Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound – Alkali metal
Patent
1995-07-17
1997-01-14
Bos, Steven
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
Alkali metal
423165, C22B 2600
Patent
active
055936504
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method for producing a high-density saline cesium and rubidium solution, i.e. a solution of a density of 1.6 to 3.3 g/cm.sup.3, by hydro-thermal decomposition of cesium- and rubidium-containing minerals.
A method for the hydro-thermal decomposition of a pollucite-spodumene concentrate for obtaining cesium carbonate is known from the magazine "Tsvetnye Metally--The Soviet Journal of Non-Ferrous Metals", vol. II, No. 5, pp. 57 to 59 (1961). In the process, the calcined minerals are subjected to hydro-thermal decomposition in an aqueous Ca(OH).sub.2 solution at 220.degree. C. and 20 atm pressure over a period of 4 hours, wherein optimum decomposition conditions are achieved with 3 mol Ca(OH).sub.2 per mol SiO.sub.2. It was possible to obtain 88.3% of the cesium contained in the mineral and to produce a cesium salt of a purity of greater than 99% by recrystallization of the alumino-cesium alum. A method for the conversion of Cs.sub.2 CO.sub.3 into CsHCO.sub.2 is furthermore known from the Chemical Abstracts article 79/4949v (1973), wherein the carbonate is reacted with formic acid in water.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a method which permits the cost-effective production of a high-density saline cesium and rubidium solution, i.e. a solution of a density of 1.6 to 3.3 g/cm.sup.3, with a comparatively high yield of the cesium and rubidium from the employed minerals.
According to the invention the method of making a high density saline cesium and rubidium solution comprises comminuting uncalcined pollucite and/or calcined lepidolite to a grain size of less than 0.1 mm; combining the comminuted material in the presence of water with Ca(OH).sub.2 at a mol ratio of SiO.sub.2 to CaO of not less than 1:2; hydro-thermally decomposing the comminuted material together with the Ca(OH).sub.2 at a temperature of 200.degree. to 280.degree. C., a pressure of 20 to 40 bar and with a suspension density of 4 to 15% by weight for a time period of one to three hours to form a suspension containing insoluble solids; filtering the insoluble solids from the suspension and washing the insoluble solids to form a filtrate and advantageously concentrating the filtrate; blowing carbon dioxide into the filtrate to precipitate calcium carbonate and lithium carbonate and filtering to separate the solid carbonates from a remaining solution; and then adding an acid or acid anhydride to the remaining solution until the pH of the remaining solution reaches about 6 and concentrating by evaporation to form the high density saline cesium and rubidium solution. The suspension density is defined as the concentration of the pollucite and/or the lepidolite as well as the undissolved CaO or Ca(OH).sub.2 in water.
In a preferred embodiment of the method the filtrate produced by the hydro-thermally decomposing is subjected to repeated, advantageously six, hydro-thermal decompositions in additional hydro-thermal decomposition batches in an autoclave.
In a surprising manner it is possible to obtain more than 80% by weight of the cesium and rubidium contained in the uncalcined pollucite and/or calcined lepidolite which have been comminuted to a grain size of less than 0.1 mm, hydro-thermally decomposed with Ca(OH).sub.2 at a decomposition temperature of 200.degree. to 280.degree. C. and a suspension density of 4 to 15 % by weight over a period of one to three hours, to convert them in a cost-effective manner to a high-density saline cesium and rubidium solution, if the filtrate obtained following the separation of insoluble solids is used at least three times in the hydro-thermal decomposition.
This embodiment of the method in accordance with the invention has the advantage that a solution with an at least three times higher content of cesium and rubidium is obtained because of the multiple use of the filtrate in the thermal decomposition, which needs to be less concentrated by evaporation to produce the high density saline cesium and rubidium solution, i.e. a
REFERENCES:
patent: 3207571 (1965-09-01), Berthold
patent: 3489509 (1970-01-01), Johnson
Chem. Abstract: 100:160074p, 1984, no month.
Chem. Abstract: 79:4949v, 1973, no month.
Chem. Abstract: 73:79009y, 1970, no month.
Tsuetnye Metallurgy, The Soviet J. Non-Ferrous Met., Bd. 2, Nr. 5, 1961, no month, pp. 57-59.
Hofmann Hartmut
K obele Klaus
Prinz Horst
Wegner Marion
Bos Steven
Metallgesellschaft Aktiengesellschaft
Striker Michael J.
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