A novel extractant-impregnated resin containing carminic acid for selective separation and pre-concentration of uranium(VI) and thorium(IV)

The present work proposes the use of a novel extractant-impregnated resin (EIR) as an adsorbent in trace separation and pre-concentration of U(VI) and Th(IV) ions. The new EIR was prepared by impregnating carminic acid onto Amberlite XAD-16 resin beads. The morphology of new EIR was studied by BET surface area measurements and SEM micrographs. A column packed with CA/XAD-16 was used for selective separation and pre-concentration of the metal ions. Maximum adsorption of Th(IV) and U(VI) ions occurred at pHs of 3.50–5.75 and 3.75–6.50, respectively. The adsorbed metals could be eluted sequentially using 0.55?mol?L^?1 HCl for U(VI) and 2.25?mol?L^?1 HCl for Th(IV). The dynamic capacity of EIR was found to be 0.832 and 0.814?mmol?g^?1 for Th(IV) and U(VI), respectively. The tolerance limit of some foreign ions was also studied. The proposed method showed a good performance in analyzing geological reference materials and a synthetic seawater sample. Furthermore, the above procedure was successfully employed for the analysis of natural water samples.     

Coordination and extraction studies of an unexplored bi-functional ligand,carbamoyl methyl pyrazole (CMPz) with uranium(VI), lanthanum(III) and cerium(III) nitrates

The bi-functional carbamoyl methyl pyrazole ligands, C₅H₇N₂CH₂CONBu₂ (L₁), C₅H₇N₂CH₂CONⁱBu₂ (L₂), C₃H₃N₂CH₂CONBu₂ (L₃), C₃H₃N₂CH₂CONⁱBu₂ (L₄) and C₅H₇N₂CH₂CON(C₈H₁₇)₂ (L₅) were synthesized and characterized by spectroscopic and elemental analysis methods. The selected coordination chemistry of L₁ to L₄ with [UO₂(NO₃)₂ · 6H₂O], [La(NO₃)₃ · 6H₂O] and [Ce(NO₃)₃ · 6H₂O] has been evaluated. Structures for the compounds [UO₂(NO₃)₂ C₅H₇N₂CH₂CONBu₂] (6) [UO₂(NO₃)₂ C₅H₇N₂CH₂CONⁱBu₂] (7) and [Ce(NO₃)₃{C₃H₃N₂CH₂CONⁱBu₂}₂] (11) have been determined by single crystal X-ray diffraction methods. Preliminary extraction studies of the ligand L₅ with U(VI) and Pu(IV) in tracer level showed an appreciable extraction for U(VI) and Pu(IV) up to 10 M HNO₃ but not for Am(III). Thermal studies of the compounds 6 and 7 in air revealed that the ligands can be destroyed completely on incineration.     

Spectrophotometric Studies of Cerium(III) and Thorium(IV) Chelates of Diethylenetriaminepentaacetic Acid (DTPA)

The interaction between diethylenetriaminepentaacetic acid (DTPA or H_sZ) and Ce(III) and Th(IV) ions has been investigated spectrophotometrically in aqueous solution at an ionic strength of 0.1 and for various temperatures. It has been found that the Ce(III)-DTPA chelate (1:1) exhibited a characteristic absorption maximum at 297 nm, and the optimum pH range is between 3.4 to 4.4. The absorption of Ce(III)-DTPA chelate is considerably diminished by adding small amounts of Th(IV) ions. This phenomenon was used to evaluate the formation constant of Th(IV)-DTPA chelate (1:1). The formation constants and the thermodynamic properties characterizing the formation of the chelates have been calculated at 25°. The results are as follows:      

Kinetic studies on the reduction of a nickel (III) oxime-imine complex by sulphur(IV) and selenium(IV)

