Production of High Purity Lithium Carbonate from Brines

Abstract

The invention relates to a process for the preparation of high-purity lithium carbonate from brines.

Claims

1. Process for the preparation of lithium carbonate, comprising the steps of: step a.) precipitating calcium and magnesium ions from a brine containing at least lithium ions, calcium and magnesium ions by adding a precipitant, generating a supernatant, and then step b.) contacting the supernatant from step a.) with at least one chelating resin containing functional groups of structural element (I) ##STR00003## in which is a polystyrene copolymer skeleton and R.sub.1 and R.sub.2 independently of one another are —CH.sub.2COOX, —CH.sub.2PO(OX.sup.1).sub.2, —CH.sub.2PO(OH)OX.sup.2, —(CS)NH.sub.2, —CH.sub.2-pyridyl or hydrogen, where R.sub.1 and R.sub.2 cannot both simultaneously be hydrogen, and X, X.sup.1 and X.sup.2 independently of one another are hydrogen, sodium or potassium, generating a mobile phase, and step c.) contacting the mobile phase from step b.) with at least one chelating resin containing functional groups of structural element (I) ##STR00004## in which and R.sub.1 and R.sub.2 have the meanings given in step b.), and step d.) eluting lithium adsorbed on the chelating resin containing functional groups of structural element (I) in step c.) by adding inorganic acids, generating a lithium-containing eluate and step e.) admixing the lithium-containing eluate from step d.) with at least one carbonate or with carbon dioxide or the acid thereof.

2. The process according to claim 1, wherein the lithium carbonate is prepared with a purity of at least 99% by weight.

3. The process according to claim 1, wherein the lithium-containing brine contains lithium at a concentration by weight of 0.1 ppm to 5000 ppm.

4. The process according to claim 1, wherein the lithium-containing brine contains lithium at a concentration by weight of 0.1 ppm to 1000 ppm.

5. The process according to claim 1, wherein the lithium-containing brine contains lithium at a concentration by weight of 0.1 ppm to 5000 ppm and sodium at a concentration by weight of 0.1 ppm to 100 g/l and calcium at a concentration by weight of 0.1 ppm to 100 g/l and magnesium at a concentration by weight of 0.1 ppm to 100 g/l.

6. The process according to claim 1, wherein the precipitant used in process step a.) is sodium carbonate, sodium hydroxide or mixtures of these compounds.

7. The process according to claim 1, wherein the molar ratio of precipitant to calcium and magnesium ions in process step a.) is 3:1 to 1:1.

8. The process according to claim 7, wherein in process step a.) a basic precipitant is used or a base is added to the precipitant and as a result the supernatant from process step a.), which is used in process step b.), has a pH of 10 to 12.

9. The process according to claim 1, wherein R.sub.1 and R.sub.2 in the chelating resin containing functional groups of structural element (I) used in process step b.) and/or the chelating resin containing functional groups of structural element (I) used in process step c.) independently of one another=—CH.sub.2PO(OX.sup.1).sub.2, —CH.sub.2PO(OH)OX.sup.2, CH.sub.2COOX or hydrogen, where R.sub.1 and R.sub.2 cannot both simultaneously be hydrogen and X, X.sup.1 and X.sup.2 independently of one another are hydrogen, sodium or potassium.

10. The process according to claim 9, wherein R.sub.1 and R.sub.2 in the chelating resin containing functional groups of structural element (I) used in process step b.) and/or the chelating resin containing functional groups of structural element (I) used in process step c.) independently of one another=—CH.sub.2PO(OX.sup.1).sub.2, —CH.sub.2PO(OH)OX.sup.2 or hydrogen, where R.sub.1 and R.sub.2 cannot both simultaneously be hydrogen and X, X.sup.1 and X.sup.2 independently of one another are hydrogen, sodium or potassium.

11. The process according to claim 9, wherein the bead polymer of the chelating resin containing functional groups of structural element (I) is monodisperse and macroporous, and the bead polymer has a diameter of 250 μm to 450 μm.

12. The process according to claim 7, wherein the concentrations by weight of calcium and magnesium in the mobile phase from process step b.) is 5 ppb to 50 ppb.

13. The process according to claim 8, wherein the mobile phase from process step b), which is used in process step c.), has a pH of 10 to 12.

14. The process according to claim 1, wherein in process step d.) hydrochloric acid is used as inorganic acid for the elution.

15. The process according to claim 1, wherein the eluate from process step d.) contains lithium at a concentration by weight of 1 g/l to 10 g/l and calcium and magnesium ions 2 ppb to 20 ppb and contains sodium at a concentration by weight of 1 ppm to 50 g/l.

16. The process according to claim 1, wherein the lithium-containing eluate from step d.) is adjusted to a pH>7.

17. The process according to claim 1, wherein the lithium-containing eluate from step d.) is recycled back into step c.).

