Why does lithium bromide solution have strong water absorption

Sources：www.worldbrom.com | PublishDate：2026.10.26

The essence of lithium bromide water absorption is that lithium bromide is a strong electrolyte, and there is a strong hydration reaction between lithium bromide ions and water molecules. At the same time, combined with the saturated vapor pressure characteristics of the solution, this is also the basic principle of lithium bromide refrigeration cycle:
1. Ionic hydration
Lithium bromide (LiBr) completely dissociates into lithium ions and bromide ions after dissolving in water. Lithium ions have a little radius and high charge density, which strongly attract polar water molecules and firmly envelop them to form stable hydrated ions. A large number of water molecules are bound around the ions, making it difficult for them to turn into water vapor and escape.
2. Significantly reduce the saturated vapor pressure of the solution
Pure water has a fixed saturated vapor pressure at a certain temperature; After lithium bromide dissolves, a large number of water molecules are bound by ions, and the number of water molecules that can freely evaporate on the surface of the solution decreases. Therefore, at the same temperature, the saturated vapor pressure of lithium bromide solution is much lower than that of pure water.
When the refrigerant water evaporates in the low-pressure chamber to produce water vapor, the water vapor will spontaneously diffuse from the high-pressure (pure water vapor pressure) side to the low-pressure (lithium bromide solution vapor pressure) side and be absorbed by the lithium bromide solution. Simple understanding: Water vapor will be driven by "pressure difference" and absorbed by the solution.
3. The higher the concentration, the stronger the water absorption capacity
The higher the concentration of lithium bromide, the more ions there are in the solution, the lower the saturated vapor pressure, and the stronger the water absorption capacity. But the concentration cannot increase infinitely. If the concentration is too high, lithium bromide crystals may precipitate at low temperatures, which is commonly known as crystallization failure.
4. Comparison and supplementation
It is not a chemical reaction that absorbs water, it belongs to physical absorption. Water molecules can also be resolved by heating: by heating a dilute lithium bromide solution, water molecules will be separated into water vapor, and the solution will be re concentrated to achieve recycling. This is the working logic of the generator.

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