EXTRACTION CHROMATOGRAPHIC BEHAVIOR OF YTTRIUM AND LANTHANIDES IN THEPETROLEUM SULFOXIDE-AMMONIUM THIOCYANATE SYSTEM

The extraction behavior of rare-earth elements on silica gel impregnat ed with petroleum sulfoxide (PSO) from an aqueous NH4SCN solution was systematically investigated. With a batch method, the distribution rat ios and separation factors of rare-earth elements in this medium were determined. The composition of the extracted complex was determined by a slope analysis as being (PSO)(3)RE(SCN)Cl-2. Through the IR spectra it was proved that the oxygen atom of the >S=O group in PSO coordinat es the rare-earth element to form the extracted complex. The standard enthalpy (Delta H(RE)degrees) in the process of PSO:extraction of rare -earth elements was measured. Delta H(RE)degrees indicated that the di stribution process of the rare-earth element between the PSO-silica ge l stationary and NH4SCN mobile phases is an exothermic process. Moreov er, the stabilities of the extracted complexes are discussed in terms of Delta(Delta G degrees)(Ln/Y), the relative standard free energy of complex formation (Delta G(Ln)degrees-Delta G(Y) degrees). The quantit ative separation of yttrium from lanthanides has been achieved by this method, which was also used in an analysis for yttrium in the Jiangxi ionic-type rare-earth ores of China.