NO163854B - PROCEDURE FOR THE EXCLUSION OF LI + IONS FROM A MACROPOROUS RESIN / ALUMINATE COMPOSITION CONTAINING POLLUTED SALT SOLUTION. - Google Patents

Description

The present invention relates to a method for leaching Li<+> ions from a macroporous resin/aluminate composite containing contaminated salt solution.

US Patents 4,116,856, 4,116,858 and 4,159,311 describe the preparation of, and use for, ion exchange resins incorporating crystalline Lix*2Al(OH)3, where X is halide, especially chloride.

When resin/aluminate composites are used for absorption

of Li<+->ions from salt solutions by Li<+> being taken up in the aluminate crystals, some of the salt solution from which the Li<+->ions have been absorbed will remain in the interstices of the composite. When the salt solution contains other metal ions (ie, ions other than alkali metal ions) such as alkaline earth metal ions, and an aqueous leach is used to elute desired Li<+-> ions from the crystals, the eluate also contains these other metal ions that were in the interstices, but not were present in the crystal structure.

It has now been found that the use of a washing step with concentrated pure Na halide solution prior to the water washing step used for leaching Li<+> results in the metal ions (such as alkaline earth metal ions) being washed out without any significant amount of Li<+ > in the aluminate crystals are leached. When then water is used for leaching Li<+> in the aluminate crystals, the ions from the Na halide solution are the only other metal ions present in any significant amount in the eluate.

The method according to the invention with preferred embodiments is stated in the claims, and reference is made to these.

According to the invention, a concentrated, mainly contamination-free alkali metal halide solution is used in the pre-washing step before the water leaching of Li<+> ions from a composite comprising an anion exchange resin in which a crystalline lithium halide aluminate is incorporated. The alkali metal halide that is washed out from the spaces in the composite during the water leaching is thus mainly present in the initial portions of the eluate and in decreasing amounts in the subsequent portions of lithium halide solution. A lithium halide solution is thus obtained which contains only alkali metal halide as impurity in any significant amount.

The "resin/aluminate composites" used in the present invention are preferably prepared by incorporating crystalline Lix*2A1(OH)3 (where X is halide) in ion exchange resins as shown in the patents mentioned above, and can also be of the type described in patent 4,381,349, filed on 19 November 1979.

As used herein, "halide" in the term "Na halide" or "LiX" refers to Cl, Br or I, of which Cl is preferred. For simplicity, "halide" in this formulation will be shown as (the preferred) chloride, with the understanding that bromine or iodine are also suitable.

The mainly pure Na halide solution, which is referred to below as NaCl solution for brevity, can also be understood to mean a different "alkali metal halide solution" than lithium halide solution, although a small amount of Li<+> in the NaCl solution is beneficial. It is this essentially pure, but concentrated, NaCl solution that is used as a prewash solution for the lithium-filled resin/aluminate composite prior to the water leaching step; the water leaching step is performed to remove much of the Li<+->ions from the composite (but not all of the Li<+->ions), thereby essentially "depleting" the composite, i.e. of lithium. This concentrated NaCl solution is preferably at or near the saturation point, but any concentration above 20% should provide reasonably efficient operation. At further reduced concentrations, operation becomes less and less efficient. From a practical point of view, for achieving an economical and efficient operation, the concentration is preferably from 24 to 26%.

The Li<+->containing aqueous solution or salt solution from which Li<+->ions are removed to a desirable extent is one that is contaminated with metal ions other than Li<+-> or alkali metal ions. These other metal ions are usually alkaline earth metal ions such as Mg<++>, Ca<++> etc., but can also be virtually any other non-alkali metal cation.

The Li<+->filled resin/aluminate composites, which have in their interstices any contaminating metal cations other than alkali metal cations, will generally be obtained by a process in which a substantially "depleted" composite is used to absorb or accommodate Li< +->ions from an impure salt solution, whereby it will be "filled" with Li<+->ions. Nevertheless, obviously any such Li<+-> filled resin/aluminate which has the "other" metal cations in its interstices can be used in the present process. The purpose and meaning of this method is to remove the contaminating metal cations from the interstices without removing any significant amount of the Li<+> ions; this is carried out by pre-washing with a mainly pure, concentrated NaCl solution, whereby the Li<+->ions remain in place, while the spaces are filled with a relatively pure NaCl solution which is essentially free of the mentioned contaminating metal cations.

When water leaching is then used to remove Li<+>

from the composite, the initial portions of eluent wash out much of the sodium chloride and some of the Li<+> ions; subsequent portions comprise mainly pure Li solutions in which NaCl is effectively the only contaminant. It is preferred that not all Li<+> is removed from the crystalline LiX'2Al(OH)3

because removal of all Li<+> can cause the crystalline aluminate structure to collapse or destroy. It is therefore best if the water used for water leaching contains a small amount of Li<+> (eg at least 80 ppm), as this prevents complete removal of Li<+> from the aluminate structure.

