PROCESS FOR IMPROVING THE FORMATION OF HYDROUS ALUMINA DISPERSED WITHIN A WEAK BASE ANION EXCHANGE RESIN AND USE OF THE COMPOSITE PREPARED FOR THE RECOVERY OF LI+ FROM BRINE

Abstract: Formation of additional hydrous alumina in the reti­ cules of a weak-base anion-exchange resin, where AlCl₃ has been precipitated as hydrous alumina by addition of ammonia, is achieved by subsequent treatment with HCl or NH₄Cl and HCl to convert the resin to the chloride form, thus increasing the reticular volume of the resin.

Description: PROCESS FOR IMPROVING THE FORMATION OF HYDROUS ALUMINA DISPERSED WITHIN A WEAK BASE ANION-EXCHANGE RESIN AND USE OF THE COMPOSITE PREPARED FOR THE RECOVERY OF LI + FROM BRINE. The present invention relates to the formation of hydrous alumina dispersed within a weak-base anion-exchange resin. Three U.S. Patents issued to Bauman et al., 4,116,858 and 4,116,856, both granted September 26, 1978, and 4,159,311, granted June 26, 1978, all relate to the formation of hydrous alumina within a particulate weak -base anion-exchange resin. The hydrous alumina is reacted with tiCl to form crystalline LiCl 2Al(OH)3, or reacted with LiOH to form crystalline LiOH 2Al(OH)3. The hydrous alumina is prepared by the ammonia precipitation of AlCl3 dispersed in the anion-exchange resin. As used herein, the term "weak-base" refers to anion-exchange resins wherein salt forms of the functional amine groups are converted to the OH form by NH4OH The patents mentioned above describe anion -exchange resins of the weak-base or strong-base varieties and disclose that the neutral halide salt forms of the strong-base resins may be used as the starting material. During the process of precipitating hydrous alumina in the resin by the ammonia precipitation of AlCi3, the halide salt forms of weak-base anion-exchange resins are converted to the CH form. Anion-exchange resins can have functional amine groups which are substantially all of the weak-base variety, some which are substantially all of the strong-base variety, and some which contain both varieties. This invention relates only to anion -exchange resins which contain any groups of the weak -base variety as the term "weak-base" is defined above. It has been found that the amount of hydrous alumina which may be incorporated into the resin by the ammonia precipitation of Al halide is limited in any one step by the maximum solubility of Al halide and the free volume in the resin. The ammonia treatment also converts the weak-base resin to the OH form, which is approximately only 80 percent of the volume of the halide form and thus there is less volume available to imbibe more Al halide solution. It would thus be desirable to be able to introduce greater amounts of aluminum halide into the resin. The defect mentioned above has been substantially removed by the present invention, which is a process for precipitating A1(OH)3 in the reticules of a weak-base anion-exchange resin by the in situ ammonia precipitation of Al halide in aqueous media, thereby forming a composite of anion-exchange resin having Al(OH)3 dispersed therein, characterized by: (1) acidifying the said composite in an aque ous medium with HX, where X is chlorine, bromine, iodine or fluorine, sufficient to provide a pH of not lower than about 5.0, thereby converting the anion-exchange resin to the halide salt form; (2) separating the composite from the aque ous portion; (3) flooding the composite with an aqueous solution of Al halide, draining the excess solu tion; and (4) adding NH4OH to precipitate additional Al(OH)3 in the resin. By the present invention, the OH form of the resin is converted to the halide form without solubilizing the Al(OH)3 in the resin. This permits additional amounts of Al halide to be imbibed and then converted by ammonia treatment to additional amounts of A1(OH)3. The preferred acid halide is HCl and the preferred Al halide is AlCl3. The acid halide treatment of the Al(OH)3-con- taining Oil resin should be done carefully, taking care that the acid addition is not so rapid that a localized drop in pil to lower than about 5 is reached. Slow addition of acid, with stirring and while monitoring the pH, is recommended. Any convenient method for lowering the pH, by addition of acid halide, may be used so long as the method does not result in solubilizing a substantial amount of the Al(OH)3 which is already in the resin. The acid halide treatment step is beneficially aided and speeded by the addition of ammonium halide, especially NH4Cl. The mount of NH4C1 added may be over a fairly broad range, with about 5-25 