Liquid–liquid extraction of cadmium(II) by Cyanex 923 and its application to a solid‐supported liquid membrane system

The extraction of cadmium(II) by Cyanex 923 (a mixture of alkylphosphine oxides) in Solvesso 100 from hydrochloric acid solution has been investigated. The extraction reaction is exothermic. The numerical analysis of metal distribution data suggests the formation of CdCl₂.2L, HCdCl₃.2L and H₂CdCl₄.2L (L = ligand) in the organic phase. The results obtained for cadmium(II) distribution have been implemented in a solid‐supported liquid membrane system. The influences of feed phase stirring speed (400–1400 min^?1), membrane composition (carrier concentration: 0.06–1 mol dm^?3) and metal concentration (0.01–0.08 g dm^?3) on cadmium transport have been investigated. Copyright © 2005 Society of Chemical Industry     

Determination of the heat change in solvent extraction of metals. The extraction of zinc (II) from hydrochloric acid solutions by high molecular weight amines in various organic solvents

The heat change associated with the uptake of zinc (II) has been examined by using a twin type isoperibol calorimeter in the extraction of zinc (II) from hydrochloric acid solutions by trioctylamine hydrochloride (TOAHCl) and trioctylmethyl-ammonium chloride (TOMAC) in various organic solvents such as benzene, chlorobenzene, o-dichlorobenzene, toluene, m-xylene, nitrobenzene, carbon tetrachloride and 1, 2-dichloroethane. It was found that the dependence of apparent molar heat change (the value of the heat change detected with regard to the concentration of zinc (II) reacted) on the aqueous chloride concentration could be attributed to the change in the distribution of zinc (II) chloride species in the aqueous phase. Taking account of this fact, variable Y, which constitutes the sum of the change in enthalpies for the relevant steps in the extraction of zinc (II), except the transformation of ZnCl_j^(2-j)+ to ZnCl₄^2-, in the aqueous phase, is introduced. From the values of Y obtained, it is concluded that in the extraction by TOMAC, Y correlates with the solubility parameter of diluent, suggesting that the organic phases may be regarded as regular solutions, while in the extraction by TOAHCl, no clear-cut relation holds between Y and the physico-chemical constants of the diluent such as dipole moment, dielectric constant and solubility parameters.     

THE SOLVENT EXTRACTION OF ZINC FROM LITHIUM CHLORIDE BY ALIQUAT 336 CHLORIDE,BROMIDE AND IODIDE IN CHLOROFORM: AN ANALYTICAL INVESTIGATION

ABSTRACT

The extraction of zinc by Aliquat CI in chloroform is studied as a function of LiCl concentration. A plot of log D versus total [Cl] shows that log D increases sharply from 0-2 M LiCl, then remains constant over a considerable range of concentrations ( 2-8 M ), before shooting up again from 8-14 M. Further work is carried out at 4 M LiCl to determine the extraction equation, and quantitative aspects determined such as a plot of log D versus log [Aliquat Cl]_free, giving a ratio of 2:1 for extractant: metal, and the ratio [Cl / Zn]_extracted, which is 2.

In order to follow the exchange of halides across the interface, Aliquat Br and Aliquat I are used as extractants in chloroform to study the extraction of zinc chloride from 4 M LiCL Organic and aqueous phases are analysed for halides and zinc, and the ratio [ΔCl] / [Zn] in the organic phase determined to be 3 for both Aliquat Br and I at 4M LiCl, indicating extraction of ZnCl₃,' and not ZnCl₄ ² at this concentration. Further work with these extractants based on plots of log D versus log [Aliquat X]_free ( X = Br, I ) is presented and extraction equations are proposed for these extractants, which fit the data.

Extraction of zinc at 4 M LiCl by Aliquat Cl is then considered in terms of the extraction of the trichlorozincate (II) species, ZnCl₃,“, and the extraction constant determined.     

