LITHIUM-ION SIEVE PROPERTY OF λ;-TYPE MANGANESE OXIDE

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Abstract
The adsorptive properties of A-Mn02for mono and divalent metal ions were investigated by pH titration and by measurements of the distribution coefficients(Kd's) of the metal ions. The pH titration curve showed an apparently monobasic acid type for a H+-Li+exchange. Those for H+-K+and H+-Cs+exchanges were nearly the same as that for blank titration. The lithium ion uptake increased with increasing solution pH and reached 5 meq/g at pH 11. X-ray diffraction analyses showed that the adsorption of lithium ions caused an increase in the lattice constant of a cubic unit cell. The potassium and cesium ion uptakes were nearly zero over a pH range between 4 and 11. A-Mn02showed a remarkably high Kd value for lithium ions, compared to a cation exchange resin. The selectivity sequences were Na+< K+< Rb+< Cs+<< Li+for alkali metal ions, Mg2+< Ca2+< Sr2+< Ba2+for alkaline earth metal ions, and Ni2+< Zn2+< Co2+< Cu2+for transition metal ions.