Electrodialytic recovery of cobalt(II) with liquid membranes based on di(2-ethylhexyl)phosphoric acid

Electrodialytic transfer of cobalt(II) from sulfuric acid solutions across liquid membranes containing di(2-ethylhexyl)phosphoric acid with addition of tri-n-octylamine in 1,2-dichloroethane was studied, with the metal electrodeposited from dilute solutions of various acids. The influence exerted by the electrodialysis current density and by the composition of aqueous solutions and liquid membranes on the rate of cobalt(II) transport and electrodeposition was examined.     

Electrodialytic separation of cobalt(II) and nickel(II) using liquid membranes based on tri-n-octylamine and trialkylbenzylammonium chloride

Electrodialytic separation of Co(II) and Ni(II) in the course of their transfer from 3–4 M HCl solutions into dilute solutions of various acids using liquid membranes that contain anion-exchange carriers was studied. The influence exerted on the metal transport rate and separation efficiency by the compositions of the feed and receiving aqueous solutions and of liquid membranes and by the electrodialysis current density was examined. Under optimal conditions, in metal recovery from a solution containing an equimolar mixture of 0.01 M CoCl₂ and NiCl₂, the separation factor β_Co/Ni is 147; when nickel in the feed solution is in excess, it reaches 330, and when cobalt(II) is in excess, it exceeds 400.     

Electrodialytic recovery of iron(III) with liquid membranes based on diphenylthiocarbamide in the presence of palladium(II)

Separation of iron(III) and palladium(III) in recovery from binary hydrochloric solutions with liquid membranes containing diphenylthiocarbamide in 1,2-dichloroethane was studied under galvanostatic electrodialysis conditions. The effect of the current density, process duration, and compositions of the receiving solution and liquid membrane on the iron(III) recovery rate was examined.     

Ion exchange recovery of chromium (VI) and manganese (II) from aqueous solutions

Sorption recovery of toxic ions – chromium (VI) and manganese (II) – from aqueous solutions with different acidity (0.001–0.5 M HCl) was investigated on cation and anion exchangers synthesized with long-chained cross-linking agents (LCA). The initial concentrations of Cr(VI) and Mn(II) were 1 g/L and 5 g/L, respectively. It was shown that the resins with LCA possess high ionic permeability due to the elasticity of polymeric skeleton. High selectivity and good kinetic properties of these sorbents allowed to achieve quantitative (∼100%) recovery and separation of manganese (II) and chromium (VI) in counter-current columns, which results in the complete purification of solutions from toxicants (below the maximum permissible limits), whereas the valuable components (chromium and manganese) can be returned back to industrial process.     

The sorption of molybdenum(VI) by ionites from solutions in hydrochloric acid

The sorption of molybdenum(VI) by KU-2 × 8 and AV-17 × 8 ionites from solutions in hydrochloric acid (1 × 10⁻⁵−6 N) was studied. Changes in the sorption of molybdenum(VI) by cationite and anionite were observed. The isoelectric point of molybdenum in solutions in hydrochloric acid was determined from sorption and electrical migration measurements.     

Supported liquid membranes (SLM) for recovery of bismuth from aqueous solutions

In this study, the extraction of Bi(III) from synthetic solutions of 2 M H₂SO₄/0.5 M HCl by supported liquid membranes (SLM) using tri-n-octylphosphine oxide (Cyanex 921) as extractant is reported. First, the nature of the Bi(III)/Cyanex 921 solvates extracted to organic phase (in a solvent extraction system) was determined by the slope method. It was found that Bi(III) reacts with 2 molecules of Cyanex 921 to form the solvate BiCl₃·2Cyanex 921. In the recovery of Bi(III) by the SLM system, parameters that influence extraction efficiency were evaluated, including: support, feed solution and stripping solution nature, and extractant concentration in the organic phase which impregnates the support. Results indicate that Cyanex 921 dissolved in kerosene is not able to extract Bi(III) from H₂SO₄ media. Moreover, transfer of H₂SO₄ was observed. HCl addition to the feed solution up to a maximum concentration of 0.5 M increases Bi(III) extraction. Further increase in HCl concentration causes a decrease in Bi(III) transfer. Likewise, the concentration of Cyanex 921 in the SLM organic phase which produced the maximum Bi(III) extraction was found to be 0.3 M. The performance of H₂O and 0.2 M H₂SO₄ as stripping solutions was evaluated, and it was found that only H₂SO₄ enabled Bi(III) transfer.     

