Sequential extraction separation for determination of technetium-99 in radwastes by ICP-MS

An approach based on sequential extraction separation and the subsequent ICP-MS measurement was introduced to determine ⁹⁹Tc in radioactive wastes. The radwastes were firstly alkaline-fused and the ⁹⁹Tc was separated by a sequential solvent extraction prior to ICP-MS measurement. NaDDC was selected as a chelation reagent in the solvent extraction processes. The influence of HCl and matrix concentration on the recovery yield and the effectiveness of removing isobar and unwanted radionuclides, such as ¹³⁷Cs, ⁵⁴Mn, ⁶⁰Co and ^110mAg, were evaluated. The designed sequential extraction procedure was optimized by an extraction experiment. The proposed technique is proven to be a simple and practical alternative for ⁹⁹Tc determination in low-level radioactive wastes; chemical separation of ⁹⁹Tc can be simplified and preconcentration such as precipitation and/or ion exchange, before the solvent extraction, can be excluded.     

Spectrophotometric determination of palladium with glyoxime and chloroform extraction

Palladium(II) reacts with glyoxime in a 1:2 mole ratio to form a yellow water-insoluble chelate, which is soluble in chloroform; the solution has an absorption maximum at 397 mμ. Absorbance measurements at 397 mμ allow determination of the palladium glyoximate in solution. The maximum amount of palladium is extracted at pH 1.0. Platinum(II), iridium(III), gold(III), and phosphate cause some positive interference, and iron(II, III) causes negative interference; the interferences can be eliminated by masking with EDTA. The species extracted has been shown to be identical with that used to prepare the original palladium glyoximate chloroform solution. With EDTA and multiple extractions, the method is satisfactory for the determination of palladium in the presence of other platinum-group elements and many other cations.     

The determination of technetium-99 in seawater and marine algae

Technetium-99 is preconcentrated from acidified seawater containing a trace of bromine by adsorbing it as the pertechnetate ion on the anion exchanger Duolite A101D. After elution with 4 M nitric acid, it is purified from other radionuclides by scavenging with hydrous iron(III) oxide and extracting from 5 M sodium hydroxide medium into methyl ethyl ketone. The organic phase is then evaporated and technetium is electrodeposited from oxalic acid medium onto a bronze disc and counted with a low background β-counter. Overall recovery is > 90% and the precision is ±0.2 pCi l^-1 at a technetium level of 0.6–1.0 pCi l^-1. Concentrations of the radionuclide in the central Irish Sea were found to lie in the range 0.4–2 pCi l^-1. The same analytical scheme can be used for determining the element in nitric acid digests of marine algae.     

Reactions of alkoxy(chloromethyl)methylsilanes with sodium diethyl phosphate and with sodium dimethylphosphinate

Summary The reactions of alkoxy(chloromethyl)methylsilanes with sodium diethyl phosphate and with sodium dimethylphosphinate provide a method for the preparation of some silicon-phosphorus organic compounds containing an Si-C-O-P linkage and functional groups attached to the silicon atom.     

Determination of technetium-99 in environmental samples by solvent extraction at controlled valence

Distribution coefficients of technetium and ruthenium are determined under different conditions with CCl₄, cyclohexanone, and 5% tri-isooctylamine (TIOA)/xylene. A method for analyzing⁹⁹Tc in environmental samples has been developed by solvent extraction in which the valences of technetium and ruthenium are controlled with H₂O₂ and NaClO. Technetium and ruthenium which are oxidized to TcO ₄ ^– and RuO ₄ ^– by NaClO are separated by extraction with CCl₄ at pH 4. The RuO ₄ ^– is reduced to low valence and technetium is kept in the TcO ₄ ^– state with H₂O₂. Technetium, ruthenium, and other nuclides are subsequently separated by solvent extraction with cyclohexanone and 5% TIOA/xylene. The decontamination of the procedure is 1.35·10⁵ for¹⁰³Ru and 1.66·10⁵ for^110mAg. The chemical yield of technetium-99 is 55%.On leave from Institute of Atomic Energy, Beijing, China     

Simultaneous determination of arsenic and antimony species in environmental samples using bis(trifluoroethyl)dithiocarbamate chelation and supercritical fluid chromatography.

