Fundamental aspects of lead extraction and stripping by a liquid ion exchange reagent

LIX 34 liquid ion exchange reagent was introduced commercially by General Mills in 1976. The fundamental aspects of lead extraction and stripping using LIX 34 as the organic extractant in acetic solution has been studied here. Equilibrium isotherms for extraction and stripping, isothermal pH effects, temperature effect, loading capacity and the rate of extraction and stripping on the system Pb²⁺-HAc-LIX 34—Kermac 470B are reported.     

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.     

The extraction of platinum from Pt(II) chloride solution by a quaternary ammonium compound

The fundamental aspects of the extraction and stripping of platinum (II) from its chloride solution by Aliquat 336 diluted with toluene have been studied. The extraction and stripping was at 99.5 and 97.6% equilibrium within 30 s and 20 min respectively. The percentage extraction increased slightly with decreasing hydrochloric acid concentration. In 0.1 mol dm^?3 hydrochloric acid, 1.0 volume percent Aliquat 336 in toluene could load 9.8 mmol dm^?3 of platinum (II). The percentage stripping of platinum (II) from Pt(II)-load organic solvent increased with increasing sodium bisulphite concentration. The enthalpy changes of extraction and of stripping were 12.8 and 114.9 kJ mol^?1 respectively. Both of the reactions were endothermic.     

SPECTROSCOPIC STUDY OF THE EXTRACTION OF NICKEL BY 2-HYDROXY-5-NONYLBENZOPHENONE OXIME (LIX 65N) AND 5,8-DIETHYL-7-HYDROXYDODECANE-6-ONE OXIME (LIX 63).

ABSTRACT

A novel method for determination of solvent extraction equilibria and kinetics using Infrared attenuated total reflectance spectroscopy (ATR) is described. The method allows complete, quantitative kinetic studies using a total of one gram of extractant. Solvent extraction of aqueous Ni²⁺ into 0.5 - 1.0 μm films of Apiezon M (ApM, aliphatic hydrocarbon) containing the title reagents was examined. In contrast with LIX 65N extraction which proceeds solely through the LIX 65N anion, extraction of Ni²⁺ by LIX 63 proceeds through both neutral and anionic forms of LIX 63. This results in a kinetic rate law having two terms, each exhibiting first order dependence on both [Ni²⁺] and [LIX 63]₀. For mixtures of LIX 65N and LIX 63 (LIX 63:LIX 65N ≤ 0.12) In the ApH films, the rate law has only one term, of orders [LIX 65N]₀ ¹, [LIX 63] ₀ ¹, [Ni²⁺]¹, and [H⁺]^?1. While the equilibrium constants favor Ni(LIX 65N)₂, the relatively large rate of reaction of the neutral LIX 63 leads to a catalysis of the overall LIX 65N extraction.     

Solvent extraction with LIX 973N for the selective separation of copper and nickel

LIX 973N diluted with Iberfluid was used to co‐extract copper and nickel from ammoniacal/ammonium carbonate aqueous media. The influence of equilibration time, temperature, equilibrium pH and extractant concentration on the extraction of both metals has been studied. It was observed that neither copper nor nickel extraction is sensitive to temperature and equilibrium pH, however nickel extraction equilibrium is reached at a longer contact time (20 min) than that of copper (5 min), in addition nickel extraction depends greatly on the extractant concentration in the organic phase. For a solution containing 3 g dm⁻³ each of copper and nickel and 60 g dm⁻³ ammonium carbonate, conditions were established for the co‐extraction of both metals, ammonia scrubbing and selective stripping (with H₂SO₄) of nickel and copper. Using the appropriate extractant concentration the yield (extraction stage) for both metals is near 100%, whereas the percentage of nickel and copper stripping is also almost quantitative. © 1999 Society of Chemical Industry     

ANAEROBIC EXTRACTION OF COBALT IN A PULSE COLUMN

The effects of excluding air (oxygen) from a cobalt solvent extraction circuit were studied for LIX 64N extractant. After solvent extraction of divalent cobalt from ammoniacal solutions with chelating extractants such as LIX 64N, the loaded Co-chelate is believed to oxidize to a stable trivalent complex which resists subsequent stripping with mineral acids. To Improve stripping efficiency, cobalt was extracted and stripped in the absence of oxygen in pulsed, perforated-plate columns that were designed and constructed by the Bureau of Mines. When the ammoniacal cobalt(II) sulfate and LIX 64N solutions were purged, blanketed, and pulsed with argon, cobalt extraction exceeded 99%, and stripping with 1 vol % H₂SO₂ reached 98.5%. The stripped extractant was recycled to the extraction column with no loss of extraction efficiency in six passes through the circuit.     

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.     

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).     

