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Activated carbon

Production
Activated carbon is carbon produced from carbonaceous source materials like nutshells, peat, wood, lignite and coal and petroleum tar. Can be produced by one of the following processes:
Physical reactivation: The precursor is converted to carbon activated gases. This is usually done using one or combination of the following processes:
Carbonization: Material containing carbon is pyrolyzed in temperatures ranging from 600 to 900 C, in the absence of air (usually in an inert atmosphere with gases like argon or nitrogen)
Activation / Oxidation: Raw material or carbonised material is exposed to an oxidizing atmosphere (carbon dioxide, oxygen or steam) at temperatures above 250 ° C, usually in the range temperature from 600 to 1,200 C.
chemical activation: Before carbonization, the raw material is impregnated with certain chemicals. Chemistry is usually an acid, a strong base or a salt (phosphoric acid, potassium hydroxide, sodium hydroxide, zinc chloride, respectively). Then, matter premium is carbonized at lower temperatures (450 to 900 C). It is believed that the carbonization / activation step proceeds simultaneously with the chemical activation. This technique can be problematic in some cases, because, for example, zinc trace residues may remain in the final product. However, chemical activation is preferred to physical activation, due to lower temperatures and shorter time required for the activation of material.
Classifications
activated carbons are complex products that are difficult to classify in terms of their behavior, surface characteristics and methods of preparation. However, some general classification is for purposes of a general nature based on physical characteristics.
powdered activated carbon (PAC)
Traditionally, activated carbons are made in particular form as powders or fine granules less than 1.0 mm in size with an average diameter between 0.15 and 0.25 mm. So have a large surface area to volume ratio with a small diffusion distance. PAC is composed of carbon particles crushed or ground, of which 95.100% pass through a mesh sieve or sieve designated. granular activated carbon is defined as activated carbon is retained in a sieve of 50 mesh (0.297 mm) and material PAC as finer material, while the ASTM standard classifies particle sizes corresponding to a 80-mesh sieve (0.177 mm) and smaller as PAC. CAP is commonly used in a specialized vessel, due to the high pressure drop that would occur. PAC is generally added directly to the processing units, such as raw water intakes, rapid mix basins, clarifiers and gravity filters.
Granular activated carbon (GAC)
granular activated carbon has a relatively large particle size compared to powdered activated carbon and, consequently, has a lower external surface. Diffusion of the adsorbate is therefore an important factor. These carbon atoms, therefore preferred for all adsorption of gases and vapors and its diffusion rate is faster. coal granules are used for water treatment, deodourisation and separation of the components of flow system. GAC can be in granular form or extruded. GAC is designated by size such as 8×20, 20×40, 8×30 or for applications in liquid phase, 4×6, 4×8 or 4×10 for vapor phase applications. A 20×40 carbon is made of particles that pass through a standard U.S. Mesh size sieve No. 20 (0.84 mm) (generally specified as 85% passing) but be retained on a U.S. standard size mesh sieve No. 40 (0.42 mm) (usually specified at 95% retained). AWWA (1992) B604 uses the 50 mesh sieve (0.297 mm) as the minimum size GAC. The most popular aqueous phase carbons are the 12×40 and 8×30 sizes because they have a good balance of size, surface, and pressure drop characteristics.
Extruded activated carbon (EAC)
Extruded activated carbon PAC combined with a binder, which are melted and extruded into a cylindrical block in the form of activated carbon with diameters of 0.8 to 130 mm. These are mainly used for gas phase applications because of its low pressure drop, high strength mechanical and low dust content.
Impregnated carbon
porous carbon containing various types of impregnating inorganic iodine, silver, education, such as Al, Mn, Zn, Fe, Li, Ca have also been prepared for your specific application in controlling air pollution, especially in museums and galleries. Due to the antimicrobial properties / antiseptic, silver loaded activated carbon is used as an adsorbent for the purification of water for domestic use. Drinking water can be obtained from natural water by treating natural waters with a mixture of activated carbon and flocculating agent Al (OH) 3. impregnated carbons are also used for adsorption of H2S and mercaptans. adsorption rates of H 2 S up to 50% by weight have been reported.
