Electrospray Ionization Mass Spectrometry Investigation of BTBP – Lanthanide(III) and Actinide(III) Complexes

In the framework of nuclear waste reprocessing, the separation processes of minor actinides from fission products are developed using liquid‐liquid extraction. To gain an understanding of the mechanism involved in the extraction process, a complex formation of actinides and lanthanides with BTBPs (6,6′‐bis(5,6‐dialkyl‐1,2,4‐triazin‐3‐yl)‐2,2′‐bipyridines) was characterized using the Electrospray Ionization Mass Spectrometry (ESI‐MS) technique. This study was carried out to compare the influence of diluents and side groups of the extractants on complex formation. Three different diluents, nitrobenzene, octanol and cyclohexanone, and two extractants, C5‐BTBP and CyMe₄‐BTBP, were selected for this experiment. It was found that the change of the diluent and of the substituent on the BTBP moiety does not modify the stoichiometry of the complexes which is L₂M(NO₃)₃. It is proposed that one nitrate is directly coordinated to the metal ion, the two other anions probably remaining in the outer coordination sphere. The difference observed in extracting properties is probably due to the solvation of the complexes by the diluent. The noncovalent force that holds complexes together are likely to be largely governed by electrostatic interactions even if the hydrophobic exterior of the complexes plays an important role in the complexation/extraction mechanism. The study of the stability of the ions in the gas phase shows that the C5‐BTBP ligand has a labile hydrogen atom, which is a fragility point of C5‐BTBP.     

Selective Eu(III) Electro‐Reduction and Subsequent Separation of Eu(II) from Rare Earths(III) via HDEHP Impregnated Resin

Abstract

Eu(III) was selectively reduced to Eu(II) at three‐dimensional glassy carbon cathode in 0.01 mol · dm^?3 hydrochloric acid medium. Eu(III) reduction took place after all the dissolved oxygen was reduced and then proceeded steadily. Separation of Eu(II) from trivalent rare earths (La, Ce, Sm, Gd, Er, Yb) was carried out using a novel impregnated resin based on bis(2‐ethylhexy1)phosphoric acid. Eu(II) showed much lower affinity towards the resin than the trivalent rare earths and broke through the column readily. Eu of purity higher than 99.8% was yielded. The back‐oxidation of Eu(II) was observed during the sorption and Eu(III) was absorbed onto the resin. Adsorbed light and middle rare earths could be stripped from the loaded resin by 3M hydrochloric acid. Stripping of heavy rare earths (Er, Yb) was problematic.     

Solid‐Liquid Extraction of Lanthanum(III), Europium(III), and Lutetium(III) by Acyl‐Hydroxypyrazoles Entrapped in Mesostructured Silica

Abstract

The solid‐liquid extraction of lanthanum(III), europium(III), and lutetium(III) by mesostructured silicas doped with 1‐phenyl‐3‐methyl‐4‐stearoyl‐5‐pyrazolone (HPMSP, bearing one chelating site) or with 1,12‐bis(1′‐phenyl‐3′‐methyl‐5′‐hydroxy‐4′‐pyrazolyl)‐dodecane‐1,12‐dione (HL‐10‐LH, bearing two chelating sites) has been studied and compared to the analogous solvent and micellar extractions in terms of the stoichiometry of the extracted complex and of the extraction efficiency. The solid‐liquid extraction order in the lanthanoid series is La<Eu<Lu; it is the usual liquid‐liquid extraction order obtained with acidic extractants. A theoretical model is used to determine the stoichiometries of the extracted complexes and the extraction yield is measured as a function of the pH, of the extractant/metal ratio (S/M) and of the volume ratio of the two phases (φ). For HPMSP, the extracted complexes involve three ligand molecules for one metal. For HL‐10‐LH, the complex stoichiometries are found to be either Ln(L‐10‐L)(L‐10‐LH) (Ln=La, Eu) or Lu₂(L‐10‐L)₃ for S/M=25, or Eu₂(L‐10‐L)₃ for S/M=5. For the first time, the synergistic solid‐liquid extraction is studied after a successful attempt at simultaneously immobilizing both extractants HL‐10‐LH and 2,4,6‐tri(2‐pyridyl)‐1,3,5‐triazine, “TPTZ”, into silica; the complex extracted in this case differs from the one obtained in solvent extraction.     

