Solvent extraction of lanthanum(III) from sulphuric acid solutions by Primene JMT

The distribution of lanthanum(III) between aqueous H₂SO₄ solutions and Primene JMT in the organic phase is described. The dependence of the extraction on acidity, extractant concentration and type of diluent was investigated. Aggregation numbers are calculated and a mechanism for the extraction is suggested. The separation of thorium(IV) from lanthanum(III), cerium(III) and cerium(IV) is outlined.     

Liquid-solid extraction system based on between 40-salt-H(2)O without organic solvents

An aqueous solution of Tween 40 forms liquid and solid phases in the presence of various salts, depending on the Tween 40 concentration, the identity and concentration of the salt, and the solution acidity. The distribution of Zr(IV), U(VI), Fe(III), Pb(II) and some organic photometric reagents between the Tween 40 phase and aqueous phase containing salt was examined. The quantitative extraction, separation and determination of Zr(IV) or U(VI) in the presence of Pb(II) was achieved by controlling the solution acidity in the system. The extraction mechanism has been tentatively studied.     

On-line extraction of metal ions using liquid-liquid segmentation and a membrane type phase separator for fluorescence detection

Summary A liquid segmented post-column reaction system has been used to extract metal ions from an aqueous eluent into an organic solvent for fluorescence detection. The metals Zr(IV), Ga(III), Sc(III), Y(III), In(III), Al(III), La(III), Zn(II), Cd(II), Ca(II) and Mg(II) have been isocratically separated on a C₁₈ column by virtue of the secondary chemical equilibrium established by an eluent containing n-octanesulfonate, tartaric acid, and hydroxyisobutyric acid. The chelating reagent 8-hydroxyquinoline dissolved in methylisobutyl ketone (MIBK) was used to extract the metals and a membrane type phase separator was effective at separating the phases and directing the organic stream to the detector. The response for this detection approach was linear for metal ion concentrations spanning the range of the detector, and detection limits for most metals were low parts-per-billion (ppb). Band broadening for the extraction system was examined and compared to a direct post-column reaction using oxine dissolved in acetone.     

Di(2-ethylhexyl)sulfoxide as an extractant for plutonium(IV) from nitric acid medium

The liquid-liquid extraction behavior of plutonium(IV) from aqueous nitric acid media into n-dodecane by di(2-ethylhexyl)sulfoxide (DEHSO) was investigated over a wide range of conditions. Optimum-parameters such as the aqueous phase acidity, reagent and metal concentrations, etc., were established for efficient extraction-separation of tracer as well as macro levels of plutonium. It was found that the extraction increased with increasing nitric acid concentration up to 6M HNO₃ and then decreased. Extraction also increased with increasing extractant concentration. After loading of the organic phase with 2 to 50 mg/ml of U(VI), extractability of Pu(IV) became considerably lower. Recovery of Pu(IV) from the organic phase was accomplished using dilute uranium(IV) nitrate as the strippant.     

Extractive photometric determination of plutonium(IV) with Aliquat-336 and xylenol orange

A rapid extractive photometric method using Aliquat-336 and xylenol organe for the determination of plutonium(IV) at μg levels has been developed. Quantitative extraction is obtained from ∼4M aqueous HNO₃ medium, affording estimation in the presence of several commonly occurring impurities, viz. iron, uranium, fission products and cladding materials. Effects of acidity, reagent concentration and diverse ions on the estimation have also been invetigated. Unlike the well-known absorptiometric method for determining plutonium(IV) employing Arsenazo III, the procedure presented here tolerates manyfold excesses of uranium(VI) as well as chromium(III), iron(III) and zirconium(IV), which are some of the major contaminants of plutonium during reprocessing.     

Extraction of bismuth(III) with 2-bromoalkanoic acid in nondonating solvent from highly acidic aqueous solution.

The extraction behaviors of bismuth(III) with carboxylic acid (HL), which have not yet been clearly elucidated, because of the precipitation of hydroxide, were studied using the 2-bromoalkanoic acid in benzene and in hexane systems under aqueous conditions of high acidity at I = 1.0 M ((H,Li)NO3). The extraction equilibria were analyzed based on the-initial concentration of nitric acid and the concentration of bismuth(III) extracted in the organic phase. The extracted species and the logarithmic values of the extraction constant (log Kex) were found to be a single species of BiL3(HL)3 for the systems of 2-bromooctanoic acid/benzene (log Kex = -1.66) and 2-bromohexadecanoic acid/benzene (-1.58), and to be two species of BiL3(HL)4 (-1.01) and Bi3L9HL (-1.62) for the system of 2-bromooctanoic acid/hexane, where the monomer was dominant at a higher reagent concentration.     