Simultaneous separation and quantitation of arsenic(III) and antimony(III) can be achieved by extraction with lithium bis(trifluoroethyl)dithiocarbamate followed by supercritical fluid chromatographic (SFC) analysis. Arsenic(V) and antimony(V) are extracted after reduction with potassium iodide and sodium thiosulfate. Detection limits of 7 pg As and 11 pg Sb are achieved using this extraction method and SFC. Application to natural water and biological sample analysis is discussed.     

The extraction of iron(III) by dioctylarsinic acid in chloroform

Dioctylarsinic acid, HDOAA, in chloroform solution has been investigated as a reagent for the extraction of iron(III) chloride. The extraction coefficient reaches two maxima, one of 1.5 at 8.5 M hydrochloric acid and another of 7 at pH 2.3. Experiments in the range 4–8 M for sulfuric, nitric and perchloric acids showed no extraction of iron(III) from these solutions for extraction times of 6 h. Evidence for the extraction of H₃FeCl₆ from 4–9 M hydrochloric acid solutions as [(H₂DOAA)⁺]₃FeCl₆^3- is presented. The species extracted from aqueous solutions of pH 1–2.3 is probably a hydroxy complex of the composition [Fe₂(DOAA)₂(HDOAA)X₄(H₂0)₂ ](X = OH and/or Cl).     

Thermal decomposition kinetics of diethyl dithiocarbamate complexes of copper(II) and nickel(II)

Thermogravimetric (TG), derivative thermogravimetric (DTG) and differential thermal analysis (DTA) curves of CuL₂ and NiL₂ (L^?=diethyl dithiocarbamate anion) in air are studied. The main decomposition temperature ranges are: For CuL₂, DTG 250–350°, DTA 300–320° and for NiL₂, DTG 290–390°, DTA 360–400°. Mass loss considerations at the main decomposition stages indicate conversion of the complex to sulphides. Mathematical analysis of TG data shows that first order kinetics are applicable in both cases. Kinetic parameters (energy and entropy of activation and preexponential factor) are reported.

     

Investigation of bis(carboxymethyl)dithiocarbamate complexes by the extraction method

The extraction of copper, lead, cadmium, nickel and zinc dithizonates was investigated in the presence of ammonium bis(carboxy-methyl)dithiocarbamate. For all metals studied, except zinc, masking of extraction was observed, depending on the amount of the dithio-carbamate in the aqueous phase. From the shift of the pH(1 2 ) values for dithizonate extraction, the stability constants beta(2) for the metal complexes with bis(carboxymethyl)dithiocarbamate were calculated. The logarithms of the constants are 21.46, 15.45,11.24 and 7.93 for the copper, lead, cadmium and nickel complexes respectively.     

The extraction of niobium (V) and Tantalum (V) by Octylarsinic acid in chloroform

Dioctylarsinic acid (HDOAA) in chloroform solution extracts Nb(V) and Ta(V) efficiently from solutions containing oxalate and oxalic acid at hydrochloric acid concentrations greater than 1M.The extraction coefficients are 92.5 at 7M hydrochloric acid and 251 at 6M hydrochloric acid for niobium and tantalum, respectively. These metals can be extracted even more efficiently from sulfuric acid solutions. The results of the reagent- and pH-dependence studies suggested that a trimeric, monobasic oxoacid of niobium, associated with ten HDOAA molecules, is extracted. Tantalum appears to be present in the organic phase as (H₂DOAA)⁺ [Ta(C₂O₄)₃ (HDOAA_n] (n=l or 2).     

