Activated carbon

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Activated carbon Activated Carbon.jpg
Activated carbon

Activated carbon, also called activated charcoal, is a form of carbon commonly used to filter contaminants from water and air, among many other uses. It is processed (activated) to have small, low-volume pores that greatly increase the surface area [1] [2] available for adsorption or chemical reactions [3] that can be thought of as a microscopic "sponge" structure (adsorption, not to be confused with absorption, is a process where atoms or molecules adhere to a surface). Activation is analogous to making popcorn from dried corn kernels: popcorn is light, fluffy, and its kernels have a high surface-area-to-volume ratio. Activated is sometimes replaced by active.

Contents

Because it is so porous on a microscopic scale, one gram of activated carbon has a surface area of over 3,000 square metres (32,000 square feet), [1] [2] [4] as determined by gas adsorption. [1] [2] [5] For charcoal, the equivalent figure before activation is about 2–5 square metres (22–54 sq ft). [6] [7] A useful activation level may be obtained solely from high surface area. Further chemical treatment often enhances adsorption properties.

Activated carbon is usually derived from waste products such as coconut husks; waste from paper mills has been studied as a source. [8] These bulk sources are converted into charcoal before being activated. When derived from coal, [1] [2] it is referred to as activated coal. Activated coke is derived from coke.

Uses

Activated carbon is used in methane and hydrogen storage, [1] [2] air purification, [9] capacitive deionization, supercapacitive swing adsorption, solvent recovery, decaffeination, gold purification, metal extraction, water purification, medicine, sewage treatment, air filters in respirators, filters in compressed air, teeth whitening, production of hydrogen chloride, edible electronics, [10] and many other applications.

Industrial

One major industrial application involves use of activated carbon in metal finishing for purification of electroplating solutions. For example, it is the main purification technique for removing organic impurities from bright nickel plating solutions. A variety of organic chemicals are added to plating solutions for improving their deposit qualities and for enhancing properties like brightness, smoothness, ductility, etc. Due to passage of direct current and electrolytic reactions of anodic oxidation and cathodic reduction, organic additives generate unwanted breakdown products in solution. Their excessive build up can adversely affect plating quality and physical properties of deposited metal. Activated carbon treatment removes such impurities and restores plating performance to the desired level.

Medical

Activated charcoal for medical use Aktivirovannyi ugol' 3.jpg
Activated charcoal for medical use

Activated carbon is used to treat poisonings and overdoses following oral ingestion. Tablets or capsules of activated carbon are used in many countries as an over-the-counter drug to treat diarrhea, indigestion, and flatulence. However, activated charcoal shows no effect on intestinal gas and diarrhea, is ordinarily medically ineffective if poisoning resulted from ingestion of corrosive agents, boric acid, or petroleum products, and is particularly ineffective against poisonings of strong acids or bases, cyanide, iron, lithium, arsenic, methanol, ethanol, or ethylene glycol. [11] Activated carbon will not prevent these chemicals from being absorbed into the human body. [12] It is on the World Health Organization's List of Essential Medicines. [13]

Incorrect application (e.g. into the lungs) results in pulmonary aspiration, which can sometimes be fatal if immediate medical treatment is not initiated. [14]

Analytical chemistry

Activated carbon, in 50% w/w combination with celite, is used as stationary phase in low-pressure chromatographic separation of carbohydrates (mono-, di-, tri-saccharides) using ethanol solutions (5–50%) as mobile phase in analytical or preparative protocols.

Activated carbon is useful for extracting the direct oral anticoagulants (DOACs) such as dabigatran, apixaban, rivaroxaban and edoxaban from blood plasma samples. [15] For this purpose it has been made into "minitablets", each containing 5 mg activated carbon for treating 1ml samples of DOAC. Since this activated carbon has no effect on blood clotting factors, heparin or most other anticoagulants [16] this allows a plasma sample to be analyzed for abnormalities otherwise affected by the DOACs.

Environmental

Activated carbon is usually used in water filtration systems. In this illustration, the activated carbon is in the fourth level (counted from bottom). Water Filtration Systems.png
Activated carbon is usually used in water filtration systems. In this illustration, the activated carbon is in the fourth level (counted from bottom).

