XX-th ARS SEPARATORIA Szklarska Poręba, Poland 2005

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1 SELECTIVE RECOVERY OF LITHIUM FROM SEAWATER USING BENCHMARK COLUMN SEPARATION PLANT Kazuharu YOSHIZUKA 1,2), Marek HOLBA 2), Ayuko KITAJOU 1) 1) Department of Chemical Processes and Environments, The University of Kitakyushu, Hibikino 1-1, Kitakyushu , Japan 2) Institute of Ocean Energy, Saga University Yamashiro-cho, Kubara, Hirao 1-48, Imari , Japan INTRODUCTION Lithium is of a great interest in many fields of science and technology recently. Nowadays, the demand for lithium has been dramatically increasing, due to its wide application as raw materials for large-capacity rechargeable batteries, light aircraft alloys, and future nuclear fusion fuel. Overall lithium land resources are about 14 million tons [1]. Lithium is then recovered from ores or brines [2]. Although the amount of lithium in those resources is sufficient at this point, alternative resources should be developed to satisfy the increasing demand in the near future. 230 billion tons of lithium in seawater is an immense source, though the lithium concentration in the seawater is quite dilute (about 0.2 ppm). The selective recovery of lithium from seawater by co-precipitation, solvent extraction, and adsorption has been investigated [3]. The adsorption technique proved to be the most suitable for the recovery of target ions from such dilute solutions in whole separation techniques. A number of different adsorbents has been investigated for the selective lithium recovery [2]. However, the adsorbent based on manganese dioxide and its composites seems to be the most proper one, because of its high sorption capacity in alkaline medium (ph of seawater is around 8.1). A novel λ-type manganese dioxide adsorbents have been developed from spinel type lithium dimanganese tetraoxide LiMn 2 O 4 and Li 1.5 Mn 2 O 4 [4,5]. The benchmark plant with seawater intake 0.2 m 3 /h was built up to verify the phenomenon after the lab-scale selective lithium recovery evaluation. EXPERIMENTAL The adsorbent is prepared from powdered Mn 3 O 4 and LiOH-H 2 O by the sintering in the electric oven. The acid treatment with HCl is performed to obtain the 27

2 corresponding -MnO 2 by cation exchange Li + with H +.[12, 14] The granulation of the adsorbent is performed by chitin based binder (LiCl, chitin and N-methyl-2-pyrrolidinone) using High Speed Mixer (Fukae Powtec FS- GC-40JB). The schematic diagram of the benchmark plat of lithium recovery is depicted at Fig 1. The benchmark plant for selective lithium recovery consists of the column packed with 60 kg adsorbent. The adsorbent is preliminary treated with 0.85 M HCl solution before the experiment. The column is then fed by prefiltered seawater. The seawater intake was about 200 L/h. The adsorbent is washed out by tap water after adsorption and then lithium is then eluted by 0.85 M HCl. The eluted solution is evaporated to precipitate the metal salts and HCl is recycled using vacuum distillation. The composition of the precipitated salt is determined with ICP-AES analysis. Seawater Desalination Plant The picture of benchmark plant for lithium recovery is shown in Fig. 2. There are two big HCl storage tanks of 1000 L (front side), an evaporation unit (left side) and two adsorption columns (right side). RESULTS AND DISCUSSION LiCl solution eluted by HCl Prefilter Solid LiCl Crystallizer of LiCl A number of lab-scale column tests were performed to evaluate the proper operational conditions for the selective recovery of lithium [4,5]. Figure 3 shows the breakthrough and elution profiles of Li + and Na +. Li + is adsorbed passing through overshooting profile. The concentration of Na + cannot be measured due to the quite high content in seawater. From elution profiles of metal ions from the adsorbent with 1 M HCl, Li + is quickly eluted from the adsorbent, while Na + and Mn 3+ is eluted in very low level. The first pilot run of the benchmark plant was scheduled in the last year [6]. The run was performed for ca. 1 month using real seawater. in Imari bay, Japan. About 150 g of the precipitated metal salt was obtained during the first pilot run with ca. 20 % of lithium recovery efficiency from 140 m 3 of seawater. The composition of dried mixture was analyzed as follows: NaCl 45 wt %, CaCl 2 30 wt %, LiCl 18 % wt, MnO 2 4 % wt, KCl 1.6 % wt. The pilot run for lithium recovery was P P Adsorption column for Li recovery with λ -MnO 2 HCl solution Figure 1. Schematic flowsheets of the column apparatus setup. 28

3 Fig. 2. Overview of the benchmark plant for selective lithium recovery 400 Metal Conc. / ppm 2 1 Na concentration was saturated Metal Conc.. / ppm Li Na Mn B.V B.V. Fig.3. Breakthrough (left) and elution (right) profiles of Li + and Na + from artificial seawater (ph = 8.1; C Li, = 1.2 ppm) 0 successful in spite of low yield of LiCl. The long run (ca. 800 m 3 of seawater) is recently been performing for expecting the increment of the lithium recovery with the prolonging adsorption time. ACKNOWLEDGMENTS 29

4 The authors are grateful to Mr. Y. Suzuka and Mr. Y. Tanaka for their assistance in some experiments. The work is supported by Grant-in-Aids for 21st Century COE Program from MEXT, and Salt Science Research Foundation, No REFERENCES 1. U.S Geological Survey, Mineral Commodity Summaries A.D. Ryabtsev, L.T. Menzheres and A.V. Ten, Russian Journal of Applied Chemistry, 7, (2002). 3. R. Chitrakar, H. Kanoh, Y. Miyai, and K. Ooi, Ind. Eng. Chem. Res., 40, (2001). 4. K. Yoshizuka, K. Fukui and K. Inoue, Ars Separatoria Acta, 1, 79 86, (2002). 5. A. Kitajou, T. Suzuki, S. Nishihama and K. Yoshizuka, Ars Separatoria Acta, 2, , (2003). 6. A. Kitajou, M. Holba, T. Suzuki, S. Nishihama, K. Yoshizuka, Journal of Ion Exchange, 16, (2005). (in Japanese) 30

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