Title of Invention	PROCESS FOR THE PRODUCTION OF CAESIUM HYDROXIDE SOLUTIONS
Abstract	The invention relates to methods for producing cesium hydroxide solutions during which: cesium-containing ore is disintegrated with sulfuric acid while forming a cesium aluminum sulfate hydrate (cesium alum), which is poorly soluble at low temperatures; the formed cesium alum is separated away in the form of a solution from the solid ore residues; the aluminum is precipitated out of the cesium alum solution while forming a cesium sulfate solution; the formed cesium sulfate solution is reacted with barium hydroxide or strontium hydroxide while forming a cesium hydroxide solution, and; the formed cesium hydroxide solution is concentrated and purified.

Title of Invention

PROCESS FOR THE PRODUCTION OF CAESIUM HYDROXIDE SOLUTIONS

Abstract

The invention relates to methods for producing cesium hydroxide solutions during which: cesium-containing ore is disintegrated with sulfuric acid while forming a cesium aluminum sulfate hydrate (cesium alum), which is poorly soluble at low temperatures; the formed cesium alum is separated away in the form of a solution from the solid ore residues; the aluminum is precipitated out of the cesium alum solution while forming a cesium sulfate solution; the formed cesium sulfate solution is reacted with barium hydroxide or strontium hydroxide while forming a cesium hydroxide solution, and; the formed cesium hydroxide solution is concentrated and purified.

