MECHANISTIC STUDIES ON THE EXTRACTION OF PALLADIUM )II) WITH 2-HYDHOXY-5-NONYLBENZOPHENONE OXIME (LIX 65N)

ABSTRACT

Mechanistic studies including equilibrium and kinetic aspects of palladium extraction from acidic chloride media with 2-hydroxy-5-nonylbenzophenone oxime (LIX 65N) in chloroform solution are reported. The extracted species was established to be PdL, and the extraction equilibrium constant K Tor the reaction:

Pd²+2HL(o)2PdL²(o)+2H+ was found to be 10 ^16.30The homogeneous chemical reaction PdCl₃+HLPdCl₂-L^minusH+ Cl^minus was established as The rate-determining step of the overall.reaction having a rate constant of 3.74x10 M-1s.     

SOLVENT EXTRACTION OF MOLYBDENUM (VI) WITH LIX 63

The equilibrium and kinetics of the extraction of molybde-num(VI) with LIX 63 was investigated. The extraction of Mo(VI) is both favored by high acidity and high LIX 63 concentration. From the equilibrium studies, the extraction constant for the reaction was found to be log K_ex - 16.43. The rate of extraction is first ex order in both metal and extractant but decreases non-linearly with pH. The rate-determining step of the reaction was deduced to be the formation of a 1:1 complex between Mo(VI) and LIX 63 in the aqueous phase. A mechanism in which different Mo(VI) species react concurrently with the neutral ligand is proposed. The logarithmic values of the second order reaction rate constants (in M^?1 s^?1 units) involving each Mo(VI) species are as follows: molybdate - 2.30, bimolybdate - 5.82, and molybdic acid - 8.16. These results agree well with the results reported for other ligands.     

Fundamental aspects of the extraction and stripping of palladium by LIX 65N

The fundamental aspects of the extraction and stripping of palladium from its chloride solution by LIX 65N diluted with Kermac 470B have been studied. Equilibria of extraction and stripping, temperature effect, the variation of sodium thiosulphate concentration on stripping and rate of extraction and stripping on the system Pd²⁺-LIX 65N-Kermac 470B are reported. The fundamental aspects of the extraction and stripping of palladium from its chloride solution by LIX 65N diluted with Kermac 470B have been studied. Equilibria of extraction and stripping, temperature effect, the variation of sodium thiosulphate concentration on stripping and rate of extraction and stripping on the system Pd²⁺-LIX 65N-Kermac 470B are reported.     

THE SELECTIVITY OF NICKEL OVER IRON IN THE LIX63-HDNNS SOLVENT EXTRACTION SYSTEM

ABSTRACT

The effects of the aqueous phase pH and the organic phase HDNNS concentration on the distribution coefficients of Ni and Fe in pure HDNNS or mixed LIX63-HDNNS systems have been investigated. With the mixed extractants, there is antagonistic extraction of iron below pH 1.4 whereas synergistic extraction occurs above this pH. At pH 2.5 and a fixed LIX63 concentration, iron distribution increases markedly in comparison with the oxime-free system and goes through a maximum with increase in HDNNS concentration. A similar behavior is shown by nickel at both pH 1.0 and 2.5. The log D_Feversus pH plot gives a curve with a slope of two for the LIX63-HDNNS mixed system, which suggests that iron is extracted in the form of a species with an ionic charge of 2, probably Fe(OH)²⁺. The extracted complexes are proposed as Ni(H₂L)₃D₂where all three oxime molecules function as bidentate ligands, and Fe(OH) (H₂L) ₃D₂where one of the oxime molecules functions as a monodentate ligand. The Ni/Fe selectivity is high at low pH and changes mainly as a result of variations in the nickel distribution coefficient, but it is low at high pH because of the synergistic extraction of iron.     

Recovery of Copper from a Waste Heat Boiler Dust Leach Liquor using LIX 84I and LIX 622N

