Use of complex-forming agents for extraction separation of cerium group of rare-earth elements in systems with neutral organophosphorus extractants

Abstract

The use of complexons: nitrilotriacetic (NTA) and diethylenetriaminepentaacetic (DTPA) acids have been studied in extraction systems with main classes of neutral organo phosphorus extractants: phosphates (tributyl phosphate-TBP), phosphonate (diisooctylmethyl phosphonate-DiOMP) and phosphine oxides (triisoamylphosphineoxide-TiAPO) to separate lanthanides of the Ce subgroup. Optimal conditions to use complexon have been determined (extractant and salting agent concentrations). The effect of the type of extractant on the lanthanide distribution coefficients' dependence on pH of equilibrium water solution have been studied in the presence of NTA and DTPA. Unextractable cation displacers have been used to regulate distribution coefficients. The values of lanthanide separation coefficients of Ce group have been determined in extraction systems with neutral phosphorus-containing extraction agents — complexon — salting agent compared with Nd macroconcentrations and for lanthanide microconcentrations in the presence of cation displacer. These systems have been shown to be suitable for lanthanide separation of the cerium group.