Extraction of U(VI), Pu(IV), Am(III) and some fission products by 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester immobilized polyvinyl alcohol hydrogels

Cross-linked hydrogel matrices immobilized with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (HA), were prepared to investigate their application in the recovery of radionuclide from acidic waste solutions. Gamma-radiation was used to produce HA immobilized polyvinyl alcohol (PVA) hydrogels (HA-gel). The hydrogels with different characteristics such as: degree of cross-linking (by varying radiation dose) and quantity of extractant immobilized (by starting with aqueous PVA solution containing different amounts of HA), were synthesised. These HA-gels were investigated for solid-liquid phase extraction of U(VI), Pu(IV), Am(III) and some fission products, under various experimental conditions. The concentration of HNO₃ in the aqueous phase was found to play an important role in the extraction of these radionuclei. Extraction of U(VI) was more favourable at lower concentration of HNO₃ (∼0.001 to 0.5M), while at higher concentrations (∼0.5 to 3M HNO₃), more than 90% of Pu(IV) present in the aqueous phase, could be extracted by the HA-gel. The extraction of Am(III) was also found predominant only at lower acidities (at pH∼2 and above). Under optimized conditions, maximum metal loading capacities obtained were 19±0.8 mg, 8±0.4 mg and 11±0.5 mg per gram of swollen HA-gel, for U(VI), Pu(IV) and Am(III), respectively. Under the experimental conditions, extractions of Cs(I) and Sr(II) were observed to be negligible. No leaching out of HA from the HA-gel particles was noted even after its repetitive use for the studied ten cycles of extraction and stripping experiments, as evident from its unchanged extraction efficiency.     

Studies on the extraction behavior of Zr(IV), Ce(III), Th(IV) and U(VI) from aqueous solutions of Arsenazo-I with HDEHP,HTTA, TDA and TCMA

The extraction behavior of Zr(IV), Ce(III), Th(IV) and U(VI) from aqueous solutions containing Arsenazo-I with the organic solvents tridodecylamine (TDA), 1-[thenoyl-(2)]-3-3-3-trifluoroacetone (HTTA), di(2-ethylhexyl) phosphoric acid (HDEHP) and tricaprylmethylammonium chloride (TCMA) in xylene has been investigated. Effect of hydrogen ion concentration in the aqueous phase, Arsenazo-I concentration, as well as the effect of solvent concentration on the extraction was studied. Some alternatives for separation of the elements studied were recommended enabling the spectrophotometric determination of these elements using Arsenazo-I without interference.     

Cloud point extraction: an alternative to traditional liquid-liquid extraction for lanthanides(III) separation

Cloud point extraction (CPE) was used to extract and separate lanthanum(III) and gadolinium(III) nitrate from an aqueous solution. The methodology used is based on the formation of lanthanide(III)-8-hydroxyquinoline (8-HQ) complexes soluble in a micellar phase of non-ionic surfactant. The lanthanide(III) complexes are then extracted into the surfactant-rich phase at a temperature above the cloud point temperature (CPT). The structure of the non-ionic surfactant, and the chelating agent-metal molar ratio are identified as factors determining the extraction efficiency and selectivity. In an aqueous solution containing equimolar concentrations of La(III) and Gd(III), extraction efficiency for Gd(III) can reach 96% with a Gd(III)/La(III) selectivity higher than 30 using Triton X-114. Under those conditions, a Gd(III) decontamination factor of 50 is obtained.     

Extraction of metal ions with a primary amine

This paper describes some experimental results obtained at the extraction of sulfate solutions of U(VI), Mo(VI), V(V), Ce(IV), Zr(IV), Fe(III), Al(III) with a benzene solution of Primene JMT. The aqueous solutions consist of metal sulfates (or other metal salts) in the presence of sulfuric acid with a concentration range of 0–2.1 mol·dm^–3, the concentration of amine in the organic phase being 0.1–0.3 mol·dm^–3. The presence of various species of metal ions in the aqueous phase is considered and the equilibrium concentration of substances extracted in the organic phase is determined. On the basis of the results of chemical analysis (concentration of metals and sulfate ions) the composition of the prevailing complexes in the organic phase is proposed.     

