Kinetics and Mechanism of Yb(III) Extraction and Separation from Y(III) with Mixtures of bis(2,4,4‐trimethylpentyl)phosphinic acid and2‐ethylhexyl phosphonic acid mono‐2‐ethylhexyl ester

Abstract

The ytterbium(III) extraction kinetics and mechanism with mixtures of bis(2,4,4‐trimethylpentyl)phosphinic acid (Cyanex272) and 2‐ethylhexyl phosphonic acid mono‐2‐ethylhexyl ester (P507) dissolved in heptane have been investigated by constant interfacial cell with laminar flow. The effects of the stirring rate, temperature, extractant concentration, and pH on the extraction with mixtures of Cyanex272 and P507 have been studied. The results are compared with those of the system with Cyanex272 or P507 alone. It is concluded that the Yb(III) extraction rate is enhanced with mixtures extractant of Cyanex272 and P507 according to their values of the extraction rate constant, which is due to decreasing the activation energy of the mixtures. Atthe same time, the mixtures exhibits no synergistic effects for Y(III), which provides better possibilities for Yb(III) and Y(III) separations at a proper conditions than anyone alone. Moreover, thermodynamic extraction separation Yb(III) and Y(III) by the mixtures has been discussed, which agrees with kinetics results. Extraction rate equations have also been obtained, and through the approximate solutions of the flux equation, diffusion parameters and thickness of the diffusion film have been calculated.     

Copper and cadmium extraction from highly concentrated phosphoric acid solutions using calcium alginate gels enclosing bis(2,4,4‐trimethylpentyl)thiophosphinic acid

The availability of alginate gels enclosing Cyanex 302 [bis(2,4,4‐trimethylpentyl)thiophosphinic acid] for the uptake of cadmium and copper from highly concentrated solutions of industrial phosphoric acid wet process phosphoric acid (WPA)] was studied. For this purpose, beads of alginate gels enclosing microdrops of kerosene solutions of the industrial extractant Cyanex 302 at different concentrations were prepared. The experimental procedure gives rise to a composite bead in which alginate is the continuous phase and the organic extractant forms the discrete homogeneously distributed phase within the bead. The equilibrium in this three‐phase system (phosphoric acid–extractant solution–alginate gel) was modelled in terms of the corresponding distribution factors, the main chemical reactions and their equilibrium constants. Retention isotherms of both metal ions were obtained experimentally at four concentrations (1.0, 2.5, 5.0 and 7.5 mol L^?1) of pure phosphoric acid. High metal removal efficiency, due to liquid–liquid extraction processes, was observed even in the most acidic conditions. High values of the extraction constants were estimated, with the distribution coefficients between aqueous and alginate phase being near unity. Finally, the results obtained with industrial WPA are in close agreement with those predicted by the physicochemical model developed in synthetic media. Copyright © 2006 Society of Chemical Industry     

Extraction of rare earths using mixtures of sec-octylphenoxy acetic acid and organophosphorus acids

The extraction of rare earths from nitrate medium using three organophosphorus acids, 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (HEHEHP), di-(2-ethylhexyl) phosphoric acid (D2EHPA), bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex272), and their mixtures with sec-octylphenoxy acetic acid (CA12) has been studied in detail. The mixtures have different extraction effects on various rare earths. Synergistic extraction effects are only found when light rare earths and yttrium (III) are extracted with mixtures of D2EHPA and CA12. The possibilities of separating the rare earths with these mixtures are investigated according to the extractabilities. It is feasible and advantageous to separate yttrium (III) from the lanthanoids (III) with HEHEHP + CA12 and D2EHPA+CA12 mixtures at proper extractant ratios. The separation of yttrium (III) from heavy rare earths is also possible with mixtures of Cyanex272 and CA12.     

