This article reviews the structure, synthesis, host-guest reaction in aqueous phase, and ion-sieve and molecular-sieve properties of porous manganese oxide crystals. Tunnel and layered manganese oxides constitute a large family of porous materials having pore size from ultramicropores to mesopores. The manganese oxide crystals consist of MnO
 6
 octahedral units shared by corners and/or edges. They can be prepared by using various metal ions or organic surfactants as templates. The templates are extracted/inserted topotactically from/into the tunnels or interlayer spaces of the manganese oxides by two different mechanisms: redox-type and ion-exchange-type. These manganese oxides show excellent ion-sieve and molecular-sieve properties for the adsorptions of cations or organic molecules. The adsorptive selectivities are dependent on their structures.

Manganese oxide porous crystals

The lattice vibrational modes of spinel-structured lithium manganese oxides have been calculated using atomistic modeling methods. The simulations allow the Raman and infrared spectra of lithiated, fully delithiated, and partially delithiated phases to be assigned for the first time. Calculations for the spinels LiMn2O4, λ-MnO2, and Li0.5Mn2O4 are compared with experimental Raman data measured for thin films of the oxides coated on a platinum electrode. The appearance of a number of new bands in the Raman spectrum of LiMn2O4 following partial extraction of lithium is shown to result from local lowering of the symmetry and Raman activation of modes which are optically inactive or only infrared active in LiMn2O4. The results support a model for the Li0.5Mn2O4 lattice in which the lithium ions are ordered. The deformation vibrations of lattice hydroxyl “defects” in λ-MnO2 have also been calculated; comparison of the calculated and experimental vibrational data supports a model in which hydroxyl species are l...

Lattice Dynamics and Vibrational Spectra of Lithium Manganese Oxides: A Computer Simulation and Spectroscopic Study

Extraction of lithium with functionalized lithium ion-sieves

Adsorption behavior of Li+ onto nano-lithium ion sieve from hybrid magnesium/lithium manganese oxide

Iron-doped lithium manganese oxides Li1.33FexMn1.67–xO4 (x = 0.15, 0.30, and 0.40) were prepared by calcination of carbonates of Li, Mn, and nitrate of Fe in air at 350, 400, 450, 550, and 650 °C. The calcined samples, characterized by X-ray diffraction (XRD) and chemical analysis, were spinels. The protonated samples after treatment with HCl solution were tested as adsorbents for lithium adsorption from the salt lake brine collected from the Salar de Uyuni, Bolivia. The precursor showed 3.7% Mn extraction upon acid treatment with Fe/Mn ratio of 0.1 obtained from calcination at 450 °C. The amount of Mn extracted in HCl solution decreased with increasing of Fe/Mn ratio, and the amounts of lithium extraction were 90%, 96%, and 91% for Fe/Mn = 0.1, Fe/Mn = 0.2, and Fe/Mn = 0.3, respectively, while the amounts of dissolved iron showed the opposite trend. By studying the lithium adsorption in the raw brine and NaOH-added brine by a batch method, the adsorbent with Fe/Mn ratio of 0.1 obtained from calcination o...

Synthesis of Iron-Doped Manganese Oxides with an Ion-Sieve Property: Lithium Adsorption from Bolivian Brine

Spinel-type metal oxides, lithium-aluminum-manganese oxide (LiAlMnO4) and lithium-iron-manganese oxide (LiFeMnO4), were prepared by a coprecipitation/thermal crystallization method. The Li+ extraction/insertion reactions with these materials were investigated by X-ray, DTA-TG analyses, FT-IR spectroscopy, pH titration, and Kd measurement. The acid treatments of LiAlMnO4 and LiFeMnO4 caused Li+ extractions of more than 80% and 60%, respectively, while the dissolutions of Al, Fe, and Mn were less than 10%. The acid-treated samples had lithium ion-sieve properties from a microamount to a macroamount of metal ion loading in aqueous solutions. The chemical analysis showed that the Li+ extraction/insertion progressed mainly by an ion-exchange mechanism. The X-ray analyses showed that the spinel structure held during the Li+ extraction/insertion, indicating the topotactic reaction.

Yi-Fan Liu

Papers

Li+ Extraction/Insertion Reactions with LiAlMnO4 and LiFeMnO4 Spinels in the Aqueous Phase