Mixtures Of LIX Research Articles

Extraction of Palladium(II) from Hydrochloric Acid Solutions by Solvent Extraction with Mixtures Containing Either Cyanex 301 or LIX 63

Cyanex 301 and 5,8-diethyl-7-hydroxyldodecane-6-oxime (LIX 63) can selectively extract Pd(II) over Pt(IV) from concentrated hydrochloric acid solutions. Therefore, solvent extraction experiments have been performed by extractant mixtures containing either Cyanex 301 or LIX 63, and the extraction behavior of Pd(II) was compared. Among the mixtures of Cyanex 301, the highest synergistic enhancement coefficient was achieved by mixing Cyanex 301 and trioctylphosphine oxide (TOPO). However, it was very difficult to strip the Pd(II) from the loaded mixture phase. Among the mixtures of LIX 63, the mixture of LIX 63 and alamine 336/TOPO enhanced the extraction of Pd(II). Although the synergistic coefficient by Cyanex 301 + TOPO was higher than that by LIX 63 + Alamine 336, the Pd(II) in the loaded mixture phase of LIX 63 and alamine 336 was easily stripped by thiourea.

Separation of zirconium and hafnium from nitric acid solutions with LIX 63, PC 88A and their mixture by solvent extraction

The separation of Zr and Hf is of importance in the production of nuclear reactor grade metals. Solvent extraction experiments were performed to separate the two metals by using LIX 63, PC 88A and mixture of PC 88A and LIX 63 in the nitric acid concentration from 0.5 to 4M. Zr was selectively extracted over Hf by the above extractants. Of the two extractants, PC 88A led to higher extraction efficiency of the two metals while LIX 63 resulted in an outstanding separation factor of 186 between Zr and Hf. The mixture of LIX 63 and PC 88A had some positive effect on the extraction of the two metals but the separation efficiency of the mixture was not as high as single LIX 63. The solvent extraction reaction of Zr and Hf by LIX 63 at 2M nitric acid solution was identified by applying a slope analysis method. Selective extraction of Zr over Hf by LIX 63 was verified by varying the initial concentration ratio of Zr to Hf from 1 to 50. An optimum concentration ratio of LIX 63 to Zr was proposed to get higher separation factor. Effective stripping of Zr and Hf from loaded LIX 63 was possible by using sulfuric acid solution.

Solvent Extractive Separation of Zirconium and Hafnium from Hydrochloric Acid Solutions by Organophosphorous Extractants and Their Mixtures with Other Types of Extractants

From 1 to 4 M HCl medium, zirconium was selectively extracted over hafnium by organophosphorous extractants (D2EHPA, PC88A, Cyanex 272). In order to increase the separation factor Zr/Hf, mixtures of organophosphorous extractants with amines (Alamine 336, Aliquat 336) or cationic extractants (Versatic acid 10, LIX 63) were employed in 1–4 M HCl medium. Mixtures with Versatic acid 10 and LIX 63 led to depression in the extraction percentages. But the mixture with LIX 63 was found to be the most effective in separating the two metals among the extractant systems tested in this study. The highest separation factor of around 9.5 was obtained with a mixture of 0.01 M LIX 63 + 0.05 M Cyanex 272 at HCl concentration of 2–4 M. The Zr and Hf were effectively stripped from the loaded mixture of LIX 63 + Cyanex 272 by sulfuric acid solution.

Extraction and separation of nickel and cobalt with hydroxamic acids LIX®1104, LIX®1104SM and the mixture of LIX®1104 and Versatic 10

Solvent extraction and separation of Ni and Co in a typical synthetic laterite leach solutions with LIX®1104 (unmodified), LIX®1104SM (modified), and the mixed LIX®1104/Versatic 10 were comparatively investigated to obtain fundamental data on pH and distribution isotherms, extraction and stripping kinetics, phase separation properties, and to identify any synergistic and antagonistic effect for potential applications.The results show that LIX®1104 was highly selective for Zn, Co and Ni over Mn, Mg and Ca, with their pH50 differences over manganese being 2.2, 1.9 and 1.8 pH units, respectively. In comparison, the pH isotherms of Zn, Ni, Co and Mn with LIX®1104SM were shifted to a higher pH range, but the pH50 differences all exceeded 2 pH units, suggesting ready separations of these valuable metals from Mn, Mg and Ca. For the synthetic laterite leach solution with 3.0g/L Ni and 0.19g/L Co, at an A/O ratio of 0.8 and pH 6.5, two theoretical stages could achieve a few mg/L Ni and Co in the raffinate. The extraction kinetics of Ni, Co, Cu and Zn with LIX®1104SM was fast. Except for copper and iron, other metals extracted can be stripped with 35g/L H2SO4 at 23°C. The copper and iron can then be stripped at higher temperature with a stronger acidic solution. The rate of phase disengagement with LIX®1104 and LIX®1104SM was comparable to commercial reagents such as D2EHPA and Versatic 10. The mixed LIX®1104 and Versatic 10 system did not offer an additional advantage in terms of selectivity and extraction efficiency.

Synergistic Extraction of Ni(II) by Mixtures of LIX 860 and Bis(2‐Ethylhexyl) Phosphoric Acid

The equilibria of extraction of Ni(II) from 1.0 M nitrate medium by mixtures of LIX 860 and bis‐(2‐ethylhexyl)phosphoric acid (HDEHP) dissolved in toluene have been studied. Synergistic effects have been obtained and explained in terms of the formation of mixed complexes of stoichiometries NiL2(HL)(HR) and NiL2(HR)4, HL being 5‐dodecylsalicylaldoxime, the active component of LIX 860, and HR representing HDEHP. Values of the equilibrium constants of the extraction reactions are given.

