United States Patent Office Patented May 30, 1967 1

3,322,531 United States Patent Office Patented May 30, 1967 1. 2 3,322,531 varieties of mica, such as lepidolite or biotite which may PRODUCTION OF CESUM contain from a few tenths to several percent rubidium. Frederick Tepper, Butler, Pa., assignor to Mine Safety Pollucite is especially suitable for the production of ce Appiances Conpany, a corporation of Pennsylvania sium; pollucite ore generally contains some other silicates No Drawing. Filed Sept. 8, 1960, Ser. No. 54,571 and has a Cs2O content of 25-28%, and these ores are 1 Claim. (C. 75-66) included within the meaning of the term pollucite as used herein. This invention relates to a new method for producing The method of this invention is especially economical rubidium and cesiums, and more particularly to their pro because the complex oxide minerals can be used as mined duction directly from minerals containing rubidium and/ IO with no pretreatment or processing. The minerals, either or cesium. dehydrated or containing the natural water of hydration, Heretofore rubidium and cesium have generally been are disintegrated by sodium or potassium at reaction con prepared from pure rubidium or cesium salts, such as ditions so that it is not necessary to finely divide the min prohibitivelyrubidium chloride expensive or cesium primarily chloride. because These the methodspreparation are eral to accomplish reaction, and any convenient lump or of the salts is expensive and tedious since rubidium and particle size may be used, including large lumps of min cesium compounds, although they are found widely scat eral as mined. Somewhat more rapid reaction is obtained tered throughout the world, are found only in small when finely divided mineral is used, e.g. less than 100 mesh amounts, usually associated with other alkali metal min but it is preferred to use minerals in lump form, e.g. 38 erals. inch or larger, because after reaction the reduced mineral 20 is in the form of a filterable slurry in the alkali metals. I The only known important cesium mineral is pollucite, have also found that water of hydration does not inter a complex cesium aluminum silicate having the approxi fere with the reaction to produce rubidium and cesium. mate formula CS4Al4SigO26. H2O, which contains a com Two moles of sodium or potassium are consumed by re paratively high proportion of cesium, i.e. up to about 35% action with each mole of water present in the mineral to Cs2O. No true rubidium mineral has yet been discovered, produce sodium or potassium oxide and hydrogen, so the although other alkali metal minerals may contain up to yield of rubidium and cesium per pound of sodium or the equivalent of about 5% rubidium oxide. Almost in potassium consumed can be increased by dehydrating the variably a mineral containing a substantial amount of ce ore prior to reaction. If desired, water of hydration is sium also contains a minor amount of rubidium, and min readily removed by heating the ore at atmospheric or erals containing a substantial amount of rubidium also 30 contain a minor amount of cesium. subatmospheric pressure; for example, water of hydration It is an object of this invention to provide a simple, di ispheric readily pressure. removed from pollucite at 1000 F. and atmos rect economical method of recovering rubidium and ce The reaction must be performed in the absence of air or sium from complex oxide minerals containing rubidium other gases reactive with alkali metals; this may be ac and/or cesium. Another object is to provide a method of 35 complished by carrying out the reaction under vacuum, directly producing alloys of rubidium and cesium with or preferably under an inert gas atmosphere, such as a other alkali metals. nitrogen or argon atmospheres. Alloys of rubidium and Another object is to provide a method of directly re cesium with other alkali metals which may be recovered covering cesium from pollucite. A still further object is directly from the reaction mixture are pyrophoric in air, to provide a method of directly recovering rubidium from 40 even at room temperature, and must be protected by lepidolite or biotite minerals which contain significant Vacuum or inert gas cover. amounts of combined rubidium. Any proportion of reactants may be used, but in general, Other objects will be apparent from the following de it is preferred to use a substantial excess of reactant so scription and claim. dium or potassium, e.g. 200 or 300% of that required by This invention is based on my discovery that rubidium 45 the reaction; any larger amount may be used without and cesium are displaced from complex oxide minerals detriment. The excess reactant promotes the reaction rate, containing them by heating and reacting the mineral with permits substantially complete recovery of the rubidium Sodium, potassium or mixtures thereof; and that the pro and cesium, facilitates contact of the reactants, and pro duced cesium and rubidium are readily recoverable, either vides a fluid carrier for easy removal of the reduced together or separately from the reaction mixture. 