How Does Desalination Evaporation Work?

Desalination involves removing salt from water.

Desalination is the process of removing salt from water to create fresh, drinkable water. Considering that most of the Earth's surface is covered with saltwater, the ability to efficiently desalinate water could be a cost-effective and environmentally safe way to deal with drinking water shortages in the future. Desalination can be accomplished in many ways, including freezing and osmosis, but the most basic way to desalinate water is through evaporation.

Solubility

A solvent is a substance capable of dissolving another substance. The substance dissolved into a solvent is called a solute. The resulting mixture is called a solution.
Salt, a solute in this case, is quite soluble in water, the solvent. According to Solubility of Things, a chemistry website, this means that salt dissolves easily in water to create a solution. We call this solution saltwater. We can not separate the elements of a solution from one another without using special processes.

Water Vapor

Evaporation is the process that describes the transformation of a chemical compound from a liquid to a gas form. The gas form of water is called "water vapor." When a solution is heated, the water in the solution will evaporate into water vapor at a certain temperature, which varies depending on altitude and a few other pressure factors. Elements within the solution that are not water, notably minerals like salt in this case, will not change form at the same temperature as water and thus will be left in solid form.

Separation

Because heating a saltwater solution will turn the water into a vapor, while leaving the salt behind, the next step is to move the water vapor to a separate chamber. This process of separation, and eventual purification, is called "distillation." Advanced distilling machines will have a small vacuum that brings the water vapor into a separate chamber and then seals it from the other chamber.

Condensation

When matter changes from a gas form into a liquid form, the process is called condensation. The distiller will cool the chamber holding the water vapor, which will cause the gas to condense back into liquid water. But, this time, the water is free of any additional particles, such as salt. This completes the desalination process.

Pressure

One of the most important factors in desalination through evaporation is the pressure at which the water is evaporated, according to Energy Recovery Incorporated, a company specializing in saltwater desalination. Higher pressure causes water to evaporate at a lower temperature, so desalination companies need to expend less energy to create heat if the process takes place in a high-pressure chamber. Saving energy means saving money and has positive environmental effects.

References

• Solubility of Things: What Is Solubility?
• Energy Recovery Incorporated: Desalination Chamber

Resources

• Read this Article in Spanish
• Polymerchemie Altmeier: Sea Water Desalination