What is filtration in chemistry?

In chemistry, filtration is a process for separating solid particles from a liquid or gas using a filter medium. The medium allows the fluid to pass through but retains the solid particles. Either the filtered fluid or the solid particles can be the desired product. Filtration is used to remove interferences from a sample before analysis. These interferences are substances other than the material being tested that can affect the accuracy of measurements. There are various filtration techniques, including gravity, vacuum, and pressure filtration, using media such as paper, cloth, or sand .

Why is filtration used in scientific experiments?

Filtration is a crucial process in scientific experiments for separating substances. It involves using a filter medium to remove solid particles from a liquid or gas, allowing the fluid to pass through while retaining the solid particles. This technique is essential in removing interferences from an analyte before an assay, which are substances that can cause erroneous analytical results. Depending on the experiment, either the filtered fluid or the solid particles may be the desired product.

What materials are needed to perform filtration?

Filtration separates solids from fluids (liquids or gases) using a filter medium. Key materials for filtration include: * A filter medium , such as filter paper , cloth, screen, or a thick barrier like sand or porous ceramic. * A fluid with suspended solids . * A driving force , such as a pressure difference, to cause the fluid to flow. * A mechanical device (the filter) to hold the filter medium and contain the fluid. In cases where the filter cake compresses and blocks the filter, a filter aid like diatomaceous earth can be added. Special media like porous ceramics or stainless steel may be needed for corrosive materials.

How does a filter separate mixtures?

Filtration separates mixtures by using a porous material to retain solid particles while allowing fluids to pass through. The filter medium, such as filter paper or a sand bed , has openings smaller than the particles to be removed. Pressure differences, gravity, or vacuum force the fluid through the filter. The retained solids form a filter cake, while the clarified fluid is collected. Various filter types, including gravity, pressure, and vacuum filters, accommodate different applications and volumes.

What are some common examples of filtration in everyday life or the lab?

Filtration is a process that separates solids from fluids (liquids or gases) using a filter medium. Everyday examples: * Water purification Filtration is used to purify water for human consumption, removing turbidity and harmful microorganisms. * Brewing coffee The filter method involves hot water slowly filtering through coffee grounds, dripping into a receptacle. * Air filters Air filters in homes and HVAC systems use pressure to force air through a medium like glass fibers, trapping dust particles. * Kidneys In the human renal system , blood plasma is filtered in the glomerulus to form urine. Lab filtration examples: * Separating precipitates Filtration separates particles based on size, such as removing a precipitate after selective precipitation in chemical analysis. * HEPA filters HEPA filters trap particles in air-purifying systems using a pleated sheet of randomly arranged fiberglass fibers.

How do different types of filters (like paper, sand, or membranes) affect the filtration process?

Different filter types impact the filtration process based on their structure and the materials they're made of. Thin Barriers: These include filter cloths or paper, which have small openings to trap particles larger than the pore size. They work well if the accumulating solid layers form a porous cake that allows fluid to pass through. Thick Barriers: These filters, like sand beds , have pores larger than the particles being filtered. Particles travel through the filter and get trapped in the small spaces within the filter bed. This type is useful for filtering soft particles, preventing the filter from clogging. Membrane Filters: Semipermeable membranes block the passage of dissolved substances, allowing only water or other solvents to pass through. Reverse osmosis uses pressure to force the solvent to flow against the concentration gradient, effectively filtering out solutes.

filtration

References & Edit History Related Topics

Images & Videos

Dual-canister tap water filtration system with transparent blue covers, attached faucet, and a white wrench for maintenance, labeled pure purified water on the base.

Diagram of a water treatment plant showing the process from water inlet through mixing, coagulation, flocculation, settling, filtering, chemical treatment with chlorine, storage, and high-lift pumping to the distribution system.

Uncover the science behind the graphene membranes for desalination of water

Row of large blue cylindrical water purification filter tanks connected by black pipes inside a factory setting.

Diagram illustrating tertiary wastewater treatment, showing two tanks: one for filtering, where water passes through filter media to produce treated water, and one for backwashing, where air and water clean the filter using sand, gravel, and anthracite layers. Key components and flow directions are labeled.

Can reed beds clean contaminated groundwater?

filtration

chemistry

Written and fact-checked by

Britannica Editors

History

Top Questions

What is filtration in chemistry?
In chemistry, filtration is a process for separating solid particles from a liquid or gas using a filter medium. The medium allows the fluid to pass through but retains the solid particles. Either the filtered fluid or the solid particles can be the desired product.

Filtration is used to remove interferences from a sample before analysis. These interferences are substances other than the material being tested that can affect the accuracy of measurements.

There are various filtration techniques, including gravity, vacuum, and pressure filtration, using media such as paper, cloth, or sand.
4 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Why is filtration used in scientific experiments?
Filtration is a crucial process in scientific experiments for separating substances. It involves using a filter medium to remove solid particles from a liquid or gas, allowing the fluid to pass through while retaining the solid particles. This technique is essential in removing interferences from an analyte before an assay, which are substances that can cause erroneous analytical results. Depending on the experiment, either the filtered fluid or the solid particles may be the desired product.
5 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What materials are needed to perform filtration?
Filtration separates solids from fluids (liquids or gases) using a filter medium. Key materials for filtration include:
* A filter medium, such as filter paper, cloth, screen, or a thick barrier like sand or porous ceramic.
* A fluid with suspended solids.
* A driving force, such as a pressure difference, to cause the fluid to flow.
* A mechanical device (the filter) to hold the filter medium and contain the fluid.