Spectrophotometric determination of tellurium in concentrates and brasses by chloroform extraction of the tellurium (IV) hexabromide-diantipyrylmethane complex after separations by iron collection and xanthate extraction

A method for determining 0.0001–0.10% of tellurium in copper, nickel, molybdenum, lead and zinc concentrates is described. After sample decomposition, tellurium is separated from most of the matrix elements by co-precipitation with hydrous ferric oxide from an ammoniacal medium. After reprecipitation of tellurium and iron, the precipitate is dissolved in 12M hydrochloric acid, tellurium(VI) is reduced to the quadrivalent state by heating, and separated from iron, lead and other co-precipitated elements by chloroform extraction of its xanthate. The yellow ion-association complex formed between tellurium(IV) hexabromide and diantipyrylmethane is extracted into chloroform from a 2M sulphuric acid-0.6M potassium bromide medium. The molar absorptivity of the complex is 1.82 × 10³ l.mole⁻¹.mm⁻¹ at 336 nm, the wavelength of maximum absorption. Small amounts of iron, copper and molybdenum are co-extracted as xanthates under the proposed conditions but do not cause error in the result. Interference from antimony, which is co-extracted as the chloro-complex, is eliminated by washing the extract with water. The proposed method is also applicable to brasses.     

Complexes formed in the chloroform extraction of uranium(VI) with oxine

Equilibrium distribution ratios have been determined for uranium(VI) with oxine between chloroform and 0.1M perchlorate as a function of pH and reagent concentration at 20 degrees . It is concluded that the extractable complex is UO(2)Ox(2)HOx. The equilibrium constants for the extraction of uranium have been determined as K(u,1) = [UO(2)Ox(2)HOx](0)/[UO(2)(2+)][Ox(-)](3)[H(+)] = 10(36.18) at low pH and K(U,2) = [UO(2)Ox(2)HOx](0)/[UO(2)Ox(2)OH(-)][Ox(-)][H(+)](2) = 10(25.40) at high pH.     

Complexes formed in the chloroform extraction of cobalt(II) with oxine

Absorption spectra of cobalt-oxine complexes-extractedinto chloroform indicate that two cobalt(II) and one cobalt(III) complexes can be extracted depending on pH and the initial concentrations of oxine in the organic phase or cobalt(II) ion in the aqueous phase. The oxidation state of cobalt in the complexes was determined by treatment of organic extracts with an 0.001 M EDTA solution at pH 4–5; cobalt(II) complexes were back-extracted, and the cobalt(III) complex was not. The equilibrium distribution ratios of cobalt(II) between aqueous perchlorate solutions and oxine solutions in chloroform were determined at 20°. A plot of logD_co-log[HO_x]_o vs. pOx gave a single curve for different concentrations of oxine; it was concluded that cobalt(II) is extracted as C_oOx₂HOx.     

Solvent extraction of Sb(III) with malachite green into chloroform

A rapid and selective method for the solvent extraction of Sb(III) using malachite green (C. I. Basic green 4) has been described. Effect of different parameters affecting the extraction coefficient value of Sb(III) such as acidity, time of equilibration, KI concentration, solvents, anions, etc. has been studied. For various elements the separation factor has been evaluated. The stoichiometry of the extracted species has been determined by the method of substoichiometric extraction. The decontamination factor for some elements using substoichiometric quantities of the extracting agent has been evaluated. Radiotracers were employed for the extraction studies. The method elaborated has been employed for the quantitative determination of antimony in normal, benign and cancerous tissues of the human brain.     

Synergic extraction of cobalt(II) by thenoyltrifluoroacetone and some amine extractants in chloroform

Synergic extraction of Co²⁺ with thenoyltrifluoroacetone and eight different amines in chloroform was investigated. It is found that the extracted adducts have the general formula Co(TTA)₂·B, where B stands for the amine. The stability sequence of the adducts obtained as related to the different classes of benzylamines is; dibenzylamine > benzylamine ⩽ tribenzylamine. A linear decrease in log β with the increase of Taft inductive constant was obtained on using tertiary long chain alkylamines as synergic ligand. UV and IR spectroscopic investigations support the direct bonding of the amine to the metal.     

Solvent extraction of Os(IV) with 2-mercaptobenzothiazole into chloroform

2-mercaptobenzothiazole has been used for the solvent extraction of Os(IV) in acidic medium. The extraction of Os(IV) was found to be better than 90% over the pH range of 3.0 to 5.0 with an equilibration time of 5.0 minutes. The stoichiometry of metal:reagent determined by substoichiometric extraction and slope ratio method was found to be 1∶4. Decontamination factor for various elements in the substoichiometric extraction of Os(IV) were also evaluated.