Synergistic Extraction of Am(III) and Eu(III) by Tris(2‐pyridylmethyl)Amine with Various Anions in 1,2‐Dichloroethane

The extraction equilibria of Am(III) and Eu(III) by using a tripodal ligand, tris(2‐pyridylmethyl)amine (tpa), with various lipophilic anions have been investigated. The extractability of both Am(III) and Eu(III) was increased by the combination of tpa and counteranions due to a synergistic effect. The separation factors between Am(III) and Eu(III) were also increased from 7.6 to 49 by the combination of counteranions and organic solvents. The extraction equilibria of Am(III) and Eu(III) with tpa in 1,2‐dichloroethane were determined by slope analysis. It was found that three anions and one molecule of the ligand coordinated to Am(III) and Eu(III) was extracted regardless of the anions.     

Lanthanide(III) complexes of a highly efficient actinide(III) extracting agent – 2,6-bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine

The addition of lanthanide(III) nitrates (Sm–Lu) to the actinide(III) extracting agent – 2,6-bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine (L¹) in a 1:1 ratio results in the crystallisation of complexes containing [Ln(L¹)₃]³⁺ moieties and a variety of anions.     

Electrodeposition of Au–Sn alloys from acid Au(III) baths

A bath for the electrodeposition of white gold alloys of interest for the electroforming of hollow jewellery is proposed and investigated. The system was an acidic Au(III)–Sn(IV) bath for the electrodeposition of Au–Sn alloys. The electrochemical investigations were based on cyclic voltammetry, linear-sweep voltammetry, galvanostatic electrodeposition experiments and in situ Raman spectroscopy. The electrode kinetics of alloy formation were elucidated by stripping voltammetry. The effects of cathodically adsorbed CN^– were studied by in situ Raman spectroscopy. Electrodeposited foils were studied from the crystallographic, compositional and morphological points of view. Codeposition of Au and Sn gives rise to a single phase of approximately equiatomic composition over a current density interval of 10 to 40 mA cm^–2. This orthorhombic phase is structurally the same as the phase of the equilibrium Au–Sn system, but its stoichiometry and lattice parameters are different. The equilibrium two-phase , structure can be obtained by heat-treatment.     

Synthesis,characterization, thermal constant and relaxation of gadolinium(III), iron(III) and manganese(II) chelates of diethylenetriamine-bis-inositol-N,N′,N″-triacetic acid

The reaction of the bicyclic anhydride of diethylenetraiamine-pentaacetic acid (DTPAA) with inositol gave diethylenetriamine-inositol-biester-N,N^′,N″-triacetic acid (DTPA-BI) (1). (1) was characterized by FAB-MS, ¹HNMR, IR and elemental analysis. Its chelates of Gd(III), Fe(III) and Mn(II) holding promise of magnetic resonance imaging (MRI) were synthesized. Gd(III) complex was obtained from Gd₂O₃ and the acid form of (1). Thermodynamic stability constant and relaxation of Gd(III) complex with DTPA-BI were determined. The spin–lattice relaxivity (R₁=5.6 l mmol⁻¹ s⁻¹) of chelate was slightly larger than that of [GdDTPA]²⁻. The results showed that the complex is a prospective MRI agent, although thermodynamic stability constant of DTPA-BI K_[GdDTPA-BI]⁻=10^18.2 was a little less than that of [GdDTPA]²⁻ (K_[GdDTPA]²⁻=10^20.73).     

Binuclear rhodium(III) and iridium(III) monoselenocarboxylates: Synthesis,spectroscopy and structure of an ortho-metallated iridium complex featuring an IrCCC(μ-Se) chelate ring

Monoselenocarboxylate–bridged binuclear complexes of Rh^III and Ir^III, [(Cp1MCl)₂(μ-SeCOAr)₂] (1) (M = Rh or Ir; Cp1 = pentamethylcyclopentadienyl; Ar = Ph, C₆H₄Me–4), have been isolated either by the reaction between [Cp1₂M₂(μ-Cl)₂Cl₂] with KSeCOAr in acetonitrile or by treatment of [Cp1MCl(solvent)₂][PF₆] with KSeCOAr in acetone. The novel binuclear complexes, [Cp1IrCl(μ-SeCOAr)(κ²-SeCOC₆H₃R–)IrCp1] (2) (R = H or Me-4) with ortho-metallation at one of the iridium centres have been isolated following the use of excess AgPF₆. The single crystal structure of [Cp1IrCl(μ-SeCOC₆H₅)(κ²-SeCOC₆H₄–)IrCp1] (2a) exhibits two phenylcarboselenolate moieties situated in syn fashion with respect to the “Ir₂Se₂” plane, one of which leans towards the metal centre in order to undergo ortho-metallation after iridium–chlorine bond dissociation.     