Selective Separation of Scandium(III) and Yttrium(III) from other Rare Earth Elements using Cyanex302 as an Extractant

Abstract

Liquid‐liquid extraction and selective separation of scandium(III) and yttrium(III) with Cyanex302 (bis(2,4,4‐trimethylpentyl)monothiophosphinic acid) has been carried out by controlling the aqueous phase pH. Scandium(III) and yttrium(III) were completely recovered from the organic phase using 5.0 M and 4.0 M nitric acid respectively and determined spectrophotometrically as their complexes with Arsenazo(III). The influence of extractant concentration, equilibration time, nature of diluents, stripping agents, and diverse ions on the extraction of scandium(III) and yttrium(III) was investigated. The extractability of scandium(III), yttrium(III), and other rare earth elements was exploited for sequential separation of scandium(III)‐yttrium(III)‐lanthanum(III) and other rare earth elements viz. lanthanum(III), cerium(IV), praseodymium(III), neodymium(III), gadolinium(III), dysprosium(III), and ytterbium(III) in binary mixtures. The method presented is simple and rapid for isolation of scandium(III) and yttrium(III) from associated elements and has been successfully applied for their selective separation from complex matrices of USGS standard soil GXR‐2 and Japanese standard stream sediment sample Jsd‐3.     

Synergistic Extraction and Separation of Heavy Lanthanide by Mixtures of Bis(2,4,4‐trimethylpentyl)phosphinic Acid and 2‐Ethylhexyl Phosphinic Acid Mono‐2‐Ethylhexyl Ester

Abstract

The extraction of Yb³⁺ from chloride solution has been studied using mixtures of bis(2,4,4‐trimethylpentyl)phosphinic acid (Cyanex272) and 2‐ethylhexyl phosphinic acid mono‐2‐ethylhexl ester (P507). The results show that Yb³⁺ is extracted into heptane as YbA₃(HA)₃ with Cyanex272, YbL₃(HL)₃ with P507, and YbA₂L₄H₃ with synergistic mixture. The equilibrium constants, formation constants, and thermodynamic functions have been determined. Extraction mechanism and extraction process are also proposed. The extraction of heavy lanthanide ions by mixtures of Cyanex272 and P507 is studied and the possibility of separating heavy rare earth ions is discussed.     

THE EXTRACTION OF SOME BASE METAL IONS BY CYANEX 30L CYANEX 302 AND THEIR BINARY EXTRACTANT MIXTURES WITH ALIQUAT 336

ABSTRACT

The extraction behaviour of Cyanex 301, Cyanex 302 and their binary extractant mixtures with Aliquat 33b towards copper(II), zinc(II), iron(III), iron(II), cobalt(II), nickel(II) and manganese(Il) is indicated. The extraction data were collected from sulphate solutions with acidities ranging from pH 10 to 8 mol/dm³ sulphuric acid. Cyanex 301 is a more efficient extractant than Cyanex 302 and is able to effect extraction at greater acidities. In combination with the organic base Aliquat 336 the extraction power of these extractants is lowered and in some cases the extraction is suppressed appreciably. However, the suppression of extraction can be useful in metal separation and affords greater control over the back-extraction. The suppression is ascribed to the high stability of the acid-base couple which must dissociate in order to effect extraction.     

Investigating the Synergistic Effect of D2EHPA and Cyanex 302 on Zinc and Manganese Separation

The synergistic effect of Cyanex 302 on the extraction of zinc and manganese with D2EHPA in sulfate media was investigated. Experiments were carried out in the pH range of 1.0–5.0, temperature of 23, 40, and 60°C with sole D2EHPA and Cyanex 302 as extractant and D2EHPA to Cyanex 302 ratios of 1:3, 1:1, and 3:1. The experimental results showed that the co-extraction of zinc and manganese increased with increasing equilibrium pH and temperature. Increasing the D2EHPA to Cyanex 302 ratio in the organic phase, caused a left shifting of the extraction isotherm of zinc and a right shifting of the extraction isotherm of manganese. Thus, a better separation of zinc over manganese was achieved. At low pHs, the separation factor is low when pure D2EHPA is used as an extractant; however, using Cyanex 302 as a synergist, the separation factor increases and results in a better separation of zinc from manganese. Stoichiometric coefficient of zinc for single D2EHPA and Cyanex 302 and their mixture was calculated to be close to 6.     

