Extraction of Alkaline Earth and Actinide Cations by Mixtures of Di(2-Ethylhexyl) Alkylenediphosphonic Acids and Neutral Synergists

Abstract

The synergistic extraction of alkaline earth (Ca 2þ , Sr 2þ , Ba 2þ and Ra 2þ ) and actinide (Am 3þ , UO 2 2þ and Th 4þ ) cations from aqueous nitric acid solutions by mixtures of P,P 0 -di (2-ethylhexyl) Downloaded by [Erciyes University] at 07:34 26 December 2014 methylene-(H 2 DEH[MDP]), ethylene-(H 2 DEH[EDP]), and butylene-(H 2 DEH[BuDP]) diphosphonic acids and neutral extractants in o-xylene has been investigated. The cis-syn-cis and cis-anti-cis stereoisomers of dicyclohexano-18-crown-6 (DCH18C6), the unsubstituted 21-crown-7 (21C7) and dicyclohexano-21-crown-7 (DCH21C7) were used as neutral synergists of the crown ether type. For Am(III) synergistic effects were also investigated using neutral organophosphorus esters, such as, tri-n-butylphosphate (TBP), diamyl amylphosphonate (DA[AP]) and tri-n-octylphosphine oxide (TOPO) as co-extractants. In all systems investigated, no synergistic extraction enhancement was observed for actinide ions. For the alkaline earth cations, synergistic effects were only observed when mixtures of H 2 DEH [EDP] or H 2 DEH-[BuDP] with DCH18C6 were used to extract Sr 2þ , Ba 2þ and Ra 2þ . No synergistic effects were observed for the extraction of alkaline earth cations by H 2 DEH [MDP] or for the extraction of Ca 2þ by any of the diphosphonic acids studied. The synergistic effects obtained with DCH18C6 were significantly higher for the cis-syn-cis than for the cis-anti-cis stereoisomer. 448MCALISTER ET AL.

Synergism in a HDEHP/TOPO Liquid–Liquid Extraction System: An Intrinsic Ligands Property?

“…In solvent extraction studies, molecular associations between extractants are often considered as responsible for antagonistic effects, implying that less chelating sites are available. However, such associations are seldom fully characterized, while they could also induce a specific organization which could also favor metal ions extraction. − Few groups have performed a detailed characterization of the organic phase organization from the atomic scale to the supramolecular scale of the self-assembled aggregates. − To our knowledge, the role of a preorganization of the solution prior to any contact with the target ions has never been evaluated to explain the synergistic mechanisms.…”

Solvent extraction of tantalum(V) from aqueous sulphate/fluoride solution using trioctyl phosphine oxide in MIBK

“…The solvent extraction of thorium (IV) and uranium (VI) was investigated by Meera and Reddy (2004) using mixtures of para-substituted 1-phenyl-3-methyl-4-aroyl-5-pyrazolones and crown ethers. Similar work was also done on lanthanoids (Ensor and Reynolds, 1989;Pavithran et al, 2003;Reddy et al, 2006); alkaline earth metals (Chiarizia, et al, 2003;McAlister et al, 2002); vanadium (Remya et al, 2005) and copper (Torkestani et al, 1996). In all the works examined, multiple solvent systems were found to exhibit synergism with respect to the species being extracted.…”

Sr(ii) extraction by crown ether in HFC: entropy driven mechanism through H2PFTOUD

“…26) and DtBuCH18C6. 27 Other than using single extractant, a combination of different extractants is useful for Sr(II) extraction, e.g., both 18C6 derivatives with didodecylnaphthalene sulfonic acid, 28 versatic acid, 28,29 cobalt dicarbolide, [30][31][32] di-n-octylphosphoric acid, 33,34 and di(2ethylhexyl)alkylenediphosphonic acid 35,36 are used for synergistic extraction. A better understanding of a given extraction process leads to optimize the extraction system.…”