FR2597004A1 - PURIFICATION OF BRINES - Google Patents

Abstract

PROCESS FOR THE SUBSTANTIAL REMOVAL OF CALCIUM OR OF OTHER DIVALENT IONS FROM NATURAL OR INDUSTRIAL BRINE CONTAINING HIGH LEVELS OF ANOTHER ION, CONSISTING OF A. ADJUSTING THE PH OF THE BRINE TO AN ALKALINE PH WITH AN ALKALINE MATERIAL; AND B. PUT THE BRINE IN CONTACT FOR AT LEAST 5 MINUTES WITH AN OXIDE HYDRATE CHOSEN FROM ZIRCONIUM, TITANIUM, TIN, MOLYBDENE, TUNGSTEN, THORIUM, NIOBIUM, TANTALUM OR CHROME OXIDES, AND OF THE HYDRATED OXIDES MIXED WITH THE ABOVE METALS, AT A TEMPERATURE BETWEEN THE ROOM TEMPERATURE AND THE VICINITY OF THE BOILING POINT OF THE TREATED BRINE.

Description

PURIFICATION OF BRINES

  The invention relates to the removal of calcium and other divalent ions from natural or industrial brines. The chlor-alkali and lithium industries use concentrated brines of sodium chloride, lithium chloride, lithium sulfate and other chemicals for the manufacture of chlorine, sodium hydroxide, hydroxide

  lithium, metallic lithium and other products.

  The presence of minor amounts of unwanted ions such as calcium, magnesium, strontium, barium etc. poses various treatment problems in

  commercial facilities. It is therefore desirable to remove unwanted ions from brines.

  The separation of unwanted ions, causing problems, process streams and desired products has so far been the subject of numerous studies, which have led to a large volume of published information, including patents. A commonly used separation technique is recrystallization. Multiple recrystallizations are often used to effect the separation of a purified product. This is the case, for example, in the lithium industry, where lithium hydroxide is subjected to multiple recrystallizations to reduce the concentration of calcium ions by approximately 125 parts per million (ppm) by weight of calcium ions at lower levels sometimes up to 20 to 25 ppm calcium. Weaker and even zero contamination is desirable, but not generally achieved by recrystallizations

of the product.

  The use of mineral ion exchangers to separate these cations or anions from aqueous solutions has been known for a long time. The use and study of ion exchangers based on hydrated oxides and insoluble salts in Separation techniques could have started with the discovery in 1943 that an insoluble compound, zirconium phosphate, can be used to separate uranium and plutonium from fission products. Although a large number of ion exchange compounds have been studied, particular attention has been paid to hydrated oxides and zirconium phosphate. A book reviewing this technology, Inorganic Ion Exchangers by C.B. AmphLett, discusses oxides in detail

  hydrates and zirconium phosphate.

  Kraus, in US-A-3 382 034, patented May 7, 1968, describes a hydrated oxide ion exchanger containing zirconium and other metals. It is noted in column 7, line 56 et seq., That "the oxides containing a particular constituent have been found to have a tendency to higher selectivities between the elements of a given charge type having a higher acidity. They tend to lose this selectivity in less acid solutions, in which the oxides can mainly exist

in the form of salts ".

  The use of microporous anion exchanging resin composites in which the reaction product of a polymeric amorphous hydrated zirconium hydroxide and a source of PO 4 ions is deposited in situ is described by Lee and Bauman in US-A-4,405,574. The anion exchange composite of Lee and Bauman is used to remove ions of alkaline earth metals such as magnesium and / or calcium from alkali metal brines such as sodium chloride. It is indicated but not demonstrated that these ion exchangers can be used on natural brines such as sea water or mineral brines such as brines of lithium chloride, calcium chloride or alkali metal salt which come from the processing of ores or mineral leach products, etc. It is claimed that the composite has a high affinity and a

  strong preference for magnesium and / or calcium ions.

  US-A-4,405,574, discussed above, describes composites of particulate microporous anion exchange resin containing zirconium phosphate and indicates in column 3, lines 12-15, that more than 99% of the calcium is removed from a 26% brine solution containing about 0.7 g of calcium per liter. This represents a reduction from about 681 ppm calcium to about 7 ppm calcium. Although this calcium level is low, it is not adequate to meet the increasingly stringent requirements in the production of metallic lithium, where there is an increasing demand for a product whose impurity level approaches 0. Similarly, in the electrolysis of sodium chloride brines, even small amounts of calcium lead to a slow accumulation of calcium hydroxide in the electrolysis cells, which must be cleaned to remove this calcium accumulation. It is therefore necessary to have a process which reduces the

  calcium present in brines near 0 ppm.

  In accordance with the present invention there is provided a method of removing calcium ions or other divalent ions from industrial or natural brines containing high levels of another ion by treating the brine, under alkaline conditions, with an exchanger. hydrated oxide ions chosen from those of zirconium, titanium, tin, molybdenum, tungsten, thorium, niobium, tantalum or chromium, and the hydrated oxides mixed with the above metals to a temperature between room temperature and around the boiling point of brine. The pH of the brine must

  be high enough to allow cation exchange to take place.