Transport of Co(II) Ions through Di(2-ethylhexyl) Phosphoric Acid-CCl4 Supported Liquid Membranes

Abstract

A liquid membrane transport study of Co(II) using di(2-ethylhexyl) phosphoric acid (D2EPHA) as carrier and CCl₄, as diluent supported on polypropylene microporous film has been carried out. The carrier concentration in the membrane and HCl concentration in the stripping phase have been varied to see the effect on transport of Co(II) ions across the membrane. Maximum flux and permeability values of 1.23 × 10^?5 mol · m^?2 · s^?1 and 7.66 × 10^?11 m²/s, respectively, at a 0.87 mol/dm³ carrier concentration in the membrane have been found. At 1 mol/dm³ HCl concentration in the stripping phase the flux and permeability have maximum values of 1.4 mol · m^?2 · s^?1 and 5.27 × 10^?11 m²/s, respectively. The distribution coefficient of Co(II) ions into organic phase has been found to increase with increasing carrier concentration. The diffusion coefficient determined varies from 13.73 × 10^?11 to 0.83 × 10^?11 m²/s, which is the reverse order of the values of the distribution coefficient and explains the permeability of the Co(II) D2EPHA complex through the membrane.     

The separation of europium from a middle rare earth concentrate by combined chemical reduction,precipitation and solvent-extraction methods

The chemical reduction of pure europium(III) chloride solutions was investigated using reagents comprising reactive metals (Zn and Mg), metal amalgams (Zn-Hg, Na-Hg and Eu-Hg), metal hydride (NaBH₄) and nitrogenous reductants (N₂H₄ and NH₂OH). Using 100% excess of reducing agent and of ammonium sulphate, efficient precipitation of europium(II) sulphate was obtained with the metal amalgams (99·7–99·9%) and with zinc metal (99·8%), whereas only partial precipitation was obtained with magnesium metal (69%), and no precipitation was observed with the other reagents. Application of the method to synthetic rare earth chloride solutions containing europium 7·5, neodymium 5, samarium 35 and gadolinium 20 g dm⁻³ gave efficient precipitation of europium(II) sulphate with zinc and europium amalgams, but no selective precipitation with sodium amalgam. Reduction of an authentic middle rare earth chloride solution with zinc amalgam gave 97·5% recovery of europium(II) sulphate containing (as a percentage of the total rare earths) europium 92, samarium 3·5, neodymium 2, cerium 1, praseodymium 0·6 and gadolinium 0·5%. Conversion of the europium(II) sulphate to europium(II) chloride, followed by re-precipitation of the sulphate increased the europium content only to 96·5%, whereas replacement of the re-precipitation by solvent extraction of the trivalent rare earth impurities into solutions of commercial organophosphorus or carboxylic acids in xylene increased the europium content to > 99·98%. The zinc ions introduced into the middle rare earth mother liquor during the reduction procedure can be removed by solvent extraction into a commercial phosphine oxide (Cyanex 925), without loss of rare earth values.     

Removal of Copper(II) from a Concentrated Sulphate Medium by Cloud Point Extraction Using an N,N′-Bis(salicylaldehyde)Ethylenediimine Di-Schiff Base Chelating Ligand

Various chelating ligands have been investigated for the cloud point extraction of several metal ions. However, limited studies on the use of the Schiff base ligands have been reported. In this work, cloud point extraction behavior of copper(II) with N,N′‐bis(salicylaldehyde)Ethylenediimine Schiff base chelating ligand, (H₂SALEN), was investigated in aqueous concentrated sulphate medium. The extraction process used is based on the formation of hydrophobic H₂SALEN–copper(II) complexes that are solubilized in the micellar phase of a non‐ionic surfactant, i.e. ethoxylated (9.5EO) tert‐butylphenol. The copper(II) complexes are then extracted into the surfactant‐rich phase above cloud point temperature. Different parameters affecting the extraction process of Cu(II), such as equilibrium pH, extractant concentration, and non‐ionic surfactant concentration were explored. The extraction of Cu(II) was studied in the pH range of 2–11. The results obtained showed that it was profoundly influenced by the pH of the aqueous medium. The concentration factor, C_f, of about 17 with extraction efficiency of E % ≈100 was achieved. The stoichiometry of the extracted complex of copper(II) was ascertained by the Yoe–Jones method to give a composition of 1:1 (Cu:H₂L). The optimum conditions of the extraction‐removal have been established as the following: (1) 1.86 × 10^?3 mol/L ligand; (2) 3 wt% surfactant; (3) pH of 8 (4) 0.5 mol/L Na₂SO₄ and (5) temperature of 60 °C.     

