The gamma-radiolysis of HEDTA in a simulated, mixed waste

The -radiolysis of the parent compound N-(2-hydroxyethyl)ethylenediaminetriaceticacid (HEDTA) in a simulant of a Hanford mixed waste, at a -dose of7.5 . 10₆±10% R, yielded 94.4% degradation. HEDTA radiolysisyielded four degradation products: glyoxylic acid, N-( nitroso)iminodiaceticacid (NIDA) and 2 dicarboxylic acids, ethandioic (oxalic) and propandioic(malonic) acids. Glyoxylic acid had been identified in previous studies byour laboratory as N-hydroxymethyl-N-methyliminoacetic acid (HMMIA). Promptedby studies from another laboratory, the chelator fragment previously reportedby our laboratory as N-(methylamine)iminodiacetic acid (MAIDA) is re-identifiedas NIDA. A methylamine moiety previously believed to be present in MAIDA,and several other chelator fragments, as well, has been re-identified as anitroso group.     

Gamma radiolysis of EDTA in a simulated, mixed nuclear waste

The effects of γ-irradiation on EDTA degradation have been studied. A simulant of Hanford's complex concentrate was prepared by adding EDTA to an inorganic matrix which was formulated based on past analyses of the actual Hanford complex concentrate waste. For, the radiolysis study, aliquots of the simulated waste were then γ-irradiated. Each waste sample was analyzed to monitor the appearance of degradation products. Based on the results of this study, an assessment of the impact of EDTA degradation on the management of mixed wastes is offered.     

Determination of synthetic chelating agents in surface and waste water by ion chromatography-mass spectrometry

Coupling of ion chromatography with electrospray mass spectrometry (IC-MS) is a simple, sensitive and quick method for the determination of polar organic traces in water samples without derivatization. Analysis of the chelating agents ethylenediamino tetraacetate (EDTA) and diethylenetriamino pentaacetate (DTPA) in aqueous samples was done by IC-MS on an anion exchange column after simple sample preparation steps. Quantification down to a concentration level of 1 microg L(-1) even in wastewater influents and effluents was achieved utilizing 13C marked internal standards and measuring the individual [M - H+]- and stable [M - 4H+ + Fe3+]- cluster ions. The method was validated against certified, but more time consuming routine methods. Applying this method a series of several European water samples were analyzed for EDTA and DTPA indicating their nature as polar persistent pollutants.     

Determination of chelating agents in Hanford tank waste simulant by capillary zone electrophoresis

A capillary electrophoretic method has been developed which achieves rapid quantitative separation and determination of ethylenediaminetetraacetic acid, N-(2-hydroxyethyl)ethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, ethylenediaminediacetic acid, and nitrilotriacetic acid in Hanford tank waste simulant (TWS). Direct UV detection of Cu²⁺/chelator complexes is used to achieve enhanced sensitivity. The qualitative and quantitative reliability of the method and the quality of separations, as given by efficiency and resolution, is presented. In addition, the limits of detection and linearity of detector response with concentration are given for each chelator. The selection of Cu as the UV-absorbing species over other transition metals present in the waste is discussed.     

Recovery of actinides extracted by Truex solvent from high level waste using complexing agents

This work deals with the batch studies on stripping of actinides extracted by a mixture octyl(phenyl)-N,N-diisobutyl-carbamoylmethylphosphine oxide (CMPO) and tri-n-butyl phosphate (TBP) in n-dodecane (Truex solvent) from simulated high level waste (HLW) solution. The stripping of americium and plutonium from acid-bearing CMPO-TBP mixture is carried out using a mixture of weak acid, weak base and complexing agent as strippant. A mixture of formic acid, hydrazine hydrate and citric acid appeared to be best suited for efficient stripping of americium and plutonium. With appropriate modifications in the concentration of individual constitutents, this strippant can be used for the recovery of actinides from loaded Truex solvent with any acid content.     

