dihexyl-N,N-diethylcarbamoylmethylphosphonate Research Articles

Understanding the Dynamics of Eu3+ Ions in Room‐Temperature Ionic Liquids – Electrochemical and Time‐Resolved Fluorescence Spectroscopy Studies

AbstractTo understand the oxidation state, coordination geometry, and physicochemical behavior of the Eu3+ complex with dihexyl N,N‐diethylcarbamoylmethylphosphonate (DHDECMP) in the ionic liquid (IL) 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][NTf2]), the spectroscopic and electrochemical properties of the system were investigated. The electrochemical behavior of Eu3+–DHDECMP in [bmim][NTf2] was studied by cyclic voltammetry (CV) and chronoamperometry at a glassy carbon (GC) electrode. The reduction of Eu3+ to Eu2+ in [bmim][NTf2] is quasireversible and controlled by diffusion as well as charge‐transfer kinetics. Photoluminescence spectroscopy confirms that the symmetry around the europium ions in Eu3+–DHDECMP in the room‐temperature IL (RTIL) is relatively low; this is further supported by calculations of the Judd–Ofelt parameters (Ω2 higher than Ω4). On the basis of fluorescence lifetime measurements, the number of water molecules in the inner sphere is six for uncomplexed europium ions, and practically no water molecules are retained in the presence of the complexing extractant DHDECMP.

Thermodynamic and Spectroscopic Studies on Am(III) and Eu(III) in the Extraction System of N,N,N',N'-Tetraoctyl-3-Oxapentane-1,5-Diamide in n-Dodecane/Nitric Acid

Thermodynamic parameters (ΔG, ΔH, and ΔS) for the extraction of trivalent f-elements, M(III) (M = Am, Eu), with N,N,N',N'-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) were determined in nitric acid/n-dodecane extraction system. The extraction of M(III) with TODGA was more exothermic than those with octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO) and dihexyl-N,N-diethylcarbamoylmethyl phosphonate (DHDECMP). The difference in ΔH between the extractants was attributed to the difference in the binding mode between them, i.e. tridentate (TODGA) and bidentate (CMPO and DHDECMP). In addition, from the results of luminescence lifetime measurement, it was found that the inner-sphere of extracted Eu(III) was dehydrated completely, and occupied by TODGA and/or NO3 −.

Extraction of actinides from simulated HLLW by DHDECMP-TBP/OK

The partitioning of actinides from simulated high level liquid waste (HLLW) originated from the Purex process has been studied using a mixture of dihexyl N,N-diethylcarbamoylmethyl-phosphonate (DHDECMP) and tributylphosphonate (TBP) in kerosene (OK). The distribution ratios of actinides were investigated as a function of a number of parameters such as the concentration of nitric acid, salting-out reagent, Gd(III) in the aqueous phase, extractant in the organic phase, and temperature. The extraction complexes, extraction reaction constant k, and thermodynamic parameters ΔH, ΔG and ΔS were determined. The extraction of actinides from simulated HLLW by DHDECMP-TBP/OK has been carried out using a miniature countercurrent centrifugal contactor. The results show that the removal efficiency of actinides is greater than 99.9%. A conceptual flowsheet for the removal of actinides from HLLW is proposed.

Extraction of Eu(III) and Co(II) by dihexyl N,N-diethyl carbamoyl methyl phosphonate (DHDECMP) and thenoyl trifluoroacetone (HTTA)

The extraction of Eu(III) has been carried out from nitrate solutionusing DHDECMP. Different parameters affecting the distribution of metal ionhave been studied. The distribution of Eu(III) was found to be first orderdependent on pH and second order with respect to [DHDECMP]. DHDECMP showedhigh stability towards α-radiation dose up to 26.5 megarad. The extractionof Co(II) by either DHDECMP or HTTA from acetate solution showed that it issecond order dependent on both the extractant concentration and the pH. Basedon the data of the distribution ratio obtained and the calculated thermodynamicparameters; reaction mechanisms are suggested.