Polymer-coated carbon
This is a process whereby a porous carbon can be coated with a biocompatible polymer to provide a smooth and permeable layer without blocking the pores. The resulting carbon is useful for hemoperfusion. Hemoperfusion is a treatment technique in which large volumes of patient's blood is passed over a substance adsorbent for removing toxic substances from the blood.
Other
Activated carbon is also available in special shapes, such as fabrics and fibers. The "carbon cloth, for example, is used in the protection of military personnel.
Properties
One gram of activated charcoal may have a surface area of 500 m2, 1500 m2 that can be achieved easily. Carbon aerogels, while more expensive, even higher surface areas, and are used in special applications.
Under an electron microscope structures of high surface area activated carbon are revealed. Individual particles are intensely complicated and display different types of porosity, can be many areas run parallel flat surfaces of graphite material as each other, separated by only a few nanometers or so. These micropores provide best conditions for adsorption to occur, since adsorbing material can interact with surfaces simultaneously. Tests of adsorption behavior usually done with nitrogen gas at 77 K under high vacuum, but in everyday terms activated carbon is perfectly capable of producing the equivalent, by adsorption its environment, liquid water to steam at 100 C and a pressure of 1 / 10, 000 of an atmosphere.
Physically, activated carbon binds materials by Van der Waals force or London dispersion force.
Activated charcoal does not bind well to certain chemicals, such as alcohols, glycols, ammonia, acids and strong bases, metals and most inorganic compounds such as lithium, sodium, iron, lead, arsenic, fluorine, and boric acid. Activated carbon is absorbed iodine very well and, in fact, the iodine in mg / g, (ASTM D28 Standard Test Method) is used as an indication of the total.
On carbon can be used as a substrate for the application of various chemicals to improve the adsorption capacity of some inorganic (and problematic organic) compounds like hydrogen sulfide (H2S), ammonia (NH3), formaldehyde (HCOH), radioisotopes of iodine-131 (131I) and mercury (Hg). This property is known as chemisorption.
Iodine number
Many small molecules adsorb preferably charcoal. iodine number is the parameter More fundamentally used to characterize the performance of activated carbon. Is a measure of activity level (higher number indicates a greater degree of activation), often reported in mg / g (range typically 5,001,200 mg / g). It is a measure of the content of micropores of activated carbon (0 to 20, or up to 2 nm) by adsorption of iodine the solution. Is equivalent to the carbon surface of 900 m / g, and 1100 m / g. Is the standard measure for liquid phase applications.
Iodine is defined as the milligrams of iodine absorbed per gram of carbon when the iodine concentration in the residual filtrate is 0.02 normal. Basically, the iodine number is a measure of iodine absorbed in the pores and, as such, is an indication of the pore volume available on the activated carbon of interest. Generally, the carbon water treatment have an iodine number between 600 and 1100. Often, this parameter is used to determine the degree of depletion of carbon in use. However, this practice should viewed with caution, since the chemical interaction with the adsorbate can affect the uptake of iodine give false results. Thus, the use of iodine as a result the degree of depletion of a coal bed can only be recommended if it has been shown to be free of the chemical interactions with adsorbates and if there is a correlation experimental between iodine number and degree of exhaustion has been determined for the particular application.
Molasses
Some coals are more skilled in the adsorption large molecules. number of molasses or efficiency is a measure of mesopore activated carbon content (greater than 20, or more than 2 nm) by adsorption of molasses of the solution. A high molasses number corresponds to an adsorption of large molecules (range 95-600). dp Carmelo (yield bleaching) is similar to the number molasses. Molasses is the efficiency reported as a percentage (range 40% -185%) and the parallel number of molasses (600 = 185%, 425 = 85%). The number of European molasses (Range 525-110) is inversely proportional to the North American molasses number.