Recovery of actinides extracted by Truex solvent from high level waste using complexing agents

The sorption and migration of radiostrontium in a calcareous soil from Yu Zhong county of Gansu province (China) was studied using batch and column experiments. Sorption isotherms, breakthrough curves and concentration profiles for the untreated soil and the soil treated to remove CaCO₃ were determined, respectively. It was found that radiostrontium is a relatively mobile nuclide in calcareous soil and removal of CaCO₃ from the soil slightly increases the retention ability for radiostrontium. The breakthrough curves were fitted to the analytical solution of a one-dimensional convection-dispersion transport model that assumes a reversible linear isotherm. Good agreement was obtained between the measured and predicted concentration profiles.     

Detailed study of the γ-radiolysis of nitrilotriacetic acid in a simulated, mixed nuclear waste

Gamma radiolysis of a simulant of an actual mixed waste, composed of nitrilotriacetic acid (NTA) and an inorganic matrix, at γ-doses ranging from 0–7.5·10⁶±10% R in a⁶⁰Co-source, resulted in total NTA degradation, but 10.8% of the simulant's original organic content remained. Radiolysis yielded 4 chelator fragments and 2 carboxylic acids, all formed at different rates. The chelator fragment N-(Methylamine)iminodiacetic acid (MAIDA) dominated at low γ-doses, while N-[N′-amino(2-iminoethyl)]iminodiacetic acid (AIEIDA) dominated at high γ-doses. Chemical degradation control studies revealed that the harsh chemistry of the inorganic matrix caused only 20.7% NTA degradation and formation of only 2 chelator fragments, while the heat generated by the⁶⁰Co-source (95°C) had little additional impact.     

Effects of complexing agents in radical copolymerization

Radical copolymerization of methyl methacrylate (MMA, M₁) with various monomers has been studied in presence of modifiers, i.e., complexing agents (CA): ZnCl₂, AlCl₃, AlBr₃, Al(C₂H₅)₂Cl, forming coordinate complexes with ester group of the monomer and of the propagating radical. The comonomers of the first group form complexes of similar structure and stability as MMA, methyl acrylate, or butyl acrylate. The comonomers of the second group do not form complexes with the modifiers (vinylidene chloride, 2,6-dichlorostyrene, p-chlorostyrene, styrene). For all systems studied the copolymer composition follows the Mayo-Lewis equation. In the first group of the systems the effective reactivity ratios (r₁, r₂) approach unity with increase of the CA molar content (r₁ = r₂ ? 1 at [(CA)/MMA] + [MA] ≥ 0,3) In the second group of the systems the values of r₁ either increase to a limit value (at [CA]/[MMA] ≥ 0.3), pass through maximum, or decrease to a limiting value with the CA molar content. The values of r₂ decrease in all systems. The character of variation of r₁ and r₂ has been explained in terms of effects of the CA's on reactivity of MMA and PMMA radical. The equations for the copolymer compositions in these systems have been derived.     

Organic complexing agents in atomic-absorption spectrometry-a review

The influence of organic completing agents on the determination of a particular element by atomic-absorption spectrometry (AAS) with flame or electrothermal atomization may increase the sensitivity and selectivity. The effect of the structure and properties of the organic ligand in connection with the particular atomization mechanism is discussed.     

Synthesis of some benzimidazole-, pyridine- and imidazole-derived chelating agents

Procedures are described for the preparation of various bidentate and potentially tridentate chelating agents. These incorporate pyridyl, benzimidazole, imidazole or phenolic moieties. Phillips condensations of carboxylic acids with o-phenylenediamines were carried out in 4 M hydrochloric acid. Syntheses are reported for 2, 6-bis(N′-methylimidazol-2′-ylthiomethyl)pyridine, 2, 6-bis(benzimidazol-2′-ylthiomethyl)pyridine, 2-(4′-piperidyl)benzimidazole, 2-(3′-piperidyl)benzimidazole, 2-(3-N′-methylpiperidyl)benziinidazole, 2-(3-N′-methylpiperidyl)-N-methylbenzimidazole, 2-(2′-hydroxybenzyl)benzimidazole and 2-(2′-hydroxyben-zyl)N-methylbenzimidazole. The compounds were characterized where appropriate by their mass, uv, and ¹H-nmr spectra. 2-(2′-Hydroxybenzyl)benzimidazole hydrochloride acts as a gelling agent in aqueous solution.     

