Extraction and separation of Zr,Nb and Hf by Aliquat 336 and its mixtures with TOPO from acidic thiocyanate media

Presence of thiocyanate ions results in appreciable extraction of Zr(IV) by Aliquat 336 from low aqueous HCl acidities, i.e., 0.1 to 4.5M. The variation of concentrations of HCl, thiocyanate and Aliquat 336 greatly influences the extent of extraction. Mixtures of Aliquat 336 and TOPO result in synergistic extraction of Zr and Hf from acidic thiocyanate media, the extracted species being the disolvate with TOPO. By controlled adjustment of HCl, SCN^– and Aliquat 336 concentrations, separation of Zr, Nb and Hf is possible. A maximum separation factor (D_Nb/D_Zr) of 3675 has been achieved under certain conditions.     

Separation of Zr and Hf from strong hydrochloric acid solution by solvent extraction with TEHA

In order to separate Zr(IV) and Hf(IV) from chloride solutions, TEHA (tri 2-ethyl hexyl amine) was used as an extractant. The aqueous phase consisted of 200 ppm of Zr and Hf in strong HCl solution. In our solvent extraction system, the extractability of the constituents by TEHA was found to be in the following order, HCl > Zr(IV) > Hf(IV). The highest separation factor between the two metals was obtained from 8 M HCl solution. Based on the selectivity towards Zr over Hf with TEHA, McCabe–Thiele plot was constructed and batch simulation of counter-current extraction studies has been conducted. Scrubbing results from the loaded TEHA showed that Hf was selectively scrubbed over Zr by strong HCl solution (9 M). Complete stripping of Zr was possible from the organic phase with distilled water after scrubbing of Hf. The extraction behavior of Zr and Hf by TEHA was compared with that by TiOA and TOA. Our results can be utilized in developing a solvent extraction process to separate Zr and Hf from concentrated chloride solutions by using TEHA.     

Separation of95Zr and95Nb from each other and from other fission products by adsorption and desorption on silica gel using hydrochloric acid solutions

The silica gel adsorption behaviour of zirconium, niobium, ruthenium and cerium in hydrochloric acid has been investigated by batch and column techniques. A satisfactory radiochemical separation of zirconium and niobium from each other and from other fission products has been achieved by a two column technique. The recommended procedure consists of sorption of all the nuclides on a primary silica gel column. Fifteen per cent of⁹⁵Nb, all of the zirconium and all of the other fission products are eluted first by washing with 5.5 M HCl. A second elution with concentrated hydrochloric acid then recovers the⁹⁵Nb (free from other products). The solution from the first elution after evaporation to 1 ml is then passed through another silica gel column and successively washed with 0.5M HCl, 5.5M HCl and concentrated HCl to obtain three fractions—other fission products—⁹⁵Zr free from other products—⁹⁵Nb free from other products, respectively.     

Extraction mechanism of rare earths from chloride acidic solution with ammonium-bifunctionalized ionic liquid extractants

A series of ammonium-bifunctionalized ionic liquid extractants(ammonium-Bif-ILEs) combined with a number of anions, including carboxylic acids and 1,3-diketonates, have been prepared and studied in this report. Their extraction behavior and properties toward rare earth ions(REs(Ⅲ)) are systematically investigated in chloride media as a function of important parameters such as aqueous phase p H, salting-out agent concentrations, and extraction temperature. The separation performance of ammonium-Bif-ILEs toward REs(Ⅲ) are systematically discussed. The results demonstrate that ammonium-Bif-ILEs have a synergistic effect between the cation and anions in separation of REs(Ⅲ). The influences of different anions on separation factor(b) values are further studied. By comparison, ammonium-Bif-ILEs containing 1,3-diketonates have more potential applications in La(Ⅲ)/RE(Ⅲ) separation than those containing carboxylic acids.     

Liquid-liquid extraction of tetravalent zirconium from acidic chloride solutions using Cyanex 272.