Kinetics of Y(III) Stripping for the System Y/HCl/Cyanex 272‐P507/Heptane with Constant Interfacial Area Cell with Laminar Flow

Abstract

Kinetics and mechanism of stripping of yttrium(III) previously extracted by mixtures of bis(2,4,4‐trimethylpentyl)phosphinic acid (Cyanex 272, HA), and 2‐ethylhexyl phosphonic acid mono‐2‐ethylhexl ester (P507, HB) dissolved in heptane have been investigated by constant interfacial‐area cell by laminar flow. The corresponding equilibrium stripping equation and equilibrium constant were obtained. The studies of effects of the stirring rate and temperature on the stripping rate show that the stripping regime is dependent on the stripping conditions. The plot of interfacial area on the rate has shown a linear relationship. This fact together with the strong surface activity of mixtures of Cyanex 272 and P507 at heptane‐water interfaces makes the interface the most probable locale for the chemical reactions. The stripping rate constant is obtained, and the value is compared with that of the system with Cyanex 272 and P507 alone. It is concluded that the stripping ability with the mixtures is easier than that of P507 due to lower the activation energy of the mixtures. The stripping rate equation has also been obtained, and the rate‐determining steps are the two‐step interfacial chemical reactions as predicted from interfacial reaction models.     

Separation of scandium(III) from lanthanides(III) with room temperature ionic liquid based extraction containing Cyanex 925

The separation of Sc(III) from Y(III), La(III) and Yb(III) in [C₈mim][PF₆] containing Cyanex 925 has been investigated, and is reported in this paper. A cation exchange mechanism of Sc(III) in [C₈mim][PF₆] and Cyanex 925 is proposed by study of the influence of anionic and cationic species on the extraction. The coefficient of the equilibrium equation of Sc(III) was confirmed by slope analysis of log D_Sc vs log [Cyanex 925], and the loading capacity also confirmed the stoichiometry of Cyanex 925 to Sc(III) was close to 3:1. Infrared data for Cyanex 925 saturated with Sc(III) in [C₈mim][PF₆] indicated strong interaction between P?O of Cyanex 925 and Sc(III). In addition, the relationship between log D_Sc and temperature showed that temperature had little influence on the extraction process, and the resulting thermodynamic parameters indicated that an exothermic process was involved. Copyright © 2007 Society of Chemical Industry     

Extraction of Lanthanides(III) with N,N′-Bis(Diphenylphosphinyl-Methylcarbonyl)Diaza-18-Crown-6 in the Presence of Ionic Liquids

The extraction of microquantities of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y from nitric acid solutions into an organic phase containing N,N′-bis(diphenylphosphinyl-methylcarbonyl)diaza-18-crown-6 and ionic liquid (IL) 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide (BMImTf₂N) has been studied. The effect of HNO₃ concentration in the aqueous phase and that of the extractant and IL concentration in the organic phase on the extraction of metal ions is considered. The stoichiometry of the extracted complexes has been determined. A considerable synergistic effect was observed in the presence of IL in the organic phase containing a neutral organophosphorus ligand. This effect is connected with the hydrophobic nature of the IL anion. The partition of IL between the equilibrium organic and aqueous phases is the dominant factor governing the extractability of lanthanide (III) ions in the extraction system. The potentialities of polymeric resin impregnated with compound I and BMImTf₂N for the preconcentration of lanthanides(III) from nitric acid solutions are demonstrated.     

Extraction and separation of rare earths from chloride medium with mixtures of 2‐ethylhexylphosphonic acid mono‐(2‐ethylhexyl) ester and sec‐nonylphenoxy acetic acid

BACKGROUND: 2‐ethylhexylphosphonic acid mono‐(2‐ethylhexyl) ester (HEHEHP, H₂A₂) has been applied extensively to the extraction of rare earths. However, there are some limitations to its further utilization and the synergistic extraction of rare earths with mixtures of HEHEHP and another extractant has attracted much attention. Organic carboxylic acids are also a type of extractant employed for the extraction of rare earths, e.g. naphthenic acid has been widely used to separate yttrium from rare earths. Compared with naphthenic acid, sec‐nonylphenoxy acetic acid (CA100, H₂B₂) has many advantages such as stable composition, low solubility, and strong acidity in the aqueous phase. In the present study, the extraction of rare earths with mixtures of HEHEHP and CA100 has been investigated. The separation of the rare earth elements is also studied. RESULTS: The synergistic enhancement coefficient decreases with increasing atomic number of the lanthanoid. A significant synergistic effect is found for the extraction of La³⁺ as the complex LaH₂ClA₂B₂ with mixtures of HEHEHP and CA100. The equilibrium constant and thermodynamic functions obtained from the experimental results are 10^?0.92 (K_AB), 13.23 kJ mol^?1 (ΔH), 5.25 kJ mol^?1 (ΔG), and 26.75 J mol^?1 K^?1 (ΔS), respectively. CONCLUSION: Graphical and numerical methods have been successfully employed to determine the stoichiometries for the extraction of La³⁺ with mixtures of HEHEHP and CA100. The mixtures have different extraction effects on different rare earths, which provides the possibility for the separation of yttrium from heavy rare earths at an appropriate ratio of HEHEHP and CA100. Copyright © 2009 Society of Chemical Industry     