Extraction of americium,lanthanides and some fission product elements by bidentate phosphonates

The extraction of Am, Eu, Ce(III), Zr(IV), and Sr from aqueous nitric acid— nitrate media by dibutyl N,N-diethylcarbamylphosphonate and dibutyl N,N-diethylcar-bamylmethylenephosphonate dissolved in carbon tetrachloride was studied. The trivalent actinide and lanthanide elements may be separated in certain aqueous phase acidity regions from Fe(III), Zr(IV), and Sr, whereas the separation of actinide elements from the lanthanide elements is poor. The extractant to metal ratio in the extracted complexes of Am, Eu, and Ce(III) is 3. The interferences in the extraction due to acidic impurities in the extracting agent are discussed.     

Effect of acidity on the extraction and kinetic stability of the copper(II)/APCD/IBMK system in strongly acidic media

The extraction of copper(II) from strongly acidic solution (0.01-8M hydrochloric acid) with ammonium 1-pyrrolidinecarbodithioate in isobutyl methyl ketone has been investigated. The shaking time needed for quantitative extraction decreases as the acidity is increased. The effect of the mutual solubility of the organic solvent and the aqueous phase is significant when the acidity of the aqueous phase is increased. The acidity of the aqueous phase mainly affects the kinetic stability of the chelate during the shaking period, rather than the decomposition of the chelating agent. The kinetic stability of the chelate apparently depends on the mole ratio of reagent to copper, the half-lives for the chelate extracted from 4M hydrochloric acid being 29.0, 40.0 and 85.0 min for reagent: metal mole ratios of 10, 100 and 1000, respectively.     

Kinetics of iron(III) bromide extraction with n-tributyl phosphate

The equilibrium and rate of solvent extraction of FeBr₂ complexes from HBr solutions into benzene solutions of tributyl phosphate (TBP) have been investigated. It is found that two reactions control the iron(III)-TBP extraction from hydrobromic acid solutions. From HBr activity of 1.2–1.55 (molarity based) the reaction is inverse third order with respect to the aqueous phase acidity. From HBr activity of 1.7–6 (molarity based) the reaction is first order in HBr concentration in the aqueous phase. Both of these reactions are first order for both Fe(III) and TBP. The rate constants for these reactions were calculated and the rate-controlling steps are discussed.     

Investigation on liquid-solid extraction system of polyvinylpyrrolidone-(NH4)2SO4-H2O by using bromopyrogallol red as extractant

In the presence of ammonium sulphate or other inorganic salts, the aqueous solution of polyvinylpyrrolidone (PVP) can be separated into liquid and solid phases. The distribution behaviour of bromopyrogallol red (BPR), Cu(II), Bi(III), Sc(III) and Zr(IV) between the liquid and solid phases was studied. The quantitative extraction separation of some metal ions based on this system was carried out by controlling the acidity of the solution. The extraction mechanism for the PVP solid phase was further discussed.     

Bis(2-ethylhexyl)sulfoxide as an extractant for americium(III) from aqueous nitrate media

Solven extraction separation of americium(III) from dilute aqueous nitrate media into n-dodecane by bis(2-ethylhexyl)sulfoxide (BESO) has been investigated over a wide range of experimentgal conditioins. Very poor extractablity of Am(III), necessitated the use of calcium nitrate as the salting-out agent. Effects of certain variables such as acidity, extractant concentration, salting-out agent concentration, organic diluents on the metal extraction by BESO have been examined in detail. By increasing the concentration of BESO in organic phase or calcium nitrate in aqueous phase, nearly quantitative extraction of americium even from moderate acidity is accomplished. Slope analyses applied to Am(III) distribution experiments from acidic nitrate solutions indicate predominant formation of the risolvated organic phase complex, Am(NO₃)₃)·3BESO for which equilibrium constant is found to be, log K_x=1.99. Extraction behavior of Am(III) has also been evlauated in the presence of several water-miscible polar organic solvents to stuy their possible synergistic effects on its extraction. Extractability of americium increased 5 to 10-fold withi increasing conentration of some of these additives, with maximum enhancement being observed in the presence of acetone or acetonitrile. Recovery of BESO from loaded americium is easily obtained using dilute nitric acid as the strippant.     

