E. Jaaskelainen et E. Paatero, Properties of the ammonium form of Versatic 10 in a liquid-liquid extraction system, HYDROMETALL, 51(1), 1999, pp. 47-71
The commercial reagent Versatic 10 (Shell Chemical) based on a mixture of h
ighly branched isomers of C-10 monocarboxylic acids is used to study the am
monium salt form of an acidic liquid cation exchanger for metal extraction.
The degree of neutralisation is varied and the neutralisation process is c
onsidered by determining the phase equilibria and analyzing the distributio
n of components between phases as a function of pH. When gradually neutrali
sing Versatic 10 with aqueous ammonia, first an ammonium carboxylate comple
x is formed in the organic phase with a stoichiometry of NH(4)A . 4HA . qH(
2)O where q = 1.0-2.5. When the amount of ammonia is further increased a ph
ase inversion is observed at about pH 8.4 as the concentration of Versatic
10 in the aqueous phase dramatically increases and the amounts of water and
ammonia dramatically decrease in the organic phase. When concentrated ammo
nia (> about 2 M) in water is used for neutralisation a one-phase microemul
sion is observed at the phase inversion pH. The one-phase region where maxi
mal solubilization takes place is at 50% degree of neutralisation. Compared
to normal organic phase this microemulsion solution has higher electrical
conductivity and viscosity. (C) 1999 Elsevier Science B.V. All rights reser
ved.