Method of separating NaCl from a LiCl solution

Details Method of separating NaCl from a LiCl solution Method of separating NaCl from a LiCl solution

1999-06-14

2000-05-16

Griffin, Steven P.

Chemistry of inorganic compounds

Treating mixture to obtain metal containing compound

Alkali metal

423184, 4234993, 4234994, 423194, 423198, C01D 1500

Patent

active

06063345&

DESCRIPTION:

BRIEF SUMMARY
This invention relates to a process of separating NaCl from a NaCl-contaminated aqueous LiCl solution by concentrating the solution to an LiCl content>25 wt-%, cooling the concentrated solution and separating the crystallized NaCl.
Lithium chloride is an industrial raw material, from which lithium compounds and in particular metallic lithium are produced. It is necessary that the raw material lithium chloride is provided in the purest form possible, as only in this way an economic and technically efficient further processing of the lithium chloride is possible. For instance, the lithium chloride from which metallic lithium is obtained must have a rather low sodium content, as the sodium content of the metallic lithium must lie below 1%.
Aqueous solutions containing lithium chloride are either obtained as industrial raw material or in the processing of brines containing lithium. Apart from lithium, these solutions contain various impurities whose separation is performed on an industrial scale by using various known processes. The impurities include in particular sodium chloride, whose separation requires a considerable economic effort.
The known prior art includes several processes for the recovery of lithium compounds and pure lithium chloride. For instance, the DE-AS 1 228 594 describes a process of separating lithium from naturally occurring brines, which contain lithium and alkaline earths, by precipitating a lithium aluminium complex in which the brine is mixed with an aluminium compound, and the precipitation of the lithium aluminium complex is performed at a pH value of 6.0 to 8.1 and at a temperature of 20 to 100.degree. C. The final recovery of the lithium from the lithium aluminium complex may then be effected according to various known processes, for instance by hydrothermal decomposition of the lithium aluminium complex and concentration of the diluted solutions by means of ion exchange resins or by direct treatment with ion exchange resins.
The DE-AS 1 093 783 describes a process of processing lithium ores by roasting, in order to obtain lithium salts and other alkali salts of high purity. During roasting, which is effected in the presence of calcium carbonate, sand and calcium chloride at about 1100 to 1200.degree. C., the chlorides of lithium, sodium and potassium are evaporated and adsorbed in water. The processing of the alkali chloride solution is effected such that the chloride solution is mixed with the mixture of sodium chloride and lithium carbonate, which is precipitated in a subsequent process stage, that from this slurry solid sodium chloride is separated at a temperature of about 25 to 30.degree. C., that by adding sodium carbonate and heating to 60 to 100.degree. C. lithium carbonate is precipitated from the mother liquor, that the remaining residual solution is evaporated to 40 to 65% solids, where at 90 to 100.degree. C. the mixture of sodium chloride and lithium carbonate is precipitated, with which there is mixed the alkali chloride solution obtained during roasting, and that from the residual solution potassium chloride is precipitated by cooling to about 0 to 5.degree. C. After this process, lithium together with sodium carbonate is precipitated as lithium carbonate from the lithium chloride solution contaminated with sodium chloride, and is discharged from the process as an end product of high purity.
The U.S. Pat. No. 4,271,131 discloses a process of producing lithium chloride of high purity from a brine which in addition to a small amount of lithium also contains sodium, potassium, magnesium, sulfate and borate. In this process, the brine is evaporated in a first pond system by means of solar energy, where a concentrated brine with a lithium chloride content of 3% is obtained, and where the chlorides of sodium and potassium are in part precipitated. During the first process stage, calcium oxide and calcium chloride are added to the brine, in order to at least partly precipitate magnesium hydroxide, calcium sulfate and calcium carbonate. Upon separation of the solids, t

REFERENCES:
patent: 2726138 (1955-12-01), Cunningham
patent: 3789059 (1974-01-01), Cuevas
patent: 4271121 (1981-06-01), Brown et al.
patent: 4723962 (1988-02-01), Mehta

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