Peter Ehrena a
S Lithium Ark Holding B.V., Savelsbosch 4, Maastricht, 6228 SB, Netherlands
Although lithium is widely distributed on Earth, there are few commercial sources where lithium is found in concentrated values suitable for producing lithium compounds, such as lithium carbonate and lithium hydroxide. One source of lithium is in minerals, such as spodumene and clays. Another source is from naturally occurring brines, such as those found in salars, salt lakes, salt mines and geothermal resources. Besides the minerals, a new source is the black mass obtained from wasted lithium-ion battery recycling streams. Once the lithium is extracted and concentrated, conventional methods react to a resulting lithium solution with one or more reagents to produce lithium hydroxide or lithium carbonate. However, these reagents, which may include lime, soda ash, hydrochloric acid, and sodium hydroxide, among others, can be expensive to get, and may contain noxious impurities. In addition, existing lithium hydroxide and lithium carbonate production processes can be inefficient, requiring improvement in waste reduction and material re-use. More cost-effective, efficient and greener methods and systems for producing lithium hydroxide and lithium carbonate are needed.
A new patented method for the production of lithium hydroxide is described. The method includes reacting a concentrated potassium hydroxide solution with a concentrated lithium chloride solution to form a reciprocal salt system comprising potassium hydroxide, lithium chloride, potassium chloride, lithium hydroxide, and water. The lithium hydroxide is produced selectively from the system by reactive and evaporative crystallization and the potassium chloride is obtained by selectively cooling.
The potassium chloride salts are dissolved and electrolyzed to get a potassium hydroxide solution, a depleted potassium chloride solution, chlorine gas, and hydrogen gas. They produce hydrochloric acid by burning the chlorine and hydrogen gas to form hydrochloric gas, which is then absorbed in water.
The new method avoids the usage of soda ash and lime and does not generate the waste stream of sodium sulfate, sodium chloride, and calcium carbonate. The energy requirements are significantly less and can be applied for most of the lithium sources.