It is assumed that the greater the concentration of NaCl in the solution, the greater the tendency of the crystalline aluminate structure to absorb and retain the Li<+> ions. During water leaching, the concentration of NaCl in the spaces of the composite is reduced, and as the reduction takes place, Li<+> becomes more and more leachable from the crystal.

One of the techniques by which Li<+-> ions are removed from aqueous solution is by precipitation as lithium carbonate (I^CC^). If other metal cations, such as alkaline earth metal cations, are present, they may also precipitate as carbonates along with the lithium. Sodium carbonate does not precipitate with the lithium carbonate, and therefore NaCl in the Li<+-> solution does not exhibit the same contamination problems as the other metal cations. Also, if NaCl is the only contaminant in the Li<+> solution, NaCl can be crystallized by evaporating most of the water, leaving behind a pure, concentrated LiCl solution; this would not be possible with the alkaline earth metals.

The water used for water leaching of Li<+> from the aluminate structure of the composite should be substantially free of other metal cations (such as alkaline earth metal cations), except that a small amount of Li<+> should be present, for the purposes stated above. Also, a small amount of other alkali metal cations, such as Na<+>, may be allowed. Deionized (softened) water can be used as well as distilled water or other reasonably pure water, as long as there is no significant amount of alkaline earth metal or other non-alkali metal cations present.

The following examples are given to illustrate certain embodiments, although the invention is not limited to the particular embodiments illustrated.

In the following example, the water leaching step is performed

using deionized water containing approx. 68 ppm Li<+->ions. The raw (impure) Li<+->containing feed brine from which Li<+->ions are to be extracted is a mineral brine from the Smackover deposit near Magnolia, Arkansas, which was predominantly saturated with NaCl and contained nominally approx. . 280 ppm Li<+->ions, approx. 6.2% Na<+>, approx. 17.05% Cl~, approx. 0.41% K<+>, approx. 0.31% Mg<++>, approx. 3.3% Ca<++>, approx. 0.23% Sr<++>, approx. 0.022% B<+++>, approx. 20-30 ppm Mn<++>, approx. 20-30 ppm Mo<++> and approx. 9-10 ppm Cu<++>; its pH was approx. 5.8. The mainly pure NaCl solution used for pre-washing before the water leaching was saturated contained approx. 200 ppm Li<+->ions and had a pH of approx. 6.3. The resin/aluminate composite was a weak base anion exchange resin, commercially available from The Dow Chemical Company under the trade name DOWEX MWA-1, into which was incorporated crystalline LiCl•2A1(OH)3. The container used was a glass ion-exchange column with a volume of 120 ml, which was equipped with a jacket for temperature regulation with circulating liquid.

Example 1

The ion exchange column was filled with the resin/aluminate composite that had been leached with water to essentially "deplete"

the composite with respect to its Li<+->content. At a temperature of approx. 77°C and a flow rate of 10 ml/min. the raw feed brine was passed through the composite bed until the total hardness (Mg<++>, Ca<++> etc), as determined by the standard "verse" method, was the same as that entering, like what went out of, the column. A relatively clean,

saturated NaCl solution was then used to displace the raw feed salt solution remaining in the interstices of the composite; The pre-wash liquid was passed through at a rate of 3.3 ml per minute until the amount of hardness in the eluate was less than 0.002 M. After this, the water leaching step was carried out, using a water flow rate of 3.3 ml per minute. minute.

The eluate from the column was withdrawn in fractions for analysis

of density, molar hardness and ppm Li<+>. Table I shows the elution pattern for a fill/saline wash/leach cycle. It will be readily understood by those skilled in the art that the "depleted" composite can be used in numerous such cycles.

The top factions (19-24). contained very little hardness, if any at all.

Example 2 - Comparative example

This example shows the effect of omitting the NaCl prewash according to the present invention. The procedure of Example 1 above is substantially followed, except that the exchange column bed had a volume of 170 ml, the resin composite contained a larger amount of the crystalline LiCl<*>2A1(OH)3 material as prepared essentially according to to the method described in US patent no.

4,381,349, the temperature in the column was 90°C, the flow rate was 2.5% of the layer volume per minute, and the water washing liquid contained approx. 60 ppm Li<+.> After enough Smackover salt solution

had passed through the resin/aluminate composite until the composite had been "filled" with Li<+> ions, the water leaching step was carried out without pre-washing with NaCl solution. As will be seen from the data in Table II below, the "peak" fractions in the case of Li<+> contained a significant amount of hardness values.

Example 3

This example is carried out essentially as Example 1. The Smackover brine was pumped downstream through a

120 ml layer of lithium chloroaluminate in DOWEX MWA-1 resin until the eluate contained the same concentration of Li<+> as the feed solution; this was investigated by standard atomic absorption methods. A prewash liquid of pure, saturated NaCl solution was allowed to pass through the bed at a flow rate of 2.75% of the bed volume per minute and the eluate collected in fractions. After approx. 0.83 bed volumes of the prewash liquid, the bed was washed through with deionized water containing 280 ppm Li, with 1.66 times the bed volume, and the eluate collected in fractions. Then the flow of Smackover brine was restarted at a flow rate of 8.2% bed volumes per minute. minute to go again

to fill the resin composite with lithium. Table III shows the elution data.