The kinetics of the reduction of [Ni^III(L¹)]²⁺ (where HL¹ = 15-amino-3-methyl-4,7,10,13-tetraazapentadec-3-en-2-one oxime) by sulphur(IV) and selenium (IV) over the regions pH 2.50–8.02 and 2.01–4.00 respectively have been investigated at 30°C. Attempts were made to evaluate the reactivity of all the reacting species, of sulphur(IV) and selenium(IV) by considering suitable pH ranges. The oxidation of SC₂·H₂O and HSO ₃ ⁻ is proposed to proceed through the formation of a hydrogen-bonded adduct. The reaction with SO ₃ ²⁻ seems to follow a direct outer-sphere route which is well supported by Marcus crossrelation calculation. The oxidation of HSeO _l3 ⁻ is ≈ 10³ times slower than that of H₂SeO₃. The kinetic data indicate that the oxidation of sulphur(IV) by [Ni^IIIL¹)]²⁺ is much more favourable as compared to the corresponding oxidation of selenium(IV).     

Preconcentration and determination of ultra-trace amounts of U(VI) and Th(IV) using titan yellow-impregnated Amberlite XAD-7 resin

A simple and sensitive method for the determination of ultra trace amounts of U(VI) and Th(IV) ions by spectrophotometric method after solid-phase extraction on a new extractant-impregnated resin (EIR) has been reported. The new EIR was synthesised by impregnating a weakly polar polymeric adsorbent, Amberlite XAD-7, with titan yellow (TY) as extractant. The analytical method is based on the simultaneous adsorption of analyte ions in a mini-column packed with TY/XAD-7 and performing sequential elution with 0.5% (w/v) Na₂CO₃ for uranium and 2.0 M HCl for thorium. The influences of the analytical parameters including pH, salting out agent and sample volume were investigated. The interference effects of foreign ions on the retention of the analyte ions were also explored. The limits of detection for U(VI) and Th(IV) were as low as 50 and 25 ng L^?1, respectively. Relative standard deviations (n = 7) for U(VI) and Th(IV) were 3.1% and 2.9%, respectively. The method was successfully applied to the determination of ultra trace amounts of U(VI) and Th(IV) in different real matrices including industrial wastewater samples and environmental waters. The proposed method was validated using three certified reference materials and the results were in good agreement with the certified values.     

Thermogravimetric and spectroscopic studies on La(III) and Ce(III) complexes with some thio-schiff bases

Solid complexes of five derivatives of thio-Schiff bases with La(III) and Ce(III) ions were prepared and characterized by elemental and thermogravimetric analyses. The suggested general formula of the solid complexes is [ML₂(H₂O)X]·2H₂O, whereM=trivalent lanthanide ion,L=Schiff base andX=Cl^? or ClO ₄ ^? . Information about the water of hydration, the coordinated water molecules, the coordination chemistry and the thermal stability of these complexes was obtained and is discussed. Additionally, a general scheme of thermal decomposition of the lanthanide-Schiff base complexes is proposed.     

Complexation studies of Cm(III), Am(III), and Eu(III) with linear and cyclic carboxylates and polyaminocarboxylates