Chromaticity characteristics of chromium(VI) solutions

The light-absorption spectra of solutions of chromium(VI) in the form of dichromate (pH 1–5) and chromate (pH 7–9) have been studied. The solutions have maxima of light absorption at 360 and 380 nm and molar extinction coefficients of 155 ± 7 and 935 ± 27 for Cr₂O ₇ ^2? and Cr O ₄ ^2? respectively. The chromaticity functions of these chromium(VI) forms have been investigated and it has been shown that they are 1.0–1.5 orders of magnitude higher than the molar extinction coefficients. In all cases, the yellowness is maximal.     

Electrodialysis of pectin-containing solutions of hydrochloric acid with ion-exchange membranes

The process of electrodialysis of 0.05 M hydrochloric acid solutions containing 0.2% pectins with different molecular mass was studied using ion-exchange membranes. It is found that occurrence of the process at the current density of 5 mA/cm² allows achieving the solution demineralization degree of 87–90% and acid regeneration degree of 86–92% at current efficiency of 63–77%. Higher process indicators are observed in the case of electrodialysis of solutions containing pectin of a lower molecular mass.     

Extraction of rhodium(III) with sulfoxides from hydrochloric acid solutions

Extraction of rhodium(III) from hydrochloric acid solutions with dihexyl sulfoxide (DHSO) and with petroleum sulfoxides (PSOs) was studied, and the optimal conditions for its recovery were found. At a phase contact time of up to 0.5 h, the extraction of rhodium(III) with sulfoxides occurred mainly by an ionassociation scenario. If the phase contact time exceeds 0.5 h, a mixed extraction scenario predominated to form the extracted complexes (L · H⁺) · [RhCl₄L₂]-(DHSO)_o and PSO (LH⁺) · [RhCl₄(H₂O) · L]⁻. The protonation of the extraction agents occurred at the donor oxygen atoms of the sulfoxide group. When rhodium was extracted with PSOs, the coordination of the extractant molecule in the inner coordination sphere of the acido complex to the metal ion occurred through the donor sulfur atom of the sulfoxide group, while with the use of DHSO, through the donor atoms of sulfur and oxygen of the sulfoxide group. Electronic, ¹H NMR, and IR spectroscopy and elemental analysis were used to determine the composition of the extracted compounds and suggest their structure.     

Iridium(IV) extraction with petroleum sulfoxides from hydrochloric acid solutions

Iridium(IV) extraction with petroleum sulfoxides (PSO) from hydrochloric acid solutions is studied. Optimum conditions of extraction are chosen. It is shown that in the investigated extraction systems for a phase contact time of 30 min, iridium(IV) is extracted by the ion-associative mechanism. Electronic, ¹H NMR, and IR-spectroscopy, and elemental analysis are used to establish the structure of the extracted compound.     

Palladium(II) extraction from hydrochloric acid solutions with diacylated triethylenetetramine

Extraction of palladium(II) with diacylated triethylenetetramine hydrochloride (with chloroform as diluent) from hydrochloric acid solutions was studied. Palladium(II) extraction from 3 mol/L HCl solutions occurs via anion-exchange mechanism. Concentrational constants were calculated and thermodynamic parameters of extraction were estimated.     

