Lanthanum and neodymium from Egyptian monazite: Synergistic extractive separation using organophosphorus reagents

A systematic liquid-liquid extraction of lanthanum and neodymium from aqueous nitric acid solutions using a mixture of two neutral extractants, namely trioctylphosphine oxide (TOPO) and trialkylphosphine oxide (TRPO) in kerosene has been investigated. The different factors influencing the extraction affinity of those metals have been studied in detail. The extracted species for both metals have been found in the form of [<(M(NO3)(3)(TOPO)(TRPO))over bar>], where M refers to the metal ion. The temperature had a negative effect on the extraction of the metals where the extraction process has been found to be spontaneous in nature and associated with exothermic reaction. Since yttrium is accompanied with these metals in monazite ore, the extraction of Y(III) has also been studied. Based on the results obtained, a proposed method has been suggested to extract and separate the above metals from the hydrous oxide cake resulted by alkaline leaching of Egyptian monazite and a schematic diagram explaining the process has been presented. (C) 2012 Elsevier B.V. All rights reserved.