Synthesis and Characterization of Tripodal Oxy-Schiff base (2,4,6-Tris(4-Carboxymethylenephenylimino-4′-formylphenoxy)-1,3,5-triazine) and the Thermal and Magnetic Properties of its Fe(III)/Cr(III) Complexes

Eight new trinuclear Fe(III)/Cr(III) complexes involving tetradentate (N₂O₂) and pentadentate (N₃O₂) Schiff bases of (salenH₂), (salophenH₂), (saldetaH₂) and (salpyrH₂) with 2,4,6-tris(4-carboxymethylenephenylimino-4′-formylphenoxy)-1,3,5-triazine were synthesized. The structure of ligand and complexes were identified using elemental and thermal analysis, magnetic susceptibility, and LC–MS, ICP-AES, ¹H NMR and FT-IR spectral data. All complexes are tripodal–trinuclear. The complexes are low-spin (S = 1/2) distorted octahedral salen- or salophen-capped Fe(III), high-spin (S = 5/2) distorted octahedral saldeta- or salpyr-capped Fe(III) and distorted octahedral (S = 3/2) salen-, salophen-, saldeta- or salpyr-capped Cr(III).     

Modifying polysulfone into a bidentate Schiff base type macromolecular ligand and study on photoluminescence property of polymer–rare earth complexes of Eu(III) and Tb(III)

Chloromethylated polysulfone (CMPSF) was directly transformed into aldehyde (AL) group-functionalized polymer via Kornblum reaction, and then polysulfone was modified to a bidentate Schiff base (BS) type macromolecular ligand, PSF-ASB, via Schiff base reaction with 3-aminopyridine as reagent. Afterward, luminescent binary and ternary polymer-rare earth complexes, PSF-(ASB)₃-Eu (III) and PSF-(ASB)₃-Eu(III)-(Phen)₁ (o-phenanthroline, Phen), were prepared. The macromolecular ligand PSF-ASB and the complexes were fully characterized by FTIR, ¹H-NMR, UV spectroscopy and TGA. The photoluminescence properties and mechanisms of the complexes were investigated in depth. The experimental results show that the macromolecular ligand PSF-ASB itself emits strong fluorescence. However, after coordinating to Eu(III) ion, its fluorescence intensity weakens remarkably, implying that there occurs an intramolecular energy transfer. The complexes of Eu(III) ion exhibit stronger characteristic fluorescence emission of Eu(III) ion, whereas the complex of Tb(III) ion has no photoluminescence property, indicating that the bonded ligand ASB can effectively sensitize the fluorescence emission of Eu(III) ion and suggesting that the triplet state energy of the bonded ligand ASB is well matched with the resonant state level of Eu(III) ion. More importantly, relative to general polymer-rare earth complexes, for these luminescent polymer-rare earth complexes prepared in this study, the backbone of the macromolecular ligand PSF-ASB also takes part in the sensitization towards Eu(III) ion because of that half of aryl rings of a greater π bond conjugate system of ASB comes from PSF skeleton, displaying a great difference with other luminescent polymer-rare earth complexes.     

Study of the Sorption and Separation Abilities of Commercial Solid‐Phase Extraction (SPE) Cartridge Oasis MAX Towards Au(III), Pd(II), Pt(IV), and Rh(III)

Abstract

This paper presents a new, simple, and rapid procedure for the separation and preconcentration of Au, Pt, Pd, and Rh based on the adsorption of the metals on a commercial solid‐phase extraction (SPE) cartridge, Oasis MAX, which contains a polymeric resin with quaternary ammonium substituents. Adsorption studies revealed that the metal affinity towards the adsorbent ranked according to Au?Pd>Pt whereas Rh was not retained. The elution of the metals was accomplished by using 0.5 M thiourea in 1 M HCl solution. This sorbent effectively recovered Pd and Pt from a spent car catalyst sample containing large amounts of metals such as Al, Fe, and Ce.     

Is the Coagulation-Filtration Process with Fe(III) Efficient for As(III) Removal from Groundwaters?