Carbon adsorption has numerous applications in removing pollutants from air or water streams both in the field and in industrial processes such as:

During early implementation of the 1974 Safe Drinking Water Act in the US, EPA officials developed a rule that proposed requiring drinking water treatment systems to use granular activated carbon. Because of its high cost, the so-called GAC rule encountered strong opposition across the country from the water supply industry, including the largest water utilities in California. Hence, the agency set aside the rule. [20] Activated carbon filtration is an effective water treatment method due to its multi-functional nature. There are specific types of activated carbon filtration methods and equipment that are indicated – depending upon the contaminants involved. [19]

Activated carbon is also used for the measurement of radon concentration in air.

Biomass waste-derived activated carbons were also succuesfully used for the removal of caffeine and paracetamol from water. [21]

Agricultural

Activated carbon (charcoal) is an allowed substance used by organic farmers in both livestock production and wine making. In livestock production it is used as a pesticide, animal feed additive, processing aid, nonagricultural ingredient and disinfectant. [22] In organic winemaking, activated carbon is allowed for use as a processing agent to adsorb brown color pigments from white grape concentrates. [23] It is sometimes used as biochar.

Distilled alcoholic beverage purification

Activated carbon filters (AC filters) can be used to filter vodka and whiskey of organic impurities which can affect color, taste, and odor. Passing an organically impure vodka through an activated carbon filter at the proper flow rate will result in vodka with an identical alcohol content and significantly increased organic purity, as judged by odor and taste. [24]

Fuel storage

Research is being done testing various activated carbons' ability to store natural gas [1] [2] and hydrogen gas. [1] [2] The porous material acts like a sponge for different types of gases. The gas is attracted to the carbon material via Van der Waals forces. Some carbons have been able to achieve binding energies of 5–10 kJ per mol. [25] The gas may then be desorbed when subjected to higher temperatures and either combusted to do work or in the case of hydrogen gas extracted for use in a hydrogen fuel cell. Gas storage in activated carbons is an appealing gas storage method because the gas can be stored in a low pressure, low mass, low volume environment that would be much more feasible than bulky on-board pressure tanks in vehicles. The United States Department of Energy has specified certain goals [26] to be achieved in the area of research and development of nano-porous carbon materials. All of the goals are yet to be satisfied but numerous institutions, including the ALL-CRAFT program, [1] [2] are continuing to conduct work in this field.

Gas purification

Filters with activated carbon are usually used in compressed air and gas purification to remove oil vapors, odor, and other hydrocarbons from the air. The most common designs use a 1-stage or 2 stage filtration principle in which activated carbon is embedded inside the filter media.

Activated carbon filters are used to retain radioactive gases within the air vacuumed from a nuclear boiling water reactor turbine condenser. The large charcoal beds adsorb these gases and retain them while they rapidly decay to nonradioactive solid species. The solids are trapped in the charcoal particles, while the filtered air passes through.

Chemical purification

Activated carbon is commonly used on the laboratory scale to purify solutions of organic molecules containing unwanted colored organic impurities.

Filtration over activated carbon is used in large scale fine chemical and pharmaceutical processes for the same purpose. The carbon is either mixed with the solution then filtered off or immobilized in a filter. [27] [28]

Mercury scrubbing

Activated carbon, often infused with sulfur [29] or iodine, is widely used to trap mercury emissions from coal-fired power stations, medical incinerators, and from natural gas at the wellhead. However, despite its effectiveness, activated carbon is expensive to use. [30]

Since it is often not recycled, the mercury-laden activated carbon presents a disposal dilemma. [31] If the activated carbon contains less than 260 ppm mercury, United States federal regulations allow it to be stabilized (for example, trapped in concrete) for landfilling.[ citation needed ] However, waste containing greater than 260 ppm is considered to be in the high-mercury subcategory and is banned from landfilling (Land-Ban Rule).[ citation needed ] This material is now accumulating in warehouses and in deep abandoned mines at an estimated rate of 100 tons per year.[ citation needed ]

The problem of disposal of mercury-laden activated carbon is not unique to the United States. In the Netherlands, this mercury is largely recovered[ citation needed ] and the activated carbon is disposed of by complete burning, forming carbon dioxide (CO2).