Molasses Number is a measure of the degree of discoloration of a standard solution of molasses has Dilitid and standardized with standard activated carbon. Due to the size of the color bodies, the number of molasses represents the potential pore volume available to large species of adsorbent. As the whole pore volume may not be available for adsorption in a particular application of wastewater, and as some of the adsorbate can enter smaller pores, is not a good measure of the value of a particular activated carbon for a specific application. Often, this parameter is useful in evaluating a series of activated carbon adsorption rates. Given two activated carbons with similar pore volumes for adsorption, which has the largest number of molasses usually have more feeder pores resulting in a more efficient transfer of adsorbate in the adsorption space.
Tannin
The tannins are a mixture of large and medium-sized molecules. Carbides with a combination of macropores and mesopores absorb tannins. The ability of carbon to adsorb tannins are expressed in parts per million concentration (range of 200 ppm, 362 ppm).
Methylene blue
Some carbon atoms have a mesopore (20 to 50, or 2 to 5 nm)-absorbing structure of medium-sized molecules, such as methylene blue dye. methylene blue adsorption is reported in g/100g (range 11-28 g/100 g).
Dechlorination
Some carbon atoms are evaluated based on the average length dechlorination of value, which measures the chlorine removal efficiency of coal activated. The average length value dechlorination of carbon is the depth needed to reduce the chlorine level of a stream that flows from 5 ppm to 3.5 ppm. Length lower half value indicates superior performance.
Bulk density
Higher density provides greater volume activity and normally indicates better quality activated carbon.
Hardness / abrasion number
It is a measure of the resistance of activated carbon for wear. Note also activated carbon to maintain their physical integrity and withstand the frictional forces imposed by washing, etc. There are large differences in hardness of activated carbons, depending on the raw material and the level of activity.
Ash content
Reduce the overall activity of activated carbon. Reduces the efficiency of reactivation. Metals (Fe2O3) can be filtered activated carbon as a result of bleaching. Acid / water soluble ash content is more important than total ash content. soluble ash can be very important for aquarists, as ferric oxide can promote growth of algae, a coal with a low soluble ash content should be used for marine fish, freshwater and reef tanks to avoid the intoxication of heavy metals and the upper level of algae growth.
Carbon tetrachloride activity
Measuring the porosity of activated carbon adsorption of saturated carbon tetrachloride vapor.
Grit
The finer size of an activated carbon particle, the better the access to the surface and the faster the rate of adsorption kinetics. In systems where this vapor should be considered the low pressure, which affect the cost of energy. Careful consideration of particle size distribution can provide significant profit.
Examples of adsorption
heterogeneous catalysis
The most common form of chemical absorption in industry occurs when a solid catalyst interacts with the raw material gas, the reagent / s. The adsorption of reactant / s to the catalyst surface creates a chemical bond altering the electron density around the molecule of reagent and allowing you to experience reactions that would not normally be available to him.
Adsorption Cooling
Adsorption refrigeration cycles and heat pump are based on the adsorption of a refrigerant gas in an adsorbent at low pressure and subsequent desorption by heating. The adsorbent acts as a "chemical compressor" driven by heat and is, from this point of view, the "pump" system. It consists a solar collector, a condenser or heat exchanger and an evaporator that is placed in a refrigerator box. Inside the collector is lined with a bed full of adsorption Activated carbon adsorbed methanol. The box is insulated cooler filled with water. Activated charcoal may absorb a large amount of methanol vapor at room temperature and released at a higher temperature (about 100 degrees Celsius). During the day, the sun radiates the collector so that the collector is heated and the methanol is desorbed coal activated. In desorption, the liquid methanol adsorbed on the coal is heated and evaporated. The methanol vapor is condensed and stored in the evaporator.