Full Text	Process for the production of caesium hydroxide solutions The invention relates to a process for the production of caesium hydroxide solutions. Current processes for the production of caesium compounds are bashed on caesium-containing ores such as pollucite. Thus US patent 6 015 535 describes a process for the production of concentrated and purified caesium salt solutions. This process includes the digestion of the ore with a hyperstoichiometric quantity of sulfuric acid, the purification by recrystallisation of the caesium aluminium sulfate hydrate obtained in this way, the precipitation of the aluminium with slurried lime Ca (OH)2 and/or calcium carbonate and the separation of the precipitate consisting of calcium sulfate hydrate (gypsum) and aluminium hydroxide from the caesium sulfate solution. There follows a reaction of this solution with a calcium hydroxide slurry and an acid, maintaining a pH of 7 to 8. Separation of the residue consisting of calcium sulfate from the caesium salt solution determined by the anion of the acid then takes place. Purification of the caesium salt solution takes place by- a multi-stage "polishing" in which the solution is rendered alkaline with barium hydroxide and then mixed with carbon dioxide or carbonate, alkaline earths and sulfate being precipitated and separated off. The by then highly dilute caesium salt solution is finally concentrated by evaporation, wherein concentration can continue until a solid is obtained. Patent DE 43 13 480 CI describes the production of a caesium hydroxide solution by reacting caesium aluminium ) sulfate hydrate or a caesium sulfate solution with calcium hydroxide in accordance with the equations (1) CsAl(S04)2 + 2Ca(0H)2 -> CsOH + Al(OH)3i + 2CaS04^ (2) Cs2S04 + Ca(OH)2 -> 2CsOH + CaS044 The yields achieved, however, are very unsatisfactory, US patent application 2002/0143209 Al attempts to remedy this by repeating the reaction according to equation (2) several times, the caesium hydroxide produced and present in a mixture with caesium sulfate in each case being neutralised with the desired acid. Due to the comparatively better solubility of the hydroxide of the barium but very low solubility of the sulfate, the reaction (3) Cs2S04 + Ba(OH)2 -» 2CsOH + BaS044 is virtually completely displaced towards the caesium hydroxide. US patent 3 207 571 describes the reaction of a caesium sulfate solution with an aqueous barium hydroxide solution. A dilute caesium hydroxide solution which is separated from the solid barium sulfate, is obtained. This solution can be converted directly with acid to the corresponding caesium salt solution, or a carbonate solution is produced from this solution by addition of C02, wherein excess barium can be precipitated from this as barium carbonate by concentrating and separated. The processes described have a number of disadvantages. According to the route proposed in US patent application 2002/0143209 Al, caesium hydroxide can only be produced in mixture with other#7c^esium salts. The production method stated in US patent 3 207 571 leads to highly dilute caesium hydroxide solutions with high, not defined, contents of sulfate ind/or barium or has a caesium carbonate solution as the end product. 'This process does not give caesium hydroxide solutions. Caesium hydroxide solutions have numerous applications, e.g. as catalysts, and are used as the starting product for the production of all neutral and basic caesium salts and of solid caesium hydroxide and other caesium compounds. Because a disadvantageous purification of the compounds is often not possible or possible only with great expense, a high purity of the caesium hydroxide solutions is desired. Furthermore, a high concentration of the caesium hydroxide solutions is aimed for. The problem of the present invention is to overcome the disadvantages of the prior art and develop a process for the production of an aqueous caesium hydroxide solution which has a caesium hydroxide concentration of at least 45 wt.% and is marked by as low as possible a content of multivalent cations in general and alkaline earth cations in particular, and low contents of sulfate and carbonate. The problem is resolved by a process for the production of caesium hydroxide solutions in which caesium-containing ore is digested, forming a caesium aluminium sulfate hydrate (caesium alum), poorly soluble when cold, with sulfuric acid, the caesium alum formed is separated off as a solution from the solid ore residues, the aluminium is precipitated out from the caesium alum solution, forming a caesium sulfate solution, the caesium sulfate solution formed is reacted with barium hydroxide or strontium hydroxide, forming a caesium hydroxide solution (this process step is described as "causticisation") and the caesium hydroxide solution formed is concentrated and purified. In the reaction, of.the caesium sulfate solution formed to the caesium hydroxide solution, the use of barium hydroxide is preferred. Any caesium-containing ore or material can be used as caesium-containing ore. However, pollucite is preferably used. A preferred pollucite has a caesium content of 20 to 2 4 wt.%. The particle size of the ore used is preferably 90 wt.%, The following reaction equation can be given for the digestion reaction: (4) 2CsAlSi206 • H20 + 4H2S04 + 18H20 -» 2CsAl(S04)2 • 12H20 + 4Si024 Digestion is preferably carried out with a hyperstoichiometric quantity of sulfuric acid (relative to the quantity of ore used). The mixture ratio of caesium-containing ore (with a Cs content of 20 to-24' wt.%): water : concentrated sulfuric acid is preferably = 1.0 : (1.0 to 1.8) : (1.0 to 1.8), particularly preferably 1.0 : (1.2 to 1.6) : (1.2 to 1.6) and especially preferably 1.0 : (1.3 to 1.5) : (1.3 to 1.5). Digestion is preferably carried out in such a way that the mixture of caesium-containing ore, water and sulfuric acid is heated for a. period of at least 2 hours at a temperature of > 90°C. A digestion time of at least 3 hours is preferred. The preferred minimum temperature is 100°C, particularly preferably 120°C. A preferred maximum temperature corresponds to the boiling point of the reaction mixture. Potentially evaporating water is preferably replaced. The reaction can also be carried out at excess pressure, e.g. at 0.5 to 6 bar excess pressure, preferably 1 to 6 bar excess pressure. Should the caesium-containing ore also not have a high enough aluminium content or should not enough aluminium be digested during digestion and pass into solution, in a preferred embodiment of the process aluminium can be added in the form of aluminium sulfate during or after digestion, so that a sufficiently high quantity of aluminium is available for the formation of the caesium alum. Without a sufficient quantity of aluminium, yield losses could occur, but performance of the process as such is not affected by an insufficient quantity of aluminium. The molar ratio of Al to Cs is preferably at least 1:1. A slight aluminium excess is particularly preferably used, the Al : Cs molar ratio being up to 1.5 : 1. At the end of the digestion reaction and cooling of the reaction mixture, a caesium aluminium sulfate hydrate heavily contaminated by other alkali elements crystallises out. Water or process solutions from later process steps (e.g. mother liquors from the subsequent separation of the Cs alum and/or subsequent crystallisation) are preferably added to the reaction mixture to improve the rate and completeness of crystallisation. The quantity of water or quantity of process solution added is preferably at least 1.2 parts by weight per part by weight of ore used. The acid excess is preferably separated off at the end of the reaction and cooling of the reaction mixture and optionally dilution of the reaction mixture. Separation can be carried out e.g. by decanting, filtering or centrifuging. The acid excess separated off can be used again for the next digestion, optionally after concentrating. The mixture ratios cited include the content of returned acid. Separation of the caesium alum formed from the solid ore residues can preferably be carried out as follows: The reaction mixture is slurried in water and/or process solutions with stirring and heated to a temperature of > 80°C. The preferred minimum temperature is 95°C, particularly preferably 100°C. A preferred maximum temperature corresponds to the boiling point of the reaction mixture. Potentially evaporating water is preferably replaced. Dissolution can be carried out even at excess pressure, e.g. at 0.5 to 6 bar excess pressure, preferably 1 to 6 bar excess pressure. The hot solution of the caesium alum is then separated from the ore residues; separation can take place e.g. by decanting, filtering or centrifuging. This process is preferably repeated several times in order to separate the caesium alum as completely as possible from the ore residues. The hot caesium alum solution can be transferred to another reactor. Alternatively, the process can be carried out in such a way that the dissolved caesium alum is separated together with the sulfuric acid from the ore residue after digestion before cooling. The caesium alum can then be crystallised out from the digestion acid (sulfuric acid). Particular materials are thereby required because of the highly corrosive action of the hot solution. In a preferred variant of the process, solid caesium alum is crystallised out from the caesium alum solution freed of the solid ore residues, by cooling and particularly preferably purified by recrystallisation. Recrystallisation can be repeated once or several times. In particular, the impurities of other alkali metal compounds are thereby removed. The mother liquors from recrystallisation can be used again as process solutions further on in the process. Mother liquors with too high contents of alkali metal salts are preferably discarded. The caesium alum is thereby dissolved with heating in a quantity of water sufficient to dissolve all of the salt and then cooled to approx. 