Synergistic Solvent Extraction System Research Articles

Separation of lithium from sodium in chloride solutions using SSX systems with LIX 54 and Cyanex 923

A novel synergistic solvent extraction (SSX) system consisting of LIX 54 and Cyanex 923 in ShellSol D70 to recover lithium and separate it from sodium in chloride solutions has been developed. With the SSX system, over 97% of lithium was extracted at pH11 from a synthetic solution with almost no extraction of sodium in a single contact, resulting in a separation factor of lithium over sodium of 1560, indicating very good separation. The co-extracted sodium could be readily scrubbed from the loaded organic solution using water. Lithium was readily stripped with acidic solution and complete strip was achieved at an equilibrium pH of 3.5. The lithium extraction McCabe Thiele diagram showed that three theoretical stages could be used to completely extract lithium from the synthetic solution using an aqueous/organic (A/O) ratio of 2:1. Based on the lithium strip McCabe Thiele diagram, two theoretical stages are required with a 0.5M HCl strip solution at an A/O ratio of 1:3. The lithium extraction and strip kinetics were very fast. The extracted lithium species was found to be LiAB, where A and B represents the deprotonated LIX 54 (A) and Cyanex 923, respectively.

Recovery of germanium from synthetic leach solution of zinc refinery residues by synergistic solvent extraction using LIX 63 and Ionquest 801

A synergistic solvent extraction (SSX) system consisting of LIX 63 and Ionquest 801 was identified and developed to recover germanium from a synthetic leach solution of zinc refinery cementation residues. A significant synergistic effect was identified with this novel SSX system, which selectively extracted germanium over other metals in the synthetic leach solution. The SSX system consisting of 0.13M anti-oxime from LIX 63 and 0.13M Ionquest 801 in ShellSol 2046 is an optimised composition for the extraction of germanium from the synthetic leach solution containing 1g/L Ge(IV) and 1.0M H2SO4.The germanium(IV) extraction kinetics was slow with the equilibrium reached after 20min of mixing at 40°C. The stripping kinetics of germanium(IV) with strip solution containing 0.5M NaOH and 1.0M Na2SO4 was very fast with the equilibrium reached in 1min of mixing.Slope analysis showed that, most possibly, the extracted Ge(IV)-organic species is 2Ge(SO4)2·(HA)·(HB)2·H2SO4 via a solvating mechanism with the SSX system consisting of Ionquest 801 (HA) and LIX 63 (HB).

The Effect of Hydroxyoxime Isomer Conformation on Metal Extraction in the LIX 63/Versatic 10 Synergistic System

LIX 63 contains an aliphatic α-hydroxyoxime as its active component, with two isomeric forms (anti and syn) being present in a 3:2 ratio in “as supplied” reagent. In the present work, > 90% pure syn hydroxyoxime was isolated from LIX 63. Examination of metal extraction properties in systems containing Versatic 10 with anti and/or syn hydroxyoxime established unequivocally that the syn isomer plays no beneficial role in metal extraction in this synergistic solvent extraction system, thereby excluding the possibility of monodentate coordination of hydroxyoxime. Economic consequences arising from this outcome and the opportunity to maximize reagent utilisation are briefly discussed.

Separation and recovery of copper, nickel, cobalt and zinc in chloride solutions by synergistic solvent extraction

The synergistic solvent extraction (SSX) system consisting of LIX63, Versatic 10 and TBP in Shellsol D70 can be used to separate copper, nickel, cobalt and zinc from strong chloride solutions and to transfer copper and nickel to sulphate media for electrowinning.In the first circuit with the SSX system, over 95% Cu was extracted after a single contact, with the co-extraction of some 12% Ni and negligible Co, Mn and Ca. The loaded organic solution could be scrubbed using water to produce the loaded strip liquor suitable for copper conventional electrowinning. In the second circuit with an SX system consisting of Alamine 336 and TBP in Shellsol D70, over 99% Zn, 87% Co and 43% Mn were extracted at pH 3.5 from the copper depleted raffinate after a single contact. The co-extraction of Ni and Ca was negligible. After stripping, the zinc, cobalt and manganese in the loaded strip liquor could be separated from each other using conventional solvent extraction or ion exchange techniques. In the third circuit for nickel with the same SSX system, over 98% Ni was extracted from the copper–cobalt–zinc depleted raffinate in a single contact. The co-extraction of chloride, manganese and calcium was small and was scrubbed. After stripping using spent nickel electrolyte, the loaded strip liquor would be suitable for conventional electrowinning. The nickel extraction and stripping kinetics were reasonably fast for industrial operation. A process flowsheet to recover copper, cobalt, zinc and nickel from strong chloride leach solutions has been proposed.