SOLVENT EXTRACTION OF PALLADIUM(II) WITH A SCHIFF BASE AND SEPARATION OF PALLADIUM FROM Pd(II)-Pt(VI) MIXTURE

ABSTRACT

A new Schiff base extractant, N,N'-bis[l-phenyl-3-methyl-5-hydroxy-pyrazole-4-benzylidenyl]-l,3-propylene diamine (H₂A) was synthesized and characterized. The extraction mechanism of palladium(II) from HNO₃ or HClO₄ medium with H₂A in chloroform or toluene was investigated. The influences of the Schiff base concentration in the organic phase, the concentration of palladium, the pH and anions (Cl^?, S0₄ ^?, NO₃ ^?, ClO₄ ^?) in the aqueous phase and the temperature on the distribution ratio for palladium (II) have been examined. The extracted complex has been confirmed by chemical analysis, thermoanalyses and IR spectroscopy. It was found that palladium is extracted according to the following extraction reaction:

The extraction equilibrium constants of palladium(II) were 8·4 and 21·3 in chloroform and toluene diluents, respectively. The values for the enthalpy and standard free energy of extraction were also obtained. The separation of Pd(II) from the mixed solution of Pd(II)-Pt(IV) was achieved by adjusting the pH.     

Recovery of zinc,cadmium and mercury (ii) from chloride and sulphate media by solvent extraction

The extraction of zinc, cadmium and mercury from chloride and sulphate media by solvating extractants, liquid anion and liquid cation exchangers has been reviewed both from the literature and by experiment. The results have been discussed in terms of both practical process possibilities and the use of slope analysis to identify the extracted species. These show that slope analysis cannot give positive unambiguous identification of extraction stoichiometry in systems in which the extracted metal species contains coordinating ligands from the aqueous phase. However, in the extraction of Zn and Cd from sulphate media by di(2-ethylhexyl)phosphoric acid (DEHPA) the extracted species is shown to be an MR₂(HR)₂ monomer by slope analysis demonstrating its use in simple systems. In the case of amines and solvating reagents such as TBP^c and TOPO zinc appears to be extracted from Cl^– media as either ZnCl₂ or sometimes HZnCl₃ whereas Cd and Hg(II) appear to be always extracted as HCdCl₃ and HHgCl₃ species. The use of aqueous phase complexing by Cl^– to improve the separation of Zn and Cd by extraction is clear. Some results are presented for the recovery of zinc from sulphate media by oximes and mercury from sulphuric acid media by amines and DEHPA.     

Modelling of the Extraction and Back‐Extraction Equilibria of Zinc from Spent Pickling Solutions

Abstract

This work reports the study of the chemical equilibria of the extraction and back‐extraction of zinc from spent pickling solutions. Tributyl phosphate was used as a selective extractant and service water as a back extraction agent. Feed solutions had an average composition of 6.4 M Cl^?, 1.2 M Zn⁺², 1.7 M Fe⁺² and traces of other heavy metals i.e., Pb, Ni, Cu, Mn. Under the experimental conditions the ion ZnCl₄ ^2? was the predominant zinc species in feed. A careful experimental design was performed obtaining the equilibria mathematical models and parameters, K_EX=0.137 (mol/L)^?4, and K_BEX=1.46 [?].     

Extraction of zinc from ammoniacal/ammonium sulphate solutions by LIX 54

The extraction of zinc from ammoniacal/ammonium sulphate aqueous media using LIX 54 has been studied. The metal extraction rate has been examined and also the effect of temperature on the extraction of zinc (ΔH° = −8·8 kJ mol⁻¹). The effect of the aqueous pH, and therefore zinc ammine complex formation, on the extraction of zinc was studied. Stripping of the metal from loaded organic phases was carried out at various rates, temperatures (ΔH° = 3·2 kJ mol⁻¹) and sulphuric acid concentrations. The results obtained were compared with others obtained from the literature wherein different extractants were used. © 1998 SCI.     

