Solvent extraction of lanthanide (ill) with dibenz0-[24]-crown-8 from aqueous picrate solution
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Date
1994
Authors
Mohamed All, Abdussalam Salhin
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Abstract
A systematic study of the extraction of fourteen metals, namely yttrium,
lanthanum, cerium, praseodymium, neodymium, samarium, europium,
gadolinium, terbium, dysprosium, erbium, thulium, ytterbium and lutetium,
from picrate media [(N02)3.c6H2.0H] was carried out with dichloromethane
solution containing various crown ethers namely, dibenzo-[24]-crown-8,
dicyclohexano-[24]-crown-8 and dibenzo-[30]-crown-10. The optimum
condition for the separation of these elements was studied.
Solvent extraction of lanthanum (III) was studied in detail. The effects
of the variables such as solvent selectivity, counter ion concentration,
hydrogen ion concentration, ligand type and concentration, stripping agent
type and concentration, time of extraction, time of equilibrium and the
selectivity from other elements were discussed.
Lanthanum (III) was quantitatively extracted from 2 X 10-4 M picric acid
at pH from 8 to 9.2, with 0.02 M [DB24C8] in dichloromethane. The extracted
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metal ion was stripped from the organic phase with various concentrations
of nitric and perchloric acids. Perchloric acid was preferred as the
suitable stripping agent (0.5 M). The extracted metal ion was determined
by U.V.spectrophotometric method at 651.5 nm as its complex with arsenazo
III (pH 3.2). The results showed that dichloromethane-[DB24C8] is the most
suitable combination for quantitative ·solvent extraction of lanthanum (III).
All other lanthanides were extracted at the optimum conditions of
lanthanum. The selectivity of the elements from each other in the grou~
has been studied. Significant selectivity of lanthan urn from other
lanthanides was observed.
The developed method was tested to determine the amount of lanthanum
(Ill) in the presence of other elements in monazite sand. The composition
of lanthanum (III) as its oxide was found 22.60 ± 0.29 %, comparable to the
reported values and the composition found by other methods.
Description
Keywords
Lanthanide , Aqueous picrate solution