The effect of individual complexed metals on hydroxyoxime stability in the LIX 63–Versatic 10–tributyl phosphate synergistic solvent extraction system under synthetic nickel laterite extract conditions

The effect of nil metal complexation and complexing nickel, cobalt, copper, zinc and manganese, both individually and collectively, on the chemical stability of LIX® 63 hydroxyoxime (‘hydroxyoxime’) when in the presence of Versatic 10 and tributyl phosphate (TBP) under synthetic nickel laterite extract conditions at 45°C has been assessed. Hydroxyoxime degradation was observed at pH 5.5–6.0 even in the absence of metal complexation, resulting in half lives of 53–56weeks. Although loading up to 0.2g/L of copper, cobalt or zinc had no material effect, progressively increasing the loading of these individual metals up to 3g/L resulted in hydroxyoxime half lives decreasing to 12, 21 and 28weeks, respectively. Manganese loading of 0.5–2.0g/L also had an adverse effect, with a half life of 31weeks. In contrast, nickel loading up to 4.6g/L had little or no adverse effect on half life (48weeks). Based on the present results, increasing hydroxyoxime half life can be achieved by minimising copper and manganese loading.

A synergistic solvent extraction system for separating copper from iron in high chloride concentration solutions

A synergistic solvent extraction (SSX) system consisting of Versatic 10 and LIX 63 has been developed to separate copper from iron in high chloride concentration solutions and to transfer the extracted copper to a sulphate solution for recovery by conventional electrowinning. The SSX system is able to selectively extract copper over iron and other impurity metals from chloride solutions in extraction stages. The co-extracted iron and chloride in the loaded organic solution are scrubbed in two separate scrub circuits. A spent electrolyte is used to strip the copper from the scrubbed organic solution for conventional copper electrowinning. A process flow sheet from leaching with chloride solutions to copper conventional electrowinning is proposed.It is proposed that in high chloride concentration solutions, copper exists as neutral molecule of CuCl2, which forms complexes with the organic components of the SSX system via a solvating mechanism. After scrubbing the chloride from the organic system with water at an appropriate pH, the copper is proposed to be re-extracted via a cation exchange mechanism by the same organic system.

The effect of temperature on hydroxyoxime stability in the LIX 63 – Versatic 10 – tributyl phosphate synergistic solvent extraction system under synthetic nickel laterite conditions

The chemical stability of LIX ® 63 hydroxyoxime (‘hydroxyoxime’) when in the presence of Versatic 10 and tributyl phosphate (TBP) has been assessed under synthetic nickel laterite extract conditions between 30 and 60 °C and strip conditions at 60 °C. In all extract systems, nominally at pH 5.5, syn to anti hydroxyoxime isomer inter-conversion was observed. The hydroxyoxime half life under extract conditions at 30 °C was almost two years. Increasing the operating temperature to 60 °C under otherwise identical conditions saw this decrease to 8 weeks. Hydroxyoxime degradation resulted in the generation of previously identified products 5,8-diethyl-6,7-dodecanedione (diketone) and 5,8-diethyldodecan-6-oxime-7-one (‘keto-oxime’) and the nett loss of 5,8-diethyl-7-hydroxy-6-dodecanone (acyloin), as expected. These products do not quantitatively account for all hydroxyoxime loss. The activation energy for hydroxyoxime decomposition under the chosen extract operating conditions was calculated to be 70 kJ/mol, with a pre-exponential factor of 9.0 × 10 9 per week. The hydroxyoxime half life when determined under strip conditions, using 10 g/l sulphuric acid, at 60 °C was 26 weeks, with degradation yielding diketone and acyloin in a near-stoichiometric manner. Analysis, in conjunction with studies performed previously, allowed the activation energy for hydroxyoxime decomposition under strip conditions to be determined as being 58 kJ/mol, with a pre-exponential factor of 3.0 × 10 7 per week.

