18-Crown-6 for the selective extraction and separation of cerium(IV) from nitrate medium containing some lanthanides

The extraction of cerium(IV) from aqueous nitric acid medium with 18-crown-6 (18C6) dissolved in kerosene was investigated. The different parameters affecting the extraction process including nitric acid, hydrogen ion, extractant and metal concentrations as well as temperature have been separately investigated. The extraction of cerium was found to depend on nitrate ion and extractant concentrations but independent of pH or nitric acid concentrations. Based on the obtained results, the stoichiometry of the extracted species was found to be <([Ce(NO(3))(4)center dot CE])over bar>, where CE refers to the crown ether used. The effect of diluents on the extraction process was also studied and correlated to their physical constants showing that the extraction of cerium(IV) increases with the diluents polarity. The separation of cerium(IV) from La(III),Nd(III) and Y(III) which could be found in the monazite ore was investigated giving 87% of extraction and 97% of stripping. The selectivity of the proposed system was successfully tested on a sample of Egyptian monazite. (C) 2011 Elsevier B.V. All rights reserved.