SYNERGISTIC EXTRACTION OF ZINC(II) BY MIXTURES OF PRIMARY AMINE N1923 AND CYANEX272

ABSTRACT

The extraction of zinc(II) and cadmium(II) from chloride solution by mixtures of primary amine N1923 and Cyanex272 (HA) was studied. The synergistic effect was observed for the extraction of zinc(II) while no synergistic effect for cadmium(II), which makes it possible to separate zinc(II) and cadmium(II) with the mixtures. The results showed that zinc(II) was extracted as (RNH₃Cl)₃·ZnClA instead of ZnA₂·2HA which was extracted by Cyanex272 alone. The extraction mechanism was discussed and the formation constants and thermodynamic functions were determined. The separation factors between zinc(II) and cadmium(II) were calculated.     

Role of amino acids and micronutrients on biosynthesis of spiramycins

The production of spiramycin using a synthetic basal medium, to which amino acids, vitamins and metallic ions were added, was investigated. L -Tryptophan was found to be the amino acid which best increased the antibiotic yield. Addition of vitamins to the fermentation medium did not increase the antibiotic output, while the addition of different concentrations of trace elements such as Co(NO₃)₂ ZnCl₂ (NH₄)₂Mo₇O₂₄ and MnCl₂ improved the antibiotic yield. High concentrations of these trace elements decreased the antibiotic yield and directed the microbial activities towards biosynthesis of spiramycin II and III—these are less toxic than spiramycin I. Optimum concentrations of Co(NO₃)₂, ZnCl₂, (NH₄)₂Mo₂₄O₇, MnCl₂ which supported the antibiotic yield were 5 × 10^?1, 5 × 10^?3, 5 × 10^?3 and 5 × 10^?3 g dm^?3, respectively.     

EXTRACTION KINETICS OF ZINC BY TRILAURYLAMM0NIUM CHLORIDE AT DIFFERENT CHLORIDE CONCENTRATIONS

The rate of the extraction of zinc by trilaurylammonium chloride (TLAHC1) dissolved in toluene was investigated at different aqueous chloride concentrations, using lithium chloride as bulk electrolyte, ranging from 0.5 mol.dm -3 to 2.0 mol dm -3. The experiments were performed using a modified Lewis cell at 25?°C. The rate of metal extraction was found to increase by increasing the aqueous chloride concentration. The data treatment indicated that ZnCl₂ and ZnCl₄ ^2- are both kinetically active species. The addition reaction with ZnCl₂ is favoured at low chloride concentration while the anion exchange of ZnCl₄ ^2- prevails at high chloride concentration. The addition reaction was explained in terms or interfacial reaction steps. The anion exchange reaction, due to its fast nature, seems to be controlled by diffusion.     

Polysulfone‐based composite membranes with functionalized carbon nanotubes show controlled porosity and enhanced electrical conductivity

Composite membranes of functionalized (–COOH, –CONH₂, –N₃) carbon nanotubes/polysulfone (CNT/PS) synthesized by the phase‐inversion method show unique properties with respect to surface characteristics and the selective separation of metal ions from aqueous solution. Apart from the reduction in the pore size depending on the type of functionalities on the nanotubes, the pure water permeation could reach up to as high as ～600 L m^?2 h^?1 (LMH) at reduced pressures and could be due to the functionalized tips of the nanotubes on the membrane surface resulting from the phase inversion process used for the membrane fabrication. The membranes were characterized by small angle neutron scattering (SANS) to confirm the uniform distribution of the nanopores and the surface morphology of the membranes. Results show that rejection of Cu(II) was better than Pb(II) depending on the surface functionality. Interestingly, these membranes also showed enhanced conductivities in the range of 1.0 × 10^?2 S cm^?1, the conductivity depending on the type of functionality on the nanotubes, thus confirming the presence of functionalized nanotubes tips on the membrane surface. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43778.     