Kinetics of chromium(VI) adsorption from model solutions on iron oxide

Adsorption of Cr(VI) on Fe₂O₃ from model solutions with various Cr(VI) concentrations was studied. The adsorption capacity was determined, the constants of chromium(VI) adsorption on iron(III) oxide for the pseudo-second-order model were calculated, and the diffusion coefficients for the process were evaluated.     

Thermal decomposition of the solvent extracted molybdenum (VI) complexes from hydrochloric acid solutions with trioctylamine and trioctylmethylammonium chloride

The complexes of molybdenum(VI) with trioctylamine (TOA, R₃N) and trioctyl methylammonium chloride (TOMAC, R₃R'NCl) were prepared by drying in vacuo the organic solutions for the extraction of molybdenum(VI) from hydrochloric acid solutions at low and higher acidities, respectively, by TOA and TOMAC in benzene. The resulting complexes were examined by thermal analysis (TG and DTA) in air and under the atmosphere of nitrogen, and their thermally decomposed products such as volatile matters and residues by gas chlomatography, X-ray diffraction study and infrared spectrophotometry. It was found that their complexes decompose thermally to MoO₃ by cracking of alkyl groups combined with molybdenum(VI) ion. Accordingly the thermal decomposition process of those complexes is discussed and the probable structure of the complexes is proposed on the basis of the results obtained.

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Zusammenfassung Komplexe von Molybdän(VI) mit Trioktylamin (TOA, R₃N) und Trioktylmethylammoniumchlorid (TOMAC, R₃R'NCl) wurden hergestellt, mittels TG und DTA in Luft und in Stickstoffatmosphäre untersucht. Die thermischen Zersetzungsprodukte der Komplexe (flüchtige Substanzen und Rückstände) wurden mittels Gaschromatographie, Röntgendiffraktion und IR-Spektroskopie untersucht. Es wurde gezeigt, daß die Komplexe thermisch zu MoO₃ zerfallen, indem die an das Molybdän(VI)-Ion gebundenen Alkylgruppen abgekrackt werden. Die Ergebnisse der thermischen Zersetzungsprozesse wird diskutiert und auf der Basis der erhaltenen Ergebnisse die wahrscheinliche Struktur der Komplexe dargelegt.

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Dedicated to Professor Dr. H. J. Seifert on the occasion of his 60^th birthday

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The author wishes to thank Dr. H. Watanabe and Mr. T. Takahashi for assistance with experimental work, and also the Koei Chemical Co., Ltd. for samples of TOA and TOMAC.     

Extraction of rhodium(III) with petroleum sulfoxides from hydrochloric acid solutions

Extraction of rhodium(III) from hydrochloric acid solutions with petroleum sulfoxides was studied. The optimal conditions of its recovery were found. The composition and structure of the compound being extracted was determined by electronic absorption, ¹H NMR, and IR spectroscopies and elemental analysis.     

Extraction of palladium(II) from hydrochloric acid solutions with triacylated ethyleneamines

Extraction of palladium(II) from hydrochloric acid solutions with novel efficient extractants, triacylated ethyleneamines, was studied. The most effective extraction of palladium(II) was observed from 0.5–1 M HCl solutions. Extraction of palladium(II) from 1 M HCl solutions was found to occur through mixed (coordination and anion-exchange) mechanism. In the field of dominance of the anion-exchange mechanism of the extraction of palladium(II) with triacylated pentaethylenehexamine the concentration constant of palladium(II) extraction was calculated, and thermodynamic parameters of extraction were evaluated.     

二-(2-乙基己基)磷酸在不同稀释剂中对钼(VI)的萃取

考察了Mo(VI)在盐酸水相与-二(2-乙基己基)磷酸的不同稀释有机相间的分配平衡,观察到萃取平稀常数按正辛烷、四氯化碳、苯、氯信、1,2-二氯乙烷、甲苯、甲基异丁基酮的次序递减,萃合物的组成也按这一顺序呈现规律性变化.文中将这些结果与稀释剂性进行了关联,得到萃取平衡常数与稀释剂的极性参数E~T间良好的线性关系.此外,本文还提出了H~2MoO~4的酸、碱式解离常数分别为0.158和1.21×10^13.     

