How To Remove Water From A Solution?
How to remove water from a solution? How do you dry a sample? There are mainly two sample drying methods: physical methods and chemical methods.
The physical methods include natural drying, vacuum drying, distillation, and adsorption. In addition, ion exchange resins and molecular sieves are also commonly used for dehydration and drying. Ion exchange resin is a high molecular polymer that is insoluble in water, acid, alkali, and organic matter. Molecular sieves are a variety of aluminosilicate crystals. Because they have many voids or holes inside, they can adsorb water molecules. After heating, water molecules can be released again, so it can be used repeatedly.
Another sample drying method is a chemical method. It is to use a desiccant for dehydration. Desiccants can be divided into two categories according to their dehydration effect: the first category can reversibly form hydrates with water, such as calcium chloride, magnesium sulfate, sodium sulfate, etc.; the second category can generate new compounds, such as metals, after reacting with water, such as sodium, phosphorus pentoxide, etc. The first type of desiccant is widely used in the laboratory.
How to remove water from a solution? We will elaborate on two examples separately chosen from the physical and chemical sample drying methods to help you better understand.
Sample dying methods — physical drying
Using fractional distillation or azeotropic mixture to remove water
For liquid organics that do not form an azeotropic mixture with water, such as a mixture of methanol and water, due to the large difference in boiling point, fractionation distillation can be used to completely separate them. Sometimes it is possible to take advantage of the characteristic of forming an azeotropic mixture between certain organic matter and water, adding another organic matter to the organic matter to be dried, and using the property of forming the lowest azeotrope between this organic matter and water, gradually carry out the water during distillation, so as to achieve the purpose of drying.
Sample dying methods — chemical drying
Using desiccant to dehydrate
When drying a liquid, generally the desiccant is directly poured into it. Therefore, it is required that the desiccant cannot chemically react with the liquid to be dried, and cannot be dissolved in the liquid. For example, alkaline desiccants cannot be used for acidic substances.
When selecting a desiccant, the water absorption capacity and drying performance of the desiccant should also be considered. Water absorption capacity refers to the amount of water absorbed per unit mass of desiccant. The greater the water absorption capacity, the more water the desiccant absorbs. Drying performance refers to the dryness of the dried liquid when it reaches equilibrium. For inorganic salt desiccants that form hydrates, the vapor pressure of crystal water after water absorption is often expressed. Desiccant absorbing water to form hydrate is an equilibrium process. Different hydrates have different water vapor pressures in equilibrium. The higher the water vapor pressure, the worse the drying effect. When drying compounds with high water content but not easy to dry, a desiccant with a larger water absorption capacity is often used to remove most of the water, and then a desiccant with a strong drying efficiency is used to remove the remaining trace moisture. When selecting, you should also pay attention to factors such as the drying speed and price of the desiccant.
How do you dry a sample? The answer is clear now. If you want to use the physical sample dying methods, you may also consider our lyophilization machine and spray drying machine. Have a nice day!