The Key Facts You Need To Know on Vacuum Filtration

Vacuum filtration is a common laboratory technique used for separating solids from liquids by applying a vacuum to draw the liquid through a filter medium. Here are key facts you need to know about vacuum filtration:

  1. Purpose:
    • Vacuum filtration is employed to separate solids from liquids in a more efficient and faster way compared to gravity filtration. It is widely used in laboratories for sample preparation, purification, and analysis.
  2. Apparatus:
    • The basic setup consists of a filter flask, filter funnel, vacuum pump or water aspirator, and a filter medium (such as filter paper or membrane). The filter medium is placed in the funnel, and the vacuum is applied to pull the liquid through the filter.
  3. Filter Medium:
    • The choice of filter medium depends on the nature of the sample. Filter paper is commonly used for routine applications, while membrane filters are preferred for fine filtration and sterilization.
  4. Filter Flask:
    • The filter flask, also known as the Buchner flask, is a round-bottomed flask with a sidearm. It is connected to the vacuum source to create suction.
  5. Filter Funnel:
    • The filter funnel is placed inside the neck of the filter flask and holds the filter medium. It allows the liquid to pass through while retaining the solid particles.
  6. Vacuum Source:
    • A vacuum source, such as a vacuum pump or water aspirator, is necessary to create the pressure difference needed for filtration. The vacuum speed can be adjusted based on the application.
  7. Wet Filtration:
    • Before starting the filtration, it’s common practice to wet the filter medium with a small amount of the liquid being filtered. This helps create a seal and improves the efficiency of the filtration process.
  8. Applications:
    • Vacuum filtration is used in various laboratory applications, including sample preparation for analysis, removal of particulate matter, purification of solutions, and sterilization of liquids.
  9. Sterile Filtration:
    • For applications requiring sterile filtration, aseptic techniques are used. Membrane filters with small pore sizes are often used to achieve microbial filtration.
  10. Pump Selection:
    • The choice of vacuum pump depends on the specific requirements of the filtration. Diaphragm pumps are commonly used for solvent filtration, while water aspirators are suitable for aqueous solutions.
  11. Safety Considerations:
    • When working with vacuum filtration, it’s important to follow safety guidelines. Avoid overfilling the filter funnel, use appropriate personal protective equipment, and be cautious with glassware to prevent breakage.
  12. Cleaning and Maintenance:
    • Regular cleaning and maintenance of the filtration apparatus are essential to ensure proper functioning. Inspect the apparatus for wear, replace damaged parts, and clean components thoroughly.
  13. Speed and Efficiency:
    • Vacuum filtration is generally faster than gravity filtration, making it a preferred method when time is a critical factor. It allows for the processing of larger sample volumes.

By understanding these key facts, you can effectively use vacuum filtration in your laboratory applications while ensuring accurate and reliable results. Always follow good laboratory practices and manufacturer recommendations for the specific equipment you are using.

Vacuum filtration is the useful technique to separate a solid-liquid mixture if you want to retain the solid in crystallization for further usage. Compared with the gravity filtration, it is similar that a solid-liquid mixture is poured onto a filter paper, but it is also very different in the way that the process is led by the force of vacuum beneath the funnel.

In the mid 19th century, vacuum filtration has been introduced to practice in the labs. Jules Piccard, who is a Swiss chemist, invented an apparatus set which consists of a two-necked Woulfe bottle and a funnel, connected with a water aspirator or a Geissler pump. He introduced the set to the more sceintists in 1865, and in the following decades, this setup has been modified from time to time. The biggest modification is the funnel designed by Ernst Büchner, which we can still  find in the modern labs nowadays.

The vacuum filtration is advaned then the gravity filtrationin, as it is faster and more efficient when we want to remove residual liquid and lead to a purer solid. Compared with the gravity filtration, the disadvantages is easy to tell too. Sometimes, the force of vacuum might draw fine crystals through the filter paper pores, and the material could not be recovered from the filter paper. Due to this, we can see that the vacuum filtration works best with large crystals. If we use it on small scales, the loss of material will be gaint. You’d better try tp find other methods for microscale work.