2 0°C, the supernatant mother liquor being separated off and optionally used again at another point in the process. This recrystallisation is preferably carried out several times. The first recrystallisations can thereby be carried out with mother liquors and the other recrystallisations with water, preferably deionised water (DI water). Surprisingly it was found that with e.g. six recrystallisations and the use of the mother liquors in the 1st, 2nd and 3rd recrystallisations and carrying out the 4th, 5th and 6th recrystallisation with deionised water (DI water), the contents of for example Rb can be reduced to In some cases, ultrapure water with a specific resistance of > 10 MQ can be used for recrystallisations- This is the case in particular if the content of radioactive cations such as 87Rb or 137Cs coming from natural and anthropogenic sources is to be reduced. In the next process step, separation of the aluminium from the caesium aluminium sulfate hydrate (caesium alum) takes place by precipitation of solid aluminium hydroxide using a base, for example calcium hydroxide, for which the following reaction equation can be given: In principle, any basic compound with which in the reaction mixture a pH suitable for the precipitation of aluminium hydroxide can be set (eq. (6)) can be used for precipitation of the aluminium hydroxide. A suitable pH is between 4 to 9, preferably 7 to 8. One or more of the hydroxides, carbonates or hydrogen carbonates of elements of the 1st and 2nd main groups of the periodic system are preferably used as basic compounds, but they are not restricted to these. As pure as possible a caesium sulfate solution, i.e. a solution that contains as low as possible a content of the sulfate of the base used, is the better to produce, the lower the solubility of this sulfate compound. This is the case in particular with the sulfates of the alkaline earth elements calcium, strontium and barium, slaked lime (calcium hydroxide) or even lime (calcium carbonate) preferably being used for economic reasons. The reaction is carried out in aqueous solution in such a way that caesium alum and the basic compound (e.g. slaked lime or lime) are caused to react with one another, so that at the end of the reaction, the reaction mixture containing a caesium sulfate solution, aluminium hydroxide and the sulfate of the added base (e.g. gypsum) has a pH of 4 to 9, preferably 6.5 to 7.5. It is advantageous to bring the caesium alum into solution before the reaction. The reaction is carried out particularly preferably at a temperature of > 60°C, especially preferably at 90 to 110°C. For example, a saturated solution of caesium aluminium sulfate (caesium alum) heated to a temperature of > 100°C can be used and reacted with a suspension of slaked lime or lime with thorough mixing until the desired pH is achieved. In order on the one hand to achieve as complete as possible a reaction and on the other to improve the filterability of the precipitate, the reaction mixture can preferably be boiled for a period of at least 1 hour with stirring at a temperature of > 100°C. This process variant has the advantage over the procedure described in patent US 3 207 571 (addition of caesium alum to a lime suspension) that the basic compound used is reacted virtually completely and the formation of a precipitate layer on the particles of the basic compound used (e.g. calcium hydroxide) is avoided. Furthermore, it was found that using slaked lime (calcium hydroxide), calcium sulfate hemihydrate (x = 0.5 in eq. (5)) and not - as assumed in patent US 6 015 535 -calcium sulfate dihydrate (x = 2 in eq. (5)) is formed under the reaction conditions described, which leads to a reduction in the mass of precipitate to be separated. The conventional processes of solid-liquid separation corresponding to the prior art are used for separating the caesium sulfate solution. For selection it should in particular be considered that the X-amorphous aluminium hydroxide obtained with the production route described is very difficult to dewater and wash. The caesium sulfate solution produced in the way described can, for example, due to a high dilution, have comparatively low contents of caesium, namely as a rule In a preferred variant of the process according to the invention, the caesium sulfate solution obtained is concentrated. This can take place e.g. by evaporating. The solution is preferably concentrated to a content of 20 to 70 wt.%, particularly preferably 40 to 60 wt.% caesium sulfate. Surprisingly it was found that any impurities still present (e.g. Mg, Ca, Sr, Ba) are precipitated out. The purification effect can be improved by adding activated carbon to the solution as a filtering aid. The added quantity of activated carbon is preferably 0.5 to 5 wt.%, particularly preferably 1 to 1.5 wt.%, based on the dissolved quantity of caesium sulfate. In this way, caesium sulfate solutions, the impurities of alkaline earth elements of which, based on the content as caesium sulfate, have the following values: Mg The caesium sulfate solution obtained is converted to a caesium hydroxide solution in the next process step. The stoichiometric reaction of a caesium sulfate solution to a caesium hydroxide solution can be carried out in principle with any base M(OH), provided that the difference in the solubilities of the base M(OH) and the corresponding sulfate M2SO4 is large enough and consequently the equilibrium according to equation (7) is displaced to a sufficient extent towards the products CsOH and M2S04: The caesium sulfate solution is reacted (preferably stoichiometrically) with barium hydroxide or strontium hydroxide (barium hydroxide is preferred). A caesium hydroxide solution is thereby formed. The precipitated barium or strontium sulfate and other poorly soluble impurities produced during this resalting ("causticisation") (e.g. chromium, iron and/or magnesium hydroxide) are separated in a known way. A caesium hydroxide solution is obtained. Causticisation can be carried in such a way that a quantity of barium hydroxide corresponding stoichiometrically to the content of the caesium sulfate solution is produced as a suspension, the .ratio by weight of barium hydroxide in the form of the monohydrate to water be.ing 1 : (1.5 to 4), preferably 1 : 2.0, this suspension being heated to a temperature between 80 and 100°C, preferably between 95 and 100°C, and then added with intensive mixing tof the caesium sulfate solution also heated to a temperature between 80 and 100°C, preferably between 95 and 100°C. From experience, the contents of the caesium sulfate solution can vary, so that it has proved useful to have a test method for determining the equivalence point of the reaction according to eq. (7). Two test solutions are produced for this test method, one solution being a carbonate-containing caesium solution, preferably a caesium hydrogen carbonate solution, and the other test solution a barium salt solution. The test is then carried out so that a sample of the reaction mixture is freed of the solid content and in each case part of the solution is mixed with the test solutions. The equivalence point is determined from the visually assessed or even measured turbidity of the mixture of the test solutions with the reaction solutions. The crude caesium hydroxide solution produced in the way described above is greatly diluted with a concentration between 1 and 5 wt.% and can contain a number of impurities, for example strontium, calcium, barium and sulfate, the solubility of barium sulfate in caesium hydroxide solutions of higher concentration surprisingly increasing. The crude, dilute caesium hydroxide solution can preferably be even further purified. This can occur by one or more of the following process steps. At the end of the precipitation reaction described above (in which the caesium sulfate solution reacts with Ba(OH)2 or Sr(OH)2), another base (preferably Ba(OH)2 or Sr(OH)2) can be added to the mixture of caesium- hydroxide solution and precipitated sulfates obtained; this addition to the reaction, mixture preferably takes place when it is still hot at between 80 and 100°C, preferably between 95 and 100°C. The addition quantity of this base is - based on the quantity of caesium hydroxide - preferably 0.7 to 3.5 wt.% and especially preferably 1.5 to 2.5 wt.%. After cooling the suspension, the precipitated barium or strontium sulfate and poorly soluble impurities produced are then separated from the caesium hydroxide solution as described above. Carrying out causticisation is not restricted to the temperature range given but can take place at corresponding excess pressure even at higher temperatures. The caesium hydroxide solution obtained can be concentrated e.g. by evaporating, e.g. to a CsOH content of 10 to 8 0 wt.%, preferably 4 5 to 55 wt.%. Very finely divided solids (e.g. carbonates and/or hydroxides) which can be separated off according to the prior art, are thereby possibly formed. Activated carbon can be used as a filter aid in separation. The caesium hydroxide solution obtained (a concentrated caesium hydroxide solution is preferred) can be mixed with carbon dioxide or a carbonate or hydrogen carbonate soluble in the hydroxide solution, preferably of the alkali metals, particularly preferably of caesium. The quantity of carbon dioxide to be used is (in each case based on 1000 kg caesium hydroxide) between 2.5 to 10 kg, preferably between 3 and 6 kg and especially preferably between 4 and 4.5 kg; the additions of carbonate or hydrogen carbonate correspond to the addition of carbon dioxide and should be converted accordingly. The precipitation products obtained, possibly very finely-divided, are separated from the solution in a known way. Activated carbon can thereby be used as a filter aid. Using one or more of these optional process steps, it is possible to obtain caesium hydroxide solutions that have a preferred concentration of 45 to 55 wt.