The liquid-liquid extraction of zirconium(IV) from acidic chloride solutions was carried out with Cyanex 272 as an extractant diluted in kerosene. An increase of the acid concentration decreased the percentage extraction of metal, which indicates that the extraction follows ion exchange-type mechanism: MO2+(aq) + 2(HA)2(org) <--> MO (HA2)2(org) + 2H+(aq), where, M = Zr(IV); HA = Cyanex 272. The extraction of Zr(IV) increases with an increase of the extractant concentration. In a plot of log D vs. log[extractant], M is linear with a slope of approximately 2, indicating the association of two moles of extractant with the extracted metal species. On the other hand, the extraction decreases with an increase of the H+ ion concentration. A plot of log D vs. log[H+] gave a straight line with a negative slope of 1.7, indicating the exchange of two moles of hydrogen ions for every mole of Zr(IV). The effect of the Cl- ion concentration at a constant concentration of [H+] did not show any change in the D values. The addition of sodium salts enhanced the percentage extraction of metal, and followed the order of NaSCN > NaNO3 > Na2SO4 > NaCl. The stripping of metal from the loaded organic (L.O) with different acids indicated sulfuric acid to be the best stripping agent. An increase of the temperature during the extraction and stripping stages increases the metal transfer, showing that the process is exothermic. The synergism, regeneration and recycling capacity of Cyanex 272; the extraction behavior of associated elements, such as Hf(IV), Ti(IV), Al(III), Fe(III); and IR spectra of the extracted Zr-Cyanex 272 complex were studied.     

Radiochemical extraction of mercury(II) from acidic chloride solutions using dialkylsulphides

The liquid-liquid extraction behavior of Hg(II) from aqueous acidic chloride solutions has been investigated by tracer techniques using dialkylsulphides (R₂S) namely, dibutylsulphide (DBS) and dioctylsulphide (DOS) as extractants. These extraction data have been analyzed by both graphical and theoretical methods by taking into account complexation of the metal ion in the aqueous phase with inorganic ligands and all plausible complexes extracted into the organic phase. The results clearly indicate that Hg(II) is extracted into xylene as HgCl₂ ^. nDBS/nDOS (where n = 2 and 3). The equilibrium constants of the extracted complexes have been deduced by non-linear regression analysis. The separation possibilities of Hg(II) from other metal ions viz. Ca(II), Mg(II), Ba(II) and Fe((III), which are present in the industrial wastes of the chlor-alkali industry has also been discussed.     

Synergistic extraction of uranium from acidic sulfate leach liquor using D2EHPA mixed with TOPO

Uranium extraction from sulfate leach liquor acid by D₂EHPA and TOPO mixture in kerosene was investigated. The effect of different factors affecting the extraction mechanism such as sulfate leach liquor acid, D₂EHPA and TOPO concentrations and temperature have been studied. The mathematical treatment for the obtained date suggested that the composition of synergistic extraction species is (UO₂(D)₂T). The logarithm of the apparent equilibrium constant, log Kex, of synergistic extraction reaction has been evaluated, to be 3.35 ± 0.1. The effect of temperature on extraction process was investigated and the apparent values of the thermodynamics parameters (?H, ?G and ?S) were 38.2 kJ/mol, ?19.1 kJ/mol and 192.5 J/mol respectively.     

聚二甲基二烯丙基氯化铵及其与CTAB混合物水溶液 的吸附动力学

用最大泡压法分别测定了聚二甲基二烯丙基氯化铵,十六烷基三甲基溴化铵以及两者混合物水溶液的动表面张力。十六烷基三甲基溴化铵的吸附服从扩散-动力学控制机理。发现聚二甲基二烯丙基氯化铵水溶液的表面张力具有独特的时间相关性。吸附的前期服从扩散控制机理,而在吸附的后期,即接近吸附平衡时服从扩散-动力学控制机理。混合物水溶液的整个吸附过程受扩散控制。     

Phosphonium ionic liquids as extractants for recovery of ruthenium(III) from acidic aqueous solutions

The aim of this work is to investigate extraction of ruthenium(III) from acidic aqueous solutions with phosphonium ionic liquids such as trihexyl(tetradecyl)phosphonium chloride (Cyphos IL 101), trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate (Cyphos IL 104) and tributyl(tetradecyl)phosphonium chloride (Cyphos IL 167) as extractants. The influence of HCl content in the feed solutions on extraction of Ru(III) was investigated. The research was performed for model solutions containing Ru(III) and a mixture of waste solutions containing Ru(III) and Rh(III). In addition, investigation of the type of extractant and its concentration in the organic phase on extraction of Ru(III) was carried out. Co-extraction of protons to the organic phase was determined. To the best of our knowledge, the extraction of Ru(III) with Cyphos IL 167 (tributyl(tetradecyl)phosphonium chloride) as an extractant has not yet been described in the scientific literature.     