Separation of Palladium and Silver from a Nitric Acid Solution by Liquid Surfactant Membranes

Abstract

The recovery of palladium from a nitric acid solution containing silver has been conducted by application of liquid surfactant membranes (LSMs) containing LIX 860, a β-hydroxyoxime, as a mobile carrier in a stirred tank. The extraction equilibria of palladium and silver using several different extractants were also studied. Palladium was selectively extracted from a silver-containing liquor with LIX 860 while it was also observed that both palladium and silver were extractable with a sulfur-containing extractant. The recovery of palladium with LIX 860 was selectively achieved by using perchloric acid solution as the LSM internal phase dosed with thiourea. In the LSM operation, the effects of several chemical parameters on the selective recovery of palladium were studied. The use of hydrochloric acid as an internal receiving phase prevented the transport of silver into the emulsion due to the formation of silver chloride in the external feed solution. Commercially available Span 80 was found suitable for the selective extraction of palladium as a surfactant in LSM operation. Under optimum conditions, palladium was successfully separated from silver and concentrated into a receiving phase in W/O emulsions.     

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.     

Recovery of Zinc by LIX 984N‐C from Electroplating Rinse Bath Solution

The development of a complete solvent extraction process at the laboratory scale for recovering zinc from the zinc electroplating first rinse bath solution (alkali solution) containing ～1.9 g/L zinc (ZEFRBS) by a solvent extraction route using LIX 984N‐C, which is a new SX reagent developed by Cognis, and dissolved in commercial kerosene was investigated. By using LIX 984N‐C, an electrolyte from ZEFRBS with ～12 g/L zinc content, which was addable to the alkali zinc electroplating bath, was generated by 10 vol.% LIX 984N‐C in commercial kerosene at the O/A ratio of 1/4 and equilibrium pH value of 8.00 ± 0.05 with a two‐stage countercurrent extraction, and stripping of the loaded organic by a strip solution with 150 g/L sulfuric acid and with the O/A ratio of 1.5 at a two‐stage countercurrent stripping process. A new complete flow sheet of 10 vol.% LIX 984N‐C process for the recovery of zinc from ZEFRBS has been demonstrated.     

Study of polymer-bound mixed valence palladium catalysts. I. Preparation and characterization of polymer-bound mixed valence palladium catalysts

Polymer-bound palladium catalysts of different valence have been prepared by reducing PdCl₂ with a proper reductant, i.e., hydrazine hydrate, under certain conditions. ESR, XPS and IR were used to characterize the catalysts. Pd ⁺ was prepared for the first time and found to be stable on the polymersupport. The authors also investigated the influences of the reducing conditions, the surface properties of polymer supports and the effectsof reducing agents on the degree of reduction of divalent palladium bound onto the polymers, and the state of the palladium after reduction. The experimental results showed that the coexistence of different valence states of palladium in the supports may be Pd ²⁺, Pd^O; Pd²⁺, Pd⁺ (or Pd^δ+); Pd^O and Pd²⁺ Pd⁺ (or Pd^δ+), Pd^O. The method of preparing catalysts of mixed valence is described.     

The Solvent Extraction Performance of N,N’-Dimethyl-N,N’-Dibutylmalonamide Towards Platinum and Palladium in Chloride Media

The solvent extraction performance of N,N’-dimethyl-N,N’-dibutylmalonamide (DMDBMA) in 1,2-dichloroethane (1,2-DCE) towards platinum(IV) and palladium(II) in hydrochloric acid media was systematically evaluated. Pt(IV) extraction (%E) increases with the HCl concentration in the aqueous phases, being always higher than 72%, whereas Pd(II) extraction decreases from 65% at 1 M HCl to 22% at 8 M HCl. Several stripping agents for the two metals were tested: Pt(IV) is successfully recovered by a 1 M sodium thiosulfate solution, whereas the best result for Pd(II) was achieved with 0.1 M thiourea in 1 M HCl. The loading capacity of DMDBMA for Pt(IV) is high, and data obtained from successive extraction-stripping cycles suggest a good DMDBMA stability pattern. Attempts to replace 1,2-DCE by more environmentally-friendly diluents showed, in general, worse %E for Pt(IV). The dependence of Pt(IV) distribution coefficients on DMDBMA and chloride ion concentrations, as well as on acidity, are the basis of a proposal for the composition of Pt(IV) extracted species.     

Study of interfacial kinetics for liquid-liquid systems—II: Intrinsic kinetics of the copper chelation reaction with an oxime-based reagent

The interfacial chelation of copper from copper sulfate-sulfuric acid solutions by the commerical oxime extractant LIX65N in toluene is studied using the liquid jet recycle reactor. The intrinsic initial rate of copper chelation by LIX65N is found to be represented in mol. cm^?2-sec^?1 by the expression R = $\text{1.22 × 10}{}^{\mathrm{?8}}\text{{Cu}{}^{\mathrm{2+}}\text{}[LIX65N]}\text{{H}{}^{\mathrm{+}}\text{} + 0.0288[LIX65N]}$ where {Cu²⁺} and {H⁺} are the cupric and hydrogen activities. The interfacial rate expression above is determined as free from diffusional contributions by using a numerical solution to model mass transfer with interfacial reaction in the LJRR. The above expression is selected on statistical and physical grounds from a set of models systematically generated from the most probable reaction pathways. The liquid jet technique has been shown to be an effective and accurate (±6% experimental error) technique for the study of liquid-liquid interfacial reactions.     