% CsOH. The impurities have, in each case based on the content of anhydrous caesium hydroxide: multivalent cations (e.g. Al, Fe, Cr, Mn) in total Another advantage of the process according to the invention is that the solids produced and separated off in the named process steps which have a not inconsiderable content of caesium compounds, can be used again within the process at a suitable point and consequently the loss of caesium in the overall process can be minimised. The reaction of the caesium sulfate solution to the caesium hydroxide solution and/or the digestion of the ore can be cited as suitable points for the use of the solids. The subject matter of the invention is explained in greater detail by means of the following examples: Example 1: A solution consisting of 328 ml deionised water (DI water) and 186 ml 96% sulfuric acid was placed in a 1 1 glass flask and 219 g ground pollucite ore added to it with stirring. The reaction mixture was heated and refluxed for 4 hours. During cooling to room temperature, the reaction mixture was diluted with 350 ml DI water. The caesium alum formed was separated from the supernatant acid together with the ore residue using a Nutsch filter and washed acid-free three times with in each case 100 ml DI water. The solid was then transferred to a 1 1 beaker and dissolved in 700 ml DI water. The hot solution was filtered using a glass-fibre filter into a 2 1 beaker and the filter residue washed twice with in each case 500 ml hot DI water, starting and wash solutions being combined. The solutions were cooled to room temperature with stirring. After the stirrer and sedimentation of the alum were stopped, the supernatant mother liquor was decanted. The caesium alum was recrystallised in 850 ml DI water and the mother liquor decanted; recrystallisation was repeated five times. The caesium alum purified in this way was dissolved in 500 ml DI water with heating. In another beaker, a suspension of 150 ml DI water and 4 0 g calcium oxide with a low water content which was added to the caesium alum solution with stirring in the boiling heat until the reaction mixture had a pH of approx. 6.5, was produced. After briefly boiling, the mixture was cooled until it had reached a temperature of approx. 40 °C. The suspension was filtered using a fluted filter and washed three times with 100 ml approx. 40°C hot DI water. The solutions were combined and concentrated to a volume of 65 ml, 800 mg activated carbon were stirred in and the solution freed of solid contents using a Nutsch filter. Analysis of the sulfate solution obtained in this way gave the values shown in the table, the contents of elements being based on the content of caesium sulfate: Example 2 150 ml of the 50% caesium sulfate solution produced in example 1 were diluted with DI water to 2500 ml and heated under reflux to boiling. A suspension consisting of 7 5 g barium hydroxide monohydrate and 2 00 g DI water was heated in a beaker to approx. 95°C and 265 g of the suspension of the hot dilute caesium sulfate solution added with intensive stirring at the boiling point. A small sample of the reaction mixture was taken and filtered and in each case half of the clear solution was mixed with a few drops of a caesium hydrogen carbonate solution or a barium salt solution. The reaction was carried out stoichiometrically with equal turbidity of both solutions. 6 g of the barium hydroxide suspension were once again added and the reaction mixture cooled to 40°C and filtered using a fluted filter. The filter residue was washed six times with in each case 100 ml 40 to 50°C hot DI water and all solutions were combined and then concentrated to a volume of 12 0 ml and cooled to room temperature. 2.2 g caesium carbonate in the form of a 50% solution and 1.5 g activated carbon were added with stirring and then the caesium hydroxide solution filtered using a Nutsch filter. Analysis of the 50% caesium hydroxide solution obtained in this way gave the following values (in each case based on the caesium hydroxide content). Patent Claims 1. A process for the production of caesium hydroxide solutions, characterised in that caesium-containing ore is digested with sulfuric acid , forming a caesium aluminium sulfate hydrate (caesium alum), poorly soluble when cold, the caesium alum formed is separated from the solid ore residues as a solution, the aluminium is precipitated from the caesium alum solution, forming a caesium sulfate solution the caesium sulfate solution formed is reacted with barium hydroxide or strontium hydroxide, forming a caesium hydroxide solution and the caesium hydroxide solution formed is concentrated and purified. 2. A process according to claim 1, characterised in that the caesium sulfate solution formed is reacted with barium hydroxide - 3. A process according to claim 1 or 2, characterised in that pollucite is used as the caesium-containing ore. 4. A process according to one of claims 1 to 3, characterised in that the caesium-containing ore has a caesium content of 20 to 24 wt.%. 5. A process according to one of claims 1 to 4, characterised in that'the caesium-containing ore has a particle size of 90 wt.%, 6. A process according-to one of claims 1 to 5, characterised in that digestion is carried out with a hyperstoichiometric quantity of sulfuric acid (relative to the quantity of ore used). 7. A process according to one of claims 1 to 6, characterised in that during digestion the mixture ratio of caesium-containing ore (which has a Cs content of 20 to 24 wt.%) to water to concentrated sulfuric acid is = 1.0 : (1.0 to 1.8) : (1.0 to 1.8). 8. A process according to claim 7, characterised in that the mixture ratio is 1.0 : (1.2 to 1.6) : (1-2 to 1.6) . 9. A process according to claim 7, characterised in that the mixture ratio is 1.0 : (1.3 to 1.5) : (1.3 to 1.5) . 10. A process according to one of claims 1 to 9, characterised in that digestion is carried out in such a way that the mixture of caesium-containing ore, water and sulfuric acid is heated for a period of at least 2 hours at a temperature of > 9Q°C 11. A process according to claim 10, characterised in that the digestion period is at least 3 hours. 12. A process according to claim 10 or 11, characterised in that the minimum temperature is 100°C. 13. A process according to claim 12, characterised in that the minimum temperature is 120°C. 14. A process according to one of claims 1 to 13, characterised in that the maximum digestion temperature corresponds to the boiling point of the . ,:. ■ reaction mixture. 15. A process according to one of claims 1 to 14, characterised in that potentially evaporating water is replaced during digestion. 16. A process according to one of claims 1 to 15, characterised in that the digestion reaction is carried out at excess pressure. 17. A process according to claim 16, characterised in that the excess pressure is 0.5 to 6 bar. 18. A process according to claim 16, characterised in that the excess pressure is 1 to 6 bar.- 19. A process according to one of claims 1 to 18, characterised in that aluminium in the form of aluminium sulfate is added during or after digestion of the reaction mixture. 20. A process according to claim 19, characterised in that the molar ratio of Al to Cs is at least 1:1. 21. A process according to claim 19, characterised in that the aluminium is added in excess relative to the caesium present and the molar ratio of Al to Cs is at most 1.5 : 1. 22. A process according to one of claims 1 to 21, characterised in that at the end of the digestion reaction, the reaction mixture is cooled and water or process solutions from later process steps (e.g. mother liquors from the subsequent separation of the caesium alum and/or of the subsequent crystallisation) are added during the crystallisation used of caesium aluminium sulfate hydrate (caesium alum). 23. A process according to claim 22, characterised in that the quantity of water or quantity of process solution added is at least 1.2 parts by weight per part by weight of ore used. 24. A process according to one of claims 1 to 23, characterised in that the acid excess is separated off at the end of the digestion reaction and cooling of the reaction mixture and optionally dilution of the reaction mixture. 25. A process according to one of claims 1 to 24, characterised in that the reaction mixture obtained after separation of the acid excess is slurried in water and/or process solutions at temperatures of at least 80°C to separate the caesium alum formed from the solid ore residues and the hot solution containing caesium alum is separated from the ore residues. 26. A process according to one of claims 1 to 23, characterised in that after the digestion reaction and before cooling of the reaction mixture the dissolved caesium alum together with the sulfuric acid is separated from the ore residue. 27. A process according to claim 26, characterised in that the caesium alum is crystallised out from the separated solution containing caesium alum and digestion acid. 28. A process according to one of claims 1 to 26, characterised in that solid caesium alum is crystallised out from the caesium alum solution freed of the solid ore residues by cooling. 29. A process according to claim 28, characterised in that the caesium alum is purified by recrystallisation. 30. A process according to claim 29, characterised in that the mother liquors from recrystallisation are used ~ "■" again further on in the process as process solutions.