Synthesis, crystal structure and magnetic properties of an enneanuclear manganese cluster containing mixed chelating ligands

A new mixed-valence [Mn₉] cluster of formulae [Mn₉O(OH)₃Cl₄(N₃)₃(hmp)₆(dpkd)₃]·1.5CH₃CN·3H₂O (1·1.5CH₃CN·3H₂O, where hmp⁻ and dpkd²⁻ are the anion of 2-hydroxymethylpyridine and the dianion of the gem-diol form of the dpk, respectively) has been synthesized and characterized by single-crystal X-ray diffraction, IR spectra, elemental analysis and magnetic measurements. Single-crystal structural analysis shows that complex 1 contains a [Mn₉] core with a new structural topology in the Mn clusters, in which the centered six Mn^III atoms compose a trigonal antiprism and the peripheral residual three Mn^II atoms can be seen as the skirt hem of this antiprism. DC magnetic susceptibility studies indicate that the overall antiferromagnetic interactions between Mn ions are present in the cluster. Fitting the data of magnetization and extrapolation of the χ_M′T suggest the spin ground states of S = 3.5, and no out-of-phase (χ_M″) signals are present in the alternating current (AC) susceptibility.     

Reverse flow injection analysis of complexing agents and its application to estimation of complexing capacity

A redox reaction of copper(II) with iron(II) proceeds slowly in the presence of neocuproine, although the reaction would not take place in its absence. This reaction is accelerated by the presence of complexing agents such as EDTA, DTPA, CyDTA, EDTA-OH, NTA, citrate, pyrophosphate, producing a copper(I)-neocuproine complex (lambda(max) = 454 nm). A reverse flow injection analysis (r-FIA) method is presented for the determination of trace amounts of complexing agents by measuring the increase in absorbance at 454 nm. Complexing agents at the 10(-6)M level can be determined at a rate of 120 samples/hr. By using this r-FIA system, a new procedure for the measurement of complexing capacity with metal ions such as Al(III), Cu(II), Zn(II), Cd(II) and Pb(II) has been developed. Complexing capacity for each metal ion can be measured at a rate of 120 samples/hr.     

A bidentate terephthalamide ligand, TAMmeg, as an entry into terephthalamide-containing therapeutic iron chelating agents

A new bidentate 2,3-dihydroxyterephthalamide ligand, 2,3-dihydroxy-N,N'-bis(2-methoxyethyl)terephthalamide (TAMmeg), has been prepared. The ligand, its synthetic precursor 2,3-bis(benzyloxy)-N,N'-bis(2-methoxy-ethyl)-terephthalamide (BnTAMmeg), and its iron complex have been structurally characterized by X-ray diffraction. BnTAMmeg crystallizes in the monoclinic space group P2(1)/n with cell parameters a = 14.4976(14) A, b = 11.5569(11) A, c = 16.3905(16) A, beta = 113.621(1) degrees , and Z = 4. TAMmeg crystallizes in the monoclinic space group P2(1)/c with cell parameters a = 13.8060(36) A, b = 8.0049(21) A, c = 19.4346(50) A, beta = 106.855(4) degrees , and Z = 4. Fe[TAMmeg] crystallizes in the triclinic space group P with cell parameters a = 12.9565(14) A, b = 13.4514(14) A, c = 20.2092(21) A, alpha = 102.093(2) degrees , beta = 95.433(2) degrees , gamma = 101.532(2) degrees , and Z = 2. The aqueous protonation and ferric ion coordination chemistry of TAMmeg were examined using potentiometric and spectrophotometric methods. Proton association constants and iron complex formation constants for the ligand are as follows: log beta(011) = 10.32, log beta(012) = 16.49, log beta(110) = 17.9, log beta(120) = 32.1, and log beta(130) = 43.0. The ferric complex of TAMmeg is surprisingly stable for a bidentate terephthalamide iron complex. The only more-stable bidentate terephthalamide iron complex that has been reported contains a ligand with positively charged pendant arms.     

