A New Type of Manganese Oxide (MnO 2 ·0.5H 2 O) Derived from Li 1.6 Mn 1.6 O 4 and Its Lithium Ion-Sieve Properties
2000; American Chemical Society; Volume: 12; Issue: 10 Linguagem: Inglês
10.1021/cm0000191
ISSN1520-5002
AutoresRamesh Chitrakar, Hirofumi Kanoh, Yoshitaka Miyai, Kenta Ooi,
Tópico(s)Supercapacitor Materials and Fabrication
ResumoA new type of adsorbent, MnO2·0.5H2O, was synthesized from Li1.6Mn1.6O4 followed by acid treatment. The hydrothermal reaction of monoclinic type γ-MnOOH with LiOH solution at 120 °C resulted in a H+/Li+ ion exchange, giving orthorhombic LiMnO2. The orthorhombic LiMnO2 was transformed to cubic Li1.6Mn1.6O4 (Li2Mn2O5) at a temperature higher than 400 °C. The conversion of Li1.6Mn1.6O4 to MnO2·0.5H2O by acid treatment resulted in contraction of the lattice constant a0 from 8.14 to 8.05 Å with little dissolution of manganese. The new adsorbent showed a markedly high ion-exchange capacity (7.5 mmol/g) for lithium ions due to its ion-sieve property. The pH titration study suggested the formation of large numbers of uniform sorption sites having relatively high acidity. The uptake of Li+ ions from lithium-enriched seawater was found to be 5.3 mmol/g (37 mg/g), which is the maximum among the adsorbents studied to date.
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