Mixed-ligand chelate extraction of thorium(IV) and uranium(VI) with thenoyltrifluroacetone and various imidazoles

N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide impregnated magnetic particles for the uptake of lanthanides and actinides from nuclear waste streams

A novel, simple technique based on magnetically assisted chemical separation (MACS) has been developed for the uptake of lanthanides and actinides from pure nitric acid solutions as well as from Simulated Pressurized Heavy Water Reactor-High Level Waste (PHWR-SHLW). Uptake profiles of various metal ions, such as Pu(IV), U(VI), Th(IV), Am(III), Eu(III), Sr(II), Cs(I) and Fe(III) were investigated as a function of time and nitric acid concentrations using N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) impregnated magnetic particles and compared with N,N′-dimethyl-N,N′-dibutyl tetradecyl malonamide (DMDBTDMA) and trialkyl phosphine oxide coated magnetic particles and also with TODGA coated extraction chromatographic resins. The uptake of various metal ions follows the order Eu(III) > Am(III) > Th(IV) > Pu(IV) > U(VI) > Sr(II) > Fe(III) > Cs(I) in pure nitric acid solutions. On the other hand, distinctly high distribution coefficient (K d) value has been observed for Pu(IV) as compared to Eu(III) and Am(III) in SHLW. Further, no significant extraction of Cs(I) or Sr(II) was observed in SHLW. Also, at any acidity the K d value of a given metal ion is less in the SHLW as compared to that in pure HNO3, apparently due to the co-extraction of the other metal ions present in SHLW. The loading capacity of the TODGA impregnated magnetic particles with respect to Th(IV), U(VI) and Eu(III) was determined, along with the distribution isotherms to simulate multiple contacts. The adsorption models of Langmuir and Freundlich were fitted to the experimental data and best correlations was obtained for Langmuir model suggesting monolayer adsorption is the prevalent mechanism. The stability and reusability of the TODGA coated magnetic particles was also assessed.

N, N′-dimethyl-N, N′-dibutyl tetradecyl malonamide impregnated magnetic particles for the extraction and separation of radionuclides from nuclear waste streams

N, N′-dimethyl-N, N′-dibutyl tetradecyl malonamide (DMDBTDMA) coated magnetic particles are being evaluated for the possible application in the partitioning of actinides, lanthanides and fission products from pure nitric acid solutions as well as from Simulated Pressurized Heavy Water Reactor-High Level Waste (PHWR-SHLW). Uptake profiles of various metal ions, such as Pu(IV), U(VI), Am(III), Eu(III), Sr(II) and Cs(I) were obtained as a function of time and nitric acid concentration by batch studies using DMDBTDMA coated magnetic particles. The order of uptake follows the order Pu(IV)>U(VI)>Am(III)>Eu(III)>Sr(II)∼Cs(I) in both nitric acid and SHLW. The uptake of various trivalent lanthanides was also investigated as a function of nitric acid concentration and found the uptake order as Pr(III)>La(III)>Eu(III)>Tb(III)>Ho(III)>Er(III)>Yb(III)>Lu(III). The sorption capacity of the DMDBTDMA coated magnetic particles with respect to U(VI) and Eu(III) was determined, along with the sorption isotherms to simulate multiple contacts. The maximum sorption capacity of DMDBTDMA coated magnetic particles was found to be 1.58 mmol/g and 0.36 mmol/g for U(VI) and Eu(III), respectively. The adsorption models of Langmuir and Freundlich were fitted to the experimental data and best correlations were obtained for both the models. The Langmuir model predicts a loading capacity of 1.61 mmol/g and 0.37 mmol/g for U(VI) and Eu(III), respectively, which is close to the experimental values. The stability and recycling capacity of the DMDBTDMA coated magnetic particles was also assessed.

Synergistic extraction of uranium(VI) by 2-hydroxy-1-naphthaldehyde thiosemicarbazone and several neutral donors

The extraction behaviour of U (VI) from an aqueous nitric acid medium employing a 2-hydroxy-1-naphthaldehyde thiosemicarbazone in ethyl acetate has been studied in presence of different neutral donors like trioctyl phosphine oxide (TOPO), dimethyl sulphoxide (DMSO) and trioctyl amine (TOA). The extraction constant (log k ex) for the binary organic phases UO2·A·X (where A=ligand, X=NO3 -1) was found to be 1.976 which is by far the largest value amongst known values for the thiosemicarbazone. The overall equilibrium constant (log K) for the ternary complexes UO2A(NO3)·TOPO, UO2A(NO3)·TOA and UO2A(NO3)·DMSO were estimated to be 6.06, 6.77 and 4.95, respectively. The effect of different diluents on the extraction behaviour has also been studied.

Studies on the equilibrium and mechanism of Th(IV) extraction by CYANEX 272 in kerosene from nitrate medium

The extraction behavior of Th(IV) from aqueous nitrate medium by the commercial bis(2,4,4-trimethylpentyl) phosphinic acid extractant, (CYANEX 272) in kerosene has been studied. Batch extraction investigation was firstly carried out to elucidate the stoichiometry of the extracted Th(IV) species and deduce the suitable conditions to be applied in the kinetic studies using Lewis cell technique. The extracted species was found to be [Th(OH)3A(HA)3] on the basis of slope analysis method. The different parameters affecting the extraction rate of Th(IV) as well as temperature were separately investigated, and a rate equation was deduced. The experimental results indicate that the rate of Th(IV) extraction is first order dependent on CYANEX 272 concentration, first order dependent on hydrogen ion concentration and inversely first order dependent on thorium concentration. The proposed mechanism for the extraction process is controlled by chemical reaction in the bulk phase rather than at the interface.

Raman spectrum, conformational stability, barriers to internal rotations and DFT calculations of 1,1,1-trifluoro-propane-2-thione with double-internal-symmetric rotor

The Raman spectrum (3500-100 cm-1) of 1,1,1-trifluoro-propane-2-thione (TFPT), CF3C(S)CH3 of the solid phase has been recorded. The internal rotation of CH3 and/or CF3 moieties around CC bonds in TFPT allow five hypothetical conformers (Cs and C1 point groups). Aided by quantum chemical (QC) calculations, the Cc conformer is the only stable form (CF3 and CH3 groups are eclipsing the CS bond) which contains a planar FCC(S)CH backbone and possess intramolecular hydrogen sulfur interactions. However, other conformations (with the orientation of sulfur atom being trans to either hydrogen or fluorine atom) are either transition states or not fully converged geometry with "gauche" orientation. Moreover, the calculation were carried out at the level of Becke three Lee-Yan-Parr (B3LYP) parameters up to 6-311++G(d,p) basis sets. The torsional barriers are adequately described by a three-fold potential, V3 which have been determined utilizing the optimized structural parameters from the B3LYP/6-31G(d) basis set along with potential surface scan. Barriers of 1.28 kcal/mol (448 cm-1) and 1.94 kcal/mol (678 cm-1) were calculated for CH3 and CF3 symmetric rotors, respectively. Complete vibrational assignments have been reported for the stable Cc isomer which is supported by normal coordinate analysis and potential energy distributions (PEDs) for all fundamentals. Moreover, equilibrium geometries, vibrational frequencies are compared to the corresponding experimental values of acetone, 1,1,1-trifluoroacetone (TFA), hexafluoroacetone (HFA) and other molecules having the CF3 moiety whenever appropriate.