The effect of solvents on the extraction of lanthanoids with 18-crown-6 and trichloroacetate

The effect of solvents on the extraction of lanthanoids with 18-crown-6 and trichloroacetic acid was investigated for the solvents, 1,1,-dichloroethane, 1,2-dichloroethane, 1,1, 2,2-tetrachloroethane, chloroform, di-2-chloroethyl ether, and methylene chloride. Distribution coefficients (25 °C) normalized to the water solubility (wt./vol.) in the solvents correlated to the polarizability index (^*) for La³⁺, Ce³⁺, Pr³⁺, and Nd³⁺ with r values=0.93,0.93,0.95, and 0.98, respectively. The distribution coefficients for Nd³⁺ also correlated with the Hildebrand solubility parameter () (r=0.98). These correlations agree with the literature that for large ions, the extraction thermodynamic properties correlate with the polarizability index and Hildebrand solubility parameter.