Synergistic Solvent Extraction of Nickel and Cobalt: A Review of Recent Developments

Synergistic solvent extraction of nickel and cobalt has been an important research subject since the 1960s. In recent years, several synergistic systems have been further developed for possible industrial application, including carboxylic acids/pyridinecarboxylates for the separation of nickel and calcium; carboxylic acids/α-hydroxyoxime systems for the separation of cobalt from manganese, magnesium, and calcium, and carboxylic acid/α-hydroxyoxime/organophosphate systems for the separation of nickel and cobalt from manganese, magnesium, and calcium. The separation of nickel and cobalt from iron and aluminum using synergistic systems has also been explored. Industrial application of synergistic solvent extraction systems is expected in the near future.

Separation of Cobalt and Zinc from Manganese, Magnesium, and Calcium using a Synergistic Solvent Extraction System Consisting of Versatic 10 and LIX 63

The Boleo leach solution contains large amounts of manganese (45 g/L), magnesium (25 g/L) and small amounts of cobalt (0.2 g/L) and zinc (1 g/L) in sea water. Due to the high manganese concentration, it is very difficult to separate cobalt and zinc from manganese, magnesium, and calcium using conventional solvent-extraction processes, which has led to the development of a synergistic solvent extraction (SSX) system consisting of Versatic 10 and LIX®63. By adding 0.4 M LIX 63 to 0.5 M Versatic 10, large synergistic shifts were obtained for cobalt (max. ΔpH50 4.24) and zinc (max. ΔpH50 1.62). After a single contact at pH 4.5, the extraction of cobalt was almost complete and that of zinc 80%. The extraction of manganese was 1.55%, and almost no magnesium and calcium were extracted, indicating excellent separation of cobalt and good separation of zinc from manganese, magnesium, and calcium. The SSX system was further optimized to reduce the co-extraction of manganese with the synthetic Boleo demonstration plant solution. It was found that with 0.33 M Versatic 10 and 0.30 M LIX 63, the SSX system composition approached optimum. After a single contact at pH 5.5, the extractions of cobalt and zinc were 93% and 70%, respectively, while the manganese concentration in the loaded organic solution was only 0.28 g/L. The extraction and stripping kinetics of cobalt and zinc were rapid. The SSX system was tested in two integrated pilot-plant trials with excellent results. Baja Mining has planned to implement the SSX circuit in their future Boleo plant.

Recovery of nickel and cobalt from laterite leach solutions using direct solvent extraction: Part 2: Semi- and fully-continuous tests

In Part 1 of this paper, two synergistic solvent extraction systems consisting of Versatic 10/LIX63/TBP and Versatic 10/4PC were assessed in batch tests for the separation and purification of nickel and cobalt from synthetic laterite leach solution after iron removal. In Part 2, semi- and fully-continuous tests are reported for the Versatic 10/LIX63/TBP system, with conditions optimised for separating nickel and cobalt from manganese, magnesium and calcium. Semi-continuous extraction tests were conducted using the synergistic organic system consisting of 0.50 M Versatic 10, 0.45 M LIX63 and 1.0 M TBP in Shellsol D70. With a pH profile of 5.5/6.1/6.5 for the three stages EX1/EX2/EX3 at 40 °C, the nickel and cobalt extractions were 99.9% with only 5 mg/L nickel and < 1 mg/L cobalt left in the raffinate. With two stages of scrubbing and a pH profile of 5.4/5.0 at 40 °C, about 2 mg/L manganese and less than 1 mg/L magnesium and calcium were left in the scrubbed organic solution. With two stripping stages and an O/A ratio of 10 at 40 °C using 50 g/L H 2SO 4 as strip solution, the stripping efficiencies of nickel and cobalt were over 95%. A fully-continuous pilot plant was operated for 280 h. With an O/A ratio of about 2 and a pH profile of 5.5/5.8/6.0/6.3 for the four stages EX1/EX2/EX3/EX4 at 40 °C, both nickel and cobalt were almost completely extracted. The nickel and cobalt concentration in the raffinate was lower than detection limit of 0.2 mg/L. The manganese, magnesium and calcium concentrations in the loaded organic solution were 34, 8 and 1 mg/L, respectively. Using a pH profile of 5.4/5.0 for SC1/SC2 at an O/A ratio of 10 and 40 °C, the manganese scrubbing efficiency was over 96% and the concentrations of manganese and magnesium in the scrubbed organic solution were < 5 mg/L and that of calcium 1 mg/L. Using three strip stages and a strip solution containing 50 g/L H 2SO 4 and 55 g/L Ni at an O/A ratio of 10 and 40 °C, over 98% Ni and 99% Co were stripped with only 64 mg/L Ni in the stripped organic solution. The nickel concentration in the loaded strip liquor was 86 g/L, giving a ΔNi of 31 g/L. The loaded strip liquor contained less than 1 g/L acid.

