ENHANCEMENT IN EXTRACTION RATES BY ADDITION OF ORGANIC-ACIDS TO AQUEOUS-PHASE IN SOLVENT-EXTRACTION OF RARE-EARTH-METALS IN PRESENCE OF DIETHYLENETRIAMINEPENTAACETIC ACID
H. Matsuyama et al., ENHANCEMENT IN EXTRACTION RATES BY ADDITION OF ORGANIC-ACIDS TO AQUEOUS-PHASE IN SOLVENT-EXTRACTION OF RARE-EARTH-METALS IN PRESENCE OF DIETHYLENETRIAMINEPENTAACETIC ACID, Journal of Chemical Engineering of Japan, 29(1), 1996, pp. 126-133
It is well known that the selectivity of rare earth metals by solvent
extraction is increased by the addition of a chelating agent such as d
iethylenetriaminepentaacetic acid (DTPA) in the aqueous phase, One of
the disadvantages of this method is the decrease in extraction rates d
ue to complexation in the aqueous phase. In this paper, further additi
on of organic acids to the aqueous phase was examined for the purpose
of enhancing the extraction rates in solvent extraction with DTPA, The
addition of several kind of organic acids such as formic acid, acetic
acid, malonic acid, lactic acid and citric acid was investigated for
a Er/Y separation system, A remarkable enhancement in extraction rates
was observed with a slight decrease in the selectivity by the additio
n of citric acid or lactic acid, Extraction rates in the presence of b
oth DTPA and citric acid increased with the increase in citric acid co
ncentration and with the increase in proton concentration, A 150 times
enhancement in extraction rates was found in the low proton concentra
tion condition. In order to analyze the extraction rates and selectivi
ties obtained, mass transfer equations were presented by considering b
oth the dissociation reaction of rare earth metal-DTPA complexes and t
he complex formation between rare earth metal and organic acid in the
aqueous phase, The experimental data were analyzed by these equations.