At night, the collector temperature decreases with temperature, and the charcoal absorbs the methanol in the evaporator. The liquid methanol in the evaporator evaporates and absorbs heat from water in the trays. Since adsorption is a process of heat release, the collector must be cooled efficiently at night. As mentioned above, adsorption refrigeration system works intermittently to produce the cooling effect.
helium gas may also be "pumped" by thermally cycling 'removal pumps "activated carbon from 4 degrees Kelvin and higher temperatures. An example of this is to provide power Cooling of the Oxford Instruments dilution refrigerator AST series. 3He vapor is pumped from the surface of the dilute phase of a mixture of liquid 4He and 3He isotope. 3He is adsorbed on the surface of coal at low temperature (typically <4K), the regeneration of the pump between 20 and 40 K, the 3He re-concentration phase of the liquid mixture. Cooling occurs at the interface between the two liquid phases as "evaporated" across the border 3He phase. If more than one pump system is a continuous flow of gas and therefore constant cooling power can be obtained, having a pump absorption of regeneration, while the other is pumping. Systems like this allow temperatures as low as 10 mK (0.01 Kelvin) for very few moving parts.
Applications
Activated charcoal used in gas purification, gold purification, metal extraction, water purification, medicine, wastewater treatment, air filters with gas masks and filter masks, air filters and many other applications.
A major industrial application involves the use of coal active in the field of metal finishing. It is very widely used for purification of electroplating solutions. For example, is a main purification technique removal of organic impurities in bright nickel plating solutions. A variety of organic chemicals are added to the plate solutions to improve their quality deposit and to improve the properties such as brightness, softness, ductility, etc. Due to the passage of direct current and electrolytic reactions of anodic oxidation and cathodic reduction, organic additives generate unwanted break on the products in solution. Their excessive accumulation can adversely affect the quality of electroplating and physical properties of the weld metal. treatment with activated charcoal removes impurities and restores the performance fashioned the desired level.
Chemical analytical applications
Activated carbon, 50% w / w combination with Celite, used as stationary phase in low-pressure chromatography separation of carbohydrates (Mono-, di-trisacchardes) with ethanol solutions (50-50%) as mobile phase in testing protocols or preparation.
Environmental applications
On carbon is usually used in water filtration systems. In this example, activated carbon is the fourth level (counted from the bottom).
adsorption Carbon has numerous applications in removing pollutants from air or water streams both in the field and in industrial processes, such as:
Spill Cleanup
Groundwater Remediation
Drinking water filtration
Air purification
Volatile organic compounds capture from painting, dry cleaning operations gasoline dispensing, and other processes.
In 2007, the University of West Flanders (Belgium) began research water treatment after festivals. A full installation of the scale of activated charcoal, was built in Dranouter music festival in 2008 [citation ] It is necessary, with plans to use technology to treat water in this festival for the next 20 years [citation needed].
Activated carbon also is used for measuring radon concentration in air.
Medical Applications
Activated carbon is used to treat poisonings and overdoses after oral ingestion.
It is believed that bind venom and prevent their absorption by the gastrointestinal tract. In cases of suspected poisoning, medical personnel administer activated charcoal at the scene or in the emergency department of a hospital. The dosage is usually empirical at 1 g / kg body weight (for teens or adults, give 50,100 g), usually given only once, but depending on the drug taken, can be administered more than once. Rarely Activated carbon is used in therapy intensive to filter out harmful drugs from the blood of poisoned patients. Activated carbon has become the treatment of choice for many poisonings, and other decontamination methods such as ipecac induced emesis or gastric lavage is now rarely used.
While activated carbon is useful in a situation acute intoxication, has been shown to be ineffective in the long-term accumulation of toxins, for example through the use of toxic herbicides.
Mechanisms of action:
The binding of the toxin to prevent the discomfort and intestinal absorption. Binding is reversible so a cathartic such as sorbitol may be added as well.
It interrupts the enterohepatic circulation of certain drugs or toxins and their metabolites
Incorrect application (for example, the lungs) results in pulmonary aspiration, which can sometimes be fatal if immediate medical treatment is not started. The use of activated charcoal is contraindicated when the ingested substance is an acid, an alkali, or petroleum product.
To pre-hospital use, these plastic tubes or bottles, commonly 12.5 or 25 grams, pre-mixed with water. Brand names include InstaChar, SuperChair, Actidose and Liqui-Char, but it is commonly called activated carbon.