Solvent extraction and potentiometric titration methods have been used to measure the stability constants of Cm(III), Am(III), and Eu(III) with both linear and cyclic carboxylates and polyaminocarboxylates in an ionic strength of 0.1?mol?L^?1 (NaClO₄). Luminescence lifetime measurements of Cm(III) and Eu(III) were used to study the change in hydration upon complexation over a range of concentrations and pH values. Aromatic carboxylates, phthalate (1,2 benzene dicarboxylates, PHA), trimesate (1,3,5 benzene tricarboxylates, TSA), pyromellitate (1,2,4,5 tetracarboxylates, PMA), hemimellitate (1,2,3 benzene tricarboxylates, HMA), and trimellitate (1,2,4 benzene tricarboxylates, TMA) form only 1?:?1 complexes, while both 1?:?1 and 1?:?2 complexes were observed with PHA. Their complexation strength follows the order: PHA～TSA>TMA>PMA>HMA. Carboxylate ligands with adjacent carboxylate groups are bidentate and replace two water molecules upon complexation, while TSA displaces 1.5 water molecules of hydration upon complexation. Only 1?:?1 complexes were observed with the macrocyclic dicarboxylates 1,7-diaza-4,10,13-trioxacyclopentadecane-N,N′-diacetate (K21DA) and 1,10-diaza-4,7,13,16-tetraoxacyclooctadecane-N,N′-diacetate (K22DA); both 1?:?1 and 1?:?2 complexes were observed with methyleneiminodiacetate (MIDA), hydroxyethyleneiminodiacetate (HIDA), benzene-1,2-bis oxyacetate (BDODA), and ethylenediaminediacetate (EDDA), while three complexes (1?:?1, 1?:?2, and 1?:?3) were observed with pyridine 2,6 dicarboxylates (DPA) and chelidamate (CA). The complexes of M-MIDA are tridentate, while that of M-HIDA is tetradentate in both 1?:?1 and 1?:?2 complexes. The M-BDODA and M-EDDA complexes are tetradentate in the 1?:?1 and bidentate in the 1?:?2 complexes. The complexes of M-K22DA are octadentate with one water molecule of hydration, while that of K21DA is heptadentate with two water molecules of hydration. Simple polyaminocarboxylate 1,2 diaminopropanetetraacetate (PDTA) and ethylenediamine N,N′-diacetic-N,N′-dipropionate (ENDADP) like ethylenediaminetetraacetate (EDTA) form only 1?:?1 complexes and their complexes are hexadentate. Polyaminocarboxylates with additional functional groups in the ligand backbone, e.g., ethylenebis(oxyethylenenitrilo) tetraacetate (EGTA), and 1,6 diaminohexanetetraacetate (HDTA) or with additional number of groups in the carboxylate arms diethylenetriamine pentaacetato-monoamide (DTPA-MA), diethylenetriamine pentaacetato-bis-methoxyethylamide (DTPA-BMEA), and diethylenetriamine pentaacetato-bis glucosaamide (DTPA-BGAM) are octadentate with one water molecule of hydration, except N-methyl MS-325 which is heptadentate with two water molecules of hydration and HDTA which is probably dimeric with three water molecules of hydration. Macrocyclic tetraaminocarboxylate, 1,4,7,10-tetraazacyclododecanetetraacetate (DOTA) forms only 1?:?1 complex which is octadentate with one water molecule of hydration. The functionalization of these carboxylates and polycarboxylates affect the complexation ability toward metal cations. The results, in conjunction with previous results on the Eu(III) complexes, provide insight into the relation between ligand steric requirement and the hydration state of the Cm(III) and Eu(III) complexes in solution. The data are discussed in terms of ionic radii of the metal cations, cavity size, basicity, and ligand steric effects upon complexation.     

Solvent extraction behaviour of lanthanum(III), cerium(III), europium(III), thorium(IV) and uranium(VI) with 3-phenyl-4-benzoyl-5-isoxazolone

The extraction behaviour of La(III), Ce(III), Eu(III), Th(IV) and U(VI) with 3-phenyl-4- benzoyl-5-isoxazolone (HPBI) in chloroform has been studied. The mechanism of extraction and the species extracted have been identified. Extraction constants for each system have been calculated. The system has been used to separate Th(IV) from U(VI) and from La(III), Ce(III) and Eu(III). A comparison of the extraction constants with those for the 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (HPMBP) and thenoyltrifluoroacetone (HTTA) systems indicates that HPBI extracts these metal species better than HPMBP and HTTA do.     

Solid phase extraction and preconcentration of uranium(VI) and thorium(IV) on Duolite XAD761 prior to their inductively coupled plasma mass spectrometric determination

A simple and effective method is presented for the separation and preconcentration of thorium(IV) and uranium(VI) by solid phase extraction on Duolite XAD761 adsorption resin. Thorium(IV) and uranium(VI) 9-phenyl-3-fluorone chelates are formed and adsorbed onto the Duolite XAD761. Thorium(IV) and uranium(VI) are quantitatively eluted with 2 mol L⁻¹ HCl and determined by inductively coupled plasma-mass spectrometry (ICP-MS). The influences of analytical parameters including pH, amount of reagents, amount of Duolite XAD761 and sample volume, etc. were investigated on the recovery of analyte ions. The interference of a large number of anions and cations has been studied and the optimized conditions developed have been utilized for the trace determination of uranium and thorium. A preconcentration factor of 30 for uranium and thorium was achieved. The relative standard deviation (N = 10) was 2.3% for uranium and 4.5% for thorium ions for 10 replicate determinations in the solution containing 0.5 μg of uranium and thorium. The three sigma detection limits (N = 15) for thorium(IV) and uranium(VI) ions were found to be 4.5 and 6.3 ng L⁻¹, respectively. The developed solid phase extraction method was successively utilized for the determination of traces thorium(IV) and uranium(VI) in environmental samples by ICP-MS.     

