Mitsuo Abe

Mechanism of Lithium Ion Insertion into λ ‐ MnO2

This paper deals with the detailed mechanisms of the lithium insertion-extraction reaction of λ-MnO 2 by means of NMR spectroscopy and chemical analyses

Synthetic inorganic ion-exchange materials. Part XLIX. Adsorption and desorption behaviour of heavy metal ions on hydrated titanium dioxide

The ion-exchange selectivity of a number of divalent metal ions was studied as a function of pH in nitrate and chloride media. The order of selectivity was Pb2+ > Hg2+ > Cd2+ > Mg2+ in nitrate solution and Pb2+ > Cd2+ > Ca2+ > Mg2+ > Hg2+ in chloride solution. A good linear relationship between the logarithm of the distribution coefficient of the heavy metal ions and their effective ionic radius was found. On the basis of the Kd values, the separation of a mixture of Cd2+, Hg2+ and Pb2+ and the group separation of Hg2+ and Pb2+ from several common metal ions were achieved on an ion-exchange column containing amorphous hydrated titanium dioxide.

Synthetic inorganic ion exchange materials XLIV: synthesis and ion exchange properties of cubic niobic acid (HNbO3)

A cubic niobic acid (C-NbA) was synthesized by Li{sup +}/H{sup +} ion exchange reaction with an 8 M (mol dm{sup {minus}3}) nitric acid solution from LiNbO{sub 3}. The LiNbO{sub 3} was obtained by heating a mixture of Li{sub 2}CO{sub 3} and Nb{sub 2}O{sub 5} with molar ratio of 1:1 at 900 C for 24 h. X-ray diffraction pattern of C-NbA was indexed to a cubic structure (space group Im3), with the lattice constant a{sub o} = 7.6445 {angstrom} ({angstrom} = 100 pm). The C-NbA product showed an exchange reaction equivalent to one proton per one Li{sup +} in a mixed solution of lithium nitrate and lithium hydroxide. The pH titration curves of C-NbA on the Li{sup +}/H{sup +} exchange system indicated a weak monobasic acid. C-NbA showed high uptake for lithium ions, whereas no appreciable amount of uptake was observed for other alkali metal ions in the pH range 4--12. An extremely high selectivity was found for lithium ions, and the separation factor ({alpha}) of lithium ions to other alkali metal ions was higher than 10{sup 3}.

Nuclear magnetic resonance study of ion-exchange reaction on cubic ammonium molybdate

Inorganic ion-exchangers generally exhibit high ion-exchange selectivity in comparison with organic ion-exchangers. The high selectivity has been ascribed to the rigid lattice of the crystal structure, e.g. ion-sieving properties of zeolites. Cubic ammonium molybdate prepared by the precipitation method (CAM) has been shown to have an unusual (compared with other inorganic ion-exchangers) selectivity for K+ among alkali-metal ions. The selectivity of K+ was assumed to result from the hydration of ions incorporated in the crystal lattice. The hydration property of alkali-metal ions incorporated in the lattice was revealed from the 1H NMR study and the selectivity for K+ was accounted for by the hydration of K+ by analogy with the well known properties of electrolyte solutions.