Ingestion of activated charcoal before ethanol consumption has been shown to reduce the absorption of alcohol in the blood. 5 to 15 milligrams of carbon per kilogram of body weight taken at the time that 170 ml of ethanol pure (equivalent to about 10 parts of alcohol of alcohol, or 12 shots) in the course of an hour, has very clear to reduce the possible contents of alcohol in the blood of other studies showed that this is not the case and that the blood ethanol concentrations increased due to the use of activated carbon. This risk ineficciency aspiration to be a dangerous drug when in wrong hands.
In the last cookie coal was sold in England in the 19th century, originally as an antidote for stomach problems and flatulence.
Activated charcoal tablets are still used as a folk remedy and prescription medicines to treat diarrhea, indigestion and flatulence. They were also used in the past by doctors for this purpose. There is some evidence of its effectiveness as a treatment for irritable bowel syndrome (IBS) and to prevent diarrhea in cancer patients who received irinotecan. May interfere with the absorption of some drugs, leading to unreliable readings in tests such as medical test guaiac card. One type of cookie coal is marketed as a pet care product.
Activated charcoal is also used for the preparation of the bowel, reducing intestinal gas content before abdominal radiography to visualize the gallstones, pancreas and kidney.
Of Fuel storage
The research is testing the ability of different activated carbons for storing natural gas and hydrogen gas. The material acts porous like a sponge for different types of gases. The gas is attracted by the carbon material by Van der Waals. Some carbon atoms have been able to reach binding energy of 5.10 kJ per mole. Then the gas can be desorbed when subjected to higher temperatures and it burned to do the job or in the case of hydrogen gas extracted for use in a hydrogen fuel cell. gas storage in activated carbon is a gas storage method attractive because the gas can be stored in a low pressure, low mass, low volume environment would be more feasible than in bulky compression tanks in vehicles. The United States Energy Department has specified certain milestones to be achieved in the field of research and development of nano-porous carbon materials. Up when all objectives have not been satisfied, but many institutions, including the ALL-CRAFT program, continue to work in this promising field.
Gas purification
Activated carbon filters are generally used in compressed air and gas purification to remove oil vapors, odors and other hydrocarbons from the air. The most common designs use a 1 or 2 stage filtration principle phase in which activated carbon is embedded inside the filter. Activated charcoal is also used in the primary spacesuit "Life Support Systems. Activated carbon filters are used to retain the radioactive gas installation nuclear turbine condenser boiling water reactor. The air sucked from the condenser contains traces of radioactive gases. The large charcoal beds to absorb these gases and held while the species decline rapidly to non-radioactive solid. The solids are trapped in the coal particles, while the filtered air is through.
Chemical purification
Commonly used to purify non-hazardous household chemicals such as sodium acetate. The following filtered.
Purification distilled spirits
See also: Lincoln County Process
Activated carbon filters can be used to filter vodka and whiskey of organic impurities that can affect color, taste and smell. Passing an organically impure vodka through a charcoal filter in the appropriate flow will result in vodka alcohol containing identical and significantly increased organic purity, judging by the smell and taste. [Citation] Need
Mercury washing
Activated charcoal, often imbued with iodine or sulfur, is widely used to trap mercury emissions from coal power plants, medical incinerators, and natural gas at the wellhead. This coal is a special product that cost more than $ 4.00 per kg. However, it is often not recycled.
The elimination in the U.S.
The mercury-loaded activated carbon presents a dilemma provision. [Citation needed] If the activated carbon contains less than 260 ppm of mercury regulations federal permit is stabilized (eg, trapped in the concrete) for landfills. [Citation needed] However, waste containing more than 260 ppm is considered that the high mercury subcategory and is unlawful (Earth-Ban Rule.) [Citation needed] It is this material now accumulated in warehouses and in-depth abandoned mines at an estimated rate of 1000 tonnes per year. [Citation needed]
The problem of disposal of mercury laden activated carbon is not unique to the U.S. In the Netherlands, the mercury is largely recovered and activated carbon disposed by burning is complete.