Food additive

Activated, food-grade charcoal became a food trend in 2016, being used as an additive to impart a "slightly smoky" taste and a dark coloring to products including hotdogs, ice cream, pizza bases, and bagels. [32] People taking medication, including birth control pills and antidepressants, [33] are advised to avoid novelty foods or drinks that use activated charcoal coloring since it can render the medication ineffective. [34]

Smoking filtration

Activated charcoal is used in smoking filters [35] as a way to reduce the tar content and other chemicals present in smoke, which is a result of combustion, wherein it has been found to reduce the toxicants from tobacco smoke, in particular the free radicals. [35]

Structure of activated carbon

The structure of activated carbon has long been a subject of debate. In a book published in 2006, [36] Harry Marsh and Francisco Rodríguez-Reinoso considered more than 15 models for the structure, without coming to a definite conclusion about which was correct. Recent work using aberration-corrected transmission electron microscopy has suggested that activated carbons may have a structure related to that of the fullerenes, with pentagonal and heptagonal carbon rings. [37] [38]

Production

Activated carbon is carbon produced from carbonaceous source materials such as bamboo, coconut husk, willow peat, wood, coir, lignite, coal, and petroleum pitch. It can be produced (activated) by one of the following processes:

  1. Physical activation: The source material is developed into activated carbon using hot gases. Air is then introduced to burn out the gasses, creating a graded, screened and de-dusted form of activated carbon. This is generally done by using one or more of the following processes:
    • Carbonization : Material with carbon content is pyrolyzed at temperatures in the range 600–900 °C, usually in an inert atmosphere with gases such as argon or nitrogen
    • Activation/oxidation: Raw material or carbonized material is exposed to oxidizing atmospheres (oxygen or steam) at temperatures above 250 °C, usually in the temperature range of 600–1200 °C. The activation is performed by heating the sample for 1 h in a muffle furnace at 450 °C in the presence of air. [30]
  2. Chemical activation: The carbon material is impregnated with certain chemicals. The chemical is typically an acid, strong base, [1] [2] or a salt [39] (phosphoric acid 25%, potassium hydroxide 5%, sodium hydroxide 5%, potassium carbonate 5%, [40] calcium chloride 25%, and zinc chloride 25%). The carbon is then subjected to high temperatures (250–600 °C). It is believed that the temperature activates the carbon at this stage by forcing the material to open up and have more microscopic pores. Chemical activation is preferred to physical activation owing to the lower temperatures, better quality consistency, and shorter time needed for activating the material. [41]

The Dutch company Norit NV, part of the Cabot Corporation, is the largest producer of activated carbon in the world. Haycarb, a Sri Lankan coconut shell-based company, controls 16% of the global market share. [42]

Classification

Activated carbons are complex products which are difficult to classify on the basis of their behaviour, surface characteristics and other fundamental criteria. However, some broad classification is made for general purposes based on their size, preparation methods, and industrial applications.

Powdered activated carbon (PAC)

A micrograph of activated charcoal (R 1) under bright field illumination on a light microscope. Notice the fractal-like shape of the particles hinting at their enormous surface area. Each particle in this image, despite being only around 0.1 mm across, can have a surface area of several square centimetres. The entire image covers a region of approximately 1.1 by 0.7 mm, and the full resolution version is at a scale of 6.236 pixels/mm. ActivatedCharcoalPowder BrightField.jpg
A micrograph of activated charcoal (R 1) under bright field illumination on a light microscope. Notice the fractal-like shape of the particles hinting at their enormous surface area. Each particle in this image, despite being only around 0.1 mm across, can have a surface area of several square centimetres. The entire image covers a region of approximately 1.1 by 0.7 mm, and the full resolution version is at a scale of 6.236 pixels/μm.

