G. N. Case

SELECTIVITY IN SOLVENT EXTRACTION OF METAL IONS BY ORGANIC CATION EXCHANGERS SYNERGIZED BY MACROCYCLES: FACTORS RELATING TO MACROCYCLE SIZE AND STRUCTURE

ABSTRACT Crown ethers and related macrocycles strongly synergize the extraction (phase transfer) of certain metal Ions from aqueous nitrate solutions to toluene solutions of organophilic sulfonic, phosphoric, and carboxylic acids. For alkali metals, the degree of synergism is related to the size correspondence between the macrocycle cavity and the metal ion if macrocycles of similar type and substitution are considered. Alkaline earth metals are similarly strongly synergized but the size-correspondence relationship is less pronounced. Other factors seem to affect selectivity of these elements. Terr.-butylbenzo-substituted crown ethers of the same size are much less effective synergists for the alkaline earths than cyclohexano- or rerr.-butylcyclohexano-substituted compounds. However, with synergism in alkali metal extraction, the reverse is generally true; that is, ferf-butylbenzo-substituted crown ethers are better synergists than cyclohexano-substituted crown ethers. Effects involving the electron-withd...

SXLSQA, A Computer Program for Including Both Complex Formation and Activity Effects in the Interpretation of Solvent Extraction Data

Abstract A previously reported computer program for the interpretation of solvent extraction data in systems that can include two extractants, one acidic and one neutral, has been extended to treat the effects of: (1) variation of activity coefficients of solute species and of water activity in the aqueous phase, calculated by the Pitzer treatment; (2) variation of activity coefficients of solute species in the organic phase, calculated by the Hildebrand-Scott treatment; and (3) product species formed in the aqueous phase. The interaction parameters of the Pitzer treatment and the solubility parameters of the Hildebrand-Scott treatment can be refined along with the formation constants of various assumed product species to fit the data. Like its predecessor, the program is capable of fitting simultaneously a variety of data, including the distribution of an extractable cation, anion, or water, as well as spectra, vapor pressure, or heats of mixing for the organic phase. Use of the program is illustrated by...

COMPLEXATION OF STRONTIUM IN THE SYNERGISTIC EXTRACTION SYSTEM DICYCLOHEXANO-18-CROWN-6, VERSATIC ACID, CARBON TETRACHLORIDE

ABSTRACT The synergism in the extraction of Sr⊃ +⊃ from 0.5M Sr(NO⊂3⊂) ⊂2⊂ by 0.05M dicyclohexano-18-crown-6 (DC18C6) + 0.1M Versatic 1519 (abbreviated v-acid or RCOOH, a neo carboxylic acid) in CCl⊂4⊂ has been found to stem from a strong 1:1 interaction between DC18C6 and Sr⊃2+ ⊃ However, both nitrate and carboxylate can function as the anion for the (DC18C6)Sr⊃2+⊃ moiety. At aqueous conditions corresponding to less than complete loading (i.e., [Sr⊃2+⊃[ org < 0.05M for pH < 11.7), (DC18C6)Sr(NO⊂3;)⊂2⊂ precipitates as a solid. As the pH is raised in the interval 7 < pH < 11.7 to deprotonate the V-acid, the precipitate (DC18C6)Sr(NO⊂3⊂) ⊂2⊂ becomes solubilized first with probable formation of a mixed-anion complex and finally with quantitative (0.05M) formation of the monoraeric complex (DC18C6)Sr(OOCR) ⊂2⊂ H⊂2⊂O at pH = 11.7 as confirmed by viscometric titration of 0.05M DC18C6 in wet CCl⊂4⊂ with Sr(OOCR) ⊂2⊂, Karl-Fischer titrations, vapor-phase osmometry, and IR spectrophotometry.

Equilibrium Analysis of Aggregation Behavior in the Solvent Extraction of Cu(II) from Sulfuric Acid by Didodecylnaphthalene Sulfonic Acid

Abstract By use of the principles of equilibrium analysis, the liquid-liquid cation exchange of Cu(II) from aqueous sulfuric acid at 25°C by didodecylnaphthalenesulfonic acid (HDDNS) in toluene may be understood in terms of small hydrated aggregated species in the organic phase. Extraction data have been measured as a function of organic-phase HDDNS molarity (1.0 × 10−4 to 1.0 × 10−1), aqueous copper(II) sulfate molarity (1.2 × 10−8 to 1.3 × 10−2), and aqueous sulfuric acid molarity (0.03 to 6.0). Graphical analysis of linear regions of the data support a model in which organic-phase aggregates of HDDNS function by cation exchange to incorporate Cu(II) ions with no apparent change in aggregation number at low loading. Supporting FTIR spectra and water-content measurements of HDDNS solutions in toluene show that the HDDNS aggregates are highly hydrated. By use of the computer program SXLSQA, a comprehensive equilibrium model was developed with inclusion of activity effects. Aqueous-phase activity coefficie...

SPECTRAL STUDIES AND EQUILIBRIUM ANALYSIS OF THE DIDODECYLNAPHTHALENE SULFONIC ACID, DICYCL0HEXAN0-18-CR0WN-6, Sr2+EXTRACTION SYSTEM

ABSTRACT The species and equilibria present in the synergistic extraction system for strontium, composed of didodecylnaphthalene sulfonic acid (HDDNS) and dicyclohexano-18-crown-6 (DC18C6) in CCI4, have been studied by IR and proton NMR spectroscopies, vapor pressure osmometry (VPO), and Karl Fischer (KF) titrations. With the aid of least-squares computer methods to fit the IR and VPO results, a series of proposed equilibria and associated equilibrium constants have been shown to adequately account for all of the observed behavior. The sulfonic acid and the salt of the acid alone in CCI4solution form the micellar species (HDDNS·xH2O) 11(× is in the range 7-8) and (Sr(DDNS)2· 11 H2O) 6respectively. The sulfonic acid alone, under conditions of intermediate loadings with Sr2+, yields the predominant species (Sr(DDNS) 2)3(HDDNS) 5·×H2O. When alone in solution, DC18C6 is a monomer, but it forms adducts with the free sulfonic acid and its strontium salt, yielding the respective product species (HDDNS) 7·DC18C6·...