See also
Black carbon
Carbon filtration
Kvrner process
Onboard refueling vapor recovery
Sumi
Zeocarbon
References
^ "Properties of activated carbon", CPL Link Caron, accessed on 02/05/2008
^ Http: / / en.mimi.hu / astronomy / granule.html
^ Value Added gasification products – carbon Acitivated by jhadhav Shoba, combustion, gasification and Propulsion Laboratory (CGPL) at the Indian Institute of Science (IIS)
^ "Http: / / www.labmeeting.com/paper/28552316/van-hulle-2008-sustainable-wastewater-treatment-of-temporary-events-the-dranouter-music-festival-case-study"> Sustainable wastewater treatment temporary events: the Festival of Music Dranouter case study </ a>. Water science and technology: a journal International Association for Research in Water Pollution. 2008, 58 (8) :1653-7.
^ M Eddleston, E Juszczak, NA Buckley, et al. (2008). "Dose Multiple charcoal in acute self-poisoning: a randomized controlled trial. "Lancet 371 (9612): 579. doi: 10.1016/S0140-6736 (08) 60.270-6.
^ C Elliott, Colby T, T Kelly, M Hicks (1989). "Lung charcoal. Bronchiolitis obliterans after aspiration of activated charcoal." Chest 96 (3): 6724. doi: 10.1378/chest.96.3.672. PMID 2766830.
^ Proctor, Richard and Anondson Stanton, "Method of altering intoxicating effects of alcohol," U.S. 4594249, issued 1986
^ Http: / / www.ncbi.nlm.nih.gov/pubmed/3723647
^ Rolland, Jacques L. (2006). The Encyclopedia of Foods: over 8,000 ingredients tools, techniques and people. Robert Rose. 148 pp. ISBN 0778801500.
^ Stearn, Margaret (2007). For all its faults: Tips speak frankly about the problems embarrassing life. London: Murdoch Books. p. 333. ISBN 978-1-92125984-5. # PPA333 http://books.google.co.uk/books?id=aSRmxC47VNMC&printsec=frontcover. Retrieved on 03/05/2009.
Hbner ^ WD, Moser EH (2002). "Charcoal tablets in the treatment of patients with irritable bowel syndrome." Adv There 19 (5): 24,552. doi: 10.1007/BF02850364. PMID 12539884. https: / / www.advancesintherapy.com/detail.aspx?ID=276.
^ Michael M, Brittain M, Nagai J, et al. (Nov 2004). "Study Phase II of active charcoal to prevent irinotecan-induced diarrhea J Clin Oncol 22 (21): .. 44,107 doi:. 10.1200/JCO.2004.11.125 PMID 15514383 ..
^ HK Gogel, Strickland D Tandberg, RG (September 1989). "The substances that interfere with guaiac card tests: implications for gastric aspirate testing." Am J Emerg Med 7 (5): 47,480. doi: 10.1016/0735-6757 (89) 90248-9. PMID 2787993.
^ BMT-Begemann, Mercury waste treatment facilities
External Links
"Activated carbon for filtration of water" – the purification systems for household water sources] AE-1029, February 1992
"Images of the atomic structure of activated carbon "- JOURNAL OF PHYSICS: CONDENSED MATTER
Engber, Daniel (Nov. 28, 2005). "How does activated carbon work? ". Slate.
EV
Carbon allotropes
Service Pack 3 ways
Diamond (cubic) Lonsdaleite (hexagonal diamond)
sp2 forms
Graphene graphite fullerenes (buckyballs (C20 +)) glassy carbon nanotubes colossal carbon tube
sp forms
Linear acetylenic of carbon
sp3/sp2 mixed forms
amorphous carbon carbon nanofoam nanobuds
other
C1 C2 C3 C8
Related
Activated carbon Chaoite carbon black carbon fiber carbon fullerenes aggregated diamond nanorods
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