Recovery of nickel and cobalt from laterite leach solutions using direct solvent extraction: Part 1 — selection of a synergistic SX system

The separation of nickel and cobalt from impurities such as manganese, magnesium and calcium using solvent extraction with Versatic 10 was largely improved by the addition of a synergistic reagent LIX63 (an α-hydroxyoxime) or 4PC (a pyridine carboxylate ester). With the organic systems containing Versatic 10 alone, the separation factors of nickel and cobalt over manganese were 6 and 15 respectively. When 4PC was added to the system, these increased to 147 and 1870 respectively, and with LIX63, they were even higher at 534 and 7720 respectively. This indicates that the synergistic solvent extraction (SSX) system with Versatic 10 and LIX63 performed very well and better than that with Versatic 10 and 4PC. The SSX system consisting of 0.5 M Versatic 10, 0.45 M LIX63 and 1.0 M TBP in Shellsol D70 performed the best among the systems tested containing LIX63. After a single contact, the extraction of Ni and Co was 99.6% and 96.9%, respectively. Only 6 mg/L Mn, 8 mg/L Mg and 1 mg/L Ca were found in the loaded organic solution. The manganese scrub efficiency was 97.7% at pH 5.3, resulting in a scrubbed organic solution containing only 0.8 mg/L Mn. Over 99% nickel, cobalt and manganese were stripped at pH 2.0, indicating easy stripping of these metals. The SSX system consisting of 0.5 M Versatic 10 and 1.0 M 4PC in Shellsol D70 performed the best among the systems tested containing 4PC. After a single contact, the extraction of Ni and Co was 99.4% and 89.4%, respectively. Some 200 mg/L Mn, 10 mg/L Mg and 48 mg/L Ca were found in the loaded organic solution. The manganese could not be scrubbed at the tested pH range of 5.4–6.0. Very fast Ni and fast Co stripping kinetics were observed, however, the Mn stripping kinetics were very slow. After 2 min of stripping, only 1.22% Mn was stripped. It is concluded that the SSX system containing 0.5 M Versatic 10, 0.45 M LIX63 and 1.0 M TBP performed much better than the SSX system containing 0.5 M Versatic 10 and 1.0 M 4PC in terms of both manganese and calcium behaviour in extraction, scrubbing and stripping.

Characterization of europium(III) carbonate complexes in simulated groundwater by solvent extraction

The complex formation of Eu(III) by bicarbonate/carbonate ions has been studied at 0.1 M ionic strength and 25°C using synergistic solvent extraction system of 1-nitroso-2-naphthol and 1,10-phenanthroline in chloroform. Concentrations of bicarbonate (5·10−3 to 1·10−1 M) and carbonate (5·10−4 to 1·10−2 M) ions in the aqueous phase have been varied in the pH range of 8.0 to 9.1 to simulate ground and natural water compositions. Under these conditions, the following species have been identified: Eu(HCO3)2+, Eu(HCO3)2+, Eu(CO3)+ and Eu(CO3)2−. Their conditional formation constants (log β) have been calculated as 4.77, 6.74, 6.92 and 10.42, respectively. These values suggest that the carbonate complexes of Eu(III) are highly stable.

THE INTERPRETATION OF EQUILIBRIUM DATA FROM SYNERGISTIC SOLVENT EXTRACTION SYSTEMS

ABSTRACT The quantitative description of synergistic solvent extraction systems is usually a difficult problem in equilibrium analysis because a relatively large number of species can be involved. Both sophisticated methods of interpretation and extensive experimental data are required. The graphical methods of “slope analysis”and “continuous variation”provide useful guidance only when the minimum number of species is present and especially when there are no competing reactions between the two synergistic extractants. A general least squares computer program (SXLSQ)is described to deal with the general case in which many possible species must be considered. It will accept six different kinds of equilibrium data for a given system in a single data set and can be used interactively at a terminal. Analysis of data on the extraction of Mn(II) by an organophilic sulfonic acid in combination with each of two crown ethers showed that a unique identification of the species formed cannot be made without additional information about the degree of association of the sulfonic acid in the organic diluent. But narrow limits could be placed on ratios of the integers defining the principal species formed.