Studies on the recovery of Pu(IV) from hydrochloric acid-oxalic acid solutions using an anion exchange method

Sorption of Pu(IV) from hydrochloric acid-oxalic acid solutions has been investigated using different anion exchangers, viz., Dowex-1X4, Amberlite XE-270 (MP) and Amberlyst A-26 (MP) for the recovery of plutonium from plutonium oxalate solutions. Distribution ratios of Pu(IV) for its sorption on these anion exchangers have been determined. The sorption of Pu(IV) from hydrochloric acid solutions decreases drastically in the presence of oxalic acid. However, addition of aluminium chloride enhances the sorption of plutonium in the presence of oxalic acid, indicating the feasibility of recovery of plutonium. Pu(IV) breakthrough capacities have been determined with a 10 ml resin bed of each of these anion exchangers at a flow rate of 60 ml per hour using a solution of Pu(IV) with the composition: 6M HCl+0.05M HNO₃+0.1M H₂C₂O₄+0.5M AlCl₃+100 mg.l^–1 Pu(IV). The 10% Pu(IV) breakthrough capacities for Dowex-1X4, Amberlite XE-270 (MP) and Amberlyst A-26 (MP) are 15.0, 8.9 and 6.2 g of Pu(IV) l^–1 of resin respectively.     

Supported liquid membrane extraction of W(VI) ions using tri-n-octylamine as carrier

Study of the extraction of W(VI) ions using supported liquid membrane has been carried out. The carrier used for this metal ion transport, is tri-n-octylamine (TOA) dissolved in xylene. The liquid was supported in microporous polypropylene film. The parameters studied are effect of carrier concentration in the membrane, acid concentrations in the feed solution, concentration of stripping agent on transport of W(VI) ions and of temperature on the transport properties of these supported liquid membranes. The optimum conditions of transport for these metal ions determined are, TOA concentration, 0.66 mol·dm^–3 (TOA); HF concentration in the feed solution, 0.01 mol·dm^–3 and concentration of NaOH used as stripping agent 2.5 mol·dm^–3. The maximum flux and permeability determined under optimum conditions are 3.06·10^–5 mol·m^–2·s^–1 and 8.44·10^–11 mol· ·m²·s^–1 at 25±2°C and 4.21·10^–5 mol·m^–2·s^–1 and 11.55·10^–11 mol·m²·s^–1 at 65°C, respectively. The diffusion coefficients for the metal ion carrier complex in the membrane have also been determined. Under the optimum conditions the value for the metal ion carrier complex is 0.14·10^–11 mol·m²·s^–1. Mechanism of transport and the complex formed in the presence of HF have also been discussed. The transport process involves two carrier amine molecules and two protons.     

Solvation of thiocyanate complexes of tungsten(VI) by 5-(4-pyridyl) nonane from aqueous hydrochloric acid solutions

5-(4-Pyridyl)nonane has been evaluated as a solvent for trace amounts (<5·10^–5 M) of tungsten(VI) from aqueous chloride-thiocyanate solutions. Remarkable enhancements in metal extractability are observed on the addition of SCN^– to aqueous hydrochloric acid solutions. Extremal partition coefficients are obtained from 0.1 M HCl in 0.2 M KSCN. Diminutions of the metal extractability are produced by relatively high (>0.5 M) SCN^– concentrations and increased concentration of the supporting acid. Slope analysis data, under optimal parameters, indicates the most probable composition of the extractable species as WO₂(SCN)₂·2P_YN. Neutral anions do not have any significant effect on the D values. Behaviour of a number of metal ions has been checked using optimal aqueous conditions of extraction. The investigation shows that the reagent has a great potential for the preconcentration of a number of metal ions including the common toxins.