What is Filtration?

By: Paweesuda Natewong

  • Filtration is a mechanical or physical operation by which insoluble solid particles are separated from a liquid-solid mixture by forcing the liquid through the pores of a filter. The liquid which has passed through the filter is called the filtrate, while the insoluble solid left on the filter paper is called the residue. It is one of the most common processes used at all scaled of operation to separate suspended particles from a liquid or gas through a porous filter. When looking for filters, many options are available to suit different applications. It is important to ensure you choose the best type for your work, but what do the different terms mean?
  • Paper or Cellulose Filters – these are manufactured from cellulose fibres and are used for general filtration. The particle retention level can go down to 2.5 µm. This type of filter paper is used for basic gravity filtration using a glass or plastic filtration funnel.
  • Glass Microfibre Filters – these are manufactured from glass microfibres allowing the particle retention to go down to the submicron range.
  • Membrane Filters – these retain particles on the membrane surface. Retention can go down as low as 0.02 µm, which is commonly used in microbiological and air pollution applications.