Full Text

Process for the production of caesium hydroxide solutions
The invention relates to a process for the production of caesium hydroxide solutions.
Current processes for the production of caesium compounds are bashed on caesium-containing ores such as pollucite. Thus US patent 6 015 535 describes a process for the production of concentrated and purified caesium salt solutions. This process includes the digestion of the ore with a hyperstoichiometric quantity of sulfuric acid, the purification by recrystallisation of the caesium aluminium sulfate hydrate obtained in this way, the precipitation of the aluminium with slurried lime Ca (OH)2 and/or calcium carbonate and the separation of the precipitate consisting of calcium sulfate hydrate (gypsum) and aluminium hydroxide from the caesium sulfate solution. There follows a reaction of this solution with a calcium hydroxide slurry and an acid, maintaining a pH of 7 to 8. Separation of the residue consisting of calcium sulfate from the caesium salt solution determined by the anion of the acid then takes place. Purification of the caesium salt solution takes place by- a multi-stage "polishing" in which the solution is rendered alkaline with barium hydroxide and then mixed with carbon dioxide or carbonate, alkaline earths and sulfate being precipitated and separated off. The by then highly dilute caesium salt solution is finally concentrated by evaporation, wherein concentration can continue until a solid is obtained.
Patent DE 43 13 480 CI describes the production of a caesium hydroxide solution by reacting caesium aluminium ) sulfate hydrate or a caesium sulfate solution with calcium hydroxide in accordance with the equations
(1) CsAl(S04)2 + 2Ca(0H)2 -> CsOH + Al(OH)3i + 2CaS04^
(2) Cs2S04 + Ca(OH)2 -> 2CsOH + CaS044

The yields achieved, however, are very unsatisfactory, US patent application 2002/0143209 Al attempts to remedy this by repeating the reaction according to equation (2) several times, the caesium hydroxide produced and present in a mixture with caesium sulfate in each case being neutralised with the desired acid.
Due to the comparatively better solubility of the hydroxide of the barium but very low solubility of the sulfate, the reaction
(3) Cs2S04 + Ba(OH)2 -» 2CsOH + BaS044 is virtually completely displaced towards the caesium hydroxide. US patent 3 207 571 describes the reaction of a caesium sulfate solution with an aqueous barium hydroxide solution. A dilute caesium hydroxide solution which is separated from the solid barium sulfate, is obtained. This solution can be converted directly with acid to the corresponding caesium salt solution, or a carbonate solution is produced from this solution by addition of C02, wherein excess barium can be precipitated from this as barium carbonate by concentrating and separated.
The processes described have a number of disadvantages. According to the route proposed in US patent application 2002/0143209 Al, caesium hydroxide can only be produced in mixture with other#7c^esium salts. The production method stated in US patent 3 207 571 leads to highly dilute caesium hydroxide solutions with high, not defined, contents of sulfate ind/or barium or has a caesium carbonate solution as the end product. 'This process does not give caesium hydroxide solutions.
Caesium hydroxide solutions have numerous applications, e.g. as catalysts, and are used as the starting product for the production of all neutral and basic caesium salts and of solid caesium hydroxide and other caesium compounds. Because a disadvantageous purification of the compounds is often not possible or possible only with great expense, a

high purity of the caesium hydroxide solutions is desired. Furthermore, a high concentration of the caesium hydroxide solutions is aimed for.
The problem of the present invention is to overcome the disadvantages of the prior art and develop a process for the production of an aqueous caesium hydroxide solution which has a caesium hydroxide concentration of at least 45 wt.% and is marked by as low as possible a content of multivalent cations in general and alkaline earth cations in particular, and low contents of sulfate and carbonate.
The problem is resolved by a process for the production of caesium hydroxide solutions in which
caesium-containing ore is digested, forming a caesium aluminium sulfate hydrate (caesium alum), poorly soluble when cold, with sulfuric acid,
the caesium alum formed is separated off as a solution from the solid ore residues,
the aluminium is precipitated out from the caesium alum solution, forming a caesium sulfate solution,
the caesium sulfate solution formed is reacted with barium hydroxide or strontium hydroxide, forming a caesium hydroxide solution (this process step is described as "causticisation") and
the caesium hydroxide solution formed is concentrated and purified.
In the reaction, of.the caesium sulfate solution formed to the caesium hydroxide solution, the use of barium hydroxide is preferred.
Any caesium-containing ore or material can be used as caesium-containing ore. However, pollucite is preferably used. A preferred pollucite has a caesium content of 20 to 2 4 wt.%. The particle size of the ore used is

preferably 90 wt.%, The following reaction equation can be given for the digestion reaction:
(4) 2CsAlSi206 • H20 + 4H2S04 + 18H20 -» 2CsAl(S04)2 • 12H20 + 4Si024 Digestion is preferably carried out with a hyperstoichiometric quantity of sulfuric acid (relative to the quantity of ore used). The mixture ratio of caesium-containing ore (with a Cs content of 20 to-24' wt.%): water : concentrated sulfuric acid is preferably = 1.0 : (1.0 to 1.8) : (1.0 to 1.8), particularly preferably 1.0 : (1.2 to 1.6) : (1.2 to 1.6) and especially preferably 1.0 : (1.3 to 1.5) : (1.3 to 1.5).
Digestion is preferably carried out in such a way that the mixture of caesium-containing ore, water and sulfuric acid is heated for a. period of at least 2 hours at a temperature of > 90°C. A digestion time of at least 3 hours is preferred. The preferred minimum temperature is 100°C, particularly preferably 120°C. A preferred maximum temperature corresponds to the boiling point of the reaction mixture. Potentially evaporating water is preferably replaced. The reaction can also be carried out at excess pressure, e.g. at 0.5 to 6 bar excess pressure, preferably 1 to 6 bar excess pressure.
Should the caesium-containing ore also not have a high enough aluminium content or should not enough aluminium be digested during digestion and pass into solution, in a preferred embodiment of the process aluminium can be added in the form of aluminium sulfate during or after digestion, so that a sufficiently high quantity of aluminium is available for the formation of the caesium alum. Without a sufficient quantity of aluminium, yield losses could occur, but performance of the process as such is not affected by