In cases where the filter cake compresses and blocks the filter, a filter aid like diatomaceous earth can be added. Special media like porous ceramics or stainless steel may be needed for corrosive materials.
3 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How does a filter separate mixtures?
Filtration separates mixtures by using a porous material to retain solid particles while allowing fluids to pass through. The filter medium, such as filter paper or a sand bed, has openings smaller than the particles to be removed.

Pressure differences, gravity, or vacuum force the fluid through the filter. The retained solids form a filter cake, while the clarified fluid is collected. Various filter types, including gravity, pressure, and vacuum filters, accommodate different applications and volumes.
4 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What are some common examples of filtration in everyday life or the lab?
Filtration is a process that separates solids from fluids (liquids or gases) using a filter medium.

Everyday examples:
* Water purification Filtration is used to purify water for human consumption, removing turbidity and harmful microorganisms.
* Brewing coffee The filter method involves hot water slowly filtering through coffee grounds, dripping into a receptacle.
* Air filters Air filters in homes and HVAC systems use pressure to force air through a medium like glass fibers, trapping dust particles.
* Kidneys In the human renal system, blood plasma is filtered in the glomerulus to form urine.

Lab filtration examples:
* Separating precipitates Filtration separates particles based on size, such as removing a precipitate after selective precipitation in chemical analysis.
* HEPA filters HEPA filters trap particles in air-purifying systems using a pleated sheet of randomly arranged fiberglass fibers.
6 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How do different types of filters (like paper, sand, or membranes) affect the filtration process?
Different filter types impact the filtration process based on their structure and the materials they're made of.
- Thin Barriers: These include filter cloths or paper, which have small openings to trap particles larger than the pore size. They work well if the accumulating solid layers form a porous cake that allows fluid to pass through.
- Thick Barriers: These filters, like sand beds, have pores larger than the particles being filtered. Particles travel through the filter and get trapped in the small spaces within the filter bed. This type is useful for filtering soft particles, preventing the filter from clogging.
- Membrane Filters: Semipermeable membranes block the passage of dissolved substances, allowing only water or other solvents to pass through. Reverse osmosis uses pressure to force the solvent to flow against the concentration gradient, effectively filtering out solutes.
4 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

filtration, the process in which solid particles in a liquid or gaseous fluid are removed by the use of a filter medium that permits the fluid to pass through but retains the solid particles. Either the clarified fluid or the solid particles removed from the fluid may be the desired product. In some processes used in the production of chemicals, both the fluid filtrate and the solid filter cake are recovered. Other media, such as electricity, light, and sound, also can be filtered.

The art of filtration was known to early humans, who obtained clear water from a muddy river by scooping a hole in the sand on a river bank to a depth below the river water level. Clear water filtered by the sand would trickle into the hole. The same process on a larger scale and with refinements is commonly used to purify water for cities.

The basic requirements for filtration are: (1) a filter medium; (2) a fluid with suspended solids; (3) a driving force such as a pressure difference to cause fluid to flow; and (4) a mechanical device (the filter) that holds the filter medium, contains the fluid, and permits the application of force. The filter may have special provisions for removal of the filter cake or other solid particles, for washing the cake, and possibly for drying the cake. The various methods used for treating and removing the cake, for removing the clarified filtrate, and for creating the driving force on the fluid have been combined in various ways to produce a great variety of filter equipment.

Filter media

Filter media may be divided into two general classes: (1) thin barriers, exemplified by a filter cloth, filter screen, or common laboratory filter paper; (2) thick or en masse barriers, such as sand beds, coke beds, porous ceramics, porous metal, and the precoat of filter aid which is often used in the industrial filtration of fluids that contain gelatinous precipitates.

A thin filter medium offers a single barrier in which the openings are smaller than the particles to be removed from the fluid. A single thin filter medium usually is satisfactory if the layers of solid particles that accumulate on the medium produce a porous cake that is permeable to the fluid. If the filter cake is gelatinous or the particles are soft and compressible, rather than firm, the filter cake may “blind”; that is, the pores in the cake may close and stop filtration. If this happens, a filter aid or a thick filter medium such as the sand bed may be used.

Contrary to the situation with the thin medium, the pores in a thick filter medium such as a sand bed may be appreciably larger than the particles to be removed. The particles may travel for some distance along the tortuous path of the fluid through the medium but sooner or later will be entrapped in the finer interstices between the particles that constitute the filter bed. In this way the soft particles removed are distributed over a volume of filter medium that is sufficient to prevent blinding and stoppage of filtration. After solids accumulate the beds may be backwashed with clear fluid to clean the bed.

Filtering force

The fluid to be filtered will pass through the filter medium only if some driving force is applied. This force may be caused by gravity, centrifugation, application of pressure on the fluid above the filter, or application of vacuum below the filter or by a combination of such forces. Gravitational force alone may be used in large sand-bed filters and in simple laboratory filtrations. Centrifuges containing a bowl with a porous filter medium may be considered as filters in which gravitational force is replaced by centrifugal force many times greater than gravity. If a laboratory filtration is difficult a partial vacuum is usually applied to the container below the filter medium to increase the rate of filtration. Most industrial filtration processes involve the use of pressure or vacuum, depending upon the type of filter used, to increase the rate of filtration and also to decrease the size of the equipment required.

Explore Britannica Premium!

The trusted destination for professionals, college students, and lifelong learners.

filtration

Thank you for signing up!

Filter media

Filtering force