Synergic extraction of lanthanoids by mixtures of LIX 54 (high molecular weight beta-diketone) and bidentate neutral amines.

The synergic extraction of lanthanoids has been investigated using mixtures of high molecular weight beta-diketone, LIX 54 (HA; major component, 1-phenyl-3-isoheptyl-1,3-propanedion) and bidentate neutral ligands (S) in toluene. The distribution behavior of bidentate amines (2,2'-bipyridine (bpy), 1,10-phenanthroline (phen) and 2,9-dimethyl-1,10-phenanthroline (dmp)) was investigated and their related equilibrium constants were evaluated. The synergic effect is produced by the formation of such adduct complexes as MA3 x S. The extraction constants with LIX 54 alone and those in the presence of bidentate ligands were determined for lanthanoid-series elements.

Batch Extraction Studies of Cationic and Anionic Heavy Metallic Species by a Mixed Solvent Extraction System

ABSTRACT Removal of toxic heavy metals from wastewaters and their recovery is a challenging problem. Simultaneous and synergistic batch extraction from water of copper present as a cation (Cu2+) and Cr6+ present as an anion (HCr2O) into a mixed solvent extraction system have been studied. The mixed solvent extraction system consists of the diluent kerosene, the cation exchanger LIX 84, and trioctyl amine (TOA) which extracts anions via ion-pair formation with a proton. Highly efficient extraction has been achieved for both copper and chromium. Simultaneous extraction of two cations, Cu2+ and Zn2+, as well as the anionic form of Cr6+, (HCr2O), has also been studied using mixtures of LIX 84, di-2-ethylhexyl phosphoric acid (D2EHPA), and TOA in the diluent kerosene. For an appropriate mixture composition, all three metallic ionic species can be simultaneously extracted with high efficiency. The extent of complexation between the basic extractant, TOA, and the acidic extractant/s is important in determining the extraction efficiency. A model developed for the extraction of Cu2+ using a mixed solvent extraction system provides a reasonable description of the observed extraction behavior and provides a first step for modeling.

Recovery of metal values from spent hydrodesulfurization catalysts by liquid-liquid extraction

The total dissolution of spent hydrodesulfurization catalysts in sulfuric acid yields an acidic solution containing a certain amount of rare metals like molybdenum, vanadium, cobalt, nickel, and a small amount of iron as well as an appreciable amount of aluminum. For the purpose of recovering the metallic values present in the solution, in the current work, the fundamental extraction characteristics of these metals with some typical commercial acidic organophosphorus compounds such as TR-83, PC-88A, PIA-8, and CYANEX 272 from the sulfuric acid media were investigated, and CYANEX 272 and PIA-8 were found to be suitable for selectively separating and recovering molybdenum and vanadium over the other metals from the specific solution at comparatively low pH. In addition, in order to further recover cobalt and nickel from the raffinate in the presence of a large excess of aluminum, a systematic investigation was conducted on the synergistic extraction behaviors of the mixed solvents consisting of LIX 63, an aliphatic α-hydroxyoxime extractant, and a series of acidic extractants such as CYANEX 272, PIA-8, PC-88A, D 2 EHPA, TR-83, and OPEHPA for cobalt, nickel, and aluminum. It was elucidated that all of these mixtures could exhibit a good synergistic effect for extraction of cobalt and nickel and that the lower the pK a of the acidic extractants, the greater the synergism. Contrarily, the extraction of aluminum, was considerably depressed by LIX 63. Using the difference in synergistic extraction performance between these metals, the effective extraction of cobalt and nickel away from aluminum was achieved from the sulfate solution at relatively low pH with the mixtures. In particular, the mixtures of LIX 63 in combination with CYANEX 272 or PIA-8 appeared to be the most feasible and economic from a practical point of view yielding acceptable separation efficiency for cobalt and nickel over aluminum and a low acidity requirement for stripping cobalt and nickel as well as negligible degradation of LIX 63. A full recovery processing route is proposed based on the experimental results.

The extraction of uranium(VI), americium and europium by LIX 64 and by a mixture of LIX 64 and tri-n-octylphosphine oxide

The extraction of U(VI), Eu and Am by the aromatic main component (HA) of LIX 64N dissolved in toluene was studied at pH 3–9. The values of pH1/2 for the extraction with 0.146 M HA are 4.0, 5.5 and 5.2, and the pH's of maximum extraction are 6.0, 6.8, and 7.0 for U(VI), Eu and Am, respectively. The stoichiometry of the extracted chelates determined by the slope analysis is UO2A2 and MA3−nYn (n=1,2) for Eu and Am, the ligand Y being probably the nitrate anion. The addition of tri-n-octylphosphine oxide (TOPO) enhances the extraction of U(VI) and especially of Eu at pH<6. An Eu chelate species solvated by 2 TOPO molecules is extracted at pH 4 by the mixture of HA+TOPO, whereas the species extracted at pH 6.5 is not solvated by TOPO.

Solvent extraction of zinc(II) and copper(II) with mixtures of LIX 34 and versatic 911 in kerosene

The solvent extraction of Zn(II) and Cu(II) with LIX 34 (HL) and mixtures of LIX 34 and Versatic 911 has been investigated. The compositions of the extracted complexes have been determined as ZnL 2 · HL and CuL 2. No synergism was found when mixtures of LIX 34 and Versatic 911 were used.