Separation of Zinc by a Non‐dispersion Solvent Extraction Process in a Hollow Fiber Contactor

Abstract

A process for recovery of zinc from acid solution with di(2‐ethyl hexyl phosphoric acid) (D2EHPA) dissolved in iso‐dodecane was carried out at 20°C in a countercurrent tubular membrane extractor using a hollow fiber as solid support. Experiments were performed at different aqueous metal concentrations (0.1–1.0 g/L), pH 0.1–2.1, and D2EHPA concentrations (2–8 v%). It was found that both the flux of metal and the extraction extent was highly influenced by the extractant concentration and the pH of the feed solution. Overall mass transfer coefficients were determined and related to the tube side, the membrane, and the shell side mass transfer by varying the aqueous flow rate (0.38–0.80 L/min) and organic flow rate (0.22–0.57 L/min) in countercurrent flow. The overall mass transfer coefficient for zinc extraction ranged from 6.2×10^?6 m/s to 25.3×10^?6 m/s. It was concluded that extraction kinetics were a major contributor to the overall resistance to mass transfer.     

Zinc(II)-bound thiolate complexes-containing cysteine derivatives modeling of methionine synthase alkylating enzyme

The reaction of thioimidazolylborate-zinc(II)-perchlorate complex [Tt^xyly·Zn? OClO₃] 1 (Tt^xyly=hydrotris[N-xylyl-thioimidazolyl]borate) with cysteine and its derivative N-acetyl cysteine and S-methyl cysteine leads to the formation of three new monomeric and dimeric thiolate complexes: [Tt^xyly·Zn? Cys? Zn·Tt^xyly] 2, [Tt^xyly·Zn? Cys(NAc)? Zn·Tt^xyly] 3, and [Tt^xyly·Zn? Cys(SMe)] 4. The attachment of the cysteine derivatives to the Tt·Zn unit serves as structural models for the active site of methionine synthase. Methylation of the coordinated thiolate in the dinuclear zinc(II) complex 2 with methyl iodide appears to occur intramolecularly at the zinc-bound thiolates, forming methyl thioether-containing zinc(II) complex [Tt^xyly·Zn? Cys(SMe)] 4 and iodo complex [Tt^xyly·Zn? I] 5 with a clean second-order reaction of k=1.0×10^?5 M^?1 s^?1.     

Spectroscopic and Thermal Studies of Mn(II), Fe(III), Cr(III) and Zn(II) Complexes Derived from the Ligand Resulted by the Reaction Between 4-Acetyl Pyridine and Thiosemicarbazide

Transition metal complexes of Mn(II), Fe(III), Cr(III) and Zn(II) metal ions with a general formulas [Mn(L)₂(Cl)₂]·4H₂O (I), [Fe(L)₂(Cl)₂]·Cl·6H₂O (II), [Cr(L)₂(Cl)₂]·Cl·6H₂O (III) and [Zn(L)₂(Cl)₂]·2H₂O (IV) where L = 4-acetylpyridine thiosemicarbazone, have been synthesized and interpreted using CHN elemental analysis, magnetic susceptibility measurements, molar conductance, thermal analysis and spectroscopic techniques; i.e., infrared, electronic UV/vis, ¹H-NMR and mass. The manganese(II), ferric(III), chromium(III) and zinc(II) complexes have octahedral geometry. The molar conductance measurements reveal that the Mn(II) and Zn(II) chelates are non-electrolytes but Fe(III) and Cr(III) have an electrolytic behavior. The IR spectra show that the 4-acetylpyridine thiosemicarbazone free ligand is coordinated to the metal(II) chlorides as a neutral bidentate ligand through both of the lone pair of electrons of the C=N azomethine group and C=S group. X-ray powder diffraction gives an impression that the resulting complexes are amorphous and different from the start materials. The thermogravimetric studies indicate that uncoordinated water molecules are lost in the first and second decomposition steps. The activation thermodynamic parameters E*, ΔH*, ΔS* and ΔG* are estimated from the differential thermogravimetric analysis (DTG) curves using Horowitz–Metzger (HM) and Coats–Redfern (CR) methods. The ligand and its complexes have been screened for antibacterial and antifungal activities against two bacteria; i.e., Escherichia coli (Gram −ve) and Bacillus subtilis (Gram +ve) and two fungi, i.e., tricoderma and penicillium activities).     