Fatty Imidazolines: A Novel Extractant for the Recovery of Palladium(II) from Hydrochloric Acid Solutions

The extraction of palladium(II) from hydrochloric acid solutions with a novel highly basic extractant, a mixture of homologous 1-[2-(alkanoylamino)ethyl]-2-alkyl-2-imidazolines (AAI) in toluene with 15% (v/v) of n-octanol was studied. Palladium(II) is rapidly and most effectively extracted with AAI hydrochloride at the low hydrochloric acid (chloride ions) concentration (up to 1 M) and can be completely separated from Fe(III), Cu(II), and Co(II). The palladium(II) extraction at the optimum acidity occurs via an anion-exchange mechanism with the formation of ionic associates (LH)₂PdCl₄ (K _ex = (1.5 ± 0.2) · 10⁴ at 0.5 M HCl) and is accompanied by the dimerization of palladium(II) in the organic phase with the formation of ionic associates (LH)₂Pd₂Cl₆ (K _dim = (3.9 ± 0.4) · 10^?4 at 0.5 M HCl). The anion-exchange extraction of palladium(II) at the acidity of 0.5 M HCl is temperature independent in the range 20–49°C. Complete stripping of palladium(II) can be performed using a 5% solution of thiourea in 0.1 M HCl.     

Extraction of copper from dilute solutions by LIX 64N. Effect of dekalin and tetralin as diluents on the equilibrium and rate of mass transfer

Liquid-liquid equilibrium data and mass transfer rates for the extraction of copper from dilute aqueous sulphate solutions by LIX 64N with dekalin (decahydronaphthalene) and tetralin (1,2,3,4-tetrahydronaphthalene) as diluents are reported. The stripping of copper from the organic phase was also studied. For an initial copper concentration of 1.5 g dm^?3 extraction efficiency decreases as the concentration of tetralin increases in the diluent mixtures of dekalin-tetralin. This behaviour is explained as a result of the formation of oxime aggregates and the interaction between the oxime and the diluent. Initial rates of extraction and stripping were determined by the single drop technique. The linear relation between initial rates of extraction and the difference of interfacial tension between the extractant in the diluent and the diluent itself holds for the system under investigation.     

RATE OF COPPER EXTRACTION WITH LIX 64N USING A LAMINAR LIQUID JET

The rates of copper extraction from aqueous sulphate solutions by LIX 64N dissolved in kerosene were studied using a laminar jet recycle reactor (LJRR). The extraction rates were fitted to an empirical equation based on the overall reaction. Results are compared with those reported for LIX 65N using the same technique and for LIX 64N using the single drop technique.     

RATE OF COPPER EXTRACTION WITH LIX 64N USING A LAMINAR LIQUID JET

The rates of copper extraction from aqueous sulphate solutions by LIX 64N dissolved in kerosene were studied using a laminar jet recycle reactor (LJRR). The extraction rates were fitted to an empirical equation based on the overall reaction. Results are compared with those reported for LIX 65N using the same technique and for LIX 64N using the single drop technique.     

N,N,N′,N′-Tetra(2-Ethylhexyl) Thiodiglycolamide T(2EH)TDGA: A Promising Ligand for Separation and Recovery of Palladium from High Level Liquid Waste (HLLW) Solutions

The extraction properties of N,N,N′,N′-tetra(2-ethylhexyl)thiodiglycolamide T(2EH)TDGA have been evaluated for the separation and recovery of palladium from simulated high-level liquid waste (SHLW). T(2EH)TDGA has shown very high selectivity for Pd (II) over other metal ions present in SHLW. The separation factor (SF) for Pd (II) over other metal ions was found to be more than 10⁵. Reusability studies of the extractant indicate that D_Pd remained almost constant even after five successive cycles of extraction and stripping. Palladium was quantitatively recovered from thiourea strip solution by treating it with ammonia and filtering the precipitate of palladium sulphide. The acid uptake constant (K_H) was found to be 0.62 which could be due to the presence of two carbonyl groups of amidic moiety. To account for very high extractability of palladium with T(2EH)TDGA over other ‘S’ donor extractants, namely Bis-(2-ethylhexyl)sulphoxide (BESO), FTIR, as well as Raman studies were carried out. FTIR and Raman studies suggested the ligation through carbonyl as well as the thio-ether group. Conditional extraction constants (log K′_ex) were determined and the thermodynamic parameters were calculated from the dependence of the conditional extraction constant (log K′_ex) on temperature. The calculated values of ΔG_ex, ΔH_ex, and ΔS_ex were ?41.78 kJmol^?1, ?55.12 kJmol^?1 and ?44.04 JK^?1 mol^?1 respectively. The extraction process is indicated to be enthalpy driven with the entropy factor counteracting it.     

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.