  It is specified that, according to the invention, the expression “hydrated oxide ion exchanger” means a metal compound in the formula duqueL there is at least one OH group.

  Zirconium carbonate, hydroxide

  Zirconium, Zirconium orthosulfate and Zirconyl octahydrate chloride are preferred ion exchangers for removing calcium from Lithium brines such as lithium chloride solutions. This does not exclude other zirconium compounds such as basic zirconium sulfate, zirconium acetate, zirconium oxynitrate, zirconium hydroxychloride, etc., from use as ion exchangers in the process of the present invention. These compounds exist commercially and are practically insoluble in concentrated brines, a characteristic which makes these compounds suitable for use in industrial operations.

  The hydrated oxide ion exchangers used in the present invention can be added to the brine in particulate form at temperatures between room temperature and around the boiling point of the brine, with stirring, for at least 5 minutes. However, hydrated oxide ion exchangers can also be used in a form carried by a support; in general, the support is a resin, a permeable membrane or a mineral substrate. The term "brine" here refers to water almost saturated with alkaline or alkaline earth salts. These salts include, among others, chlorides, bromides, sulfates, hydroxides, nitrates, bromides, etc. of alkali or alkaline earth metals and natural brines.

  The present process must be carried out under alkaline conditions. Although it is sufficient that the solution has a pH high enough to allow cation exchange to occur, it is preferred that the pH of the brine be in the range of 9 to 11. The process is useful at alkaline pHs less than 9, but removing calcium takes longer; pH above 11 can also be used, but process improvements do not justify the costs

higher pH.

  Surprisingly, in the process of the invention for removing calcium ions from lithium chloride brine, it is very desirable to operate in the high pH range of 9 to 11. This is unexpected given from US-A-4,405,574, which in the paragraph linking pages 2 and 3 states that an important working variable of the process is the pH of the brine. As measured by glass electrodes. the Lee and Bauman method claims a working pH in the range of about 5 to about 8.5, so these authors have no preference between

  slightly basic and slightly acidic conditions.

  In the preferred process of the present invention for removing calcium ions from lithium brines, lithium hydroxide is added to adjust the alkalinity of the brine to a pH between 9 and 11. The use of hydroxide High purity lithium for pH adjustment prevents the introduction of unwanted contaminants at this stage. The zirconium compound is added, and the resulting slurry is stirred at a temperature ranging from room temperature to 80 C, for a period of 15 minutes to several hours. The separation of the phases gives a brine practically free of calcium and a solid phase of the exchanger charged with calcium. The exchanger can then be regenerated for later reuse, as

  it is demonstrated in the examples.

  The determination of the calcium in the following illustrative examples was carried out by atomic absorption spectroscopy. The lowest amount detectable by this technique is in the range of 1 to 2 ppm for calcium. The present invention will be more completely

  understood on reading the description below and the examples which accompany it, in which are

  described particular embodiments of the invention. It should be noted, however, that technicians can modify the invention described in this specification while obtaining the favorable results of

this invention.

Example 1

  A sample of 0.60 g of zirconium hydroxide is introduced in the form of a fine powder with a size of about 150 millimicrons (sieve n 100) in 200 ml of a solution of lithium chloride brine at 26% containing 24 ppm calcium ions. The pH of the solution is adjusted to 10 by adding a small amount of lithium hydroxide, then it is stirred for 2 hours at 70 ° C. and filtered. Content

  The calcium ion in the filtrate is 2 ppm.

Example 2

  Example 1 is repeated, except that the solution is stored at room temperature (approximately 21 to

  22 C). The calcium ion content of the filtrate is 2 ppm.

Example 3

  Example 1 is repeated using basic zirconium carbohydrate in place of zirconium hydroxide. Basic zirconium carbonate has a particle size of about 150 millimicrons. The

  calcium ion content of the filtrate is 2 ppm.

Example 4

  100 ml of an alkaline solution (pH 11) of 36% lithium chloride containing 120 ppm of calcium ion are stirred with 15 ml of a 20% solution of zirconyl octahydrate chloride for 5 and a half hours at room temperature ( 22 C). The calcium ion content of the filtrate is 2 ppm and the final pH is 9.

Example 5

  Lithium hydroxide monohydrate is added to a 26% lithium chloride brine containing 19 ppm calcium to adjust the pH to 10. Then zirconium hydroxide is added, and the solution is stirred for 100 minutes at 22 C. The content of

calcium from the filtrate is 1.7 ppm.

Example 6

  Example 5 is repeated except that the solution is stirred at 450C for 100 minutes. Content

calcium from the filtrate is 1.4 ppm.

Example 7

  Example 5 is repeated, except that the

  solution at 65 C for 100 minutes. The calcium content of the filtrate is 1.5 ppm.