The coagulation–filtration process using Fe(III) salts is the most frequently practiced technology for As(V) removal in full scale water treatment plants. The co-existing As(III) is usually oxidized to As(V) prior to removal. Nonetheless, research studies applying high As(III) initial concentrations showed significant As(III) removal capacities, however, the efficiency of the process for initial As(III) concentrations commonly encountered in drinking water, i.e., 10-100 μg/L is not sufficiently investigated. The experimental results of this study indicated that the coagulation–filtration process using Fe(III) can safely meet the drinking water regulation limit of 10 μg/L, only when the initial As(III) concentration is < 25 μg/L and the Fe(III) dose ≥ 5 mg/L, for experiments performed with NSF challenge water. The limitations for efficient As(III) removal are attributed to the fact that As(III), under circumneutral pH values is mostly present with the uncharged H₃AsO₃ form, which is not efficiently adsorbed onto iron oxy hydroxides (FeOOH), the product of Fe(III) hydrolysis. Adsorption isotherms data were best fitted to BET model, indicating multi-layer adsorption and low affinity of As(III) for Fe(III) hydroxides.     

Controlled radical polymerization of n-hexadecyl methacrylate mediated by tris(2,2′-bipyridine)iron(III) complexes

Poly(n-hexadecyl methacrylate) (PHMA) with narrow molecular weight distribution has been synthesized by atom transfer radical polymerization (ATRP) and reverse ATRP of n-hexadecyl methacrylate (HMA) at 80 °C in N, N-dimethylformamide (DMF) using the CBr₄/tris(2,2′-bipyridine)iron(III) complex initiation system in the presence of 2,2′-azobisisobutyronitrile (AIBN). From the kinetic studies and molecular weight data, it reveals the controlled nature of polymerization. The effect of various reaction parameters on number-average molecular weight (M _n ) and molecular weight distribution (M _w /M _n ) have been investigated. For the reverse ATRP, the catalyst tris(2,2′-bipyridine)iron(III)complex, [Fe(bpy)₃]³⁺, played an important role in polymerization rate and M _w /M _n . The resulting PHMA that obtained by reverse ATRP shows the best control of molecular weights and its distribution as compared to normal ATRP system. PHMA has been characterized by different techniques such as GPC, XRD and NMR spectroscopy.     

Thermal decomposition of cerium(III) acetate studied with sample-controlled thermogravimetric–mass spectrometry (SCTG—MS)

Thermal decomposition of cerium(III) acetate hydrate, Ce(CH₃CO₂)₃·1.5H₂O, to cerium(IV) oxide, CeO₂, in helium has been successfully investigated by sample-controlled thermogravimetry combined with evolved gas analysis by mass-spectrometry (SCTG–MS). Cerium(III) anhydrous acetate decomposed to cerium (IV) oxide through four decomposition steps in the temperature range of 250–800 °C. SCTG–MS was very useful to distinguish the successive decomposition accompanying the formation of the intermediate products to identify simultaneous gas evolution during the mass losses. The decomposition intermediates quenched from SCTG were characterized by X-ray diffraction (XRD) and X-ray absorption near-edge structure (XANES). The XANES revealed clearly the coexistence of Ce(III) and Ce(IV) and the valence change from cerium(III) to cerium(IV). The three decomposition intermediate products were presumed to be Ce₂O(CH₃CO₂)₄, Ce₂O₂(CH₃CO₂)₂ and Ce₂O₂CO₃. A detailed thermal decomposition mechanism of Ce(CH₃CO₂)₃·1.5H₂O is discussed.     

Hydration of a low-alkali CEM III/B–SiO2 cement (LAC)

The hydration of a low-alkali cement based on CEM III/B blended with 10 wt.% of nanosilica has been studied. The nanosilica reacted within the first days and 90% of the slag reacted within 3.5 years. C-S-H (Ca/Si ~ 1.2, Al/Si ~ 0.12), calcite, hydrotalcite, ettringite and possibly strätlingite were the main hydrates. The pore water composition revealed ten times lower alkali concentrations than in Portland cements. Reducing conditions (HS^?) and a pH value of 12.2 were observed. Between 1 month and 3.5 years of hydration more hydrates were formed due to the ongoing slag reaction but no significant differences in the composition of the pore solution or solid phase assemblage were observed.On the basis of thermodynamic calculations it is predicted that siliceous hydrogarnet could form in the long-term and, in the presence of siliceous hydrogarnet, also thaumasite. Nevertheless, even after 3.5 year hydration, neither siliceous hydrogarnet nor thaumasite have been observed.     