Synthesis and Characterization of Plutonium(IV), Uranium(VI), Morium(IV) and Neodymium(III) Nitrate Complexes with Bidentate Organophosphorus Ligands

Solid adducts of actinide and lanthanide nitrates of the type [M(NO3(X)y], where M = Pu4+, UO2 2+, Th4+ and Nd3+; n = 2 for UO2 2+, 3 for Nd3+ and 4 for Th4+ and Pu4+; y = 1 for UO2 2+, 1.5 for Th4+ and 2 for Pu4+ and Nd3+; and X = dihexyl N, N-diethylcarbamoylmethylphosphonate (DHDECMP) or octyl (phenyl) (N, N-diisobutylcarbamoylmethyl) phosphine oxide (CMPO), were isolated and purified by a solvent extraction route from benzene. These compounds have been characterized by elemental analyses, and their melting points. The IR and visible absorption spectra of these complexes indicate that they are O-bonded. The extract ant in all the complexes acts as a bidentate ligand whereas the nitrate ion acts as a bidentate group in the Th4+, UO2 2+ and Nd3+ complexes but in the case of the Pu4+ complexes one of the nitrate ions probably is acting as monodentate ligand. A slight upfield shift of phenyl, methyl and methylene protons around phosphoryl and carbamoyl oxygens in the 1H NMR spectra of the uranium, thorium and neodymium complexes, as compared to the pure ligand, further reaffirms the bidentate nature of CMPO. Thermal studies of the uranyl and thorium complexes are reported.

Extraction studies of uranyl ion UO 2 2+ by dihexyl-N, N-diethyl carbamoyl methyl phosphonate (DHDECMP)

The extraction of UO22+ from nitrate solution has been carried out using DHDECMP. Different parameters affecting the distribution coefficient of UO22+ have been determined. The extraction of UO22+ was found to have second order dependency on both extractant and H+ concentrations. Addition of some bases as TBP and TOPO to the phosphonate extractant increased the distribution of UO22+ to a great extent. LogD for UO22+ with respect to both synergistic bases was found to be a first order dependent. The thermodynamic parameters have been calculated and the extraction mechanisms have been suggested.

THE ITINERANT EXTRACTION BEHAVIOR OF f-ELEMENTS AND TTRIUM WITH OCTYL(PHENYL)-N,N-DIISOBUTYLCARBAMOYL-ETHYLPHOSPHINE OXIDE

ABSTRACT The extraction behaviour of selected trivalent lanthanides, actinides and yttrium was studied from thiocyanate and nitrate solutions using octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide(CMPO) in xylene as an extractant. It was found that these trivalent metal ions were extracted as MX3.3CMPO (where X - SCN - or N03-). The equilibrium constants(K) of the above species were determined by non-linear regression analysis. The K values of trivalent lanthanides in nitrate solutions do not increase monotonically with increasing atomic number(Z), but have a maximum at Eu. On the other hand, in thiocyanate solutions, the K values increase with increasing Z. In the extraction systems containing soft ligands like thiocyanate the distribution ratio (D) of Y is lower than that of La, whereas trivalent actinides Am and Cm have much higher D values than their corresponding counterparts in the lanthanide series. However, in the extraction systems containing a hard ligand such as nitrate, it is interesting to note that yttrium fits close to Tm which is the expected position based on its hydration energy and ionic radius. The reasons for these itinerant properties of yttrium, americium and curium have been discussed. The separation factors between these trivalent metal ions were calculated and compared with those obtained using the commercially important solvents like tributylphosphate (TBP), dihexyl-N,N-diethylcarbamoylmethylphosphonate (DHDECMP) and dibutylbutylphosphonate (DB[BP]). In the SCN-CMPO system high separation factor between Am and Eu has been obtained. The possibility of utilizing CMPO in the recovery of Y in a pure form from the mixtures containing Y, trivalent lanthanides and actinides has also been discussed.