percent aqueous strength of NH4C1 being particularly beneficial. Other amine hydrochlorides may be used, but NH4C1 is preferred. The ammonium halide acts as a buffer against localized over-acidification during the acid halide addition, thereby allowing faster addition of the acid halide. The ammonium halide added initially, prior to the acid halide addition, may. be mostly removed when the resin is drained before addition of more Al halide. Then when NH4OH is added to convert Al halide to Al(OH)3, more ammonium halide is formed. HC1 is the most appropriate acid to use if one intends to convert the hydrous alumina, Al(OH)3, to- LiCl 2Al(OH)3. However, if one intends to convert to LiX 2Al(OH)3, where X is a different halogen than chlorine, then it is recommended that the corresponding acid halide be used and that the corresponding ammonium halide be used, thus avoiding a mixture of halo compounds. The temperature for use with the HC1 or the NH4Cl/HCl treatment should be in the range of about 200C to about 1000C, preferably about 450C to about 1000C. If higher temperatures are desired so as to speed the treatment, superatmospheric pressures may be needed to avoid substantial loss of ingredients through vaporization. It appears that the HC1 or NH4Cl/RCl treatment swells the resin, thereby permitting further sequential treatment steps, thus providing for appreciable increases in the aluminum content of the resin. As much as a three -fold increase or more in the Al content of the resin is readily attained. By this increase in the Al content in the resin (first as hydrous alumina and then as LiX-2Al( OH)3), the composite has greater capacity for recovering Li values from brines and a more efficient Li+ recovery process is attained. The higher loading of aluminate in the resin permits greater concentration of Lix in the effluent of the exchange column when recovering Li from brines. We have also found that the formation of crystalline LiX-2Al(OH)3, formed by heating LiX (where X is Cl or OH-) within the resin/AI(OH)3 composite, is enhanced by performing the heating at high pH of, say, about 11 to about 11.5 which is done in a metal (non-glass) container to avoid heating the highly alkaline mixture in glass. Heating of highly alkaline mixtures in glass can result in minute amounts of lithium silicate which can interface to some extent with the formation of highly crystalline LiX 2A1(OH)3. The following examples illustrate the invention. For purposes of comparison, the same resin is employed in each of the following examples. This resin is a particulate, macroporous anion-exchange resin comprising a styrene-divinylbenzene cross-linked polymer having pendant tertiary amine groups. Example 1 A portion of the above resin is flooded with a concentrated aqueous solution of aluminum chloride, dried until it is freely flowing, and then treated with ammonium hydroxide to cause precipitation of aluminum hydroxide dispersed within the resin. Ammonium chloride, ammonium hydroxide and aluminum hydroxide are washed out, leaving the resin in OH form containing the A1(OH)3 dispersed therein. At this point the resin contains about 1.1 millimole per cubic centimeter of Al per cc of dry resin in the base form. The resin preparation in the dried form is screened and 223.58 g of -30 mesh beads are further treated in the following manner: Enough water is added to make a slurry, which is stirred from above with a paddle blade stirred About 40 g of NH4Cl is stirred into the slurry; the temperature is raised to about 80-950C and 750 meq of HCl are slowly added, during which the pH is not permitted to go lower than pH 5. After all the acid is in, the pH remains at 5.2. Yield is 645 ml of resin. After the product is well washed with water and drained dry to 460.3 g, a saturated solution of AlCl3 (200 cc) is added to the resin with stirring, then 20 g of AlC13 additional is added. After the exotherm begins to decrease, the resin is filtered. The filtrate has a specific gravity of 1.28. The product resin is dried in a dry nitrogen stream to a weight of 476.8 g. The dried material is slurried in 380 cc of 30 percent NH4OH and the resulting exotherm allowed to decrease. After stirring for one-half hour, the solids are washed well by decanting the Al(0E)3 which forms outside of the resin. The washed resin is reslurried in water and heated. Again, NH4Cl and 720 meq of HC1 are added to again attain slight acidity not lower than pH 5. The washed resin volume is 640 cc after drying back to 507.3 g. Then 250 cc of saturated AlCl3 solution and 83 g of anhydrous AlC13 are