Extraktionsmethode zur Trennung kleiner Tellurmengen von Begleitelementen

Zusammenfassung Zur Trennung von Tellur aus Lösungen mit komplizierter Zusammensetzung wurde eine kombinierte Extraktionsmethode entwickelt. Die Extraktion von Eisen(III), Arsen(V), Antimon(V), Gold(III), Thallium(III), Wismut(III), Zinn(IV) und Selen(IV) erfolgt mit Diisopropyläther aus 8 M Salzsäure, wobei das gesamte Te(IV) in der wäßrigen Phase verbleibt. Diese wird dann mit Methylisobutylketon aus 4 M Salzsäure extrahiert, während in der wäßrigen Phase Kupfer(II), Aluminium(III), Silber(I), Nickel (II), Kobalt(II), Zink(II), Cadmium(II) und Blei(II) verbleiben. Die vollständige Abtrennung der Begleitelemente des Tellurs erfolgt durch zusätzliche Extraktion ihrer Kupferronate mit Methylisobutylketon bei pH 3–5. Das vorgeschlagene Extraktionsverfahren kann mit jeder bekannten Methode zur Bestimmung geringer Tellurmengen kombiniert werden.

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Extraction method for the separation of small quantities of tellurium from accompanying elements

A new combined solvent extraction method is proposed for the separation of tellurium from solutions of complex composition. Iron(III), arsenic(V), antimony(V), gold(III), thallium(III)J bismuth(III), tin(IV) and selenium(IV) are extracted with diisopropyl ether from 8 M hydrochloric acid. Under these conditions tellurium(IV) is quantitatively retained in the aqueous phase. Subsequently tellurium(IV) is extracted from 4 M hydrochloric acid with methylisobutyl ketone, so that copper(II), aluminium(III), silver(I), nickel(II), cobalt(II), zink(II), cadmium(II) and lead(II) remain in. the aqueous phase. The complete separation of the accompanying elements is realized by an additional extraction of their cupferronates with methylisobutyl ketone at pH 3–5. The separation described can be combined with any known method for the determination of small amounts of tellurium(IV).

     

Palladium(II) extraction with 1-{[2-(2,4-Dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]-methyl}-1H-1,2,4-triazole from nitric acid solutions

Palladium(II) extraction from nitric acid solutions with 1-{[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]-methyl}-1H-1,2,4-triazole in toluene is studied. The reagent efficiently extracts palladium(II) from 0.2–6 M HNO₃ by a coordination mechanism yielding the complex Pd₂(NO₃)₄ S ₃ in the organic phase. The reagent can be used for selective separation of palladium(II) from nickel(II), copper(II), and iron(III) in the specified aqueous phase acidity range.     

Extraction of gallium(III) by 1-{[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl}-1H-1,2,4-triazole from hydrochloric acid solutions

The extraction of gallium(III) with 1-{[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2- yl]methyl}-1H-1,2,4-triazole from hydrochloric acid solutions into toluene was studied. It was found that gallium( III) was efficiently extracted from 5–10 M solutions of HCl by the anion-exchange mechanism. The following metal extraction order was determined in the above aqueous phase acidity range: Ga(III) > In(III) > Al(III). The concentration constants and the thermodynamic parameters of the reaction of gallium(III) extraction from 6 M solutions of HCl at 25 °C were calculated.     

A modified method of separating Tl(I) and Tl(III) in aqueous samples using solid phase extraction

In spite of the development of new measurement techniques in recent years, the rapid and accurate speciation of thallium in environmental aqueous samples remains a challenge. In this context, a novel method of solid phase extraction (SPE), involving the anion exchange resin AG1-X8, is proposed to separate Tl(I) and Tl(III). In the presence of diethylene triamine pentacetate acid (DTPA), Tl(III) and Tl(I) can be separated by selective adsorption of Tl(III)-DTPA onto the resin, Tl(III) is then eluted by a solution of HCl with SO₂. The validity of this method was confirmed by assays of standard solutions of Tl(I) and Tl(III). The proposed method is shown to have an outstanding performance even in solutions with a high ratio of Tl(I)/Tl(III), and can be applied to aqueous samples with a high concentration of other electrolytes, which could interfere with the measurement. Portable equipment and reagents make it possible to use the proposed method routinely in the field.     

Selective separation and extraction of copper(II), iron(II,III), and Cerium(III,IV) ions from aqueous solutions by electroflotation method

Possibility of the electroflotation separation and extraction of cerium(II, IV), copper(II), and iron(II, III) from aqueous solutions is demonstrated. The optimal pH value and the concentration ratio of ions of the metals being separated, at which their electroflotation separation and extraction from aqueous solutions is the most efficient, was determined. It was shown that the electroflotation method is promising for selective separation and extraction of metal ions with various hydrate-formation pH values from aqueous solutions.