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Filtration – Definition, Types, Procedure, Examples, Applications, Practice Problems and FAQ

Filtration – Definition, Types, Procedure, Examples, Applications, Practice Problems and FAQ

Have you ever cherished a drizzling evening on your cosy balcony over a cup of filter coffee? If your answer is yes, you are probably a dual admirer of nature and coffee. 

Since the world may be divided between coffee and tea-lovers, you may take your own side with all pride. Eventually, if you are a tea connoisseur, you could imagine something similar – with all your love for nature and “cutting chai”

But for a while now, allow me to slightly put some light on how exactly a filter coffee is made. Filter coffee is a very common and traditional South Indian coffee.


Pouring hot water over coffee grinds is how filter coffee is brewed. The hot water and the gritty coffee powder mix are allowed to pass through a straining filter paper or muslin cloth which allows the decoction to seep through it into the mug or carafe. Hence only the aromatised, liquid decoction seeps through the strainer paper/muslin cloth as gravity forces it through the coffee grounds.

The decoction is intense and strong and is generally mixed with boiling milk or water to make the filter coffee that we drink. 

The sole purpose of describing the process was to give you an idea of what filtration in chemistry also looks like! It is a process of separating granulated or particulate solid matter from a fluid mixture – Even somewhat analogous to how tea is strained!!

So, let’s understand “Filtration” in detail.



  • Separation Techniques
  • Filtration – Definition
  • Filtration – Physical Processes Involved
  • Filtration – Procedure
  • Filtration – Types
  • Filtration – Examples
  • Filtration – Applications
  • Practice Problems
  • Frequently Asked Questions – FAQ

Separation Techniques

The term "separation technique" refers to methods used to remove components from mixtures, either in order to purify or further investigate a particular component. There are many methods used in chemistry to separate components. Several of the methods utilised include the following techniques.

1. Chromatography: It is a separation method that is based on the mass and charge of each component as the mixture passes through a media (which could be solid or liquid).
2. Distillation: This method is based on the fact that a mixture's constituent parts have distinct boiling points. The combination is heated to the same temperature as one of the component's boiling points, which causes the component to vaporise and then condense.
3. Evaporation: Evaporation is the fundamental step in the traditional method of removing salt from saltwater.
4. Filtration: Using a filtration medium, the separation of solid particles from a combination of liquid or gas.

Filtration – Definition

The art of filtration was renowned among early humans, who dug a hole in the sand on the bank of a muddy river to a depth below the water's surface. Sand-filtered, clear water would seep into the opening. The same procedure is frequently used to purify water for cities, although on a greater scale and with improvements.

Filtration is the act of removing suspended solids from a liquid by forcing the latter to move through the pores of a filter, which is usually a membrane with pores.

Filtration is a physical separation procedure that uses a filter medium with a complicated structure that only allows fluid to pass through it to separate solid particles and liquid from a combination. ‘Filtrate’ is the term for the fluid that passes through large solid particles that cannot pass through the filter media.


Filtration – Physical Processes Involved

  • The fluid in a suspension can be a liquid, a gas, or a supercritical fluid, and the particles are separated by filtration. Both or one of the components may be isolated, depending on the application.
  • Materials with various chemical compositions can be separated through filtration, which is a physical process.
  • For example, in a mixture, one component is dissolved using a solvent, whereas the others are left undissolved. One component will enter the solution and pass through the filter as the combination is dissolved in the selected solvent, while the other remains on top of the filter.
  • Chemical engineering frequently uses filtering. To process the feed stream, it may be integrated with other unit functions, as in the biofilter, a filter and biological digestion device all in one.
  • A multilayer lattice (for example a filter paper) is used in filtering to hold onto particles that can't travel through the filter's convoluted channels.
  • In order to prevent the fluid phase from passing through the filter, oversized particles may create a cake layer on top of the filter and may obstruct the filter lattice (blinding). Although these products could be referred to as sieves, the term "filter" is used commercially to refer to membranes where the separation lattice is so thin that the surface becomes the primary zone of particle separation.
  • Adsorption relies on surface charge for separation, unlike filtration. Although filtration is not their primary mechanical function, some adsorption devices with activated charcoal and ion-exchange resin are referred to in the marketplace as filters.
  • Filtration differs from the magnetic separation technique as the latter involves the removal of magnetic impurities from fluids with magnets (usually lubrication oil, coolants, and fuel oils). Magnetic filters are commercially available devices, however, their name refers to their usage rather than their mode of operation.

Filtration – Procedure

Homogeneous and heterogeneous mixtures are the two basic categories of mixtures. A mixture that is uniform all over is said to be homogenous. Uneven distribution of the compounds, or a mixture that is not consistent throughout, is referred to as a heterogeneous mixture. Oxygen, nitrogen, carbon dioxide, and water vapour are among the many gases that make up air.