HPLC analysis of metal chelating agents in micronutrients

The separation and quantitative determination of organic chelating agents such as DTPA, EDDHA, EDDHMA, EDTA and HEDTA as their copper chelates using HPLC and UV detection is described. Analysis is performed on a Spherogel^TM TSK column. The eluent consists of methanol/water (50: 50, v/v) and 0.25 mmol/L Cu(NO₃)₂. The pH value, the composition of the eluent, the temperature, the sample concentration, the flow rate of the eluent and the influence of the detection wavelength were optimized. The linearity of the UV detector was in the range of 0.5 mmol/L to 2.5 mmol/L.     

Separation of impurities from cobalt with complexing agents

Chemical purification of cobalt powders to remove iron, silicon, copper, and sodium with complexing oxalate ions was studied.     

Synthesis and evaluation of 3-acyltetronic acid-containing metal complexing agents

Potential metal chelators containing one or several acyltetronic acid moieties were prepared from cyclic or acyclic amines and polyamines, and from bis(phenols) by reaction with 1–4 equiv of 3-bromoacetyltetronic acid in the presence of potassium carbonate. The affinity constants of the chelating agents for toxic metallic cations Cd²⁺, Cs⁺, and Pb²⁺ and for dimethylarsinic acid were measured, at pH 7.5 and 9.3. Compound 4, an acyclic triamine containing four acyltetronic moieties, was found to complex efficiently all the tested species.     

Probing electronic environment in gamma irradiated sodium borosilicate glass and simulated waste glass: a perturbed angular correlation spectroscopy study

Journal of Radioanalytical and Nuclear Chemistry - Time Differential Perturbed Angular Correlation (TDPAC) has been used to investigate the local structural changes (if any) in Sodium borosilicate...     

Synthesis of some imidazole- and pyrazole- derived chelating agents

Procedures involving condensation of o-phenylenediamines with carboxylic acids, and reaction of bifunctional alkyl halides with bifunctional nucleophiles are described. Syntheses are reported of 2,6-bis-(2-benzimidazyl)-pyridine, 1,3-bis(2-benzimidazyl)-2-thiapropane, 1,7-bis(2-benzimidazyl)-2,6-dithiaheptane, 2-hydroxymethyl-5,6-dimethylbenzimidazole, 2-chloromethyl-5,6-dimethylbenzimidazole hydrochloride, 1,7-bis(5,6-dimethyl-2-benzimidazyl)-2,6-dithiaheptane, 3,6-bis(1-pyrazolyl)pyridazine, 2-(2-hydroxy-3-methyl–phenyl)benzimidazole, 2-(2-hydroxyphenyl)benzimidazole, 5-(2-hydroxphenyl)-3-methyl-1-phenylpyrazole, 3(5)-(2-hydroxyphenyl)-5(3)-methylpyrazole, 3(5)-(2-hydroxyphenyl)-5(3)-phenylpyrazole, and 1,3-bis((5-methylpyridyl)imino)isoindoline.     

Theoretical conformational analysis of cyclopendant organophosphorus chelating agents,derivatives of cyclam

Results are presented from conformational analysis of new organophosphorus ligands, derivatives of cyclam. The calculations were performed within the framework of the molecular mechanics method. For the ligands investigated, the strain energy in complexes with metal cations was estimated. The appearance of maximal dentaticity is limited to high levels of energy. Corresponding to the optimal structure of the complex with participation of phosphoryl groups in coordination is the pentadentate ligand contour. The desired topology of a hexadentate complex is possible for a ligand with an extended phosphoryl group. Conclusions are drawn regarding the stability of the complexes, the selectivity of action, and the hypothetical structure.Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 26, No. 2, pp. 184–190, March–April, 1990.