Mononuclear and homobinuclear vanadium(IV), chromium(III), molybdenum(III), and uranium(VI) chelates with ortho-cresolphthalein complexone

Mononuclear and homobinuclear o-cresolphthalein complexone complexes with VO²⁺, Cr³⁺, MoO⁺, and UO₂ ²⁺ have been prepared and their structures investigated. The empirical formulas, the mode of bonding, and the geometry of the complexes were obtained from elemental and thermal analyses, IR, electronic and ESR spectra, magnetic moment determinations, DC and CV polarographic studies.     

Solid-state compounds of 4-methoxybenzylidenepyruvate and cinnamylidenepyruvates with thorium (IV)

By close control of experimental variables affecting precipitation, solid-state compounds of the type Th(OH)_mL_4-m·nH₂O, where L stands for 4-methoxy-benzylidenepyruvate, cinnamylidenepyruvate or 4-dimethylaminocinnamylidene-pyruvate; m=0 to 3 andn=0.5-3 were isolated. Chemical analysis, TG, DTG, DSC and X-ray powder diffractometry have been employed to characterize and to study the thermal behavior of these compounds in dynamic air atmosphere. In all cases, hydration water is slowly lost between 30 and 160°C; a continuous, slow rate, mass loss is observed thereafter and beyond 280-400°C the rate of decomposition/oxidation increased rapidly, to give ThO₂as the final product, beginning at 412-510°C. The results associated with the hydroxo-compounds indicate that the loss of constitution water (OH ions) and the decomposition / oxidation of the organic moieties occur as simultaneous process. This revised version was published online in August 2006 with corrections to the Cover Date.     

X-ray structurally characterized Mo (VI), Fe (III) and Cu (II) complexes of amide-imine conjugate: (bio)catalytic and histidine recognition studies

An amide-imine conjugate, (E)-N′-((2-hydroxybenzen-1-yl) methylene)-4-methylbenzohydrazide (H₂L^PTASAL), derived from 4-methyl-benzoic acid hydrazide (PTA) and 2-hydroxybenzaldehyde is used to prepare Mo (VI), Cu (II) and Fe (III) complexes. The X-ray structurally characterized complexes have been explored as catalyst for amine assisted asymmetric ring opening (ARO) of epoxide, carbon-heteroatom cross-coupling and ethyl benzene oxidation. In addition, their catecholase like activities have thoroughly been investigated. Moreover, the Cu (II) complex selectively recognizes histidine by fluorescence spectroscopy.     

Complex formation studies on Ho(III) and Lu(III) with 1-(2-pyridylazo)-2-naphthol (PAN) in alcohol-water solutions

The formation ofPAN complexes in the systemsLn(III)—PAN—alcohol-water (where:Ln(III)=Ho, Lu and alcohol=ethanol,n-propanol,iso-propanol) was investigated by a spectrophotometric method. Equilibrium constants for the reactionLn ³⁺ + HLLnL ²⁺ + H⁺ (HL=PAN) and stability constants of complexesLnL ²⁺ were calculated.

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Untersuchungen zur Komplexbildung von Ho(III) und Lu(III) mit 1-(2-Pyridylazo)-2-naphthol (PAN) in alkoholisch-;wä\rigen Lösungen

Zusammenfassung Die Bildung der Komplexe vonPAN in den SystemenLn(III)—PAN—Alkohol-Wasser (Ln(III)=Ho, Lu; Alkohol=Ethanol,n-Propanol,iso-Propanol) wurde mit einer spektrophotometrischen Methode untersucht. Die Gleichgewichtskonstanten der ReaktionenLn ³⁺ + HLLnL ²⁺ + H⁺ (HL==PAN) und die Stabilitätskonstanten der KomplexeLnL ²⁺ wurden berechnet.

