Selective transport of lanthanides through supported liquid membranes containing non-selective extractant, di-(2-ethylhexyl)phosphoric acid, as a carrier
J. Dolezal et al., Selective transport of lanthanides through supported liquid membranes containing non-selective extractant, di-(2-ethylhexyl)phosphoric acid, as a carrier, J MEMBR SCI, 168(1-2), 2000, pp. 175-181
Permeation of lanthanides (Ln) between aqueous nitrate solutions of differe
nt acidity through supported kerosene membrane containing di-(2-ethylhexyl)
phosphoric acid (DEHPA) as a carrier has been studied. Mass transfer of Ln
cations has been determined in terms of permeability coefficients (P) by on
-line FIA measurement of metal concentrations in strip solution.
Acidity of feed solution ranged from pH 1.2 to 4.2 (ionic strength 0.1 mol
l(-1) (HNO3, NaNO3)) while that of strip solution was kept constant at 0.1
mol l(-1) HNO3. Carrier concentration has been changed in the range from 10
to 10(3) mmol l(-1). Both, the P versus feed pH plots measured at low and
at high DEHPA concentrations as well as P versus DEHPA concentration plots
exhibited maxima. Permeability coefficients were decreasing when advancing
in the lanthanide series and significant differences in behaviour of indivi
dual lanthanides has been observed. The conditions of separation of light a
nd heavy lanthanides and mutual separation of light lanthanides have been s
uggested. Based on these and previous results, composition of transported s
pecies, presence of maxima on measured curves, and formation of gel-like su
bstance in feed solution and on membrane-feed solution interface are discus
sed. (C) 2000 Elsevier Science B.V. All rights reserved.