stirred with the resin, then allowed to stand overnight. The resin is filtered to a weight of 563.3 g and the damp-dry resin slurried in 380 cc of 30 percent NH4OH. After washing, the volume of product is now 580 cc. About 500 cc of the resin are then added to excess 35 percent AlCl3 solution, slurried, then filtered and dried in a N2 stream to 446.8 g. The dry resin then is slurried in 300 ml of 30 percent NH4OH. After washing thoroughly to remove external Al(OH)3, the resin volume is 450 ml. Each ml contains about 3.33 millimole of Al. Fifty grams of LiCl and saturated NaCl brine (low Ca and Mg) are added to volume of 750 ml and warmed to 680C. The pH is 7.75. After cooling 20 hours, the slurry is heated to boiling and 250 meq NaOH added slowly to pH 8.5. The resin, a LiX.2A1(OH)3 composite, is filtered and put in a metal beaker at 950C in the oven for 24 hours. Then 40 g NH4C1 are added and heated with stirring as 722 meq of HC1 are added to give pH 5 at 900C. The Al content is now about 3.1 millimole per cubic centimeter of resin. Yield is 470 cc of resin composite. A 118 cc sample of the resin is tested in a temperature controlled, jacketed column. A lithium-containing brine from Arkansas is passed through at 20 cc per minute and 900C until the effluent is the same as the influent with respect to Li+. Water containing 60 ppm Li+ is passed through at 3.08 cc per minute and 90"C and the effluent collected. The first cut is 50 cc; all others are 10 cc. The analysis by flame photometer shows in milligrams of Li+ per liter: Cut 4 - 740 ) 5 - 5000 ) 6 - 7650 ) (taking #5, 6, 7, the average LiCl 7 - 6800 ) content is 3.97 percent, or about 20 8 - 3266 ) times the loading brine) 9 - 2450 ) Example 2 Following the method employed in Example 1, it is found that multiple precipitations of Al(OH)3 in the anion-exchange resin, prior to reaction with LiCl to form crystalline LiCl2Al(OH)3, is beneficial in giving increased strength of Li in the effluent from the Li recovery process than is a single precipitation, such as is shown in the patents mentioned on page 1. Data are shown below: Al loading Conc. Li+ in resin in Effluent Precipitations (mmole Mg Li /liter of A1(OH) AlXcc resin) (peak) single* ¯1.2 3000 multiple 2.0 4000 multiple 3.0 5200 multiple 4.0 6200 *For comparison purposes with prior patents.

Claims: m m S 1. A process for precipitating A1(OH)3 in the reticules of a weak-base anion-exchange resin by the in situ ammonia precipitation of Al halide in aqueous media, thereby forming a composite of anion-exchange resin having Al(OH)3 dispersed therein, characterized by: (1) acidifying the said composite in an aque ous medium with HX, where X is chlorine, bromine, iodine or fluorine, sufficient to provide a pH of not lower than about 5.0, thereby converting the anion-exchange resin to the halide salt form; (2) separating the composite from the aque ous portion; (3) flooding the composite with an aqueous solution of Al halide, draining the excess solu tion; and (4) adding NH4OH to precipitate additional Al(OH)3 in the resin. 2. A process as in Claim 1 wherein HX is hydrochloric acid and the aluminum halide is aluminum chloride. 3. The process of Claim 1 wherein ammonium halide is added before or during the acidification step. 4. The process of Claim 3 wherein the ammonium halide is ammonium chloride. 5. The process of Claim 4 wherein the amount of ammonium halide is in the range of 5 percent to 25 percent of the aqueous portion. 6. The process of Claim 1 wherein steps 1 through 4 are repeated one or more times. 7. The process of Claim 1 wherein the acidification in step 1 is performed in the temperature range of 200C to 1000C. 8. The process of Claim 1 wherein the acidification in step 1 is performed in the range of 450C to 1000C. 9. The process of Claim 1 and further characterized by reacting, in aqueous media at elevated temperature, the so-formed composite of resin and A1(8H)3 with LiOH and/or Lick, to convert the A1(OH)3 to crystalline LiOH-2Al(OH)3 and/or LiCl2Al(OH)3. 10. The process of Claim 9 wherein any crystalline LiOH.2A1(OH)3 is converted to crystalline LiCl.2A1(OH)3 by being contacted with acidic Lick. 11. A process for recovering Li+ from brine by the use of a composite comprising an ion-exchange resin having dispersed therein crystalline LiCl 2Al(OH)3, characterized by the use of the composite prepared in accordance with Claim 9 or 10.

Inventors: BAUMAN, WILLIAM CARREL, LEE, JOHN MALCOLM
Applicants: THE DOW CHEMICAL COMPANY
Application year: 1980
Main classification: B01J41
IPC codes: B01J41, B01J39, C01F7, C01D15