Oxidation of Esculetin,a Model Pollutant Present in Cork Processing Wastewaters,by Chemical Methods

The ozonation of esculetin (6,7-dihydroxycoumarin), a major pollutant present in the wastewater generated in the cork industry, was accelerated at high pH, with apparent second-order rate constants in the range from 3.3 × 10⁴ L/(mol·s) at pH=2 to 8.4 × 10⁷ L/(mol·s) at pH=9. The acid-base equilibrium of esculetin was studied, resulting in a pK_a value of 7.37. Taking into account this pK_a, the rate constants for the reaction between ozone and the un dissociated and dissociated forms of esculetin were 3.0 × 10⁴ and L/(mol·s) 6.67 × 10⁸ L/(mol·s), respectively. Apparent first-order rate constants for the photolysis by UV irradiation were also evaluated, with values between 0.12 × 10^?2 min^?1 at pH=2 and 1.15 × 10^?2 min^?1 at pH=9, while the quantum yields for this photo-degradation reaction varied from 0.99 × 10^?2 mol/Eins to 11.1 × 10^?2 mol/Eins at these pHs. The Fenton's reagent system was used for the generation of hydroxyl radicals, and the rate constant for the reaction between esculetin and these radicals was determined to be 1.06 × 10¹⁰ L/(mol·s). Finally, several chemical oxidation systems were used in the degradation of this pollutant: single oxidants (ozone, UV irradiation) and advanced oxidation processes (Fenton's reagent, UV/H₂O₂, O₃/H₂O₂, O₃/UV, O₃/H₂O₂ /UV, and photo-Fenton system). The results revealed that the most efficient methods in terms of esculetin removal were ozonation among the single oxidants, and the photo-Fenton system among the combined processes.     

Highly Efficient and Selective Transport of Cu(II) with a Cooperative Carrier Composed of Tetraaza-14-Crown-4 and Oleic Acid through a Bulk Liquid Membrane

Tetraaza-14-crown-4 and oleic acid was successfully applied for transport of Cu(II) in chloroform bulk liquid membrane. The uphill moving of Cu(II) during the liquid membrane transport process has occurred. The main effective variable such as the type of the metal ion acceptor in the receiving phase and its concentration, tetraaza-14-crown-4 and oleic acid concentration in the organic phase on the efficiency of the ion-transport system were examined. By using L-cysteine as a metal ion acceptor in the receiving phase, the maximum amount of copper (II) transported across the liquid membrane was achieved to 96 ± 1.5% after 140 minutes. The selectivity of copper ion transport from the aqueous solutions containing Pb²⁺, Tl⁺, Ag⁺, Co²⁺, Ni²⁺, Mg²⁺, Zn²⁺, Hg²⁺, Cd²⁺ and Ca²⁺ ions were investigated. In the presence of CH₃COONH₄ and Na₄P₂O₇ as suitable masking agents in the source phase, the interfering effects of Pb⁺² and Cd²⁺ were diminished drastically.     

Supported Liquid Membrane Extraction Study of (MoO4)2- Ions using Tri-n-octylamine as Carrier

Abstract

The transport of (MoO₄)^2- ions across a tri-n-octylamine (TOA) xylene-based supported liquid membrane has been studied at various HCl concentrations in the feed, TOA concentrations in the membrane, and NaOH concentrations in the strip solution. The distribution coefficient and flux of the Mo(VI) ion species vary with the HCl concentration, indicating that different polymeric species of this metal ion are present in the aqueous solution. A TOA concentration increase of up to 1.308 mol/dm³ enhances flux and permeability of this metal ion, which beyond this concentration is reduced due to an increase in carrier liquid viscosity. An increase in NaOH solution concentration has been found to increase flux and permeability values. The continuous increase in pH of the feed with the transport of metal ions indicates that the (MoO₄)^2- transport does not involve a decrease or increase in concentration as a result of association of lower to higher or decomposition of higher to lower metal ions polymeric species. The optimum conditions of transport of Mo(VI) metal ions across these membranes have been found to be HCl = 0.01, [NaOH] = 1, and [TOA] = 1.308, furnishing flux and permeability values of the order of 2.49 × 10^?4 mol·m^?2·s^?1 and 2.32 × 10^?10 m²·s^?1, respectively.