an insufficient quantity of aluminium. The molar ratio of
Al to Cs is preferably at least 1:1. A slight aluminium
excess is particularly preferably used, the Al : Cs molar
ratio being up to 1.5 : 1.
At the end of the digestion reaction and cooling of the reaction mixture, a caesium aluminium sulfate hydrate heavily contaminated by other alkali elements crystallises out. Water or process solutions from later process steps (e.g. mother liquors from the subsequent separation of the Cs alum and/or subsequent crystallisation) are preferably added to the reaction mixture to improve the rate and completeness of crystallisation. The quantity of water or quantity of process solution added is preferably at least 1.2 parts by weight per part by weight of ore used.
The acid excess is preferably separated off at the end of the reaction and cooling of the reaction mixture and optionally dilution of the reaction mixture. Separation can be carried out e.g. by decanting, filtering or centrifuging. The acid excess separated off can be used again for the next digestion, optionally after concentrating. The mixture ratios cited include the content of returned acid.
Separation of the caesium alum formed from the solid ore residues can preferably be carried out as follows:
The reaction mixture is slurried in water and/or process solutions with stirring and heated to a temperature of > 80°C. The preferred minimum temperature is 95°C, particularly preferably 100°C. A preferred maximum temperature corresponds to the boiling point of the reaction mixture.
Potentially evaporating water is preferably replaced. Dissolution can be carried out even at excess pressure, e.g. at 0.5 to 6 bar excess pressure, preferably 1 to 6 bar excess pressure. The hot solution of the caesium alum is

then separated from the ore residues; separation can take place e.g. by decanting, filtering or centrifuging. This process is preferably repeated several times in order to separate the caesium alum as completely as possible from the ore residues. The hot caesium alum solution can be transferred to another reactor.
Alternatively, the process can be carried out in such a way that the dissolved caesium alum is separated together with the sulfuric acid from the ore residue after digestion before cooling. The caesium alum can then be crystallised out from the digestion acid (sulfuric acid). Particular materials are thereby required because of the highly corrosive action of the hot solution.
In a preferred variant of the process, solid caesium alum is crystallised out from the caesium alum solution freed of the solid ore residues, by cooling and particularly preferably purified by recrystallisation.
Recrystallisation can be repeated once or several times. In particular, the impurities of other alkali metal compounds are thereby removed. The mother liquors from recrystallisation can be used again as process solutions further on in the process. Mother liquors with too high contents of alkali metal salts are preferably discarded.
The caesium alum is thereby dissolved with heating in a quantity of water sufficient to dissolve all of the salt and then cooled to approx. 2 0°C, the supernatant mother liquor being separated off and optionally used again at another point in the process. This recrystallisation is preferably carried out several times. The first recrystallisations can thereby be carried out with mother liquors and the other recrystallisations with water, preferably deionised water (DI water).
Surprisingly it was found that with e.g. six recrystallisations and the use of the mother liquors in the 1st, 2nd and 3rd recrystallisations and carrying out the 4th,

5th and 6th recrystallisation with deionised water (DI water), the contents of for example Rb can be reduced to In some cases, ultrapure water with a specific resistance of > 10 MQ can be used for recrystallisations- This is the case in particular if the content of radioactive cations such as 87Rb or 137Cs coming from natural and anthropogenic sources is to be reduced.
In the next process step, separation of the aluminium from the caesium aluminium sulfate hydrate (caesium alum) takes place by precipitation of solid aluminium hydroxide using a base, for example calcium hydroxide, for which the following reaction equation can be given:

In principle, any basic compound with which in the reaction mixture a pH suitable for the precipitation of aluminium hydroxide can be set (eq. (6)) can be used for precipitation of the aluminium hydroxide. A suitable pH is between 4 to 9, preferably 7 to 8.

One or more of the hydroxides, carbonates or hydrogen carbonates of elements of the 1st and 2nd main groups of the periodic system are preferably used as basic compounds, but they are not restricted to these. As pure as possible a caesium sulfate solution, i.e. a solution that contains as low as possible a content of the sulfate of the base used, is the better to produce, the lower the solubility of this sulfate compound. This is the case in particular with the sulfates of the alkaline earth elements calcium, strontium

and barium, slaked lime (calcium hydroxide) or even lime (calcium carbonate) preferably being used for economic reasons.
The reaction is carried out in aqueous solution in such a way that caesium alum and the basic compound (e.g. slaked lime or lime) are caused to react with one another, so that at the end of the reaction, the reaction mixture containing a caesium sulfate solution, aluminium hydroxide and the sulfate of the added base (e.g. gypsum) has a pH of 4 to 9, preferably 6.5 to 7.5. It is advantageous to bring the caesium alum into solution before the reaction. The reaction is carried out particularly preferably at a temperature of > 60°C, especially preferably at 90 to 110°C. For example, a saturated solution of caesium aluminium sulfate (caesium alum) heated to a temperature of > 100°C can be used and reacted with a suspension of slaked lime or lime with thorough mixing until the desired pH is achieved.
In order on the one hand to achieve as complete as possible a reaction and on the other to improve the filterability of the precipitate, the reaction mixture can preferably be boiled for a period of at least 1 hour with stirring at a temperature of > 100°C. This process variant has the advantage over the procedure described in patent US 3 207 571 (addition of caesium alum to a lime suspension) that the basic compound used is reacted virtually completely and the formation of a precipitate layer on the particles of the basic compound used (e.g. calcium hydroxide) is avoided.
Furthermore, it was found that using slaked lime (calcium hydroxide), calcium sulfate hemihydrate (x = 0.5 in eq. (5)) and not - as assumed in patent US 6 015 535 -calcium sulfate dihydrate (x = 2 in eq. (5)) is formed under the reaction conditions described, which leads to a reduction in the mass of precipitate to be separated.

The conventional processes of solid-liquid separation corresponding to the prior art are used for separating the caesium sulfate solution. For selection it should in particular be considered that the X-amorphous aluminium hydroxide obtained with the production route described is very difficult to dewater and wash.
The caesium sulfate solution produced in the way described can, for example, due to a high dilution, have comparatively low contents of caesium, namely as a rule In a preferred variant of the process according to the invention, the caesium sulfate solution obtained is concentrated. This can take place e.g. by evaporating. The solution is preferably concentrated to a content of 20 to 70 wt.%, particularly preferably 40 to 60 wt.% caesium sulfate. Surprisingly it was found that any impurities still present (e.g. Mg, Ca, Sr, Ba) are precipitated out. The purification effect can be improved by adding activated carbon to the solution as a filtering aid. The added quantity of activated carbon is preferably 0.5 to 5 wt.%, particularly preferably 1 to 1.5 wt.%, based on the dissolved quantity of caesium sulfate. In this way, caesium sulfate solutions, the impurities of alkaline earth elements of which, based on the content as caesium sulfate, have the following values: Mg The caesium sulfate solution obtained is converted to a caesium hydroxide solution in the next process step. The

stoichiometric reaction of a caesium sulfate solution to a caesium hydroxide solution can be carried out in principle with any base M(OH), provided that the difference in the solubilities of the base M(OH) and the corresponding sulfate M2SO4 is large enough and consequently the equilibrium according to equation (7) is displaced to a sufficient extent towards the products CsOH and M2S04:

