Inorganic metal (IV) phosphate-based ion exchanges in the hydrogen form, HTi x Zr 2−x (PO 4 ) 3 (x=0, 1), have been prepared by leaching lithium ions from the precursors, LiTi x Zr 2−x (PO 4 ) 3 (x=0, 1), through ion exchange with protons. The degrees of leaching of lithium ion were more than 99%. Both ion exchangers showed high selectivity toward lithium and sodium ions and little affinity to rubidium and cesium ions among alkali metal ions. The lithium ion uptakes from aqueous solutions were monotonously increasing functions of pH. Isotopically, both ion exchangers were 6 Li-specific like other inorganic ion exchangers so far examined. The 7 Li-to-6 Li isotopic single-stage separation factor, S, of HTiZr(PO 4 ) 3 was larger than that of HZr 2 (PO 4 ) 3 at a given pH-value. The relatively large S-values of 1.022 and 1.042 were found for HZr 2 (PO 4 ) 3 for HTiZr(PO 4 ) 3 , respectively, at 25 • C when the pH of the solution phase was around 5.

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Inorganic metal (IV) phosphate-based ion exchanges in the hydrogen form, HTi x Zr 2−x (PO 4 ) 3 (x=0, 1), have been prepared by leaching lithium ions from the precursors, LiTi x Zr 2−x (PO 4 ) 3 (x=0, 1), through ion exchange with protons. The degrees of leaching of lithium ion were more than 99%. Both ion exchangers showed high selectivity toward lithium and sodium ions and little affinity to rubidium and cesium ions among alkali metal ions. The lithium ion uptakes from aqueous solutions were monotonously increasing functions of pH. Isotopically, both ion exchangers were 6 Li-specific like other inorganic ion exchangers so far examined. The 7 Li-to-6 Li isotopic single-stage separation factor, S, of HTiZr(PO 4 ) 3 was larger than that of HZr 2 (PO 4 ) 3 at a given pH-value. The relatively large S-values of 1.022 and 1.042 were found for HZr 2 (PO 4 ) 3 for HTiZr(PO 4 ) 3 , respectively, at 25 • C when the pH of the solution phase was around 5.