Example 8

  A slurry of a 0.90 g sample of zirconium hydroxide exchanged with calcium with distilled water is formed. Concentrated hydrochloric acid is added to the solution until a pH of 1.5 to 1.7 is obtained. The filtrate obtained contains all the calcium previously adsorbed on the ion exchanger. Reusing this solid gives 97% calcium fixation from 26% lithium chloride brine. Several successive reuse and regeneration showed no decrease in

calcium fixation.

Example 9

  A sample of 0.60 g of basic zirconium carbonate exchanged with calcium is treated as in Example 8. No reduction in the fixation of calcium is observed after several reuse

and regenerations.

Example 10

  200 ml of an 11.3% by weight lithium chloride solution containing 1880 ppm of Ca and 520 ppm of Mg are basified (at pH 10) by adding lithium hydroxide monohydrate and then treated with 6 g of zirconium hydroxide. The mixture is stirred at 70 ° C. for 90 minutes. The final calcium content is 13 ppm (99.3% calcium fixation), and the final magnesium content is 0.2 ppm (Mg fixation

%). The final pH is 10.2.

Example 11

  200 ml of a 9% lithium hydroxide solution containing 61 ppm of calcium ion are treated with 0.4 g of zirconium hydroxide (particle size approximately 150 millimicrons). The mixture is stirred in an agitator having the action of the wrist at 70 ° C. for 20 minutes. Calcium ions are fixed

85%.

Example 12

  100 ml of a 5% lithium hydroxide solution containing 30 ppm of calcium are treated with 0.2 g of zirconium hydroxide. The mixture is stirred in a stirrer at 700C for 100 minutes. We get a

  fixation of 97% calcium (1 ppm Ca).

Example 13

  200 ml of a 9.6% by weight lithium hydroxide solution containing 39 ppm of Ca are treated with 0.82 g of zirconium hydroxide. The solution is stirred at room temperature for 100 minutes. Content

  in calcium of the filtrate is 3.8 ppm; the zirconium content is 2.7 ppm. Calcium fixation is 90%.

  ExemptDle 14 200 ml of a 4.8% by weight solution of lithium hydroxide containing 38 ppm of Ca are treated with 0.81 g of zirconium hydroxide. The mixture is stirred at room temperature for 120 minutes. Calcium fixation is 95%; the calcium content of the filtrate is 1.9 ppm. The zirconium content of

filtrate is 2 ppm.

Example 15

  Stirred at 70 ° C. for 100 minutes 100 ml of a 10% solution of lithium sulphate containing 363 ppm of calcium ion and 1 678 ppm of magnesium ions with 0.53 g of lithium hydroxide monohydrate and 0, 53 g of zirconium hydroxide. 75% calcium ions are bound and the ions are bound

  67% magnesium. The final pH is 9.5.

Example 16

  Stirred at 70 ° C. for 100 minutes 100 ml of a 10% lithium sulphate solution containing 20,432 ppm of calcium ions with 1 g of orthosulphate

  zirconium and 0.6 g of lithium hydroxide monohydrate.

  A calcium ion fixation of 82 Z is obtained.

final pH is 11.

Claims (12)

  1. Process for the substantial elimination of calcium and / or other divalent ions from brines containing high levels of another ion, characterized in that (a) the pH of the brine is adjusted if necessary to an alkaline pH with an alkaline material; and (b) the brine is brought into contact for at least 5 minutes with a hydrated oxide ion exchanger chosen from those of zirconium, titanium, tin, molybdenum, tungsten,   thorium, niobium, tantalum and chromium, and the mixed hydrous oxides of the above metals.   2. Method for the removal of calcium ions from a lithium brine according to claim 1, characterized in that the pH of the lithium brine is adjusted to a value of 9 11 and in that the Contacting the brine with a zirconium compound chosen from basic zirconium carbonate, zirconium hydroxide, zirconium orthosulfate and zirconyl octahydrate.   3. Method according to claim 1 or 2, characterized in that the pH is adjusted to 9 to 11 in using lithium hydroxide.   4. Method according to claim 1, characterized in that a zirconium salt chosen from zirconium acetate, basic zirconium sulfate, zirconium oxynitrate, zirconium hydroxychloride is used as the ion exchanger. .   5. Method according to claim 1 or 2, characterized in that the temperature is between room temperature and 80'C.   6. Method according to claim 1, characterized in that other divalent ions are removed from the brines.   7. Method according to claim 1, characterized in that the ion exchanger is practically insoluble in concentrated brines.   8. Method according to claim 1, characterized in that the contact time varies from minutes to several hours.   9. Method according to claim 1, 5 characterized in that the ion exchanger is any one of those defined in claims 1,   2 or 4, supported by a resin, a permeable membrane or a mineral substrate.   10. Method according to claim 1, 10 characterized in that the ion exchanger is one   any of those defined in claims 1, 2,   4 or 9, in which the ion exchanger is regenerated   with an acid and reintroduced into the process.   11. The method of claim 1, characterized in that the calcium is removed from the brines containing other alkali or alkaline earth metal salts. 12. Method according to claim 11, characterized in that the calcium is eliminated from industrial or natural brines containing sulfates, hydroxides, nitrates, bromides or chlorides   of alkali or alkaline earth metals.