Production of lithium hydroxide

1. A process for the production of lithium hydroxide, the process comprising the steps of:

(i) Causticising lithium chloride with sodium hydroxide to produce solids comprising a lithium hydroxide product;

(ii) Filtering the solids resulting from the causticisation of step (i);

(iii) Passing the filtered solids from step (ii) to a heating step in which anhydrous lithium hydroxide is produced;

(iv) Filtering the anhydrous lithium hydroxide product of step (iii); and

(v) Quenching the anhydrous lithium hydroxide of step (iv) with water to produce lithium hydroxide monohydrate crystals.

2. The process according to claim 1 , wherein the lithium chloride of step (i) is a purified lithium chloride.

3. The process according to claim 1 or 2 , wherein the lithium chloride of step (i) is obtained from either a brine or spodumene source.

4. The process according to claim 1 , wherein the causticising step (i) employs a stoichiometric ratio of lithium chloride and sodium hydroxide.

5. The process according to claim 1 , wherein the causticising step (i) is conducted in a series of three or more reaction vessels.

6. The process according to claim 5 , wherein the residence time in each reaction vessel is between about 15 and 60 minutes.

7. The process according to claim 5 , wherein the residence time in each reaction vessel is about 30 minutes.

8. The process according to claim 1 , wherein after the relevant residence time of step (i) the product is filtered, producing a filtrate comprising precipitated lithium hydroxide monohydrate, sodium chloride and some un-reacted lithium chloride.

9. The process according to claim 8 , wherein remaining solution from filtration, containing both lithium chloride and sodium hydroxide, is recycled to a first of a series of reaction vessels.

10. The process according to claim 1 , wherein the heating step (iii) is conducted at about 500° C. in a closed nitrogen atmosphere.

11. The process according to claim 1 , wherein the filtering step (iv) utilises ceramic filters.

12. The process according to claim 1 , wherein the lithium hydroxide monohydrate crystals produced in step (v) are dried at about 45° C. under vacuum.

13. The process according to claim 1 , wherein the lithium hydroxide monohydrate product is of a purity of greater than 99.9% by weight.

14. A process for the treatment of lithium chloride obtained from either spodumene or brine source to produce a lithium hydroxide monohydrate product, the process comprising the steps of:

(i) Passing purified lithium chloride product obtained through either a brine or spodumene source to react with sodium hydroxide solution thereby producing lithium hydroxide;

(ii) Wherein a stoichiometric ratio of solutions of LiCl and NaOH are allowed to react in series of reaction vessels for a residence time of fifteen minutes to an hour in each vessel, this reaction being exothermic;

(iii) Wherein after completion of residence time of the stoichiometric solutions of LiCl and NaOH in each reaction vessel, a mass which consists of precipitated lithium hydroxide monohydrate, sodium chloride and in part un-reacted LiCl is filtered;

(iv) All solids thus formed in all reaction vessels are collected, whereas spent mixture of solution of LiCl and NaOH is recycled to a first reaction vessel;

(v) The solids of step (iv) are heated at about 500° C. in closed nitrogen atmosphere, thereby melting lithium hydroxide which is in turn filtered; and

(vi) Lithium hydroxide anhydrous thus obtained is quenched with water to form lithium hydroxide monohydrate crystals which are dried at 45° C. under vacuum, and packaged.

15. The process according to claim 14 , wherein the lithium hydroxide monohydrate obtained is of a quality suitable for use as high purity battery grade cathode material.

16. The process according to claim 14 , wherein a solid product of the filters of step (v), which consists of NaCl, but also some LiCl, are sent to re-leaching where LiCl is separated.