PURPOSE: To effectively take out a trace element Li existing in seawater by separating Na, XK and Mg chlorides from seawater to raise the Li concn.; adding a surfactant to separate Li-contg. bubbles; and extracting the bubbles with an org. solvent.
CONSTITUTION: Seawater is evaporation-concentrated to separate salt and bittern. This bittern is cooled to separate potassium chloride, and the liquid residue is blown with chlorine gas to separate bromine, mixed with slaked lime, neutralized, and concentrated to separate carnalit. The resulting liquid residue is further cooled to separate magnesium chloride, giving mother liquor of high lithium concn. To this liquor is added a surfactant, and by bubble-separation Li is recovered in bubbles. The Li-contg. bubbles are extracted with an org. solvent to take out an org. layer, which is then back-extracted. To the extract is added sodium carbonate or the like to recover lithium carbonate precipitates. This carbonate is converted into lithium chloride with acid and electrolyzed to obtain Li.