Fusion Engineering and Design 87 (2012) 1186–1189 Contents lists available at SciVerse ScienceDirect Fusion Engineering and Design jo ur nal homep age : www.elsevier.com/locate/fusengdes Lithium isotope separation with displacement chromatography using crown ether resin immobilized on porous silica beads Takahiko Sugiyama a,∗ , Kei Sugiura a , Masahiro Tanaka b , Youichi Enokida a a Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan b National Institute for Fusion Science, Oroshi-cho 322-6, Toki 509-5292, Japan a r t i c l e i n f o Article history: Available online 22 March 2012 Keywords: Lithium isotopes Displacement chromatography Intraparticle diffusion Numerical simulation Porous silica beads a b s t r a c t A crown ether resin immobilized on porous silica beads was investigated as a chromatographic packing for lithium isotope separation by displacement chromatography. In order to develop an effective chro- matographic packing, effects of the diameter of the packing particle on the transport phenomena in the particle were investigated by numerical simulation. Transient change of the concentration profiles in the both solution phase and resin phase were obtained and lithium-6 enrichment in the resin phase was well simulated. A dimensionless coefficient, which represents a ratio of the diffusive mass transfer rate to the adsorption rate, was found in the mass balance equation. The magnitude of the factor was also evaluated for various values of diameter of the packing particle. © 2012 Elsevier B.V. All rights reserved. 1. Introduction There are two naturally existing isotopes of lithium, lithium-6 at 7.5% and lithium-7 at 92.5% in relative abundance [1]. A tech- nology to enrich lithium-6 over 90 isotopic percent is necessary to establish the fuel cycle for fusion reactors. The displacement chromatography is one of the suitable methods for a large-scale production of the enriched lithium-6, because a scale-up of a pro- cess seems easy based on chemical engineering. A wide variety of ion exchange resins has been investigated for a chromatographic enrichment of lithium-6 [2–4]. Recently, a good performance has been reported using a crown ether resin immobilized on porous sil- ica beads [5–7]. An equilibrium separation factor of a crown ether resin is larger than ion exchange resins by an order of magnitude. On the other hand, the HETP (Height Equivalent to a Theoretical Plate) value of such a crown ether immobilized resin is relatively larger than ion exchange resins. A small HETP value means an effec- tive separation, that is, a short length of column is required for an equilibrium separation. To maximize the merit of large equi- librium separation factor we need to shorten the HETP value of the crown ether immobilized resin. One of the reasons which cause the large HETP value was pointed out as a large mass transfer resistance in intraparticle diffusion. According to the assumption, an overall mass transfer coefficient is used in the model and the concentration profile in the particle is not calculated for separative analyses. ∗ Corresponding author. E-mail address: t-sugiyama@nucl.nagoya-u.ac.jp (T. Sugiyama). Recently, porous silica beads with small diameter are easily obtained, and such kind of beads can reduce the resistance of intraparticle diffusion. In advance of manufacturing an effective chromatographic packing using porous silica beads as a support matrix, it is very helpful to investigate effects of the diameter on the transport phenomena in the beads. The purpose of the present study is to establish a model applicable to the separative analyses of a chromatographic enrichment of lithium-6 using a crown ether resin immobilized on porous silica beads, where the resistance of intraparticle diffusion is not necessarily large. 2. Simulation procedure 2.1. Mass transfer model in the porous silica beads The mass transfer process in a chromatographic column is con- sisted of many steps, such as convection and dispersion in the column, transfer through laminar films, intraparticle diffusion and adsorption or desorption at the local adsorption sites, as shown in Fig. 1. In a present study, we focused on the mass transfer process in the particle. The assumptions in the present model are as follows. (1) Three kinds of ions, which are lithium-6, lithium-7 and proton, are treated. (2) The system is adiabatic. The temperature and pressure are con- stant at a local position in the column. (3) The chromatographic column is uniformly packed with the adsorbent particles having the same diameter. (4) The micro pore and adsorption site are uniformly distributed in the adsorbent particle. 0920-3796/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.fusengdes.2012.02.092