L Journal of Alloys and Compounds 311 (2000) 46–52 www.elsevier.com / locate / jallcom Solvent extraction of lanthanides with triisoamylphosphate and di-(2-ethylhexyl)phosphoric acid from trichloroacetic acid and nitric acid solutions a, a b * Luu Minh Dai , Dang Vu Minh , Pham Van Hai a National Centre for Science and Technology of Vietnam, Institute of Materials Science, Nghia Do, Cau Giay, Hanoi, Viet Nam b University of DaNang, DaNang, Viet Nam Abstract The study on solvent extraction of some rare earth elements with triisoamyl phosphate (TiAP) and a mixture of TiAP and di-(2-ethylhexyl)phosphoric acid (D2EHPA) from trichloroacetic acid and nitric acid solutions has been carried out. It was found that Y has been more effectively extracted with TiAP from the trichloroacetic acid solution than from the mono and dichloroacetic acid solutions. The influence of various factors such as acid, RE and salting-out agent concentrations on the distribution ratio has been studied. The synergistic extraction effects were observed for low trichloroacetic acid and high nitric acid concentrations. The influence of the TiAP–D2EHPA ratio and the total concentration of two extractants, as well as acid concentration on the synergistic extraction ratio has been investigated. RE extraction isotherms by TiAP and D2EHPA alone and by a mixture of these extractants in the above extraction systems were established.  2000 Published by Elsevier Science S.A. Keywords: Solvent extraction; Triisoamyl phosphate; Di-(2-ethylhexyl)phosphoric acid (D2EHPA); Rare earth elements; Extraction isotherms 1. Introduction oxalate precipitation. Extractant concentration was given by volume percent. Tri-n-butyl phosphate and di-(2-ethylhexyl)phosphoric The synergistic extraction ratio was given by [5]: acid are widely used as extractants for RE separations D [1,2]. However, there are some studies relevant to the RE 1,2 ]]] S 5 lg (1) k extraction with triisoamyl phosphate (TiAP) [3,4]. In this D 1 D 1 2 paper, we present results from study on RE extraction with TiAP and a mixture of TiAP and D2EHPA from trichloro- where D is the distribution ratio in the system with two 1,2 acetic acid and nitric acid solutions. extractants, D is the distribution ratio in the system with 1 extractant 1 alone and D is the distribution ratio in the 2 system with extractant 2 alone. The effect of synergistic extraction are positive if the 2. Experimental value S .0. K The RE solvent extraction with TiAP was carried out in a 50-ml separatory funnel. The phase volume ratio was 1:1. The duration of the solvent extraction was 5 min. 3. Results and discussion After phase separation, the RE concentration in the aque- ous phase was determined by DTPA titration with arsenazo 3.1. Influence of equilibrium acid concentration on the III as an indicator. The acid concentration in the aqueous yttrium distribution ratio in the Yx – Hx – 50%TiAP – 3 2 2 phase was determined by NaOH titration with methyl kerosene system (x 5 CH COO , CHCl COO , 3 2 2 orange or phenolphthalein as an indicator. In the case of CCl COO ) 3 CH COOH before titration, the RE were separated by 3 In order to select a suitable aqueous solution for the RE *Corresponding author. Tel.: 184-4-8363-082; fax: 184-4-8352-483. extraction with TiAP, we studied the influence of the 0925-8388 / 00 / $ – see front matter  2000 Published by Elsevier Science S.A. PII: S0925-8388(00)00859-8