Solvent extraction of europium from aqueous-organic solutions by solvating extractants

The partition of Eu(III) between benzene containing solvating extractants (TBP, TOPO, dioctylsulfoxide) and aqueous nitrate, perchlorate and thiocyanate solutions containing various organic solvents miscible with water (alcohols, acetone, acetonitrile, ethylene glycol, dimethyl sulfoxide and dimethylformamide) was investigated. Depending on the specific extraction system, the presence of organic solvents in the mixed phase showed various effects on the distribution ratio of Eu(III). These were discussed in terms of solute-solvent interactions. The results in the systems containing dimethylformamide and dimethyl sulfoxide indicated complexation of Eu(III) with these solvents in the polar phase.     

Sorption of Hf, Zr and Nb on organic and inorganic ion-exchangers from mineral acids solutions

Sorption coefficients of Hf, Zr and Nb on nickel-potassium hexacyanoferrate(II) (NF), nickel hexacyanoferrate(II) composite ion exchanger (NCF) and on the ion exchange resins (Dowex-1 and Dowex-50) from inorganic acids solutions were determined. The results obtained indicate that hafnium, zirconium and niobium in dilute sulphuric and hydrochloric acids form anionic and cationic complexes which sorbed on the ion exchangers studied.     

Mathematical modeling of solvent extraction of uranium from sulphate media employing 2-ethylhexyl phosphonic acid-mono-2-ethylhexyl ester (PC88A) and its mixture with trioctylphosphine oxide (TOPO) as extractants

The extraction of U(VI) from sulphate medium with 2-ethylhexyl phosphonic acid-mono-2-ethylhexyl ester (PC88A, H₂A₂ in dimeric form) in n-dodecane has been investigated under varying concentrations of sulphuric acid and uranium. Slope analysis of uranium (VI) distribution data as a function of PC88A concentration suggests the formation of monomeric species, viz. UO₂(HA₂)₂. This observation was further supported by the mathematical expression obtained during non-linear least square regression analysis of U(VI) distribution data correlating the percentage extraction (%E) and the acidity (H _i). A mathematical model correlating the experimental distribution ratio values of U(VI) (D _U) with initial acidity (H _i) and initial uranium concentrations (C _i) was developed: D_\textU = 12.98( ±0.90)/{ C_\texti ^{- 0.75( ±0.05)} ×[ H_\texti ]² } D_{\text{U}} = 12.98( \pm 0.90)/\left\{ {C_{\text{i}}^{ - 0.75( \pm 0.05)} \times \left[ {H_{\text{i}} } \right]^{2} } \right\} . This expression can be used to predict the concentration of uranium in organic as well as in aqueous phase at any C _i and H _i. The extraction data were used to calculate the conditional extraction constant (K _ex) values at different acidities (2–7 M H⁺), uranium (0.02–0.1 M) and PC88A (0.2–0.6 M) concentrations. These studies were also extended for the extraction of U(VI) using synergistic mixtures of PC88A and TOPO from sulphate medium.     

Extraction of tungsten and rhenium by basic or neutral extractants in xylene from mineral acidic media

Extraction of WO ₄ ^2– and ReO ₄ ^– by Adogen-381, tricaprylmethylammonium chloride, Hyamine 10-X, trioctylphosphine oxide or dibenzylsulphoxide in xylene from HNO₃, HCl or H₂SO₄ acid medium was investigated. Based on the separation factors obtained, the separation of ReO ₄ ^– from WO ₄ ^2– was elucidated. ReO ₄ ^– was separated from WO ₄ ^2– in high radiochemical purity: >99.9% by three successive extractions and strippings using Adogen-381 from HCl or HNO₃ acid medium.     

Removal of zinc ions as zinc chloride complexes from strongly acidic aqueous solutions by ionic exchange

The aim of this study was to compare several anion exchangers and to investigate the capacity of Amberlite IRA410 to remove zinc as chloride [ZnCl₃]^? from hydrochloric solutions (1 M). Influence of the process parameters such as stirring rate, resin quantity and zinc initial concentration over the removal process, was considered. The highest experimental ionic exchange capacity between the considered anionic exchangers, in the same working conditions (500 rpm, 5 g resin and 500 mg L^?1), was obtained for Amberlite IRA410, 8.34 mg g^?1. With an increase of zinc ions concentration, ionic exchange capacity increased up to 19.31 mg g^?1 (1100 mg L^?1). The experimental data were analysed using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. The results were also analyzed using sorption kinetics models, pseudo-first-, pseudo-second-order, intra-particle and film diffusion models. From the Dubinin-Radushkevich and Temkin isotherm models the mean free energy and heat of sorption were calculated to be 7.45 kJ mol^?1, respectively 1×10^?4 kJ mol^?1, which indicates that zinc sorption is characterized by a physisorption process. Kinetic studies showed that the adsorption followed a pseudo-second-order kinetic model.     