Di-μ-hydroxy macrocyclic ytterbium(III) complex

The mononuclear [YbracL]Cl₃·2H₂O and dinuclear [Yb₂(OH)₂Cl₂(racL)₂]Cl₂·4CH₃OH·2H₂O complexes of the macrocyclic ligand L derived from trans-1,2-diaminocyclohexane and 2,6-diformylpyridine have been obtained. The formation of the dinuclear species upon addition of hydroxide to the [YbracL]Cl₃·2H₂O or the enantiopure [YbrrrrL(NO₃)₂](NO₃) has been followed using ¹H NMR spectroscopy. The X-ray crystal structure of [Yb₂(OH)₂Cl₂(racL)₂]Cl₂·4CH₃OH·2H₂O complex has been determined. The complex is a dimer consisting of two macrocyclic units. The Yb(III) ion is coordinated by six nitrogen atoms of the macrocyclic ligand, two bridging OH groups and chloride anions. The chiral macrocycle L in this complex exhibits twist-bent conformation of approximate C₂ symmetry.     

Preparation of polyacrylamide–montmorillonite nanocomposite and its application in Cr(III) adsorption

The polyacrylamide–montmorillonite “water in water” (PAM-MMT W/W) emulsion was prepared by dispersion polymerization method in the presence of organo-montmorillonite (OMMT). Based on the analysis of the polymerization process, the structure of material was investigated using thermogravimetry, Fourier transform infrared spectroscopy, X-ray diffractometry, scanning electron microscopy, and transmission electron microscopy experiments. Here, the dispersion was determined to be a blend of PAM W/W emulsion and PAM network interspersed by MMT particles, this unique structure of the material was considered to provide better adsorption ability compared to PAM without MMT. Therefore, a PAM-MMT adsorbent was made from the PAM-MMT W/W emulsion, and its adsorption capacity toward Cr(III), one of the heavy metal pollutants from the tannery waste was investigated. The PAM-MMT nanocomposite was demonstrated to have good Cr(III) removal performance, the maximum adsorption capacity of the nanocomposite was found to be 59.74 mg/g at a pH of 5.5 and temperature of 70°C. Results show that pseudo-second-order kinetic model and Langmuir isotherm were applicable for Cr(III) adsorption.     

Kinetics and Mechanism of Yb(III) Extraction and Separation from Y(III) with Mixtures of bis(2,4,4‐trimethylpentyl)phosphinic acid and2‐ethylhexyl phosphonic acid mono‐2‐ethylhexyl ester

Abstract

The ytterbium(III) extraction kinetics and mechanism with mixtures of bis(2,4,4‐trimethylpentyl)phosphinic acid (Cyanex272) and 2‐ethylhexyl phosphonic acid mono‐2‐ethylhexyl ester (P507) dissolved in heptane have been investigated by constant interfacial cell with laminar flow. The effects of the stirring rate, temperature, extractant concentration, and pH on the extraction with mixtures of Cyanex272 and P507 have been studied. The results are compared with those of the system with Cyanex272 or P507 alone. It is concluded that the Yb(III) extraction rate is enhanced with mixtures extractant of Cyanex272 and P507 according to their values of the extraction rate constant, which is due to decreasing the activation energy of the mixtures. Atthe same time, the mixtures exhibits no synergistic effects for Y(III), which provides better possibilities for Yb(III) and Y(III) separations at a proper conditions than anyone alone. Moreover, thermodynamic extraction separation Yb(III) and Y(III) by the mixtures has been discussed, which agrees with kinetics results. Extraction rate equations have also been obtained, and through the approximate solutions of the flux equation, diffusion parameters and thickness of the diffusion film have been calculated.     

Self-healing and anticorrosive properties of Ce(III)/Ce(IV) in nanoclay–epoxy coatings

The self-healing and anticorrosion effects of cerium nitrate in epoxy–clay nanocomposite coatings systems were studied. Different amounts of cerium (III) were added to epoxy–montmorillonite clay composites and the nanocomposite coatings were prepared and applied on cold rolled steel panels. Ultrasonication was applied to disperse the nanoclay into the epoxy cerium nitrate composition. Electrochemical impedance spectroscopy (EIS) was used to study the self-healing and anticorrosion behaviors of the coatings. The structure of the dry coating and the protective mechanism of the pigments in the coating were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) analysis and field emission electron microscopy (FESEM). Transmission electron microscopy (TEM) illustrated the separation of clay layers which interacted with the epoxy resin. Electrochemical impedance data indicated that the epoxy cerium (III)–montmorillonite nanocomposite coatings were superior to the epoxy coatings in corrosion protection properties. The self-healing behavior of such coatings was due to the presence of cerium nitrate that could be released at the defects within the coating and hindered the corrosion reactions at the defective sites. It was shown that the best corrosion protection was achieved with nanocomposite coatings containing 4 wt% clay and 2 wt% cerium nitrate.