Extraction of thorium with 2-ethyl hexyl phosphonic acid mono-2-ethyl hexyl ester (PC-88A)

The extraction of thorium from chloride medium with 2-ethyl hexyl phosphoni c acid mono-2-ethyl hexyl ester. commercially known as PC-88A, in dodecane has been investigated as a function of metal ion and hydrogen ion concentra tions in the aqueous phase and extractant concentration in the organic phas e. Slope analysis and non linear least square regression of the data to the mathematical expression correlating percent extraction and equilibrium pH, suggested the formation of monomeric neutral complex of the type ThCl2 (HA (2))(2)(H(2)A(2)) in the PC-88A phase upto an aqueous acidity of 4N. Deviat ions from this behavior have been observed at high acid concentrations. The basic experimental data on the distribution ratio (D) of Th(IV) against in itial aqueous acidity (H-i) at varying initial thorium concentration (C-i) has been determined and utilised to develop a mathematical model correlatin g D with H-i and C-i. The mathematical model D = 2.06 +/-0.31 / C-i((0.72 /-0.04).)[H-i](2) can be used to predict the concentration of thorium in or ganic as well as in the aqueous phases at any C-i and H-i. The extraction c onstant (K-ex = D.[H+]((a))(2)/[H(2)A(2)](3)((o))) has been calculated and is found to be 3.65 +/-0.03. The mechanism of extraction has been discussed in the light of the results obtained.