When a solid has been dissolved in a liquid, homogeneous mixtures are sometimes referred to as solutions. Sand and water mixed together is an illustration of a heterogeneous mixture. Sand will not dissolve during shaking and will be distributed unevenly. It is a heterogeneous combination because there are sand particles floating around, which will eventually settle to the bottom of the bottle. To cleanse and separate mixtures from impurities, many types of filters are employed. Even at home, filters with various pore sizes can be employed depending on the size of the pollutant, whether it is big or little.

To carry out the filtration process effectively, four major parts are required:

  • A liquid mixture containing suspended solid.
  • A Filtering Media

A filtering media or filter plays a crucial role in the filtration process because it acts as a barrier, allowing only liquid to flow through. The medium might be thin, like filter paper or muslin cloth, or thick, like a sand bed or porous ceramic.

  • Any type of pressure that would permit the fluid to pass through the filtering media.

Centrifugal, pressure, or vacuum forces can all be used to propel liquid through the filter medium and cause separation. In the laboratory, the liquid is occasionally permitted to trickle as a result of gravity; however, this is time-consuming and not advised.

  • A mechanism to keep the entire contraption in place.
  • Beakers, Vessels, Funnels, and Stirring Rod are also needed. 

Filtration – Types

  • Gravity Filtration

The principle of gravitational force is the basis of this type of filtration. Gravity filtering is pouring the mixture from a higher to a lower position.

It is often done using basic filtration, which includes putting filter paper in a glass funnel and letting the liquid flow through it by gravity while the filter paper traps the insoluble solid particles. Depending on the quantity of the substance at hand, filter cones, fluted filters, or filtering pipettes can all be used.

  • Vacuum Filtration

To swiftly dry out tiny crystals, vacuum filtering technology is typically utilised for small quantities of solution. A Büchner funnel, filter paper with a smaller diameter than the funnel, a Büchner flask, and rubber tubing to connect to a vacuum source are needed for this technique.

These funnels are employed in organic chemistry to collect recrystallised molecules as they aid in drying out the final product.

  • Centrifugal Filtration

The material to be filtered is rapidly rotated during centrifugal filtration. The horizontal rotation separates the less dense substance from the more dense material. The solid particles exit the liquid and adhere to the tube walls as a result of the tube's fast rotations and centrifugal force.

  • Hot Filtration

The main purpose of the hot filtration process is to remove particles from a hot solution. In order to avoid the formation of crystals in the filter funnel and other equipment that comes into contact with the solution, this is done. 

In order to prevent a sharp drop in temperature, which would then cause the solids in the funnel to crystallise and obstruct the filtration process, the equipment and the solution employed are heated.

  • Cold Filtration

Instead of allowing the solution to cool down slowly at ambient temperature, the cold filtration process uses an ice bath to quickly chill the solution down. 

By using this method, very tiny crystals are formed as opposed to massive crystals when the solution is cooled to room temperature.

  • Mechanical Filtration

Mechanical filtering makes use of a mechanical force in the form of a pressure pump. Industries employ this filtration on a big scale.

  • Conventional Filtration

Conventional filtration is the method that has been used to cleanse water by passing it through layers of sand, rock, and granules from the beginning of time.

  • Chemical Filtration

Carbon or chemical resins that remove pollutants from the water provide chemical filtering. Up until the point of saturation, activated filter carbon eliminates contaminants from your water. Your filtration system's activated carbon filters, however, need to be changed frequently.

  • Biological Filtration

The process by which helpful bacteria break down ammonia and nitrite and transform them into the far less hazardous nitrate molecule is known as biological filtration. It is necessary for beneficial bacteria to survive in oxygen-rich water as well as on surfaces like rocks or sand where they can attach. With very few fish, this alone could be enough to keep the aquarium maintained. Biological filtration should be included in all aquariums.


Filtration – Examples

  • The most typical illustration is brewing tea. Tea leaves and water are separated during tea preparation using a filter or sieve.
  • Granular-activated carbon filters (GAC), depth filters, metallic alloy filters, microporous ceramic filters, and carbon block resin (CBR) filters with microfiltration and ultrafiltration membranes are some of the water filters available for home use. Some filters employ a multi-barrier system, which combines multiple filtration techniques.
  • Sand Filtration: The 'porous' quality of a sand layer, which traps water-borne particles, is used to purify the water in the sand filtering process. Wastewater management facilities employ this technology extensively all around the world.
  • Water Treatment Plants: Both water and sewage are treated via filtration. When treating water, filtration is a crucial step. Filtration in water-treatment plants completely remove solid particles from the water. This may come from pre-treated wastewater, surface water, or even groundwater.