Extraction of Lanthanum and Samarium from Nitrate Medium by some Commercial Organophosphorus Extractants

Abstract

The extraction of lanthanum(III) and samarium(III) from nitrate solutions by some phosphine oxide compounds (Cyanex 921, Cyanex 923, and Cyanex 925) in kerosene was investigated. The influence of the different factors affecting the extraction was studied in detail. The extraction of these metals using the above extractants was compared and the sequence of extraction was found to be Cyanex 921>Cyanex 923?Cyanex 925. The stripping percent of La(III) and Sm(III) by 0.75 M HNO₃ from the loaded organic phase after two stages were 72% and 5.2%, respectively, which could enable a good separation between these two lanthanides.     

Complexation Behavior of Iron(III) with Aloxime 800, D2EHPA,CYANEX 272, CYANEX 302, and CYANEX 301

Abstract

The extraction of iron(III) has been studied from chloride solutions with di(2‐ethylhexyl)phosphoric acid (D₂EHPA), bis(2,4,4‐trimethylpentyl)phosphinic acid (CYANEX 272) and its sulfur‐substituted analogs, called CYANEX 302, and CYANEX 301, and 5‐dodecylsalicylaldoxime (Aloxime 800).

Job's method was applied for the characterization of the iron(III) complexes dissolved in hexane. In the case of D₂EHPA and CYANEX 272, a 1:1 ligand‐to‐metal ratio was observed, thus inferring the coordination of additional compounds. No chloride transport occurred during extraction, therefore suggesting the formation of [Fe(OH)₂L] complexes. With CYANEX 302, a ratio of 2:1 was obtained, whereas for CYANEX 301, the results of Job's method indicated the presence of four extractant molecules around the metal ion. Less hydrolysis or the possible oxidation of the sulfur‐substituted organophosphinic acids and the corresponding reduction of Fe(III) towards Fe(II) may explain this behavior. In the case of Aloxime 800, the formation of the [FeL₃] species is suggested.

A comparative study was carried out to identify the ligand‐to‐metal ratio of the iron(III) complexes in anhydrous circumstances. These studies showed that 1:1 ligand‐metal complexes are easily formed in the case of the organophosphoric‐ and organophosphinic‐acid extractants. A higher ligand‐metal ratio may be possible, but is not always a necessary condition for iron(III) extraction. Even the coexistence of [FeCl₂L], [FeClL₂] and to a smaller extent [FeL₃] is quite presumable in anhydrous media. Finally, FT‐IR spectra as well as UV‐VIS spectra of the hexane phases make it possible to gain a better insight into the complexation characteristics of iron(III).     

Ion Imprinted Polymer Solid Phase Extraction (IIP‐SPE) for Preconcentrative Separation of Erbium(III) From Adjacent Lanthanides and Yttrium