The dust collected from the waste heat boiler of a copper plant was leached with sulfuric acid and the leach liquor contained 31.63 kg/m³ Cu, 14.78 kg/m³ Fe, 2.21 kg/m³ Zn, 0.26 kg/m³ Co, 0.09 kg/m³ Ni, and 0.23 kg/m³ Cd. The iron content in the leach liquor was precipitated out using Ca(OH)₂ and from the filtrate copper was extracted with the extractants LIX 84I and LIX 622N in kerosene. Extraction of copper with either extractant increased with increasing equilibrium pH and extractant concentration. The McCabe-Thiele plots for quantitative extraction of copper indicated 3-stages at O:A ratio of 3:2 with 30% extractants. The counter-current extraction study showed 0.21 kg/m³ and 6.77 g/m³ copper in the third stage raffinates of LIX 84I and LIX 622N indicating 98.64% and 99.95% extraction, respectively. For extraction of a mole of copper ion, two moles of the extractant was required to release two moles of hydrogen ion to the aqueous phase. The quantitative stripping of copper from the loaded organic phases of LIX 84I and LIX 622N with 180 kg/m³ H₂SO₄ was possible in 3-stages at O:A ratio of 3:1 and 3:2, respectively. The thermodynamic parameters such as ΔH, ΔG, and ΔS were calculated for both the systems. The enthalpy change (ΔH) values were positive for extraction of Cu with either extractant indicating the processes to be endothermic. The IR spectra indicated the association of phenolic-OH group of oxime molecules in the formation of copper complexes.     

Mechanistic study of active transport of copper (II) using LIX 54 across a liquid membrane

The present work describes the mechanism of active transport of copper(II) through an immobilized liquid membrane (ILM) containing LIX 54 (β‐diketone) dissolved in Iberfluid as mobile carrier. An uphill transport model has been described and equations have been derived taking into account aqueous boundary layer diffusion and liquid membrane diffusion as simultaneous controlling factors. In the present model, various cases were discussed using the carrier LIX 54 and different chemical species; the diffusional membrane resistance for lower and higher concentrations of extractant was evaluated. The diffusion coefficients were observed to decrease with increase in ­the extractant concentration, ranging from 4.1 × 10⁻³ to 1.65 × 10⁻² mol dm⁻³ Plotting [Cu]₀−[Cu]_t vs time resulted in a slope of [HR]₀A/2Δ_orgV taking into account the complex species, CuR₂, in the membrane. The mass transfer coefficient (Δ_org ⁻¹), the diffusion coefficient of the metal carrier species (D_org) and the thickness of the aqueous boundary layer were calculated from the proposed model for LIX 54. More than 90% of the Cu(II) could be separated using LIX 54 in the presence of various metals such as Ni, Co(II) and Zn. © 2000 Society of Chemical Industry     

Solvent Extraction of Copper from Nitrate Media with Chelating LIX‐Reagents: Comparative Equilibrium Study

Abstract

Comparative experimental studies were carried out on extraction of copper(II) cations from aqueous acid nitrate media using four LIX‐reagents, representatives of different extractant classes: LIX 984N‐I, LIX 860N, LIX 84‐I and LIX 65N. As a diluent, liquid hydrocarbon undecane was used. The extraction behavior of the LIX‐reagents was compared based on an analysis of the influence of the main factors on the two‐phase mass transfer process: aqueous pH‐value, initial copper and extractant concentrations, and temperature. The experimental data received were used in the calculation of important parameters characterizing the efficiency of copper extraction from nitrate media with different LIX reagents: distribution ratios D, concentration extraction constants K _ex, pH_0.5‐values, and thermodynamic parameters such as enthalpy, entropy, and free energy changes (ΔH ⁰, ΔS ⁰, ΔG ⁰‐values).     

Reactivity studies of 2,3,5,6-Tetra(2-pyridyl) pyrazine (tppz) with first-row transition metal ions

Reactions of 2,3,5,6-tetra(2-pyridyl) pyrazine (tppz) with [ML₆][X]₂ (L = CH₃CN, H₂O;X = [BF₄]⁻, [ClO₄]⁻, [NO₃]⁻ [BArF]⁻(BArF - B[3,5-C₆H₃(CF₃)₂]₄) lead to the high-yield formation of mononuclear [M(tppz)₂]²⁺, (M = Mn^II, Fe^II, Co^II, and Ni^II) and dinuclear [Ni₂(tppz)(CH₃CN)₆]⁴⁺ species. The new compounds were fully characterized by X-ray crystallographic, spectroscopic, and magnetic susceptibility measurements. Surprisingly, the 2:1 M:tppz reactions did not lead to isolation of the dinuclear species except in the case of Ni(II). It was further noted that even in the case of the Ni reactions, the nuclearity of the product depends on the choice of anions and the reaction conditions. Magnetic measurements of the mononuclear species [Co(tppz)₂]²⁺ revealed thermally induced spin-crossover behavior from a high-spin S = 3/2 at higher temperatures to a low-spin S = 1/2 complex at lower temperatures. The dinuclear compound [Ni₂(tppz)(CH₃CN)₆]⁴⁺ exhibits a weak anti-ferromagnetic interaction through the bridging tppz ligand.     