Of the above-mentioned fractions, 18-21 were selected as the product fraction, as this had approx. 3912 ppm Li<+> and low hardness.

The remaining fractions were used as follows, most of them being used in a concentrating cycle, the data for which are shown in Table IV below.

Fractions 1-6 were recycled back to the feed tank. Fractions 7, 8 and 9 were mixed and allowed to flow through a resin/aluminate bed to "fill" Li<+> in the resin. Fractions 10-13 were mixed and passed through the resin bed. Fractions 14-15 were mixed and passed through the resin bed. Then 33 ml of fresh buffering salt solution was passed through to

replace parts of fractions 7-15 that had been lost or removed during sampling. Fractions 16 and 17 were collected, saturated with NaCl and passed through the bed. Fractions 18-21 were kept as product samples. Fractions 22-23 were mixed and then passed through the bed. A leveling amount (34 ml) of deionized water with 280 ppm Li<+> was passed through the bed. The data are shown in Table IV.

Example 4

In order to show further concentration of Li<+-> ions when carrying out a large number of absorptions and desorptions of the Li<+-> ions, selected fractions are taken for this test from the fractions shown in Table IV above.

This preferred method of operation thus includes the use] of portions of the eluate in subsequent runs. This can be done by storing the eluate in a spiral tube or a series of tanks to approximate the gradients. Thus, the only "new" feed material needed for each elution cycle would be an equalization amount of fresh deionized water

(containing a small amount of Li<+>), equivalent in volume to the product fraction, and enough NaCl to re-saturate part of the gradient to be called "reflux". In successive runs, using Li-containing fractions from previous runs, the concentration of the product is increased above what is possible in a single cycle.

With reference to the fractions according to Table IV above, the first 6 fractions, which have a relatively high hardness and low Li content, are recycled back to the Smackover brine feed. Fractions 7, 8 and 9 are mixed and used as the first solution to be pumped into a column to elute an equivalent volume of Smackover salt solution. Fractions 10, 11 and 12 are mixed and pumped through after the 7,8,9 mixture. This is then followed by a solution made by mixing 13, 14, 15 and 16; then 17, 18 and 19 are saturated again with NaCl and pumped into the column. Fractions 20-23 were taken as product. Fractions 24-30 were mixed and followed the "reflux" mixture of 17, 18 and 19. Then a volume of deionized water with 280 ppm Li<+> (equivalent to the volume of the product fractions) follows the 24-30 fraction mixture. The eluate from all of these was collected in fractions as before for use in a subsequent concentration cycle. This procedure was followed until the product, after the fifth cycle, had increased from 3912 ppm Li<+> (first cycle) to 5531 ppm Li<+> (fifth cycle), with little or no increase in total hardness. '

Claims (9)

1. Process for leaching Li<+->ions from a macroporous resin/aluminate composite containing contaminated salt solution, wherein the resin/aluminate composite comprises an anion exchange resin in which crystalline Lix*2A1(OH)3 is dispersed, wherein X is Cl, Br or I, and which is almost filled with respect to Li<+-> ions, by water leaching of the Li<+-> ions from the resin, characterized in that the composite is pre-washed with a substantially pure, contaminant-free, concentrated alkali metal halide solution, where halide means chloride, bromide or iodide, to wash out the contaminated salt solution from the composite without removing Li<+-> ions to a significant extent, and that the substantially pure alkali metal halide solution and a significant amount of lithium ions are leached from the composite with water, whereby the composite is mainly depleted with respect to Li<+->ions, but still contains such an amount of lithium ions that breakdown of the composite's crystal structure is prevented. 2. Method according to claim 1, characterized in that X is chloride. 3. Method according to claim 1 or 2, characterized in that a saturated sodium chloride solution is used as the alkali metal halide solution. 4. Method according to claim 3, characterized in that a sodium chloride solution is used with a concentration in the range of 20-26%. 5. Method according to any one of the preceding claims, characterized in that the water used for water leaching contains at least 80 ppm Li<+.> 6. Method according to one of the preceding claims, characterized in that a concentrated alkali metal halide solution containing a small amount of lithium halide is used during the pre-washing. 7. Method according to claim 6, characterized in that the Li halide is obtained from the pre-washing step and/or the water leaching step from at least one previous ify11ings/depletion cycle. 8. Method according to claim 6, characterized in that the alkali metal halide solution, containing a minor amount of Li halide, is prepared by adding NaCl to at least part of the eluate from the water leaching step from a previous fill/drain cycle. 9. Method according to any one of claims 1-6, characterized in that the mainly depleted anion exchange resin is again supplied with Li<+> ions by bringing it into contact with a Li<+>-containing, contaminated salt solution.