1990 Volume 16 Issue 1 Pages 184-187
Measurements were made on interfacial tension between aqueous and n-heptane solutions under conditions of Ni (II) -and Co (II) -extraction by two organophosphorous esters : di (2 -ethylhexyl) phosphoric acid (DE) and 2-ethylhexyl phosphonic acid mono2 -ethylhexyl ester (ME). For the systems of Ni-DE and Ni-ME, the interfacial tension during the extraction, γ, fell with increasing metal loading in the organic phase, unlike the Co-ME system. In addition, the γ -values were smaller than interfacial tensions obtained under no-reaction condition, the difference between the two being large in the lower region of metal loading. On the other hand, no significant change in interfacial tension during back-extraction was observed for any of the systems. This suggests that the reactions for the back-extraction proceed at a fast rate in comparison with the forward extraction.
