Carbon filtering
Encyclopedia
Carbon filtering is a method of filtering that uses a piece of activated carbon
to remove contaminants and impurities, utilizing chemical adsorption
.
Each piece of carbon is designed to provide a large section of surface area, in order to allow contaminants the most possible exposure to the filter media. One pound (454g) of activated carbon contains a surface area of approximately 100 acres.
This carbon is generally activated with a positive charge and is designed to attract negatively charged water contaminants. Carbon filtering is commonly used for water purification
, but is also used in air purifier
s.
Carbon filters are most effective at removing chlorine
, sediment
, and volatile organic compounds (VOCs) from water. They are not effective at removing minerals, salts, and dissolved inorganic compounds.
Typical particle sizes that can be removed by carbon filters range from 0.5 to 50 micrometre
s. The particle size will be used as part of the filter description. The efficacy of a carbon filter is also based upon the flow rate regulation. When the water is allowed to flow through the filter at a slower rate, the contaminants are exposed to the filter media for a longer amount of time.
or KDF-55
, to prevent bacteria
growth within the filter.
cultures for both air and water sanitization. 2000 B.C. Sanskrit text refers to filtering water through charcoal (1905 translation of "Sushruta Samhita" by Francis Evelyn Place). The first modern use of a carbon filter to purify potable water occurred in 1862. Carbon filtration was further advanced in the mid-1970s by H. Allen Rice and Alvin E. Rice when they first manufactured a porous carbon block for drinking water use.
Currently, carbon filters are used in individual homes as point-of-use water filters and, occasionally, in municipal water treatment facilities. They are also used as pre-treatment devices for reverse osmosis
systems and as specialized filters designed to remove chlorine-resistant cysts, such as giardia
and cryptosporidium
.
water purifiers are installed to prevent formation of minerals on the surface of the electrodes and to remove organics and chlorine from utility water. First the water passes through a 20 micrometer interference (mesh
or screen filter
) filter to remove sand and dust particles, second, a charcoal filter (activated carbon
) to remove organics and chlorine
, third stage, a de-ionizing filter to remove metallic ions. A test can be done before and after the filter for proper functioning on barium
, calcium
, potassium
, magnesium
, sodium
and silicon
.
filters, are widely used in the construction of hot cell
s. This allows the room to exhaust air that contains infinitesimal quantities of radioactivity and contaminants.
Activated carbon
Activated carbon, also called activated charcoal, activated coal or carbo activatus, is a form of carbon that has been processed to make it extremely porous and thus to have a very large surface area available for adsorption or chemical reactions.The word activated in the name is sometimes replaced...
to remove contaminants and impurities, utilizing chemical adsorption
Adsorption
Adsorption is the adhesion of atoms, ions, biomolecules or molecules of gas, liquid, or dissolved solids to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. It differs from absorption, in which a fluid permeates or is dissolved by a liquid or solid...
.
Each piece of carbon is designed to provide a large section of surface area, in order to allow contaminants the most possible exposure to the filter media. One pound (454g) of activated carbon contains a surface area of approximately 100 acres.
This carbon is generally activated with a positive charge and is designed to attract negatively charged water contaminants. Carbon filtering is commonly used for water purification
Water purification
Water purification is the process of removing undesirable chemicals, materials, and biological contaminants from contaminated water. The goal is to produce water fit for a specific purpose...
, but is also used in air purifier
Air purifier
An air purifier is a device which removes contaminants from the air. These devices are commonly marketed as being beneficial to allergy sufferers and asthmatics, and at reducing or eliminating second-hand tobacco smoke...
s.
Carbon filters are most effective at removing chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
, sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
, and volatile organic compounds (VOCs) from water. They are not effective at removing minerals, salts, and dissolved inorganic compounds.
Typical particle sizes that can be removed by carbon filters range from 0.5 to 50 micrometre
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
s. The particle size will be used as part of the filter description. The efficacy of a carbon filter is also based upon the flow rate regulation. When the water is allowed to flow through the filter at a slower rate, the contaminants are exposed to the filter media for a longer amount of time.