Selective removal of copper ions from aqueous solutions using modified silica beads impregnated with LIX 84

Silica beads immobilized with 2‐hydroxy‐5‐nonylacetophenoneoxime (LIX 84) were prepared after silica surface modification by γ‐aminopropyltriethoxysilane (SB‐L). Batch and packed‐column tests were conducted to evaluate the metal ion removal capabilities of the prepared adsorbent. Equilibrium isotherms of the SB‐L with aqueous solutions containing copper ions were obtained. In addition, the kinetic performances for copper ion removal from aqueous solutions were investigated. The results showed that the amount of extraction increases with solution pH in the range between 1.5 and 5. The selectivity was also experimentally investigated, these results showed that the SB‐L adsorbed copper ions selectively in the presence of other metal ions such as Ni²⁺, Co²⁺, Zn²⁺, Cd²⁺, Ca²⁺ and Mg²⁺. From the regeneration experiments, it was found that the copper ions adsorbed at the SB‐L surface were recovered by acidic solutions. The recovery ratios were between 78% and 90%, depending on the types of acidic solutions. The results showed that the SB‐L prepared may be used for the selective extraction of copper ions from aqueous solutions. © 1999 Society of Chemical Industry     

INTERFACIAL ADSORPTION OF 2-HYDROXY-5-NONYLBENZOPHENONE OXIME IN STATIC AND VIGOROUSLY STIRRED DISTRIBUTION SYSTEMS

ABSTRACT

The interfacial adsorption of 2-hydroxy-5-nonylbenzo-phenone oxime (LIX65N) at a n-heptane/water interphase was examined under static and vigorously stirred conditions, varying the aqueous pH from 2 to 12. In static systems, the pH and the concentration dependences of the interfacial tension were analysed on the basis of the Gibbs equation. The acid dissociation equilibrium at the interface was evaluated. In vigorously stirred systems, the interfacial adsorption was observed as a reversible, reproducible decrease of the organic phase concentration in response to stirring. A Langmuir isotherm was applicable for the adsorption of neutral LIX65N in acidic condition. The greater adsorption of the anionic form of LIX65N occurring in alkaline condition required an alternative isotherm.     

EXTRACTION OF ALKALINE EARTH AND ACTINIDE CATIONS BY MIXTURES OF DI(2-ETHYLHEXYL) ALKYLENEDIPHOSPHONIC ACIDS AND NEUTRAL SYNERGISTS

ABSTRACT

The synergistic extraction of alkaline earth (Ca²⁺, Sr²⁺, Ba²⁺ and Ra²⁺) and actinide (Am³⁺, UO₂ ²⁺ and Th⁴⁺) cations from aqueous nitric acid solutions by mixtures of P,P^′-di(2-ethylhexyl) methylene-(H₂DEH[MDP]), ethylene-(H₂DEH[EDP]), and butylene-(H₂DEH[BuDP]) diphosphonic acids and neutral extractants in o-xylene has been investigated. The cis-syn-cis and cis-anti-cis stereoisomers of dicyclohexano-18-crown-6 (DCH18C6), the unsubstituted 21-crown-7 (21C7) and dicyclohexano-21-crown-7 (DCH21C7) were used as neutral synergists of the crown ether type. For Am(III) synergistic effects were also investigated using neutral organophosphorus esters, such as, tri-n-butylphosphate (TBP), diamyl amylphosphonate (DA[AP]) and tri-n-octylphosphine oxide (TOPO) as co-extractants. In all systems investigated, no synergistic extraction enhancement was observed for actinide ions. For the alkaline earth cations, synergistic effects were only observed when mixtures of H₂DEH[EDP] or H₂DEH-[BuDP] with DCH18C6 were used to extract Sr²⁺, Ba²⁺ and Ra²⁺. No synergistic effects were observed for the extraction of alkaline earth cations by H₂DEH[MDP] or for the extraction of Ca²⁺ by any of the diphosphonic acids studied. The synergistic effects obtained with DCH18C6 were significantly higher for the cis-syn-cis than for the cis-anti-cis stereoisomer.     