Separation of95Zr and95Nb by means of sorption on silica gel from hydrochloric acid solutions

The adsorption behaviour of zirconium and niobium on silica gel from hydrochloric acid solutions was studied by batch equilibrations and passage through columns. On the basis of this, new methods are suggested for the separation and purification of⁹⁵Zr and⁹⁵Nb in hydrochloric acid and hydrochloric acid—methanol solutions. The methods are comparatively simple and rapid, and both zirconium and niobium can be obtained in a radiochemically pure state.     

Preconcentration of trace metals from acidic solutions by coprecipitation with dithizone

Traces of Ag, Bi, Cd, Cu, Hg, Pb, Pd and Zn are separated by carrier precipitation with dithizone from diluted HNO₃ and HCl solutions. The separated trace elements are determined by flame AAS and/or by spectrophotometry. The preconcentration recovery is dependent on the acid concentration of the sample solution. The amount of dithizone precipitated is optimized. The detection limits (ng/ml) are 15.0 (Pb, Zn), 12.0 (Pd), 10.0 (Bi), 6.0 (Ag), 5.0 (Hg), 2.0 (Cu) and 1.0 (Cd). Aluminium, aluminium sulfate and gallium are analyzed with the method. The accuracy of the results was checked by differential pulse voltammetry.     

Electrical conductivity investigation of diluted potassium chloride solutions in binary mixture triethylamine-water near its consolute point

The binary liquid mixture of triethylamine + water (TEA-W) has a lower consolute point at a critical composition of 32.27 mass % triethylamine. Starting at a temperature within the one-phase region, the electrical conductivity of a sample of this mixture with addition of (K⁺, Cl⁻) ions was measured and found to be accurately described by the Vogel-Fulcher-Tammann (VFT) law. Before that, for the pure system, in a temperature range ΔT = T_c − T < 2 °C where T_c is the critical temperature, the electrical conductivity (σ) exhibits a monotonous deviation from the VFT behaviour. This anomaly is finite at T_c. The asymptotic behaviour of the electrical conductivity anomaly is described by a power law t^1−α, where t is the reduced temperature |(T−Tc)/Tc| and α is the critical exponent of the specific heat anomaly at constant pressure. For the electrolyte mixtures, by combining the viscosity and the electrical conductivity data, the value of the computed Walden product has been determined and the salt dissociation degrees as well as the Debye screening length have been estimated.     

Liquid-liquid solvent extraction of rare earths from chloride medium with sec-nonylphenoxy acetic acid and its mixtures with neutral organophosphorus extractants

In the present study, sec-nonylphenoxy acetic acid (CA100) and its mixtures with four neutral organophosphorus extractants, tri-butyl-phosphate (TBP), 2-ethylhexyl phosphonic acid di-2-ethyl ester (DEHEHP), Cyanex923, and Cyanex925 have been applied to the extraction of rare earths. Results show that all the four mixing systems do not have evident synergistic effects on the extraction of rare earths. The different extraction effects have been considered to the separation of rare earths. The four mixtures may be applied to the separation of yttrium from some certain lanthanoids at proper mole fractions of CA100.     

TOPO萃取色谱分离钨,钼的研究

研究了用TOPO的二甲苯溶液从盐酸水溶液中单取分离钨、钼的条件,测定了萃取配合物的组成及萃取平衡常数,提出了分离钨、钼的萃取色谱法,并用于合金钢及地球化学样品中钨和钼的测定。     

Separation of poly (vinyl chloride) from poly(ethylene terephthalate) and other plastics using automatic sortation devices

While most poly(vinyl chloride) (PVC) produced in the United States is used in the manufacture of durable building products, emphasis recently has been directed at recovery of PVC from post-consumer disposable items such as bottles, rigid containers and rigid film. Manual sortation involving visual inspection for either the characteristic blow molding scar or code marking is at best only 90% accurate. Recent activity has focused on development of automatic sortation based on recognition of the chlorine atom which serves as a “fingerprint” for identifying PVC. Two separate technologies for sortation of such packaging are discussed in this paper - the first involves X-ray fluorescence, the second utilizes electromagnetic radiation absorption.