Journal of Membrane Science 390–391 (2012) 76–83 Contents lists available at SciVerse ScienceDirect Journal of Membrane Science j ourna l ho me pag e: www.elsevier.com/locate/memsci A highly efficient supported liquid membrane system for selective strontium separation leading to radioactive waste remediation D.R. Raut, P.K. Mohapatra ∗ , V.K. Manchanda Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India a r t i c l e i n f o Article history: Received 17 August 2011 Received in revised form 28 October 2011 Accepted 3 November 2011 Available online 12 November 2011 Keywords: Crown ether Radio-strontium Supported liquid membrane Radioactive waste remediation a b s t r a c t The present paper deals with the selective separation of radio-strontium from acidic feeds using a highly efficient novel supported liquid membrane method suggesting possible applications in radioactive waste remediation. This method is a first ever report on near quantitative (∼99%) Sr transport with crown ether carrier from acidic feeds (∼3 M HNO 3 ) using a supported liquid membrane method. The supported liq- uid membrane consists of a solution of di-tert-butyl-dicyclohexano-18-crown-6 (DTBCH18C6) dissolved in a mixture of 2-nitrophenyl ether and n-dodecane absorbed into a microporous polytetrafluoroethy- lene film. A mixture of 80% 2-nitrophenyl ether and 20% n-dodecane was found to be the most suitable diluent system and was evaluated in the present studies. The transport rates were correlated with the carrier extractant concentration, strontium concentration as well as the feed acid concentration. Trans- port of Sr from Pressurized Heavy Water Reactor Simulated High Level Waste (SHLW) was also studied with encouraging results. Selective transport of Sr(II) was observed from a feed solution constituting a mixture of fission products spiked individually. Radiation stability of the carrier solvent with respect to the efficiency and selectivity was also investigated. The stability of the membrane was remarkably good when tested over 20 days of continuous operation. © 2011 Elsevier B.V. All rights reserved. 1. Introduction 90 Sr (T 1/2 = 28.5 years) is one of the major heat emitting radionu- clide present in the high level waste (HLW, composition given in Table 1). The accepted methodology for the safe management of HLW involves its vitrification in glass matrices followed by burial in deep geological repositories. However, there are concerns due to the possible deformations of the glass matrices from the heat ema- nating from the radioactive strontium (specific power: 0.93 W/g). Therefore, recent strategies relevant for high level waste remedia- tion often focus on the development of methods for the separation of radio-strontium [1]. Its separation from high level waste (HLW) prior to the vitrification not only reduces the risk of matrix defor- mation, but the separated radionuclide also has many applications viz. as a fuel for thermoelectric and thermo-mechanical power gen- erators [2]. The HLW contains a host of fission products in 3–4 M nitric acid and the separation method for 90 Sr requires to be not only highly selective for the metal ion, but also should be effective under mod- erately acidic conditions. Amongst various methods used for 90 Sr recovery from acidic wastes, solvent extraction based separation ∗ Corresponding author. Tel.: +91 22 25594576; fax: +91 22 25505151. E-mail address: mpatra@barc.gov.in (P.K. Mohapatra). methods involving 18-membered crown ethers are found to be the most efficient due to their size selective complexation [3,4]. Additionally, a direct role of diluent on Sr(II) extraction has been reported [5]. The SREX process, developed at Argonne National Laboratory, USA utilized the Sr(II)-specific extraction property of the 4,4 ′ (5 ′ )-di-tert-butyl dicyclohexano 18-crown-6 (DTBCH18C6, Fig. 1) in 1-octanol [6]. A systematic study carried out with many aliphatic alcohols, ketones, carboxylic acids and esters had shown a direct correlation with the water uptake ability of the diluents with their extraction efficiencies [7]. In spite of the popularity of the solvent extraction based meth- ods, they have major disadvantages such as large solvent inventory and hence VOC burden to the environment, phase entrainment and formation of third phase. Liquid membrane based separation methods, particularly those involving supported liquid membranes (SLM) have significantly low solvent inventory which are relevant not only from environmental point of view but also are preferred for separation methods involving expensive reagents such as crown ethers. Moreover, SLM based separation methods are efficient due to the simultaneous extraction and stripping [8–11]. Additionally, due to the non-dispersive mass transfer, SLM based methods do not have limitations such as third phase formation and slow phase separation. There are several studies on the transport behaviour of Sr using liquid membrane based methods using various extractants [12–15]. 0376-7388/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.memsci.2011.11.015