The extraction of cerium(III) and lanthanum(III) from chloride solutions with LIX 54

A study has been made of the extraction equilibrium of cerium(III) and lanthanum(III) from NaCl solution with dodecylphenyl-methyl-beta-diketone (LIX 54)(1) in n-heptane. It was found that the extraction of both metals depends strongly on pH as well as on the extractant concentration and does not depend on chloride concentration. The extraction of lanthanum is independent of its concentration in the aqueous phase up to 0.05 M but the extraction of cerium diminishes markedly when its concentration exceeds 1.5 mM. Experimental results show that the predominant complexes extracted are CeR(3) and LaR(3) . 3HR. The extraction equilibrium constants are: log K-ex = -15.67, for the CeR(3) complex, log K-ex = -14.2, for the LaR(3) . 3HR complex, and log K-ex = -18.2 when the LaR(3) complex is assumed. The change in enthalpy associated with the extraction for lanthanides is about 7.3 kJ/mol. Cerium is better extracted with LIX 54 than lanthanum. During simultaneous extraction of the metals with 0.1 M LIX 54 the selectivity of their separation is appreciable if the pH range is strongly limited.