Electrochimica Acta 55 (2010) 1097–1106 Contents lists available at ScienceDirect Electrochimica Acta journal homepage: www.elsevier.com/locate/electacta Selective transfer of cations between two electrolytes using the intercalation properties of Chevrel phases S. Seghir a , C. Boulanger a,∗ , S. Diliberto a , M. Potel b , J.-M. Lecuire a a Institut Jean Lamour - Electrochimie des Matériaux UMR 7198, Nancy-Université, Université Paul Verlaine Metz, CNRS, 1 Bd. Arago, F-57078 Metz, France b Sciences Chimiques de Rennes - Chimie du Solide et Matériaux UMR 6266, Université de Rennes 1, CNRS, Av du Général Leclerc, F-35042 Rennes Cedex, France article info Article history: Received 3 June 2009 Received in revised form 23 September 2009 Accepted 24 September 2009 Available online 4 October 2009 Keywords: Chevrel phase Mo6X8 Mineral junction Cationic electrochemical transfer Selectivity abstract A device based on an electrochemical transfer junction (constituted by M x Mo 6 S 8 or M x Mo 6 Se 8 ) placed between two tanks allows the transfer of cations by application of current density controlled between electrodes placed in tanks. The transfer protocol was tested on different mixed electrolytes contain- ing cations directly engaged in the batteries industry (M 2+ = Co 2+ , Ni 2+ , Cd 2+ , Zn 2+ , Mn 2+ , Cu 2+ ). Good performances of the process are provided until 1.6 mA cm -2 . The electrolysis through an electrochem- ical transfer junction made of Chevrel phases represents a suitable method for the selective extraction of cations with appreciable selectivity rates with an appropriate choice of the host lattice (sulfide or selenide). Remarkable separations between Co/Ni, Zn/Mn with Mo 6 S 8 and Cd/Zn, Cd/Ni, Cd/Co and Zn/Ni, with Mo 6 Se 8 were observed. © 2009 Elsevier Ltd. All rights reserved. 1. Introduction The high mobility of cations in Chevrel phases M x Mo 6 X 8 (where M = ternary metal cation and X = S, Se) is well known since the mid 1970s and led to synthesize new metastable materials, in particular the binary phase Mo 6 S 8 by acidic leaching [1]. The use of electro- chemical techniques was largely investigated in the 1980s to tune the stoichiometry of Chevrel compounds in view to obtain materi- als with unusual properties or with new applications (rechargeable batteries) [2–11]. These electrochemical studies are based on the ability of molybdenum cluster chalcogenides to undergo reversible reduction/oxidation reactions by electron/ion transfer according to the following relation: Mo 6 X 8↓ + xne - + xM n+ ⇆ M x Mo 6 X 8↓ This reaction is easily realized when the guest cation radius is less than 0.1 nm (case of alkali, alkaline earth, transition metal ions). This reaction can open also the way for a practi- cal application in mineral liquid waste management through an original electrochemical protocol that we have recently proposed [12]. The device is built around an electrochemical transfer junction (ETJ) consisting in a compacted Mo 6 X 8 disk which is a watertight ∗ Corresponding author. Tel.: +33 387 315 465; fax: +33 387 315 460. E-mail address: clotilde.boulanger@univ-metz.fr (C. Boulanger). mineral junction between two electrolytes compartments (Fig. 1). When a global electrolysis (in a galvanostatic mode) of the two whole cells between the anode A 1 and the cathode C 2 , two reactions occur: -M 2+ cation insertion at the interface M x Mo 6 S 8 (electrolyte 1) - reversible deinsertion of the same cation at the interface M x Mo 6 X 8 (beneficiation electrolyte 2) The cation mobility into the Chevrel phase allows the de- solvated cation transfer from the source electrolyte (liquid waste) to the second electrolyte (up-grading solution or valorization) without any transfer of other chemical species from any compart- ment. The initial published development was led and validated for the Co 2+ ion [12]. The aim of this study was to test the protocol on other different cations directly engaged in the industry of batteries such as Co, Ni, Cd, Zn or Mn. The work investigated the influence of the current density, the nature of chalcogenide on the trans- fer for various cations. A second part was devoted to the selective extraction of these cations present in various mixed solutions. 2. Experimental 2.1. Junction development The device is based on the arrangement between two tanks of a host lattice membrane offering insertion capabilities. The junction 0013-4686/$ – see front matter © 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2009.09.064