Types of carbon filters
There are two predominant types of carbon filters used in the filtration industry: powdered block filters and granular activated filters. In general, carbon block filters are more effective at removing a larger number of contaminants, based upon the increased surface area of carbon. Many carbon filters also use secondary media, such as silverSilver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
or KDF-55
Kdf-55
KDF is a water filtration media used in a number of water filtration applications.-Introduction:KDF media , is a chemical compound used in water filtration applications. KDF is often used along side activated carbon to maximise the filters efficiency...
, to prevent bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
growth within the filter.
History of carbon filters
Carbon filters have been used for several hundred years and are considered one of the oldest means of water purification. Historians have shown evidence that carbon filtration may have been used in ancient EgyptianAncient Egypt
Ancient Egypt was an ancient civilization of Northeastern Africa, concentrated along the lower reaches of the Nile River in what is now the modern country of Egypt. Egyptian civilization coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh...
cultures for both air and water sanitization. 2000 B.C. Sanskrit text refers to filtering water through charcoal (1905 translation of "Sushruta Samhita" by Francis Evelyn Place). The first modern use of a carbon filter to purify potable water occurred in 1862. Carbon filtration was further advanced in the mid-1970s by H. Allen Rice and Alvin E. Rice when they first manufactured a porous carbon block for drinking water use.
Currently, carbon filters are used in individual homes as point-of-use water filters and, occasionally, in municipal water treatment facilities. They are also used as pre-treatment devices for reverse osmosis
Reverse osmosis
Reverse osmosis is a membrane technical filtration method that removes many types of large molecules and ions from solutions by applying pressure to the solution when it is on one side of a selective membrane. The result is that the solute is retained on the pressurized side of the membrane and...
systems and as specialized filters designed to remove chlorine-resistant cysts, such as giardia
Giardia
Giardia is a genus of anaerobic flagellated protozoan parasites of the phylum Metamonada in the supergroup "Excavata" that colonise and reproduce in the small intestines of several vertebrates, causing giardiasis, commonly known as Beaver fever...
and cryptosporidium
Cryptosporidium
Cryptosporidium is a protozoan that can cause gastro-intestinal illness with diarrhea in humans.Cryptosporidium is the organism most commonly isolated in HIV positive patients presenting with diarrhea...
.
Hydrogen production
For small scale production of hydrogenHydrogen production
Hydrogen production is the family of industrial methods for generating hydrogen. Currently the dominant technology for direct production is steam reforming from hydrocarbons. Many other methods are known including electrolysis and thermolysis...
water purifiers are installed to prevent formation of minerals on the surface of the electrodes and to remove organics and chlorine from utility water. First the water passes through a 20 micrometer interference (mesh
Mesh
Mesh consists of semi-permeable barrier made of connected strands of metal, fiber, or other flexible/ductile material. Mesh is similar to web or net in that it has many attached or woven strands.-Types of mesh:...
or screen filter
Screen filter
A screen filter is a type of filter using a rigid or flexible screen to separate sand and other fine particles out of water for irrigation or industrial applications...
) filter to remove sand and dust particles, second, a charcoal filter (activated carbon
Activated carbon
Activated carbon, also called activated charcoal, activated coal or carbo activatus, is a form of carbon that has been processed to make it extremely porous and thus to have a very large surface area available for adsorption or chemical reactions.The word activated in the name is sometimes replaced...
) to remove organics and chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
, third stage, a de-ionizing filter to remove metallic ions. A test can be done before and after the filter for proper functioning on barium
Barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...
, calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
, potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
, magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
, sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
and silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
.
Radiation or nuclear medicine
Carbon filters, along with HEPAHEPA
High-Efficiency Particulate Air or HEPA is a type of air filter. Filters that are awarded the HEPA accolade are used in various locations, whether in medical facilities, automotive vehicles, airplanes, home filters, or wherever very pure air is sought. The filter must satisfy certain standards of...
filters, are widely used in the construction of hot cell
Hot cell
Shielded nuclear radiation containment chambers are commonly referred to as hot cells. The word "hot" refers to radioactivity.Hot cells are used in both the nuclear-energy and the nuclear-medicines industries....
s. This allows the room to exhaust air that contains infinitesimal quantities of radioactivity and contaminants.