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.

A method for precipitating aluminum hydroxide in the network structure of a weakly basic anion exchange resin.

The present invention relates to the preparation of aluminum hydroxide dispersed in a weakly basic anion exchange resin.

U.S. Patent Nos. 4,116,858, 4,116,856 and 4,159,311 disclose the formation of aluminum hydroxide in a very weak base anion exchange resin. The aluminum hydroxide is reacted with LiCl to form crystalline LiCl.2A1 (OH), or is reacted with LiOH to form crystalline LiOH.2A1 (OH). Aluminum hydroxide is prepared by precipitating with ammonia AlCl 2 dispersed in an anion exchange resin.

As used herein, the term weakly basic refers to anion exchange resins in which the salt forms of the amine functional groups have been converted to the OH form by NH.OH.

The above patents describe anion exchange resins which are in weakly basic or strong base form, they mention that neutral halogen salt forms of strong base resins can be used as starting material. Upon doping of aqueous alumina with a resin using a process performed by precipitation with AlCl 2 with ammonia, the halogen salt25 forms of the weakly basic anion exchange resins are converted to the OH form. Anion exchange resins may have amine functional groups that are predominantly weakly basic or strongly basic, or both. This invention relates to anion exchange resins having amine groups containing only weak base modifications as defined above.

It has been found that the amount of aluminum hydroxide that can be bound to the resin by precipitating the Al halide with ammonia is limited at all stages by the maximum solubility of the Al halide and the free volume of the resin. The ammonia treatment also converts the weakly basic resin to the OH form, which is on average only 80% of the volume of the halide form, leaving less room for the absorption of the Al halide solution.

Thus, it would be desirable to be able to incorporate larger amounts of aluminum halide into the resin.

The above drawback has been substantially eliminated by the present invention, which thus relates to a process Al (OH)₃to precipitate in the network structure of a weakly basic anion exchange resin by precipitating the Al halide with ammonia in situ in an aqueous medium to form an anion exchange resin mixture in which Al (OH)₃is dispersed.

The process is characterized in that (1) the mixture is acidified in an aqueous medium using sufficient HX, where X is chlorine, bromine, iodine or fluorine, to bring the pH to a value not lower than about 5.0, whereby the anion exchange resin changes in the form of a halide salt,₍ (2) the mixture is separated from the aqueous portion, (3) the mixture is rinsed with aqueous Al halide solution and the excess solution is removed, (4) NH 4 OH is added to the residue to precipitate additional Al (OH) 2 in the resin, and (5) if desired, Al (OH) is converted to crystalline LiOH.2A1 (OH) and / or LiCl.2A1 (OH).

In the present invention, the OH form of the resin is converted to the halide form without dissolving the AliOH) in the resin. In this case, more Al halide can be absorbed, from which more Al (OH) is obtained by means of ammonia treatment.₃: a. The most preferred acid halide is HCl and the most preferred Al halide is AlCl 2.

Al (OH>₃ acid halide treatment of OH-containing resin must be carried out carefully so that the acid addition is not so rapid that the pH drops unnoticed below

to a value of 5. It is recommended to add the acid slowly while stirring and monitoring the pH. Any suitable method can be used to lower the pH by adding an acid halide, as long as the method does not significantly cause dissolution of the Αΐ (0Η) ^: η already present in the resin.

The acid halide treatment step is aided and accelerated by the addition of ammonium halide, preferably NH₄C1. The amount of NH 2 Cl 2 to be added can vary within wide limits, with the concentration of NH 4 Cl 2 in the water preferably being about 5-25%. Other amine hydrochlorides may be used, although NH 4 Cl is most preferred. The ammonium halide acts as a buffer during the addition of the acid halide, against localized over-acidification, allowing for a faster addition of the acid halide. The ammonium halide initially added before the addition of the acid halide can be removed for the most part in the step of filtering the resin before the next addition of the AL halide. Then, when NH 2 OH is added to convert the Al halide to Al (OH), more ammonium halide is formed.

HCl is the most preferred acid to use if aluminum hydroxide is to be converted to LiCl.2A1 (OH). However, if it is to be converted to LiX.2A1 (OH), where X is a halogen other than chlorine, it is recommended to use the corresponding acid halide and the corresponding ammonium halide, thus eliminating the mixture of halogen compounds.

The temperature used in the HCl or NH 4 Cl / HCl treatment should be between n 20 ° C and about 100 ° C, preferably

between about 45 ° C and 100 ° C. If higher temperatures are to be used, e.g. to speed up the treatment, an overpressure is required to prevent substantial loss of components due to evaporation.

It turned out that the HCl or NH 4 Cl / HCl treatment swells the resin, making it possible to carry out further treatment steps, whereby the amount of aluminum in the resin is considerably increased. It is easy to achieve up to three times or more additional amount of aluminum in the resin. As this amount of aluminum increases in the resin (first as aluminum hydroxide and then as LiX.2A1 (OH)), the product is better able to bind Li ions from the solution + 3 mm.

Li ⁺ to the recovery method. The higher aluminate content in the resin results in a higher Lix concentration in the effluent of the ion exchange column when taking Li⁺ions recovered from brine.