Extraction of tri- and tetravalent actinides with dihexyl N,N-diethylcarbamoylmethyl phosphonate (DHDECMP) and TBP from nitric acid solutions

Extraction of trivalent (Pu3+, Am3+, actinides and Eu3+, a representative of lanthanides) and tetravalent (Np4+ and Pu4+) actinides has been studied with dihexyl N,N-di-ethylcarbamoylmethyl phosphonate (DHDECMP) in combination with TBP in benzene from 2M nitric acid. The stoichiometries of the species extracted were found to be M(NO3)3·(3−n) TBP·n DHDECMP (for trivalent ions) and M(NO3)4·(2−n) TBP·n DHDECMP (for tetravalent ions) by the slope ratio method. The extraction constants evaluated (from the distribution data) indicate that for tetravalent ions (with solvation number two) the extraction constant increases when TBP (Kh=0.17) molecules are successively replaced by more basic DHDECMP (Kh=0.34) molecules. However, for trivalent ions (with solvation number three) when TBP molecules are totally replaced by DHDECMP molecules stereochemical factors appear and instead of increase, a substantial decrease in extraction constants is observed for Eu3+ and Am3+, a lesser decrease being observed for Pu3+ (larger ion).

Solvent Extraction of Eu(III) by Dihexyl-N,N-Diethylcarbamoyl Methyl Phosphonate (DHDECMP) from Perchlorate and Nitrate Media

Eu(III) extraction by DHDECMP has been studied from aqueous solution of perchlorate and nitrate. In case of perchlorate the distribution of Eu was found to be first power dependent on pH and third power dependent on extractant concentration. From nitrate it was found that D for Eu(III) is also first power with respect to pH but second power dependency on DHDECMP. The reaction mechanisms have been suggested and discussed in the light of the data obtained. The effect of adding some electron donor compounds decreases the extractability of DHDECMP for Eu(III) but does not change the nature of extracted species. The equilibrium constants of all the extracted species have been calculated and discussed. The extractant behaves as a chelate in low acidic media and extracted complex species is suggested to be Eu(NO3)2DHDECMP·DHDECMP from nitrate solutions.

SYNTHESIS, PURIFICATION, AND DERIVATIVE CHEMISTRY OF DIHEXYL-N,N-DIETHYLCARBAMOYLMETHYLPHOSPHONATE

ABSTRACT Recently developed commercial scale synthesis of solvent extraction grade dihexyl-N,N-diethylcarbamoylmethylphosphonate ( DHDECMP ) is described. Identification and removal of impurities are discussed. Several new substituted derivatives of DHDECMP and its analogues are reported

Solvent Extraction of Plutonium (IV) Polymer by Dihexyl-N, N-Diethyl-carbamoylmethylphosphonate (DHDECMP)

Abstract The bifunctional organophosphorus compound DHDECMP (dihexyl-N, N-diethylcarbamoylmethylphosphonate) is effective in the extraction of hydrolytic plutonium (IV) polymer from both 0.04 and 7.0M nitric acid. Stripping the polymer- is difficult, even with hydrofluoric acid. However, 1.0M sodium carbonate is a very effective stripping agent. The extracted complex contains one to two molecules of DHDECMP per plutonium ion and the plutonium (IV) maintains a polymeric structure.

THE EXTRACTION OF ZIRCONIUM FROM NITRIC ACID BY DIHEXYL N, N-DIETHYLCARBAMOYLMETHYLPHOSPHONATE∗

ABSTRACT The extraction behavior of Zr from aqueous HNO3 was studied using dihexyl N, N-diethylcarbamoylmethylphosphonate (DHDECMP). Distribution ratios were examined as a function of contact time, concentration of solute, acid, and extractant and extraction temperature. It was found that the extractant dependency for Zr is second power. Temperature dependency studies were hindered by an apparent Zr specie change above 30°C. Extraction of Zr is strongly NO3 dependent

The Extraction of Am(III) and Eu(III) from Aqueous Ammonium Thiocyanate by Dihexyl-N,N-diethylcarbamoylmethylphosphonate and Related Compounds