The caesium sulfate solution is reacted (preferably stoichiometrically) with barium hydroxide or strontium hydroxide (barium hydroxide is preferred). A caesium hydroxide solution is thereby formed. The precipitated barium or strontium sulfate and other poorly soluble impurities produced during this resalting ("causticisation") (e.g. chromium, iron and/or magnesium hydroxide) are separated in a known way. A caesium hydroxide solution is obtained.
Causticisation can be carried in such a way that a quantity of barium hydroxide corresponding stoichiometrically to the content of the caesium sulfate solution is produced as a suspension, the .ratio by weight of barium hydroxide in the form of the monohydrate to water be.ing 1 : (1.5 to 4), preferably 1 : 2.0, this suspension being heated to a temperature between 80 and 100°C, preferably between 95 and 100°C, and then added with intensive mixing tof the caesium sulfate solution also heated to a temperature between 80 and 100°C, preferably between 95 and 100°C. From experience, the contents of the caesium sulfate solution can vary, so that it has proved useful to have a test method for determining the equivalence point of the reaction according to eq. (7).
Two test solutions are produced for this test method, one solution being a carbonate-containing caesium solution, preferably a caesium hydrogen carbonate solution, and the other test solution a barium salt solution. The test is

then carried out so that a sample of the reaction mixture is freed of the solid content and in each case part of the solution is mixed with the test solutions. The equivalence point is determined from the visually assessed or even measured turbidity of the mixture of the test solutions with the reaction solutions.
The crude caesium hydroxide solution produced in the way described above is greatly diluted with a concentration between 1 and 5 wt.% and can contain a number of impurities, for example strontium, calcium, barium and sulfate, the solubility of barium sulfate in caesium hydroxide solutions of higher concentration surprisingly increasing. The crude, dilute caesium hydroxide solution can preferably be even further purified. This can occur by one or more of the following process steps.
At the end of the precipitation reaction described above (in which the caesium sulfate solution reacts with Ba(OH)2 or Sr(OH)2), another base (preferably Ba(OH)2 or Sr(OH)2) can be added to the mixture of caesium- hydroxide solution and precipitated sulfates obtained; this addition to the reaction, mixture preferably takes place when it is still hot at between 80 and 100°C, preferably between 95 and 100°C. The addition quantity of this base is - based on the quantity of caesium hydroxide - preferably 0.7 to 3.5 wt.% and especially preferably 1.5 to 2.5 wt.%. After cooling the suspension, the precipitated barium or strontium sulfate and poorly soluble impurities produced are then separated from the caesium hydroxide solution as described above.
Carrying out causticisation is not restricted to the temperature range given but can take place at corresponding excess pressure even at higher temperatures.
The caesium hydroxide solution obtained can be concentrated
e.g. by evaporating, e.g. to a CsOH content of 10 to
8 0 wt.%, preferably 4 5 to 55 wt.%. Very finely divided

solids (e.g. carbonates and/or hydroxides) which can be separated off according to the prior art, are thereby possibly formed. Activated carbon can be used as a filter aid in separation.
The caesium hydroxide solution obtained (a concentrated caesium hydroxide solution is preferred) can be mixed with carbon dioxide or a carbonate or hydrogen carbonate soluble in the hydroxide solution, preferably of the alkali metals, particularly preferably of caesium. The quantity of carbon dioxide to be used is (in each case based on 1000 kg caesium hydroxide) between 2.5 to 10 kg, preferably between 3 and 6 kg and especially preferably between 4 and 4.5 kg; the additions of carbonate or hydrogen carbonate correspond to the addition of carbon dioxide and should be converted accordingly. The precipitation products obtained, possibly very finely-divided, are separated from the solution in a known way. Activated carbon can thereby be used as a filter aid.
Using one or more of these optional process steps, it is possible to obtain caesium hydroxide solutions that have a preferred concentration of 45 to 55 wt.% CsOH. The impurities have, in each case based on the content of anhydrous caesium hydroxide: multivalent cations (e.g. Al, Fe, Cr, Mn) in total Another advantage of the process according to the invention is that the solids produced and separated off in the named process steps which have a not inconsiderable content of caesium compounds, can be used again within the process at a suitable point and consequently the loss of caesium in the overall process can be minimised. The reaction of the

caesium sulfate solution to the caesium hydroxide solution and/or the digestion of the ore can be cited as suitable points for the use of the solids.
The subject matter of the invention is explained in greater detail by means of the following examples:
Example 1:
A solution consisting of 328 ml deionised water (DI water) and 186 ml 96% sulfuric acid was placed in a 1 1 glass flask and 219 g ground pollucite ore added to it with stirring. The reaction mixture was heated and refluxed for 4 hours. During cooling to room temperature, the reaction mixture was diluted with 350 ml DI water. The caesium alum formed was separated from the supernatant acid together with the ore residue using a Nutsch filter and washed acid-free three times with in each case 100 ml DI water. The solid was then transferred to a 1 1 beaker and dissolved in 700 ml DI water. The hot solution was filtered using a glass-fibre filter into a 2 1 beaker and the filter residue washed twice with in each case 500 ml hot DI water, starting and wash solutions being combined. The solutions were cooled to room temperature with stirring. After the stirrer and sedimentation of the alum were stopped, the supernatant mother liquor was decanted. The caesium alum was recrystallised in 850 ml DI water and the mother liquor decanted; recrystallisation was repeated five times.
The caesium alum purified in this way was dissolved in 500 ml DI water with heating. In another beaker, a suspension of 150 ml DI water and 4 0 g calcium oxide with a low water content which was added to the caesium alum solution with stirring in the boiling heat until the reaction mixture had a pH of approx. 6.5, was produced. After briefly boiling, the mixture was cooled until it had reached a temperature of approx. 40 °C. The suspension was filtered using a fluted filter and washed three times with

100 ml approx. 40°C hot DI water. The solutions were combined and concentrated to a volume of 65 ml, 800 mg activated carbon were stirred in and the solution freed of solid contents using a Nutsch filter.
Analysis of the sulfate solution obtained in this way gave the values shown in the table, the contents of elements being based on the content of caesium sulfate:

Example 2
150 ml of the 50% caesium sulfate solution produced in example 1 were diluted with DI water to 2500 ml and heated under reflux to boiling. A suspension consisting of 7 5 g barium hydroxide monohydrate and 2 00 g DI water was heated in a beaker to approx. 95°C and 265 g of the suspension of the hot dilute caesium sulfate solution added with intensive stirring at the boiling point. A small sample of the reaction mixture was taken and filtered and in each case half of the clear solution was mixed with a few drops of a caesium hydrogen carbonate solution or a barium salt solution. The reaction was carried out stoichiometrically with equal turbidity of both solutions. 6 g of the barium hydroxide suspension were once again added and the reaction mixture cooled to 40°C and filtered using a fluted filter. The filter residue was washed six times with in each case

100 ml 40 to 50°C hot DI water and all solutions were combined and then concentrated to a volume of 12 0 ml and cooled to room temperature. 2.2 g caesium carbonate in the form of a 50% solution and 1.5 g activated carbon were added with stirring and then the caesium hydroxide solution filtered using a Nutsch filter. Analysis of the 50% caesium hydroxide solution obtained in this way gave the following values (in each case based on the caesium hydroxide content).