     

Effect of acrylamide concentration on the kinetics of oxidation of tartaric acid by cerium(IV) in sulfuric-perchloric acid media

The kinetics of oxidation of tartaric acid by Ce(IV) in the absence and presence of acrylamide has been investigated spectrophotometrically in aqueous H₂SO₄–HClO₄ media at a constant ionic strength 2.0M and 25°C. Oxidation of tartaric acid in both cases was first order with respect to Ce(IV). Kinetic data showed that the reaction involves the formation of an unstable complex and an intermediate free radical. The activation parameters were calculated to be E _a =91.3±0.4 kJ-mol^–1, S=20.2±1.0 J-mol^–1-K^–1, H=88.8±0.4 kJ-mol^–1. A polymerization mechanism is discussed.     

Nucleophilic attack by bromide ions as a first step of conversion of Se(VI) to Se(IV)

Numerous commonly used analytical methods allow only determination of a total amount of selenium in a given sample. Electroanalytical methods as well as those based on hydride generation or on formation of piazselenol allow only determination of Se(IV). To determine Se(VI) by these procedures, present alone or in mixtures with Se(IV), it is first necessary to convert Se(VI) to Se(IV). Such conversion is effective in the presence of excess of halides in acidic media or by photoreduction. In the often used conversion of Se(VI) in the presence of chlorides or less frequently of that of bromides, it has been assumed that the halide ion acts as a reducing agent. Kinetic studies of conversion of Se(VI) in acidic solutions containing an excess of bromide ions indicated that the rate determining first step of the reaction with Se(VI) is a nucleophilic substitution of the OH₂⁺ group in the protonated form of H₂SeO₄ by bromide ions. For the overall reaction with rate −d[Se(VI)]/dt = k₁[H⁺][Br⁻]^1.15[Se(IV)] the rate constant 1 × 10⁻³ L² mol⁻² s⁻¹ was found. The following formation of Se(IV) from the bromo derivative is a fast reaction probably resulting in elimination of HBrO.     

Pectin based cerium (IV) and thorium (IV) phosphates as novel hybrid fibrous ion exchangers synthesis,characterization and thermal behaviour

Summary Pectin based cerium (IV) and thorium (IV) phosphates have been synthesized as new phases of hybrid fibrous ion exchangers. Both materials were characterized using X-ray diffraction, infrared (IR) spectra, thermogravimetric analysis (TG), differntial thermogravimetry (DTG), differntial thermal analysis (DTA) and scanning electron microscopy (SEM), as well as the determination of their ion exchange capacity, elution and pH titration. The X-ray study reveals the amorphous nature of the materials, while SEM studies confirm the fibrous nature of the materials. The thermal studies of these materials indicate that both of them are highly stable on heating as they retain about 97% of their ion-exchange capacity (i.e.c.) on heating up to 100°C and about 81% on heating up to 200°C.     

Column chromatographic speciation of chromium for Cr(VI) and several species of Cr(III)

Summary Chromium can be present in aqueous solution as Cr(VI) or in monomeric, dimeric, trimeric and higher polymeric forms of Cr(III). Many monomeric forms of Cr(III) are possible, with the water molecules of Cr(H₂O) ₆ ³⁺ substituted by anionic or neutral species. This proliferation of Cr(III) species makes the complete speciation of chromium a continuing challenge to the analyst. A simple and effective cation exchange procedure for the separation of various of these species uses a small glass column containing 1 mL of pre-treated cation exchange resin (Na⁺ form). Stepwise elution with solutions of perchloric acid, Ca²⁺ (pH=2) and La³⁺ (pH=2) separates Cr(VI) and seven Cr(III) species from CrX₃ to tetramer. Radiometric (Cr-51), spectrophotometric and other detection methods can be employed; the use of radiochromium gives the lowest detection limit.