The liquid-liquid extraction of Germaniun with the 7-alkylated 8- hydroxyquinoline derivative - KELEX 100.
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Date
1990
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Abstract
Germanium can be extracted from aqueous solutions by
KELEX 100 dissolved in an appropriate diluent.
KELEX 100 is a commercially available chelating
extractant containing the active constituent 7-(4ethyl-l-methyloctyl)-8-hydroxyquinoline. Previous
work in the solvent extraction of germanium with
this reagent has shown that germanium is extracted
most efficiently at low pH. When the germanium is
present in sulphuric acid solutions at pH less than
2, the extracted complex is GeL3+HS04-,however at pH
3 to 8, the metal is extracted as GeL2(OH)2 (where HL
= KELEX 100).
In this work, the extraction kinetics and
equilibrium extraction of germanium in the GeKELEX
100 solvent extraction system is examined by
AKUFVE and shaking assemblies, which both employ
rapid mixing of the organic and aqueous phases, and
by a quiescent interface Lewis Cell.
The AKUFVE is a Swedish designed apparatus for
solvent extraction, its performance and suitability
for solvent extraction studies is evaluated using
the extraction experiments carried out on the GeKELEX
100 solvent extraction system.
Experiments conducted using an experimental set-up
with a large interfacial area to phase volume ratio
reveal that the extraction of germanium occurs in
two distinct kinetic regimes. The first regime
occurs in the first few minutes of an extraction
experiment and is fast relative to the second
kinetic regime which follows this fast initial
extraction period and occurs until the extraction of
germanium attains the equilibrium value. In this
work an extraction mechanism involving interfacial
reaction of germanium and extractant is proposed to
explain this kinetic behaviour.
An increase in ionic strength is shown to reduce the
rate of germanium extraction in the Ge-KELEX 100
solvent extraction system. Modifiers, such as
organic alcohols, are shown to greatly improve
extraction kinetics.
Description
Thesis (M.Sc.)-University of Natal, Durban, 1990.
Keywords
Germanium., Extraction (Chemistry), Solvents., Theses--Chemistry.