Selective Transport of Copper through Liquid Membranes Using LIX 860 as Mobile Carrier

Abstract

Copper has been selectively extracted from aqueous solutions containing metal ions (Cu²⁺, Co²⁺, Ni²⁺, Fe²⁺, Fe³⁺, Mg²⁺, and Zn²⁺) by a liquid membrane technique. Experiments were carried out in a beaker equipped with a baffle, and the system was stirred by a variable-speed mixer equipped with a turbine impeller; the mixing speed was 300 rpm. A typical membrane formulation was 2.0% Span 80, 4.0% LIX 860, and 94.0% of commercial kerosene, all values being by weight. Copper was selectively separated and concentrated from both synthetic and natural aqueous mine solutions containing various metal ions.     

Selective and Synergistic Extraction of Nickel from Simulated Cr-Ni Electroplating Bath Solutions using LIX 63 and D2EHPA as Carriers

The main goal of the present study is to explain synergistic extraction of nickel from simulated Cr-Ni electroplating bath solutions (SEBS) using 5,8-diethyl-7-hydroxydodecane-6-one oxime (LIX 63) and di-(2-ethylhexyl) phosphoric acid (D2EHPA) as extractants by emulsion liquid membrane (ELM) technique. The importance of membrane composition and aqueous phase properties on nickel extraction percentage has been highlighted for the selective extraction of nickel. Some important parameters like acid concentration, stripping solution type and concentration, mixing speed, extractant concentrations, phase ratio, and surfactant concentration was studied to improve the extraction and stripping efficiencies. Higher than > 99% of nickel was recovered at optimum conditions within 6 min. The higher separation factors (β_Ni/Cr) were obtained as 580. As a result, the nickel extraction kinetic with D2EHPA has been defined as faster than LIX63. So, the kinetic transport of nickel mainly depends on LIX63 than D2EHPA. According to these results, D2EHPA behaves as a synergistic extractant in the present extraction mechanism.     

EXTRACTION OF COPPER BY LIX65N IN A VESSEL AND A MULTI-STAGE COLUMN UNDER STIRRED CONDITIONS

ABSTRACT

The extraction experiments of copper from aqueous solutions of copper sulfate by LIX65N-kerosene solutions were carried out at 25^°C in liquid-liquid dispersions. Both reaction rates of the forward and backward extractions were obtained in a stirred vessel, being combined with the equilibrium data. For a multistage column in continuous operation, the holdup data of the dispersed organic phase were correlated with the stirring speed, flow rates and LIX65N concentration. It was found that the extracted fraction of copper in the multi-stage column can be predicted from a stage-to-stage calculation using the extraction kinetics and the holdup obtained in the present work.     

NONDISPERSIVE LIQUID-LIQUID EXTRACTION OF COPPER AND ZINC FROM AN AQUEOUS SOLUTION BY DEHPA AND LIX 984 IN A HOLLOW FIBER MEMBRANE MODULE

ABSTRACT

A liquid-liquid extraction procedure was used to study the amounts of Zn²⁺ and Cu²⁺ that could be simultaneously extracted from aqueous solution with di(2-ethylhexyl) phosphoric acid (DEHPA) and LIX 984 diluted with n-heptane at equilibrium. LIX 984 is a 1:1 volume blend of LIX 860 (5-dodoecylsalicylaldoxime) and LIX 84 (2-hydroxy-5-nonylacetophenone oxime). At equilibrium, a 0.3 mol/L DEHPA-20% (v/v) LIX 984 solution extracted 99% of both the zinc and copper from a solution that had 100 ppm of each metal.

A polysulfone hollow-fiber membrane module with 1 mm ID and 5,000-molecular weight cutoff was used to study the amounts of Zn²⁺ and Cu²⁺ that could be simultaneously extracted with a mixture of DEHPA and LIX 984. The aqueous and organic streams were operated at 100% recycle. With a 0.6 mol/L DEHPA-10% (v/v) LIX 984 solution, a 90.5 ± 1.7% (s.d.) extraction of zinc and a 93.70 ± 0.79% (s.d.) extraction of copper was obtained after 180 min.     

Selective and Simultaneous Extractions of Zn and Cu Ions by Hollow Fiber SLM Modules Containing HEH(EHP) and LIX84

Abstract

The selective extractions of Zn²⁺ and Cu²⁺ from their mixed solutions of sulfate medium have been studied using hollow fiber supported liquid membranes (HFSLM). The HFSLM contained two kinds of extractants; one contained 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester [HEH(EHP)], the commercial name of which is PC88A, for Zn extraction; the other contained the hydroxy oxime reagent LIX84 for Cu extraction. Individual runs of each HFSLM were made to determine the effect of operational variables on the permeation rates of metal ions and their separation factors. In addition, the simultaneous and selective extractions of both Zn²⁺ and Cu²⁺ from their mixed solutions were demonstrated using the PC88A and LIX84 HFSLMs together. The performance of simultaneous extraction was compared with those of the individual runs.     