Description

EXAMPLE 1

A) Removal of Calcium Ions, Magnesium Ions and Strontium Ions by Precipitation

[0165] To 1 l of brine (37 g/l of Ca.sup.2+, 3.7 g/l of Mg.sup.2+, 2.3 g/l of Sr.sup.2+, 65 g/l of Na.sup.+ and 140 ppm of Li.sup.+ (0.014 g/l) was added 0.32 l of a solution of Na.sub.2CO.sub.3 (400 g/l, 129.3 g) and 0.05 l of NaOH (1000 g/l, 48.8 g) at 60° C. over a period of 30 min. The brine and the precipitant were mixed here at a stirring rate of 350 rpm. The dispersion formed was filtered off over a filter funnel at a pressure of 2 bar. The purified brine contained Ca.sup.2+, Sr.sup.2+ and Mg.sup.2+ at a concentration of below 20 ppm and also 140 ppm of Li.sup.+ and had a pH of 11.

B) Removal of Ca.sup.2+, Sr.sup.2+ and Mg.sup.2+ by Means of an Aminomethylphosphonic Acid Group-Containing Chelating Resin

[0166] A measuring cylinder was filled with 50 ml of a macroporous, monodisperse chelating resin containing functional groups of structural element (I) where R.sub.1 and R.sub.2 independently of one another=—CH.sub.2PO(OX.sup.1).sub.2, —CH.sub.2PO(OH)OX.sup.2 or hydrogen, where both cannot simultaneously be hydrogen and X.sup.1 and X.sup.2=hydrogen. The bead polymer of the chelating resin had a diameter of 430 μm. The average degree of substitution of the chelating resin used here and containing functional groups of structural element (I) is 2.0. The resin has a total capacity of 3.2 mold. The resin was then transferred into a 100 ml chromatography column having a diameter of 3 cm, with attention being paid to ensure that there were no air bubbles between the polymer beads. 267 l of the purified brine from A) was pumped onto the chromatography column at a pumping rate of 1000 ml/h. The resin was loaded in the process with 42 g of Ca.sup.2+, Sr.sup.2+ Mg.sup.2+ per litre of resin. Breakthrough was reached after 52 h and the obtained brine contained Ca.sup.2+, Sr.sup.2+ and Mg.sup.2+ at a concentration of below 20 ppb and the concentration of Li.sup.+ was additionally 140 ppm. After the brine was removed from the column by flushing with 4 BV (bed volumes) (1 BV=50 ml of resin) of demineralized water, the resin was regenerated with 2 BV of 7.5% HCl, 4 BV/h. Thereafter, the resin was washed again with 4 BV (1 BV=50 ml of resin) of demineralized water and converted into the sodium form with 2 BV of 4% NaOH, 4 BV/h.

C) Lithium Adsorption and Concentration on the Aminomethylphosphonic Acid Group-Containing Chelating Resin

[0167] A measuring cylinder was filled with 50 ml of a macroporous, monodisperse chelating resin containing functional groups of structural element (I) where R.sub.1 and R.sub.2 independently of one another=—CH.sub.2PO(OX.sup.1).sub.2, —CH.sub.2PO(OH)OX.sup.2 or hydrogen, where both cannot simultaneously be hydrogen and X.sup.1 and X.sup.2=hydrogen. The bead polymer of the chelating resin had a diameter of 430 μm. The average degree of substitution of the chelating resin used here and containing functional groups of structural element (I) is 2.0. The resin has a total capacity of 3.2 mold. The resin was then transferred into a 100 ml chromatography column having a diameter of 3 cm, with attention being paid to ensure that there were no air bubbles between the polymer beads.

[0168] 9.2 l of the brine purified from B) was pumped onto the resin at a constant flow rate of 250 ml/h. The resin was loaded with 1.83 g of lithium per litre of resin and thus has a usable capacity of 1.83 g/l. 8% of the total capacity was therefore occupied by lithium. Breakthrough was reached after 4 h. After the brine was removed from the column by compressed air, the resin was regenerated with 1 BV of 7.5% HCl, 4 BV/h. The eluate was adjusted to a pH of 10.5 with sodium hydroxide and applied to the column again. This process was repeated 5 times, with 50%-96% of the total capacity being occupied by lithium. A solution having 7 g/l of lithium was obtained here, from which lithium chloride was obtained.

D) Obtaining of Lithium Carbonate by Precipitation

[0169] The pH of the solution (1 l) that was obtained from the resin from C) by the regeneration and contained 7 g/l of lithium was adjusted to pH=10 by addition of NaOH. After this, 0.3 l 18 g of a 400 g/l solution of Na.sub.2CO.sub.3 was added at 90° C. and the Li.sub.2CO.sub.3 precipitated as a white solid. The mixture was filtered at 2 bar and 32.5 g of Li.sub.2CO.sub.3 was obtained with a purity of 99.5%. This corresponds to a yield of 88%.

