METHOD OF PREPARING A CAESIUM AND RUBIDIUM SALT SOLUTION

摘要

The invention concerns a method of preparing a caesium and rubidium salt solution with a density between 1.6 and 3.3 g/cm<3> by hydrothermally digesting uncalcinated pollucite and/or calcinated lepidolith with an aqueous Ca(OH)2 solution over a period of 0.5 to 3 hours at a temperature of 200 to 280 DEG C and a pressure of 15 to 65 bar, and at a suspension density between 8 and 18 % by wt, filtering off the insoluble solids, removing, if necessary, calcium and lithium ions by purging with carbon dioxide and filtering the precipitated carbonates from the filtrate obtained from the digestion, and forming the salts of caesium and rubidium by the addition of an acid or acid anhydride until a pH of at least 6 is reached, the required density of the caesium and rubidium salt solution being ensured by including a concentration stage by evaporating after the digestion, after filtering off the precipitated carbonates and/or after adding the acid or acid anhydride. The invention calls for the uncalinated pollucite and/or calcinated lepidolith to have a mean particle size of up to 0.5 mm and to be digested in a rotary autoclave, the molar ratio of SiO2 to CaO being in the range between 1:2.5 and 1:1.25.