It has also been found that the formation of crystalline LiX.2A1 (OH), which occurs by heating LiX (where X is Cl or OH) in the resin / Al (OH) ^ product, increases when heating at a high pH, ​​e.g. n. Between 11 and 11.5, which heating is carried out in a metal container (not glass) to avoid heating the strongly alkaline mixture in the glass. Heating strongly alkaline mixtures in a glass vessel can result in the formation of small amounts of aluminosilicate, which can interfere to some extent with strongly crystalline LiX.2A1 (OH)₃formation.

The following examples illustrate the invention.

For comparison, the same resin has been used in all of the following examples. This resin is a special, high-porosity anion exchange resin that is a crosslinked polymer of styrene-divinylbenzene with protruding quaternary amine groups.

The above resin is treated with an aqueous solution of concentrated aluminum chloride, after which the resin is dried until free-flowing, and then treated with ammonium hydroxide to precipitate aluminum hydroxide dispersed in the resin. Ammonium chloride, ammonium hydroxide and aluminum hydroxide are washed off to leave the resin in OH form, containing Al (OH)₃dispersed therein. In this case, the resin contains about 1.1 millimoles of aluminum per cubic centimeter of dry resin in base form.

The resin preparation in dry form is screened and 223.8 g of 30 mesh (sieve opening diameter 0.548 mm) whole beads are further processed as follows: Sufficient water is added to form a pulp which is mixed from above with a paddle mixer. About 40 g of NH 4 Cl are added to the mass with stirring, the temperature is raised to about 80-95 ° C and 750 meq (milliequivalents) of HCl are added slowly, so that the pH is not allowed to fall below 5.

After the reed acid is added, there is a pH value

5.2. The yield is 645 ml of resin. The product is washed well with water and sucked dry to 460.3 kg, then 3 saturated AlCl2 solutions (200 cm) are added to the resin with stirring and then a further 20 g of AlCl2 are added. When the heat evolution has begun to weaken, the resin is filtered off. The specific gravity of the filtrate is 1.28. The resulting resin is dried in a dry stream of nitrogen to a weight of 476.8 g. The dried product is slurried to 380 cm 3 of 30% NH 4 OH and the resulting exotherm is allowed to end. After stirring for half an hour, the solid is washed well by decanting off the AliOH formed outside the resin. The washed resin is reslurried in water and heated. Again NH 2 Cl and 720 meq are added

HCl so that the pH does not fall below 5. The volume of the washed resin is 640 cm after the resin has been dried back to 507.3 g. The resin is then mixed with 250 cm 3 of saturated AlCl 2 solution and 83 g of anhydrous AlCl 2, and the mixture is then allowed to stand overnight.

The resin is filtered to a weight of 563.3 kg and the wet resin 3 is slurried to 380 cm 3 of 30% NH.OH. After washing the product 3⁴ the volume is now 580 cm.

About 500 cm of resin is then added to a 35% AlCl 2 solution, slurried, filtered and dried under a stream of nitrogen to 446.8 g. The dry resin is then slurried in 300 ml of 30% NH 4 OH. After a well-washed wash to remove external Al (OH) 2, the volume of the resin is 450 ml. Each ml contains approx.

3.33 millimoles of aluminum.

g of LiCl and saturated aqueous NaCl solution (small amount of Ca and Mg) are added until the volume is 750 ml and the mixture is heated to 68 ° C. The pH is 7.75. The mixture is allowed to cool for 20 hours, after which the slurry is heated to boiling point and 250 meq (milliequivalents) of NaOH is slowly added to pH 8.5. The resin-LiX.2A1 (OH) combination is filtered and placed in a metal beaker in a 95 ° C oven for 24 hours. 40 g of NH 4 Cl are then added and the mixture is heated with stirring

722 meq HCl is added, which lowers the pH

90 ° C to 5. The amount of aluminum is now about 3.1 millimoles per cubic centimeter of 3 resin. The yield is 470 cm of resin mixture.

118 cm of resin sample is tested on a thermally controlled, jacketed column. The lithium-containing brine from Arkansas is passed through the column at a rate of 20 cm 2 / min and at a temperature of 90 ° C until the Li content of the effluent solution is the same as that of the inflow solution. Water containing 60 ppm Li⁺, is passed through at a speed of 3.08 cm³/ min at 90 ° C and the effluent is collected. The first 3-pointed verse is 50 cm and all the others 10 cm. Analysis of the flame photometer shows Li⁺ in milligrams per liter:

Verses 4 - 740)

- 5000)

- 7650)

- 6800) the average LiCl content of the fractions 5,6,7 is

- 3266) 3.97%, ie about 20 times the feed water)

- 2450)

Example 2

Following the procedure used in Example 2, it was found that repeated Al (OH) 2 precipitations on the anion exchange resin prior to the reaction with LiCl gave crystalline LiCl 2 Al (OH)

are preferred to give a higher Li

4 * concentration in the effluent in the Li recovery process compared to simple precipitation, as seen from the patents mentioned on page 1. The results are shown below:

<td>Ai (OH)₃precipitation of</td><td>Al-added with resins (mmol) Al / cin resin</td><td>Li crowd. outflow mg Li / liter (top)</td>

<td>... x one and only</td><td>about 1.2</td><td> 3000</td>

<td>several</td><td> 2,0</td><td> 4000</td>

<td>several</td><td> 4,0</td><td> 6200</td>

(x) for comparison with prior patents