EXAMPLE 2

A) Removal of Calcium Ions, Magnesium Ions and Strontium Ions by Precipitation

[0170] To 1 l of brine (37 g/l of Ca.sup.2+, 3.7 g/l of Mg.sup.2+, 2.3 g/l of Sr.sup.2+, 65 g/l of Na.sup.+ and 140 ppm of Li.sup.+ (0.014 g/l) was added 0.32 ml of a solution of Na.sub.2CO.sub.3 (400 g/l, 129.3 g) and 0.05 l of NaOH (1000 g/l, 48.8 g) at 60° C. over a period of 30 min. The brine and the precipitant were mixed here at a stirring rate of 350 rpm. The dispersion formed was filtered off over a filter funnel at a pressure of 2 bar. The purified brine contained Ca.sup.2+, Sr.sup.2+ and Mg.sup.2+ at a concentration of below 20 ppm and also 140 ppm of Li.sup.+ and had a pH of 11.

B) Removal of Ca.sup.2+, Sr.sup.2+ and Mg.sup.2+ by Means of an Iminodiacetic Acid Group-Containing Chelating Resin

[0171] A measuring cylinder was filled with 50 ml of a macroporous, monodisperse chelating resin containing functional groups of structural element (I) where R.sub.1 and R.sub.2 independently of one another=—CH.sub.2COOX or H, but R.sub.1 and R.sub.2 cannot simultaneously be hydrogen and X is hydrogen. The bead polymer of the chelating resin has a diameter of 430 μm. The average degree of substitution of the chelating resin used here and containing functional groups of structural element (I) is 1.6. The resin has a total capacity of 2.8 mold. The resin was then transferred into a 100 ml chromatography column having a diameter of 3 cm, with attention being paid to ensure that there were no air bubbles between the polymer beads. 267 l of the purified brine from A) was pumped onto the chromatography column at a pumping rate of 1000 ml/h. The resin was loaded in the process with 42 g of Ca.sup.2+, Sr.sup.2+ Mg.sup.2+ per litre of resin. Breakthrough was reached after 52 h and the obtained brine contained Ca.sup.2+, Sr.sup.2+ and Mg.sup.2+ at a concentration of below 20 ppb and the concentration of Li.sup.+ was additionally 140 ppm. After the brine was removed from the column by flushing with 4 BV (bed volumes) (1 BV=50 ml of resin) of demineralized water, the resin was regenerated with 2 BV of 7.5% HCl, 4 BV/h. Thereafter, the resin was washed again with 4 BV (1 BV=50 ml of resin) of demineralized water and converted into the sodium form with 2 BV of 4% NaOH, 4 BV/h.

C) Lithium Adsorption and Concentration on the Iminodiacetic Acid Group-Containing Chelating Resin

[0172] A measuring cylinder was filled with 50 ml of a macroporous, monodisperse chelating resin containing functional groups of structural element (I) where R.sub.1 and R.sub.2 independently of one another=—CH.sub.2COOX or H, but R.sub.1 and R.sub.2 cannot simultaneously be hydrogen and X is hydrogen. The bead polymer of the chelating resin had a diameter of 430 μm. The average degree of substitution of the chelating resin used here and containing functional groups of structural element (I) is 1.6. The resin has a total capacity of 2.8 mold. The resin was then transferred into a 100 ml chromatography column having a diameter of 3 cm, with attention being paid to ensure that there were no air bubbles between the polymer beads.

[0173] 9.2 l of the brine purified from B) was pumped onto the resin at a constant flow rate of 250 ml/h. The resin was loaded with 1.75 g of lithium per litre of resin and thus has a usable capacity of 1.75 g/l. 9% of the total capacity was therefore occupied by lithium. Breakthrough was reached after 4 h. After the brine was removed from the column by compressed air, the resin was regenerated with 1 BV of 7.5% HCl, 4 BV/h. The eluate was adjusted to a pH of 10.5 with sodium hydroxide and applied to the column again. This process was repeated 5 times, with 50%-96% of the total capacity being occupied by lithium. A solution having 7 g/l of lithium was obtained here, from which lithium chloride was obtained.

D) Obtaining of Lithium Carbonate by Precipitation

[0174] The pH of the solution (1 l) that was obtained from the resin from C) by the regeneration and contained 7 g/l of lithium was adjusted to pH=10 by addition of NaOH. After this, 0.3 l 18 g of a 400 g/l solution of Na.sub.2CO.sub.3 was added at 90° C. and the Li.sub.2CO.sub.3 precipitated as a white solid. The mixture was filtered at 2 bar and 32.5 g of Li.sub.2CO.sub.3 was obtained with a purity of 99.5%. This corresponds to a yield of 88%.