Lithium hydroxide is a white, monoclinic, fine crystal. It has a pungent odor and is strongly alkaline. When exposed to air, it absorbs carbon dioxide and moisture. It is a water-soluble chemical, slightly soluble in ethanol, insoluble in ether, and is a corrosive substance.
I. Uses of Lithium Hydroxide
Lithium hydroxide can be used as a developing agent in spectral analysis and as a lubricant. It is also an additive in alkaline battery electrolytes, which can increase battery capacity by 12%–15% and extend service life by 2–3 times.
It can be used as a carbon dioxide absorbent to purify the air inside submarines. The chemical equation is: 2LiOH(s) + CO2(g) = Li2CO3(s) + H2O(l).
Used in the manufacture of lithium salts and lithium-based greases, electrolytes for alkaline batteries, absorbents for lithium bromide refrigerators, lithium soap, lithium salts, developing solutions, etc., or as analytical reagents; used in the petroleum, chemical, light industry, and nuclear industries. When used in alkaline batteries, the aluminum content is no more than 0.06%, and the lead content is no more than 0.01%. Used as an analytical reagent, photographic developer, and also in the manufacture of lithium; primarily used as a raw material for the production of lithium compounds. Also used in the metallurgical, petroleum, glass, and ceramic industries.
II. Preparation methods of lithium hydroxide
1. Double decomposition method
Lithium hydroxide is typically prepared by mixing lithium carbonate and lime milk into a slurry, heating it with steam at 100°C, and then filtering off the calcium carbonate. This method is quite common. Li₂CO₃(s) + Ca(OH)₂ = 2LiOH(s) + CaCO₃↓
2. Oxidation-reduction method
Lithium is produced by reacting metallic lithium with water. This method uses relatively expensive raw materials and is therefore rarely used.
2Li + 2H₂O = 2LiOH + H₂↑
3. Lime sintering method
(1) Spodumene concentrate (generally containing 6% lithium oxide) is mixed with limestone, ground finely, and sintered at 1150-1250℃ to produce lithium aluminate and calcium silicate. After wet grinding, lithium hydroxide is leached with washing liquid. After sedimentation and filtration, the leachate is evaporated and concentrated to crystallize into lithium hydroxide monohydrate. Its chemical equation is:
Li2O·AI2O3·4SiO2+8CaO→Li2O·Al2O3+4[2CaO·SiO2]
Li2O·AI2O3+Ca(OH)2→2LiOH+CaO·AI2O3
(2) Dissolve industrial lithium hydroxide in cold water under stirring, filter out the insoluble matter, heat the filtrate to evaporate until crystals appear, cool and spin dry to obtain lithium hydroxide monohydrate reagent.
(3) Anhydrous lithium hydroxide can be obtained by drying lithium hydroxide monohydrate in a desiccator containing phosphorus pentoxide for several days. Alternatively, it can be obtained by slowly heating lithium hydroxide monohydrate to 140°C in a hydrogen stream to dehydrate it.
III. Storage Precautions for Lithium Hydroxide
1. Store in a dry, clean warehouse. Keep away from fire and heat sources. Prevent direct sunlight. Keep packaging sealed. Store separately from oxidizers, acids, carbon dioxide, and food chemicals; do not mix with other substances. The storage area should be equipped with suitable materials to contain leaks.
2. Transportation Precautions
When transporting dangerous goods by rail, the loading and unloading must strictly adhere to the dangerous goods loading table in the Ministry of Railways' "Rules for the Transport of Dangerous Goods." Packaging must be intact and loading secure at the time of shipment. During transport, ensure containers do not leak, collapse, fall, or become damaged. Mixing or transporting dangerous goods with oxidizers, acids, or food chemicals is strictly prohibited. Transport vehicles must be equipped with spill response equipment. Protect from exposure to sunlight, rain, and high temperatures during transport. When transporting by road, follow designated routes and avoid stopping in residential areas and densely populated areas.
3. Discard
Treat and neutralize at a wastewater treatment plant. If possible, reuse the container or bury it in a designated location. For small quantities, neutralize the aqueous solution of this product, filter out the solids for landfill disposal, and flush the solution into the sewer system. The reaction produces heat and fumes, which are controlled by adjusting the addition rate.