Patent Claims
1. A process for the production of caesium hydroxide
solutions, characterised in that
caesium-containing ore is digested with sulfuric acid , forming a caesium aluminium sulfate hydrate (caesium alum), poorly soluble when cold,
the caesium alum formed is separated from the solid ore residues as a solution,
the aluminium is precipitated from the caesium alum solution, forming a caesium sulfate solution
the caesium sulfate solution formed is reacted with barium hydroxide or strontium hydroxide, forming a caesium hydroxide solution and
the caesium hydroxide solution formed is concentrated and purified.
2. A process according to claim 1, characterised in that the caesium sulfate solution formed is reacted with barium hydroxide -
3. A process according to claim 1 or 2, characterised in that pollucite is used as the caesium-containing ore.
4. A process according to one of claims 1 to 3, characterised in that the caesium-containing ore has a caesium content of 20 to 24 wt.%.
5. A process according to one of claims 1 to 4, characterised in that'the caesium-containing ore has a particle size of 90 wt.%, 6. A process according-to one of claims 1 to 5, characterised in that digestion is carried out with a hyperstoichiometric quantity of sulfuric acid (relative to the quantity of ore used).

7. A process according to one of claims 1 to 6, characterised in that during digestion the mixture ratio of caesium-containing ore (which has a Cs content of 20 to 24 wt.%) to water to concentrated sulfuric acid is = 1.0 : (1.0 to 1.8) : (1.0 to 1.8).
8. A process according to claim 7, characterised in that the mixture ratio is 1.0 : (1.2 to 1.6) : (1-2 to 1.6) .
9. A process according to claim 7, characterised in that the mixture ratio is 1.0 : (1.3 to 1.5) : (1.3 to 1.5) .
10. A process according to one of claims 1 to 9, characterised in that digestion is carried out in such a way that the mixture of caesium-containing ore, water and sulfuric acid is heated for a period of at least 2 hours at a temperature of > 9Q°C
11. A process according to claim 10, characterised in that the digestion period is at least 3 hours.
12. A process according to claim 10 or 11, characterised in that the minimum temperature is 100°C.
13. A process according to claim 12, characterised in that the minimum temperature is 120°C.
14. A process according to one of claims 1 to 13, characterised in that the maximum digestion
temperature corresponds to the boiling point of the . ,:. ■ reaction mixture.
15. A process according to one of claims 1 to 14,
characterised in that potentially evaporating water is
replaced during digestion.

16. A process according to one of claims 1 to 15, characterised in that the digestion reaction is carried out at excess pressure.
17. A process according to claim 16, characterised in that the excess pressure is 0.5 to 6 bar.
18. A process according to claim 16, characterised in that the excess pressure is 1 to 6 bar.-
19. A process according to one of claims 1 to 18, characterised in that aluminium in the form of aluminium sulfate is added during or after digestion of the reaction mixture.
20. A process according to claim 19, characterised in that the molar ratio of Al to Cs is at least 1:1.
21. A process according to claim 19, characterised in that the aluminium is added in excess relative to the caesium present and the molar ratio of Al to Cs is at most 1.5 : 1.
22. A process according to one of claims 1 to 21, characterised in that at the end of the digestion reaction, the reaction mixture is cooled and water or process solutions from later process steps (e.g. mother liquors from the subsequent separation of the caesium alum and/or of the subsequent crystallisation) are added during the crystallisation used of caesium aluminium sulfate hydrate (caesium alum).
23. A process according to claim 22, characterised in that the quantity of water or quantity of process solution added is at least 1.2 parts by weight per part by weight of ore used.
24. A process according to one of claims 1 to 23, characterised in that the acid excess is separated off at the end of the digestion reaction and cooling of

the reaction mixture and optionally dilution of the reaction mixture.
25. A process according to one of claims 1 to 24,
characterised in that the reaction mixture obtained
after separation of the acid excess is slurried in
water and/or process solutions at temperatures of at
least 80°C to separate the caesium alum formed from
the solid ore residues and the hot solution containing
caesium alum is separated from the ore residues.
26. A process according to one of claims 1 to 23,
characterised in that after the digestion reaction and
before cooling of the reaction mixture the dissolved
caesium alum together with the sulfuric acid is
separated from the ore residue.
27. A process according to claim 26, characterised in that
the caesium alum is crystallised out from the
separated solution containing caesium alum and
digestion acid.
28. A process according to one of claims 1 to 26,
characterised in that solid caesium alum is
crystallised out from the caesium alum solution freed
of the solid ore residues by cooling.
29. A process according to claim 28, characterised in that
the caesium alum is purified by recrystallisation.
30. A process according to claim 29, characterised in that
the mother liquors from recrystallisation are used ~ "■" again further on in the process as process solutions.

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Patent Number

264431

Indian Patent Application Number

3298/CHENP/2007

PG Journal Number

01/2015

Publication Date

02-Jan-2015

Grant Date

29-Dec-2014

Date of Filing

26-Jul-2007

Name of Patentee

CHEMETALL GmbH

Applicant Address

TRAKEHNER STRASSE 3, D-60487 FRANKFURT

Inventors:

#	Inventor's Name	Inventor's Address
1	HARMS, GERD, J.,	GOLDENE AUE 18, 38640 GOSLAR
2	SCHIEDT , ALEXANDER	NEUEKRUG 32, 38729 HAHAUSEN.,GERMANY
3	BICK, MANFRED	EICHENSTRASSE 23, 6144 OBERURSEL, GERMANY
4	HILDEBRANDT, WOLFGANG	UNTERER SCHMIEDEKAMP 12, 38685 LANGELSHEIM, GERMANY

PCT International Classification Number

C01D 17/00

PCT International Application Number

PCT/EP06/00634

PCT International Filing date

2006-01-25

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	102005003999.5	2005-01-27	Germany