50 Tubidium and cesium minerals. The amount of reactant In the practice of this invention sodium and/or potas sodium and potassium consumed in the reaction depends, sium and the mineral containing rubidium and/or cesium of course, on the mineral used, and is readily ascertain are mixed together and heated to, or otherwise contacted able. Generally, 1 mole of sodium or potassium is re at, an elevated temperature at which sodium and potas quired for each mole of contained rubidium and cesium. sium react to displace rubidium and cesium from the min In addition, sodium will at least partially free potassium eral; the produced rubidium and cesium are separated from minerals containing it. I have also found that about from the reaction mixture by distillation, filtration, or 3 to 4 moles of reactant alkali metal are consumed for similar fluid solid separations. Generally, the rubidium and each mole of other alkali metal produced when aluminum cesium are recovered alloys with excess reactant sodium silicate minerals are used. The increased consumption ap or potassium. These alloys are in themselves useful for 60 pears to be due to secondary reactions of the alkali metals many purposes; for example, many of them have unusually with the alkali metal aluminum silicates. Illustrative of low freezing temperatures and are therefore particularly the preferred reactant proportions, I have found that the useful in low temperature heat transfer applications. Ru desired excess is obtained if about 5 to 10 moles of reac bidium and cesium can be separated, if desired, from the tant alkali metal is used for each mole of cesium con alloying alkali metals by distillation, partial freezing, oxide 65 slagging or combinations of these and other methods as is tained in pollucite; about 1 part by weight reactant alkali hereinafter described in detail. metal is used for each 2 parts of an alkali metal mineral Suitable complex oxide minerals for use in this inven containing small amounts of rubidium and cesium, e.g. tion include silicate, aluminum silicate, and phosphate lepidolite, which generally contains up to 5% rubidium. 70 Sodium, potassium, or mixtures thereof may be used minerals or ores which contain some rubidium or cesium. as the reactant alkali metal, and excess reactant alkali Especially suitable for the preparation of rubidium are metal can be recovered and reused for further reaction 3,322,531 3. 4. with additional mineral. Generally it is preferred to use g. of sodium was charged under an argon atmosphere to sodium because of its lower cost. When minerals contain the stainless steel combination reactor and distillation ing potassium are used as a rubidium or cesium source it column referred to above. The charged reactor was is convenient and economical to recycle sodium-potas heated to about 1300 F. for 2 hours and the temperature sium alloy, formed from excess sodium and the reaction was then increased to distill the alkali metals from the produced potassium for reuse. reactor. Substantially all the rubidium was recovered in The reaction to liberate rubidium and cesium from the distillate alloy which had the composition 43.5% Na, complex oxide minerals proceeds readily at about 900 35.6% K, 16.5% Rb, and 2.4% Cs. The lepidolite used F. or any higher temperature desired, e.g. 1600 F., and had the composition LiO, 3.75%; KO, 7.84%; F, 5.5%; it is generally preferred to use a temperature between O Al2O3; 29.06%; SiO, 55.88%; Rb2O, 3.28%; Cs2O2, about 1000 F. and 1300 F. The rate of reaction in trace; and the remainder heavy metal oxides. creases with increasing temperature, so that a higher pro Sodium and potassium are readily separated from duction rate is realized at temperatures substantially alloys with the produced cesium and rubidium by distilla above 900 F. At temperatures below about 1300 F., tion at atmospheric or subatmospheric pressures. The the reduced ore is readily removed as a finely divided distillation may be done concurrently with the re solid when large excesses of sodium or potassium are action, as a still pot and passing the metal vapors through used; when smaller amounts of sodium or potassium distillation column; the produced cesium and rubidium are used, or when the mineral is charged as a finely di potassium are returned to the reactor. Or the alloys pro vided power, the reduced mineral is in the form of an duced by reaction may be recovered and subsequently easily frangible sintered cake. However, if higher tem 20 distilled separate sodium and potassium. The distillative peratures are used, the reaction mixture goes through a Separation of sodium and potassium from cesium and totally fused state apparently due to the formation of rubidium is readily accomplished by conventional methods comparatively low melting eutectic mixtures of complex inasmuch as the vapor pressures of cesium and rubidium oxide reaction products. These fused mixtures are ex are much higher than that of sodium and potassium. tremely viscous and difficult to remove from the reactor 25 Rubidium and cesium may also be separated from each in a fused state, and when cooled form a solid rock-like other by distillation, or separately recovered from their residue. At least higher temperature I have found it alloys with other alkali metals by fractional distillation, convenient to use a removable disposable reactor liner as is disclosed in my co-pending application Ser. No. to hold the reaction mixture. 