3,495,953 United States Patent Office Patented Feb. 17, 1970 1 2 be removed by evaporation and filtration before further 3,495,953 proceSSIng. METHOD OF SEPARATING STRONTUM CHELORIDE FROMMXED SOLUTIONS The aqueous solution is selectively cooled to, e.g., 25 USENGETHANOL C. to 15 C., to crystallize a mixture of CaCl2.6H2O and Remigius A. Gaska, Midland, and Robert A. Canute, 5 SrCl2.2H2O having a CaCl to SrCl weight ratio of the Mount Pleasant, Mich., assignors to The Dow Chemical order to 20:1. The solid mixture is separated from the Company, Midland, Mich., a corporation of Delaware mother liquor by conventional means such as filtration or No Drawing. Filed June 17, 1968, Ser. No. 737,378 centrifugation. Int. C. C01f 11/32; B01d 9/02, 57/00 The solid mixture is heated to, e.g., 28° C. to 50° C. to U.S. C. 23-308 5 Claims O selectively melt the CaCl2.6H2O crystals. The melted por tion is separated from the solid SrCl2.2H2O by filtration or similar means. However, as previously disclosed the solid ABSTRACT OF THE DISCLOSURE strontium chloride still contains some impurities, e.g., 5-25 In a process of separating strontium chloride from brine percent CaCl2 as CaCl2.6H2O. solutions containing strontium chloride and calcium chlo We have unexpectedly discovered that washing this im ride comprising selectively crystallizing the brine, selec purity containing solid strontium chloride hydrate with tively melting the resulting precipitate to produce a solid -ethanol effectively removes substantially all the remaining strontium chloride containing calcium chloride impuri CaCl2.6H2O impurity. The ethanol may be added to the ties, the improvement of washing the strontium chloride impure strontium chloride in any conventional manner in with ethanol to produce a substantially pure solid stronti 20 an amount of from about 5 grams to about 50 grams per um chloride. gram of CaCl2 impurity, preferably from about 10 grams to about 30 grams per gram of CaCl impurity. The eth anol selectively dissolves the CaCl2 impurity to produce BACKGROUND OF THE INVENTION a substantially pure solid strontium chloride hydrate which 25 Strontium is useful in preparing strontium compounds can be dried to produce anhydrous SrCl if desired. and as an alloying element. Sources of strontium include Although the present invention is particularly adapted strontium chloride found as a minor constituent, e.g., to be used in conjunction with a conventional recovery a fraction of a percent, in aqueous brine solutions also process for obtaining strontium chloride from brines and containing other alkaline earth metal and alkali metal 30 the like, it is to be understood that a strontium chloride halides such as calcium chloride, sodium chloride, and hydrate containing calcium chloride produced by other potassium chloride. methods also can be purified by the improved process of Heretofore strontium chloride generally has been re the present invention. covered from these brines by selective crystallization of The following example is representative of the present the brines under controlled conditions of concentration invention but it is understood that the invention is not lim and temperature to precipitate hydrated crystals of stron 35 ited thereto. tium chloride and calcium chloride. The hydrated chlo EXAMPLE rides may then be separated by selectively melting the cal cium chloride hydrate, thereby separating the solid stron A sample of aqueous brine solution was selected having tium chloride hydrate. Such a process is disclosed in U.S. 40 the following weight percent analysis: Patent No. 1,831,251. However, strontium chloride recov Percent ered from such a process still contains undesirable impuri CaCl2 ------22.2 ties, e.g., calcium chloride. NaCl ------5.2 A primary object of the present invention, therefore, is KC ------1.4 to provide an improved method of separating and recover 45 SrC2 ------0.45 ing highly pure strontium chloride from brines or mixed LiCl ------0.03 halide solutions or from a strontium chloride solid product contaminated with calcium chloride hydrate. The Solution was concentrated by evaporation to a specific These and other objects and advantages are found in gravity of 1.45, i.e., CaCl2 concentration of about 42 per the present process which is an improvement to the meth 50 cent. The brine was then cooled to 25° C. and filtered to od of strontium chloride recovery practiced heretofore, remove any crystallized NaCl. The concentrated brine had i.e., of selective crystallization of metal values from brines an analysis by weight of: and melting of the crystallized product to effect a separa Percent tion of strontium chloride hydrate from the co-crystallized CaCl2 ------42.1 compound, e.g. calcium chloride hydrate. The present in 55 NaCl ------0.35 vention comprises washing the calcium chloride contam KCl ------a ------2.27 inated solid strontium chloride hydrate with the ethanol SrC2 ------0.91 after the melting step thereby dissolving calcium chloride hydrate, and separating the ethanol washing solution from About 5 gallons of the concentrated brine was cooled to the remaining solid, thereby obtaining highly pure stron 60 about 18 C. and held at that temperature for about 21 tium chloride hydrate, which may then be dried to obtain hours. The resulting precipitate was separated from the fil anhydrous strontium chloride. trate by filtration. The precipitate and filtrate analyses by In the practice of the present invention the initial aque Weight percent are as follows: ous solution should contain from about 38 to about 43 weight percent calcium chloride and an amount of stron Compound Precipitate Filtrate tium chloride such that the weight ratio of CaCl2 to SrCla CaCl2- 43.8 40, 1 is at a maximum of about 100:1. Where the solution ini NaCl. 0.47 0.40 tially contains less than about 38 percent CaCl2, the solu KC---- 0.79 176 tion may be conventionally concentrated as by evapora SrCl2------4, 19 0.34 tion. The solution may also contain other alkaline earth IO metal and alkali metal halides, e.g., potassium chloride A portion of the precipitate was warmed at about and sodium chloride. If sodium chloride is present, it may 30° C. for about 20 hours to melt the CaCl26HO im 3,495,953 3 4. purity. Subsequent filtration yielded a cake and filtrate of aqueous solutions containing strontium chloride and cal the following analyses by weight percent: cium chloride comprising selectively crystallizing by evaporating and cooling said solution to precipitate mixed Compound Cake Filtrate crystals of CaCl26H2O and SrCl2.H2O, selectively melt 2.46 44.75 ing said mixture at a temperature of from about 28 to 0.06 0.37 about 50° C. to provide a solid phase concentrated in 0.16 1.0 SrCl22H2O but which contains calcium chloride as an 41.2 0.96 impurity, and separating said solid phase from the co The cake purity is equivalent to 76.5 SrCl2 on an an produced calcium chloride rich liquid phase; the im hydrous basis. O provement which comprises washing the concentrated Ten grams of the filtered cake was washed with 40 strontium chloride solid phase with ethanol to preferen grams of ethanol at about 25 C. and the resulting slurry tially extract said calcium chloride impurity thereby to filtered to yield the following cake analysis by weight produce a substantially pure strontium chloride hydrate percent: depleted in calcium chloride, and separating said strontium 15 chloride hydrate solid phase from the residual calcium Compound: Cake chloride containing ethanol solution. CaCl2 ------3.4 2. The process as defined in claim 1 wherein the amount SrCl2 ------49.9 of ethanol used is from about 5 grams to about 50 grams NaCl ------0.03 per gram of CaCl2 impurity in the concentrated precipi KCl ------0.07 20 tate. The cake purity is about 93.5 percent SrCl2 on an anhy 3. The process as defined in claim 2 wherein the amount drous basis. of ethanol used is from about 10 grams to about 30 As shown in the above example, while selective crystal grams per gram of CaCl2 impurity in the concentrated lization and melting did improve the CaCl2 to SrCl ratio precipitate. of the filtered cake, there remained significant CaCl 25 4. The process as defined in claim 1 and including the impurities as well as smaller KCl and NaCl impurities. step of drying said strontium chloride dihydrate at a tem The improvement of the present invention, an ethanol perature sufficient to remove the water of hydration there wash of the filtered cake, is extremely effective in puri from thereby to provide a substantially anhydrous stron fying the SrCl cake, thereby obtaining an acceptable com tium chloride product. mercial purity level. 30 5. The process as defined in claim 1 wherein the wash The solid SrCl product may be even further purified ing is repeated at least once. by rewashing the product with ethanol in a manner simi lar to the first washing. References Cited In a similar matter other brines containing strontium UNITED STATES PATENTS chloride and calcium chloride may be processed by con 35 centration, cooling, melting, and washing with ethanol 2,030,659 2/1936 Shreve ------23-90 as hereinbefore disclosed to produce substantially pure 2,980,502 4/1961 Goodenough ------23-90 X SrCl product. Strontium chloride hydrate containing 3,029,133 4/1962 Goodenough ------23-90 X calcium chloride materials produced by other methods 3,239,318 3/1966 Goodenough ------23-304 X can be purified by the practice of the present invention. 40 NORMANYUDKOFF, Primary Examiner Various modifications can be made in the present inven tion without departing from the spirit or scope thereof and S. J. EMERY, Assistant Examiner it is understood that the invention is limited only as defined in the appended claims. U.S. C. X.R. What is claimed is: 45 23-90, 297, 299, 304 1. In a process of separating strantium chloride from