Extraction and separation of thorium and rare earths with 5,11,17,23-tetra (diethoxyphosphoryl)-25,26,27,28-tetraacetoxycalix[4]arene

A calixarene derivative, 5,11,17,23-tetra(diethoxyphosphoryl)-25,26,27,28-tetraacetoxycalix[4]arene (L), was studied for the extraction and separation of thorium and rare earths in nitrate medium. Thorium was extracted into the organic phase by a complex of Th(NO3)4·L with the logarithm of the equilibrium constant of 2.77. Thermodynamic functions, ΔH, ΔG and ΔS were calculated to be −2.49, −15.55 kJ/mol and 44.53 J/(mol·K), respectively. The results indicated that this calixarene derivative might be used to separate thorium from rare earths and the separation factors were larger than 26. However, the salting-out agents affected the separation.