The pure water is extracted through filters constructed of various materials and with various pore sizes during the filtration process (such as sand, gravel, and charcoal). These filters eliminate germs and dissolved contaminants such as dust, chemicals, parasites, bacteria, and viruses.

  • masks: The most penetrating particle size () for respirators made by various companies were found to have varying filtration efficiency, although all were at least 95% efficient at that size for particles.
  • High-efficiency particulate air-filter is referred to as . A mechanical air filter called a HEPA captures harmful particles like pollen, pet dander, dust mites, and tobacco smoke by forcing air through a small mesh.

In reality, HEPA filtering systems are frequently included with high-energetic ultraviolet light systems or anti-microbial layer panels to get rid of live bacteria and viruses stranded on filter media. With a performance rating of , some of the most effective HEPA systems guarantee high standards of safety against the spread of airborne diseases.

  • Automotive Filters: By preventing early wear and tear, automobile filters contribute significantly to the longevity of the life of cars. An automotive filter typically consists of fibrous mesh material to stop particles from entering the car and harming it. 

The four main filter types found in most cars are the oil filter, the cabin filter, the fuel filter, and the air filter.

  • In RO purifiers, water passes through a number of filters, including sediment, carbon, RO, UV, UF, and post-carbon filters. Each of these filters has unique qualities that work to get rid of particulate pollutants.

Filtration – Applications

Excellent industrial uses exist for filtration. Following are a few of them:

  • To treat the effluents gathered from diverse chemical businesses at sewage treatment plants before releasing them into water bodies.
  •  In the brewing sector, the clearing process is based on filtration principles.
  • Filtration is utilised in the automotive industry to clean up any used pipes or tubes. The tube would be more resilient and wouldn't corrode as a result.
  • HEPA filters, a type of mechanical air filter, are used to remove viruses, bacteria, and suspended dust particles from the air.

Practice Problems

Q 1. What are the features of a filter paper? Give a few examples of it.

Answer: The pores of a semipermeable filter paper or the sieve should only let pure fluid through. The filtrate should be obtained following filtration and resist the solid particulate matter to pass through. Paper, cloth, cotton wool, asbestos, slag or glass wool, unglazed pottery, sand, or any other porous material may be used as the filter.

Q 2. Which parameter does not affect the filtration process?

b. Density
c. Temperature
d. Pressure

Answer: A
There are various types of filtration such as mechanical, hot or cold filtration. The density of particles present as solid
suspended matter also determines the separation efficiency. But does not affect the process as the process is a physical process. 

So, option A is the correct answer. 

Q 3. Define filtrate.

Answer: By inserting a medium that only the fluid can flow through, filtration is a common mechanical or physical process used to separate particles from fluids (liquids or gases). The filtrate is the liquid that makes it through down to the collection vessel.

Q 4. Can a solution of two miscible liquids be separated by filtration using filter paper?

Answer: No, two miscible liquids will have almost similar particle sizes; hence, a filter paper cannot distinguish between the two. There is a high chance of both liquids passing through it. A mixture of two or more miscible liquids (also known as "components") is separated from one another using the distillation process. This physical separation process involves boiling and then condensation.

Frequently Asked Questions – FAQ

Q 1. What is Whatman filter paper?
Answer: The most popular filter paper for standard laboratory applications, qualitative analytical separations, and liquid clarification is Whatman Grade 1 Qualitative Filter Paper. They are medium-flow-rate cellulose filter papers of standard quality.

Q 2. What is the difference between filtration and decantation?
Answer: Decantation and filtration are both methods for removing contaminants from liquids. The process of separating an entire solution through a filter is called filtration. Filtering out the solid substance permits the liquid to pass through. Decantation is the procedure used to separate liquid from solid contaminants that have accumulated at the bottom of a container.

Q 3. What is an Oil-Filter?
Answer: An oil filter is a filter used to filter pollutants out of hydraulic fluid, lubricating oil, engine oil, or transmission oil. Their primary applications are in internal combustion engines for powered aircraft, locomotives for railroads, ships and boats, and stationary engines like generators and pumps.

Q 4. What is the use of in vacuum cleaners?
Answer: The way a HEPA filter functions is by pushing air through a tiny mesh that captures dangerous particles. Commercial vacuums equipped with HEPA filters catch 99.97% of airborne particles, including dust, pet dander, smoke, mould, and other allergens down to 0.3 microns, thereby enhancing air quality. This technology is used in the creation of vacuum cleaners. The HEPA filter in a vacuum cleaner must be constructed in such a way that it only disperses the air pulled into the device from the filter and not the contaminants for it to function well.

Related Topics

NMR Spectroscopy IR Spectroscopy
Column Chromatography Decantation
Thin Layer Chromatography Phosphorus Halide
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