapour equilibria (LVE) and liquid-liquid equilibria (LLE) for dimethylsulfoxide (DMSO)+n-alkanes, cyclohexane, benzene or alkylbenzenes (mono-, dialkyl-and trialkyl-) or tetrachloromethane, trichloromethane, dichloromethane and monochloroalkanes are treated in the framework of DISQUAC, an extended quasi-chemical group contribution theory. The systems are characterized by three types of contact surfaces: sulfoxide (S=O group), aliphatic (CH3, CH2, CH groups), cycloaliphatic (c-CH2 group), aromatic (C6H6, C6H5 groups) and chlorine (C1 group). Using a set of adjusted contact interchange energies parameters, structure dependent, the model provides a fairly consistent description of the thermodynamic properties as a function of concentration. The model may serve to predict missing data.
Abstract
The synthesis and characterization of lanthanide(III) citrates with stoichiometries 1:1 and 2:3; [LnL·xH2O] and [Ln2(LH)3·2H2O], Ln=La, Ce, Pr, Nd, Sm and Eu are reported. L stands for (C6O7H5)3− and LH for (C6O7H6)2−. Infrared absorption spectra of both series evidence coordination of carboxylate groups through symmetric bridges or chelation. X-ray powder patterns show the amorphous character of [LnL·xH2O]. The compounds [Ln2LH3·2H2O] are crystalline and isomorphous. Emission spectra of Eu compounds suggest C 2v symmetry for the coordination polyhedron of [LnL·xH2O] and C 4v for [Ln2(LH)3·2H2O]. Thermal analyses (TG-DTG-DTA) were carried out for both series. The thermal analysis patterns of the two series are quite different and both fit in a 4-step model of thermal decomposition, with lanthanide oxides as final products.