Abstract The extraction behavior and separation factors of Am(III) and Eu(III) from low acid ammonium thiocyanate solutions were studied using dihexyl-N,N-diethylcarbamoylmethylphosphonate (DHDECMP) and related compounds. It was found that very dilute (<0.1 M) solutions of ammonium thiocyanate were sufficient to allow quantitative extraction of Am(III) with DHDECMP. Significant differences between DHDECMP and dibutylbutylphosphonate (DB[BP]) in the extraction of Am(III) and Eu(III) from thiocyanate were found and indicate chelation is occurring with DHDECMP, unlike the situation in the low acid lithium nitrate system. Infrared spectroscopy of the extracted complexes of La(III) and extraction studies with dihexyl-N,N-diethylcarbamoylethylphosphonate (DHDECEP), dihexyl-N,N-diisobutylcarbamoylmethylphosphonate (DHDIBCMP), and di-(2-ethylbutyl)-N,N-diethylcarbamoylmethylphosphonate (DEBDECMP) confirm that chelation occurs with thiocyanate complexes of Am(III) and Eu(III). Separation factors, α, for Am(III) and Eu(III) were the lowest with DB[BP] (α = 5.84) and the highest with DHDIBCMP (α = 10.8).

The Extraction of Am(III) and Fe(III) by Selected Dihexyl N,N-Dialkylcarbamoylmethyl-phosphonates, -Phosphinates and -Phosphine Oxides from Nitrate Media

Abstract A series of neutral bifunctional extractants related to dihexyl N,N,-diethylcarbamoylmethylphosphonate (DHDECMP) have been prepared and studied for the liquid-liquid extraction of Am(III) and Fe(III) from nitrate solutions. Changes in the steric bulk of the substitutent alkyl chains and in the electro-negativity of the groups attached to the phosphoryl center in these compounds have brought about large changes in distribution ratios and selectivities for the extraction of these metals. Comparisons of these extractants to related monofunctional phosphorus-based compounds have revealed that these bifunctional species behave as monodentate, rather than chelating, extractants. The presence of the carbamoyl portion of the extractant molecules is important not for coordination to the metal, but for the ability to buffer the extractant against the effects of HNO3.

The Extraction of Th(IV) and U(VI) by Dihexyl-N, N-diethylcarbamoylmethylphosphonate from Aqueous Nitrate Media

Abstract The extraction behavior of Th(IV) and U(VI) from nitrate media was studied using relatively pure dihexyl-N, N-diethylcarbamoylmethylphosphonate (DHDECMP). The data were compared with analogous measurements obtained with dibutyl butylphosphonate (DB[BP]). It was found that the extractant dependency is second power for U(VI) with both DHDECMP and DB[BP]. However, the extractant dependency for Th(IV) is third power for DB[BP] but varied from 2.5 to 2.0 power for DHDECMP depending on the total nitrate concentration. The Kd data do not support the theory that DHDECMP is an effective chelating agent for actinide ions. Significant differences between DHDECMP and DB[BP] do appear in the extraction behavior of Th(IV) from 1 to 5 M HNO3. These differences are explained by the ability of DHDECMP to buffer itself against the effects of HNO3 by protonation of the amide group.

The Extraction of Selected Transplutonium(III) and Lanthanide(III) Ions by Dihexyl-N, N-diethylcarbamoylmethylphosphonate from Aqueous Nitrate Media

Abstract The extraction behavior of selected transplutonium(III) and lanthanide(III) ions fromnitrate solution was studied using relatively pure dihexyl-N, N-diethyl-carbamoylmethylphosphonate (DHDECMP). The data obtained for Am(III) and Eu(III) using DHDECMP were compared with analogous measurements obtained with dibutyl butylphosphonate (DB[BP]) and in certain cases with dihexyl-N, N-diethylcarbamoylethylphosphonate (DHDECEP). It was found that both the nitrate and extractant concentration dependencies were third power. The Kd 's for Am(III) and for Eu(III) measured from low acid LiNO3 solutions were similar for DHDECMP, DHDECEP, and DB[BP], thus giving no evidence for any significant chelation effect for DHDECMP. Significant differences among DHDECMP, DHDECEP, and DB[BP] are found for the extraction of Am(III) and Eu(III) from 1 to 5 M HNO3. These differences are explained by the ability of DHDECMP (and to a lesser extent, DHDECEP) to buffer itself against HNO3 by protonation of the amide group. The Kd...