Mechanistic Studies on the Extraction of Copper by 5,8-Diethyl-7-hydroxy-dodecane-6-one Oxime (LIX 63)

A detailed study of equilibrium and kinetic aspects of the extraction of Cu(II) from solutions containing nitriloacetic acid (NTA) or iminodiacetic acid (IDA) (H n Y) into chloroform solutions of LIX 63 (HL) (found to be monomeric) established the following equilibrium: with-K'ex values of 10−7.23 and 10−5.26 at 25°C and 0.1 M Na2SO4 when H3Y or H2Y represented NTA and IDA, respectively. From these data the extraction constant applicable in the absence of masking agents was calculated as K ex = 10−3.82·0.10. The experimental expression for the rate of extraction of Cu(II) by LIX 63 was found to be -d[Cu]/dt = k'[Cu2+][HL]/[HY2−]x. The fractional order dependence on NTA (x = 0.51) or IDA (x = 0.34) is consistent with a mechanism in which concurrent reaction paths for CuOH+ and CuY− with neutral LIX 63 molecules in the aqueous phase to form CuL+ represent the rate-limiting steps.