Lithium isotope selectivities of lithium-specific adsorbents

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Three lithium specific adsorbents have been prepared and their lithium isotope selectivity has been investigated. They were a manganese oxide-based adsorbent designated as MnO_2(Li) prepared by extracting lithium ions from the precursor, LiMn_2O_4, another manganese oxide-based adsorbent, HMnO(2Mg) prepared by extracting magnesium ions from Mg_2MnO_2 and antimonic acid, HSbO_3, with the monoclinic structure prepared by extracting lithium ions from LiSbO_3. Ammonium peroxodisulfate was found to be an excellent extractant of lithium and magnesium ions in the preparation of MnO_2(Li) and HMnO(2Mg). Isotopically, the three adsorbents examined were all ^6Li specific. The magnitude of the lithium isotope effect of MnO_2(Li) slightly decreased with the increase in the degree of manganese dissolution in the process of lithium extraction from the precursor and also decreased with the increase in the lithium/manganese molar ratio in the precursor between Li/Mn=0.5 and 0.8. The maximum separation factor for the lithium isotopes with MnO_2(Li) was 1.014 at 25ﾟC.Various properties of HMnO(2Mg) depended on the degree of magnesium extraction in the process of its preparation. With the increase in the degree of magnesium extraction, the lithium uptake increased, selectivity for the lithium ions increased, but unfortunately the separation factor value decreased. HSbO_3 showed the largest lithium isotope effect among the three adsorbents examined while the amount of lithium uptake was comparable to those of the other two adsorbents. The maximum separation factor value of HSbO_3 was 1.025 at 25ﾟC.However, it was very difficult to extract lithium ions adsorbed in HSbO3, which seemed a serious drawback of HSbO_3 as a lithium isotope separator.