Maximizing selectivity in liquid-liquid extraction of lanthanoids with sym-dibenzo-16-crown-5-oxyacetic acid and 18-crown-6 crown ethers
Selectivity of lanthanoids (Ln) in liquid-liquid extraction with sym-dibenzo-16-crown-5-oxyacetic acid (I) and 18-crown-6 was maximized. With liquid-liquid extraction of Ln[sup 3+] with 18-crown-6, ethylene-diaminetetraacetic acid (EDTA), and trichloroacetic acid (TCA) into 1,2-dichloroethane, very large selectivities of the light Ln were obtained. A model was developed and verified by varying 18-crown-6 and TCA concentration. Experiments on the effect of solvents on the extraction of Ln[sup 3+] with 18-crown-6 and TCA showed a correlation of the log of the distribution coefficients of La[sup 3+], Ce[sup 3+], Pr[sup 3+], and Nd[sup 3+], minus the log of the solubility of H[sub 2]O in the solvents to a power (log (s[sup n])), with the polarizability index ([pi]asterisk) of the solvents. For Nd[sup 3+] a correlation with the Hildebrand solubility parameter was found. The effect of aqueous complexonates, EDTA and diethylene-triminepentaacetic acid (DTPA) with displacer cations, Ni[sup 2+] and Zn[sup 2+], showed DTPA unsuitable, and Zn[sup 2+] unsuitable because of competition with the Ln for (I). EDTA with Ni[sup 2+] was found suitable with a favorable kinetic effect. The effect of solvents on Lu[sup 3+]/La[sup 3+] selectivity was found in extraction experiments with (I). Halocarbons gave the highest selectivities, except for 1,1-dichloroethane, because of its high hydrogen bonding parameter. By varying the concentration of Ln[sup 3+], selectivity was found to reach a maximum of D[sub Lu]/D[sub La] of about 40 in chloroform at near substoichiometric ratios of (I)/Ln. Lu[sup 3+] was extracted as a 1:1 complex with (I) at all ratios of pH less than 5, while La[sup 3+] was extracted as (I)/Ln = 3:2 at high ratios of (I)/Ln, but (I)/Ln = 1:3 at low ratios of (I)/Ln. The maximum selectivity of Lu[sup 3+] over La[sup 3+] was believed to be because Lu[sup 3+] extracted as a hydroxo-complex at a lower pH than La[sup 3+].
- Research Organization:
- Idaho Univ., Moscow, ID (United States)
- OSTI ID:
- 5517958
- Resource Relation:
- Other Information: Thesis (Ph.D)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
EXTRACTION
SOLVENT PROPERTIES
RARE EARTHS
CATIONS
CHLOROFORM
CROWN ETHERS
DTPA
EDTA
POLARIZABILITY
SOLUBILITY
SOLVENTS
AMINO ACIDS
CARBOXYLIC ACIDS
CHARGED PARTICLES
CHELATING AGENTS
CHLORINATED ALIPHATIC HYDROCARBONS
DRUGS
ELECTRICAL PROPERTIES
ELEMENTS
ETHERS
HALOGENATED ALIPHATIC HYDROCARBONS
IONS
METALS
ORGANIC ACIDS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RADIOPROTECTIVE SUBSTANCES
SEPARATION PROCESSES
400105* - Separation Procedures
400200 - Inorganic
Organic
& Physical Chemistry