54,572, filed on even date herewith, now abandoned. The following examples are illustrative of the reactions 30 Cesium produced from pollucite and separated as a of this invention to liberate rubidium and cesium 50 g. single volatile fraction from sodium or potassium con of 38 inch to /2 inch lump pollucite containing about tains from about 2 to 5% rubidium, depending on the 25% CSO and 50 g. of sodium were charged to a rubidium content of the pollucite used. I have found stainless steel reactor under a nitrogen atmosphere. The that the rubidium can be simply and effectively removed amount of sodium used was sufficient when melted to 3 5 by oxide slagging, that is, by the reaction of the alloy completely immerse the pollucite. The reactor was equip with a controlled amount of oxygen. One fourth mole of ped with an exhaust vent to permit argon flushing and Oxygen (O2) is required for each mole of rubidium present venting of the expanded cover gas during heating. The for substantially complete removal of the rubidium, and reactor was heated to 1200 F. for four hours and then if oxygen in excess of this amount is used, a correspond cooled to room temperature. The reduced ore was dis 40 ing loss of cesium will result. Thus, for example, cesium integrated to particles having an average size of less than containing 4.5% rubidium was melted and contacted with 40 mesh, and was readily filterable from the produced OXygen in the amount of 1 mole of oxygen for each 4 fluid cesium-sodium alloy. An 83.5% yield of cesium, moles of rubidium. The cesium was then distilled from recovered as alloy, was obtained. the Solid oxide produced and over 99% of the cesium In another reaction, a stainless steel tube 1/2' in was recovered having a purity of 99.1%. Similar purities diameter and 12' long was used as a reactor and distilla and recoveries are realized by filtering the solid oxide tion column, and opened overhead to a condenser for from the purified cesium. produced liquid metals. A charge of 50 g. of -200 Even higher purity cesium may be produced using mesh pollucite containing about 25% Cs-O and 55 g. of multiple step slagging; a portion of the required oxygen Sodium was charged to the reactor, and a 6' depth of is reacted, the produced oxides are separated by distilla 4' stainless steel raschig rings was supported in the tion or filtartion, and the cycle is repeated until a total tube above the charge. The reactor was heated to about of 4 mole of oxygen (O2) for each mole of rubidium 1500 F. for about one hour and the alkali metal prod is used in all the cycles. For example, when 4 of the uct, distilled through the short column, was condensed, desired amount of oxygen was used in each of two slag periodically sampled, and analyzed. Over 80% of the 5 5 ging cycles, 99.5% cesium was recovered with substantial cesium in the charge was freed and recovered in the ly no processing loss. distillate alloy; the cesium content of the produced alloy Ores containing substantial amounts of rubidium gen was initially about 85% and decreased during the re erally contain a much smaller amount of cesium. The action to about 70%, the remainder of the alloy being minor amount of cesium in rubidium separated from Sodium and a very small amount of rubidium which was 60 Sodium or potassium by simple distillation can be sepa freed from the ore along with the cesium. The produced rated by fractional freezing. For example, the alloy is alloy composition is, of course, dependent on the amount cooled to about -38 C. to freeze out rubidium in excess of Separation accomplished by the distillation. of that required for the formation of a CS-Rb eutectic In another example 50 g. of -60 mesh pollucite and 50 Imixture, which has a conjunction of 87% Cs and 13% g. of sodium were charged to a closed-end stainless steel Rb. The fluid eutectic is then filtered or otherwise sepa tube reactor and heated to 1500 F. for /2 hour. With the rated from the solid pure rubidium. closed reactor, none of the alkali metals were removed According to the provision of the patent statutes, I have from the reaction mixture during the reaction. The re explained the principle and mode of practicing my in actor was then cooled to room temperature, and the vention and have described what I do now consider its fluid alloy of cesium and excess sodium was filtered 70 best embodiment. However, I desire it to be understood from the solid residue under an inert atmosphere, giving that, within the scope of the appended claim, the inven a cesium yield of over 95%. A similar yield of cesium tion may be practiced otherwise than as specifically de was obtained in the same manner using a temperature scribed. of 1000 F. and a reaction time of two hours. I claim: In still another example, 100 g. of lepidolite and 50 75 A method of producing cesium which comprises the 5 3,322,531 steps of reacting sodium and pollucite at a temperature 6 between about 900' F. and 1300 F. and in the absence 2,073,631 3/1937 Gilbert ------75-66 of atmosphere reactive with alkali metals, using at least 2,424,512 7/1947 Stauffer ------75-66 about 5 moles of sodium for each molecular weight of cesium contained in said pollucite, said pollucite being FOREIGN PATENTS in the form of lumps of at least about 3% inch size, and 590,274 7/1947 Great Britain. recovering by filtration the cesium produced thereby ad mixed with sodium. DAVID L. RECK, Primary Examiner. RAY K. WINDHAM, WINSTON A. DOUGLAS, MAR References Cited CUS U. LYONS, ROGER L. CAMPBELL, BEN UNITED STATES PATENTS ) JAMIN HENKIN, HYLAND BIZOT, Examiners. R. W. MACDONALD, H. W. CUMMINGS, H. W. TAR 2,054,316 9/1936 Gilbert ------75-66 RING, Assistant Examiners.