Abstract

Erbium(III) ion imprinted polymer (IIP) materials were prepared by photochemical polymerization of the ternary complex, Erbium(III)—5,7‐dichloroquinoline‐8‐ol‐4‐vinylpyridine, with methyl methacrylate (functional monomer) and ethylene glycol dimethacrylate (crosslinking monomer) in the presence of 2,2′‐azobisisobutyronitrile (initiator). The synthesis was carried out in 2‐methoxy ethanol (porogen) medium and the resultant material was filtered, dried and powdered to form unleached polymer particles. The imprint ion (erbium(III)) was removed by stirring the above particles with 6 mol/l HCl to obtain leached polymer particles. These leached particles are termed erbium(III) ion imprinted polymer (IIP) particles as it selectively rebind erbium(III) ions. Non‐imprinted/control polymer (CP) particles were similarly prepared without the imprint ion. CP and unleached and leached IIP particles were characterized by XRD, microanalysis, and UV‐visible spectrophotometric studies. Various parameters that influence ion imprinted polymer—solid phase extraction such as pH, weight of polymer particles, preconcentration time, elution time, eluent volume, and aqueous phase volume were varied and optimal conditions for each parameter for quantitative enrichment of erbium(III) were established. The selectivity coefficients of erbium(III) ion over Y, Dy, Ho and Tm were compared with separation factors reported for two of the best liquid—liquid extractants viz. di‐2‐ethylhexyl phosphoric acid and 2‐ethylhexyl‐ethylhexyl phosphate.     

Removal of Zinc(II) and Manganese(II) from Crude Phosphoric Media by Bis(2,4,4‐Trimethylpentyl) Phosphinic Acid (Cyanex‐272)

Purification of commercial phosphoric acid produced by the wet process from toxic heavy metals such as zinc and manganese is considered to be a very important environmental and economical process. The commercial bis(2,4,4‐trimethylpentyl)‐ phosphinic acid (Cyanex‐272) is proposed as an extractant for the efficient removal of Zn(II) and Mn(II) from crude phosphoric acid samples of concentrations of 25% and 45%. Various parameters affecting the extraction rate of Zn(II) and Mn(II) were investigated. The results were assessed to obtain the optimum conditions for the fast and efficient removal of both cations from crude phosphoric acid using Cyanex‐272 as an extractant in various diluents. The selectivity sequence of different diluents for Zn(II) and Mn(II) extraction were: kerosene > n‐hexane > cyclohexane > toluene > benzene > chloroform. The stripping of the investigated metal ions is efficiently performed with ammonium thiocyanate which has been selected as a suitable stripping agent.     

有机磷(膦)酸萃取钴和镍的动力学行为比较

依据实验结果和文献数据讨论了有机磷酸类萃取剂萃取钴及镍的动力学行为.结果表明,有机磷酸酸性强,溶入水相的速度快,则萃取速度亦快,钴和镍的萃取速度差异由溶剂交换速度决定.     

Removal of Cadmium(II) Ions from Chloride Solutions by Cyanex 301 and Cyanex 302

The main goal of this work was to study and compare the extraction of cadmium(II) ions by the two organophosphorous extractants: Cyanex 301 and Cyanex 302. The effect of different variables influencing the extraction of cadmium(II) ions such as the concentration of acid or metal ion and type of extractant has been investigated. Obtained results from the extraction process were compared with the FT-IR spectra. Results of spectrophotometric analysis confirm the observations of the extraction process, for example, the negative effect of hydrochloric acid on cadmium extraction by Cyanex 302.     

Extraction of Lanthanides(III) from Aqueous Nitrate Media with Tetra‐(p‐tolyl)[(o‐Phenylene)Oxymethylene] Diphosphine Dioxide

A novel tridentate neutral organophosphorus compound, tetra‐(p‐tolyl)[(o‐phenylene)oxymethylene] diphosphine dioxide (I) has been synthesized and its extracting ability for microquantities of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y from HNO₃ and NH₄NO₃ aqueous solutions has been studied. The effect of HNO₃ concentration in the aqueous phase and that of the extractant concentration in the organic phase on the extraction of metal ions is considered. The stoichiometry of the extracted complexes and conditional extraction constants of Ln(III) have been determined. The extraction behavior of compound I is compared with that of the diglycolamide ligand TODGA. The potentialities of polymeric resin impregnated with compound I for the preconcentration of lanthanides(III) from nitric acid solutions are demonstrated.     

Use of mixtures based on organophosphorous acids for the extraction of vanadium(IV) from model and industrial sulfurous solutions

We investigated the distribution of vanadium(IV) during extraction from model and actual technological sulfurous solutions by the organophosphorous acids di(2-ethylhexyl)phosphoric acid (DEHPA) and di(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272) using various solvents. We determined the most effective organic and organomineral mixtures for the extraction of vanadium(IV) from model and technological solutions of aqueous leach of used vanadium catalysts.