LIQUID-LIQUID EQUILIBRIUM ANALYSIS IN PERSPECTIVE.PART 1. SLOPE ANALYSIS OF THE EXTRACTION OF URANYL NITRATE FROM NITRIC ACID BY DI-2-ETHYLHEXYLSULFOXIDE

ABSTRACT Slope analysis is critically examined as a stand-alone method for analyzing the representative extraction system uranyl nitrate, nitric acid, sodium nitrate, water, di-2-ethylhexylsulfoxide (DEHSO). n-dodecane at 25 °C. The use of detailed computer calculations of free extractant concentrations and activity coefficients has permitted assessment of commonly employed assumptions of slope analysis in the data treatment. On the basis of slope analysis alone, the extraction of nitric acid in the absence of U(VI) can be partly described by the formation of the 1:1 adduct (DEHSO)(HNO3), but complications due to nonideality effects and the formation of at least two other species hinder further reliable analysis. Under the limiting conditions of low DEHSO molarity, low aqueous nitric acid molarity, and low U(VI) loading, a slope-analysis treatment of U(V1) extraction data shows unambiguously that the predominant extracted species of U(VI) is UO2(N03)2(DEHSO)2(H20)w (w not determined). However, it is diffi...

THE SYNERGISTIC SOLVENT EXTRACTION OF RADIUM FROM ALKALINE NITRATE MEDIA BY DICYCLOHEXANO-21-CROWN-7 COMBINED WITH 2-METHYL-2-HEPTYL NONANOIC ACID EQUtUBRIUM REACTIONS AND METAL ION COMPETITION∗

ABSTRACT The equilibria in the solvent extraction of radium from aqueous sodium nitrate/sodium hydroxide solutions by toluene solutions of dicyclohexano-21-crown-7 (DC21C7). 2-methyl-2-heptylnonanioc acid (HMHN). and mixtures of the two reagents are examined. The mixed reagents are synergistic in the extraction of radium and selective for radium over other alkali and alkaline earth elements. The dependencies of the extraction on pH and reagent concentration were utilized in computer modeling to estimate the stochiometry of the extracted complexes and equilibria involved the extraction. Three organic-phase species were identified in the extraction under basic (pH 11-13) conditions. With A = MHN−. B = DC21C7 and assuming NaA is a 10-fold aggregate they are. RaA2B.NaA. Log K = 3.57: RaA NaA. Log K = 0.99: and B 2NaA. Log K = − 0.41. The effect of the presence of various concentrations of sodium

Selective Extraction of Cu2+ and Ag+ Ions from Sulfuric Acid by Synergistic Combinations of Tetradentate Thia Macrocycles with Dioodecylnaphthalene Sulfonic Acid

Abstract The aqueous-insoluble thia macrocycles tetrathia-14-crown-4 (TT14C4) and tetrathia-16-crown-4 (TT16C4) strongly and selectively synergize the extraction of Cu2+ and Ag+ ions from aqueous sulfuric acid solutions by the organophilic cation exchanger didodecylnaphthalene sulfonlc acid (HDDNS) in toluene diluent. Over a range of sulfuric acid concentrations, the selectivity is given by the order Ag2 > Cu2+ > Mn2+, Fe2+, Fe3+, Co2+, Ni2+, and Zn2+, where synergism occurs only for Ag+ and Cu2+. Selectivity factors greater than 300 have been achieved for Cu2+ over ubiquitous Fe3+. The synergistic extraction of Cu2+ and Ag+ was explored as a function of sulfuric acid concentration, relative concentration of macrocycle vs. HDDNS, and loading.

SOLVENT EXTRACTION OF RADIUM AND BARIUM CATIONS INTO CHLOROFORM BY A LIPOPHILIC ACYCLIC POLYETHER DICARBOXYLIC ACID

The lipophilic acyclic polyether carboxylic acid bls-l,8(2 -carboxy-3-naphthoxy)-3,6-dioxaoctane exhibits selectivity for Ra2+ over Ba2+ in competitive extractions into chloroform. Solubility characteristics of the compound suggest that the addition of branched alkyl substituents would be required to make it a practical separation agent.

Comprehensive equilibrium analysis of the complexation of Cu(II) by tetrathia-14-crown-4 in a synergistic extraction system employing didodecylnaphthalene sulfonic acid

Abstract Liquid-liquid extraction experiments, UV/vis spectra, and equilibrium modeling by use of the program SXLSQA have been employed to reveal the origin of synergism in the extraction of Cu(II) from sulfuric acid by the tetradentate macrocycle tetrathia-14-crown-4 (TT14C4) combined with the cation exchanger didodecylnaphthalene sulfonic acid (HDDNS) in toluene. The key feature of the system is the 1:1 complexation of Cu(II) by TT14C4. HDDNS functions both as a source of exchangeable protons and as a solvating agent that promotes the formation of small, hydrated aggregates. In the absence of the cation-exchange vehicle provided by HDDNS, the macrocycle does not extract Cu(II) detectably. Combined with HDDNS, however, TT14C4 significantly enhances the extraction of the metal by HDDNS. Comparative UV/vis spectrophotometry indicates the formation of the deep-blue chromophore attributed to the complex ion Cu(TT14C4)2+, wherein the planar set of four endo sulfur donor atoms of TT14C4 circumscribes the metal...