Properties of the ammonium form of Versatic 10 in a liquid-liquid extraction system

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.