Extraction of Pr(III), Nd(III), and Dy(III) from HTFSA Aqueous Solution by TODGA/Phosphonium-Based Ionic Liquids

The extraction behavior of rare earth (RE) elements using N,N,N′,N′-tetraoctyl diglycolamide (TODGA) in an ionic liquid (IL) system was investigated by slope analyses. Metallic salts of Pr(III), Nd(III), and Dy(III) with bis(trifluoromethylsulfonyl)amide (TFSA) were synthesized and studied for their extraction mechanism. The selected concentration of TODGA was diluted with triethylpentylphosphonium bis(trifluoromethylsulfonyl)amide ([P₂₂₂₅][TFSA]) to prepare an extracting phase for the slope analyses. The stoichiometry of RE(III) was determined in order to estimate the extracted species. Furthermore, the complexation state of the extracted species was evaluated by spectroscopic analyses, including Fourier-transform infrared (FT-IR) spectroscopy, Raman spectroscopy, and ultraviolet–visible (UV–Vis) spectroscopy. The FT-IR and Raman spectra were estimated using density functional theory (DFT) calculations. Thorough analysis of the FT-IR spectrum was carried out in order to assign the TODGA group that mainly coordinated the metal ion. The solvation of the [TFSA]^? anion in the coordination sphere of [Nd(TODGA)_(2–3)]³⁺ was investigated by Raman spectroscopic analysis. The coordination ability of TODGA was investigated from the peak shift of the hypersensitive transition (⁴I_9/2→²G_7/2) in UV–Vis spectroscopic measurements. From electrochemical analysis, the extracted [Nd(TODGA)₃]³⁺ complex in [P₂₂₂₅][TFSA] was found to be reduced as per the following reaction: [Nd(TODGA)₃]³⁺ + 3e^? → Nd(0) + 3[TODGA] at ?3.0 V, and the diffusion coefficient of [Nd(TODGA)₃]³⁺ was calculated to be 1.6 × 10^?11 m² s^?1 at 373 K. The direct electrodeposition of the extracted [Nd(TODGA)₃]³⁺ in [P₂₂₂₅][TFSA] at 373 K allowed us to conclude that the middle layer of Nd electrodeposits was the metallic state, while a part of the top surface was the oxidation state by XPS analysis.     

Separation of cobalt and nickel from sulfate media using P507-N235 system

Separation of cobalt and nickel from sulfate media was investigated, using a extraction system of 30% 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (P507)+15% trioctyl/decylamine (N235)+55% sulfonated kerosene. About 41 wt% Co²⁺ was extracted with 1.6 wt% co-extraction of Ni²⁺ at O/A ratio of 2:1. Scrubbing of Ni²⁺ and stripping of Co²⁺ could be achieved from the loaded organic phase, using water and 0.05 mol/L H₂SO₄, respectively. Cobalt extraction percentage decreased with increasing Mg²⁺ concentration, but this influence was negligible as [Mg²⁺] < 0.1g/L. The favorable equilibrium pH was 4–4.8. A different E-pH curve was observed in the P507-N235 system compared to the saponified P507 system.     

Selective removal of copper ions from multi‐component aqueous solutions using modified silica impregnated with LIX 84

A silica support impregnated with 2‐hydroxy‐5‐nonylacetophenone oxime (LIX 84) was prepared after surface modification by ‐aminopropyltriethoxysilane. Fixed‐bed tests were conducted to investigate the capabilities of the prepared adsorbent with respect to the selective removal of copper ions from multi‐metal solutions. Break‐through curves were obtained using the modified silica for a solution containing Cu²⁺, Cd²⁺, Ni²⁺, Co²⁺ and Zn²⁺, as well as an industrial electronics wastewater sample. The copper adsorption capacities for the multi‐metal solution and the wastewater were 0.175 and 0.198 mmolg⁻¹, respectively under the conditions used in this study. The copper recovery ratios for the modified silica treated with the multi‐metal solution and the wastewater were 86 and 91%, respectively after treating with 0.1 moldm⁻³ HNO₃. The results show that the modified silica, prepared here, has potential value for the selective removal of copper ions from multi‐component aqueous solutions containing multi‐metals using a fixed‐bed reactor. © 2000 Society of Chemical Industry