MICROCHEMICAL JOURNAL 42, 294-299 (1990) Extraction of Praseodymium (ill), Europium (Ill), and Erbium (III) from Nitrate Solution by Ethyl Hydrogen Benzyl Phosphonate E. A. SAAD,' A.M. EL-ATRASH, E.R. SOUAYA,AND M.S.A. HAMZA Chemistry Department, Faculty of Science, Ain Shams University, Abbassia, Cairo, Egypt Received November 28, 1989; accepted July 9, 1990 The extraction of Pr”, Et?+, and E? + from aqueous nitrate solutions by ethyl hydrogen benzyl phosphonate (HEBP) dissolved in six different organic solvents was studied. The extractant, hydrogen ion, and nitrate dependencies were found to be 2.0,2.0, and 1 .O power, respectively, HEBP was found to be a good extractant for separation of these three lan- thanide ions by varying the pH. o 1990 Academic press, IN. INTRODUCTION The generic liquid-liquid extraction in a carrier diluent versus an opposing aqueous phase containing a mineral acid has become a standard tool in the field of metals separation (14). Solutions of acidic phosphonates generally represented as (RO)(R)PO(OH) dissolved in carrier diluents are reported (2, 5-7) to be very effective extractants for M(II1) lanthanides and actinides from an aqueous nitrate solution. One of these extractants, namely 2-ethyl hexyl hydrogen 2-ethyl hexyl phosphonate, dissolved in different carrier diluents has been reported (8) to ex- tract Pm (III) and Cm (III) on a tracer level from an aqueous solution. Peppard (9) found that the extracted complex contains one or two nitrate groups per atom of Th(IV). The purpose of this work is to propose the stoichiometries of the extraction of Pr(III), Eu(III), and Er(II1) from aqueous nitrate solutions at constant ionic strength of 0.5 M (H+, NaNO,) and constant pH using HEBP dissolved in six different solvents of different dielectric constants. EXPERIMENTAL The praseodymium, europium and erbium oxides were purchased from Aldrich. Preparation and purification of ethyl hydrogen benzyl phosphonate were carried out as recommended by Peppard (10). n-Hexane, carbon tetrachloride, benzene, chlorobenzene, o-dichlorobenzene, and nitrobenzene were of analytical grade reagents and used without further purification. All experiments were carried out at constant ionic strength of 0.5 it4 adjusted with NaNO, and HNO,. The extraction process was carried out as described in a previous study (II). All data were obtained at 25 2 O.l”C. After equilibrium, the two phases were com- pletely separated by standing 15 min. Duplicate aliquots of 1 ml each, of the ’ To whom correspondence should be addressed. 294 0026-265XFMl $1.50 Copyright 0 1990 by Academic Press. Inc. All rights of reproduction in any form reserved.