Lithium-specific adsorption and lithium isotope separation characteristics were investigated on adsorbents, HMnO (Mg), prepared by treating MgMn2O4with hydrochloric acid or hydrochloric acid-ammonium peroxodisulfate ((NH4)2S2O8) mixture solution. Lithium-specific adsorption was observed for the adsorbents with the spinel structure and magnesium extractability of more than about 90%. The use of (NH4)2S2O8with an appropriate concentration may reduce the degree of manganese dissolution in acid treatments while keeping high extractability of magnesium. Lithium isotope fractionation between the adsorbent thus prepared and a supernatant in equilibrium with each other was observed. The lighter isotope, 6Li, was found to be preferentially fractionated into the adsorbent phase and the value of the single-stage separation factor minus one was 5.4-7.4×10-3at 25°C. No apparent relation was found between acid treatment conditions andthe lithium isotope effect as long as the adsorbent retained the spinel structure and had magnesium extractability more than about 90%
We investigated the process of production of hard-to-dissolve matter, which was caused by the decomposition of magnesium chloride hydrate on drying and was formed in dry salt, and the preventive measure of hard-to-dissolve matter. As the results, magnesium chloride hydroxide(Mg2(OH)3Cl·4H2O, Mg3(OH)5Cl·4H2O)was formed by storing under the moisture absorption environment after heating MgCl2·6H2O at high temperature which forms MgOHCl. Calcium carbonate was also formed when the dry salt was stored for a long time. From these results, it was considered that magnesium chloride hydroxlde was resolved by proton from CO2 absorbed in moisture, and calcium carbonate was formed from Ca dissolved in moisture and CO32-increased by the decomposition. The alkalinity(pH 4.8)of dry salt which did not form magnesium chloride hydroxide and calcium carbonate was under 1mg-eq./kg. Therefore, it was considered that the production of hard-to-dissolve matter in dry salt was to be prevented by the control of alkalinity in the salt after drying.
Granular manganese oxide adsorbents with different particle sizes were prepared by the acidtreatment of the granulated precursors which were obtained by the hardening-coating-in-liquid method using poly-vinyl-chloride as a binder. Physical and mechanical properties, column adsorption conditions, and lithium adsorptivity from sea water were investigated for the granular samples. The mechanical strength (above 99%) against shaking, wet-bulk density (about 1g·cm-3), and water content (about 0.6g·cm-3) of the samples were almost constant independent of the particle size, while the height of fluidized bed in the column flow was greatly influenced by the particle size. Column adsorptivity of lithium from sea water was dependent on the particle size. Lithium uptake after 17-day adsorption was well correlated with the external surface area of the granule. The rate of lithium adsorption was constant at the space velocities above 300h-1 for the adsorbent 0.5-0.7mm in size. The lithium uptake reached 5.5mg·g-1for the adsorbent of 0.25-0.5mm in size by the 25-day adsorption in sea water.
We estimated the existence state and the amounts of potassium and bromide ion in salt crystal from the analytical results of solar salt imported and the samples washed. The results were as follows; 1) It was estimated that potassium and bromide ion in solar salt were mostly included in salt crystal. 2) It was confirmed that 20 to 118ppm of potassium and 55 to 150ppm of bromide ion were included in salt crystal and those were different by the salt producing area. 3) Mole ratio of Br/K in salt crystal was higher than that in seawater.