Normally, activated carbons (R 1) are made in particulate form as powders or fine granules less than 1.0 mm in size with an average diameter between 0.15 and 0.25 mm. Thus they present a large surface to volume ratio with a small diffusion distance. Activated carbon (R 1) is defined as the activated carbon particles retained on a 50-mesh sieve (0.297 mm).

Powdered activated carbon (PAC) material is finer material. PAC is made up of crushed or ground carbon particles, 95–100% of which will pass through a designated mesh sieve. The ASTM classifies particles passing through an 80-mesh sieve (0.177 mm) and smaller as PAC. It is not common to use PAC in a dedicated vessel, due to the high head loss that would occur. Instead, PAC is generally added directly to other process units, such as raw water intakes, rapid mix basins, clarifiers, and gravity filters.

Granular activated carbon (GAC)

A micrograph of activated charcoal (GAC) under a scanning electron microscope Activated Charcoal.jpg
A micrograph of activated charcoal (GAC) under a scanning electron microscope

Granular activated carbon (GAC) has a relatively larger particle size compared to powdered activated carbon and consequently, presents a smaller external surface. Diffusion of the adsorbate is thus an important factor. These carbons are suitable for adsorption of gases and vapors, because gaseous substances diffuse rapidly. Granulated carbons are used for air filtration and water treatment, as well as for general deodorization and separation of components in flow systems and in rapid mix basins. GAC can be obtained in either granular or extruded form. GAC is designated by sizes such as 8×20, 20×40, or 8×30 for liquid phase applications and 4×6, 4×8 or 4×10 for vapor phase applications. A 20×40 carbon is made of particles that will pass through a U.S. Standard Mesh Size No. 20 sieve (0.84 mm) (generally specified as 85% passing) but be retained on a U.S. Standard Mesh Size No. 40 sieve (0.42 mm) (generally specified as 95% retained). AWWA (1992) B604 uses the 50-mesh sieve (0.297 mm) as the minimum GAC size. The most popular aqueous-phase carbons are the 12×40 and 8×30 sizes because they have a good balance of size, surface area, and head loss characteristics.

Extruded activated carbon (EAC)

Extruded activated carbon (EAC) combines powdered activated carbon with a binder, which are fused together and extruded into a cylindrical shaped activated carbon block with diameters from 0.8 to 130 mm. These are mainly used for gas phase applications because of their low pressure drop, high mechanical strength and low dust content. Also sold as CTO filter (Chlorine, Taste, Odor).

Bead activated carbon (BAC)

Bead activated carbon (BAC) is made from petroleum pitch and supplied in diameters from approximately 0.35 to 0.80 mm. Similar to EAC, it is also noted for its low pressure drop, high mechanical strength and low dust content, but with a smaller grain size. Its spherical shape makes it preferred for fluidized bed applications such as water filtration.

Impregnated carbon

Porous carbons containing several types of inorganic impregnate such as iodine and silver. Cations such as aluminium, manganese, zinc, iron, lithium, and calcium have also been prepared for specific application in air pollution control especially in museums and galleries. Due to its antimicrobial and antiseptic properties, silver loaded activated carbon is used as an adsorbent for purification of domestic water. Drinking water can be obtained from natural water by treating the natural water with a mixture of activated carbon and aluminium hydroxide (Al(OH)3), a flocculating agent. Impregnated carbons are also used for the adsorption of hydrogen sulfide (H2S) and thiols. Adsorption rates for H2S as high as 50% by weight have been reported. [ citation needed ]

Polymer coated carbon

Woven activated carbon cloth Woven activated carbon cloth.jpg
Woven activated carbon cloth

This is a process by which a porous carbon can be coated with a biocompatible polymer to give a smooth and permeable coat without blocking the pores. The resulting carbon is useful for hemoperfusion. Hemoperfusion is a treatment technique in which large volumes of the patient's blood are passed over an adsorbent substance in order to remove toxic substances from the blood.

Woven carbon

There is a technology of processing technical rayon fiber into activated carbon cloth for carbon filtering. Adsorption capacity of activated cloth is greater than that of activated charcoal (BET theory) surface area: 500–1500 m2/g, pore volume: 0.3–0.8 cm3/g)[ citation needed ]. Thanks to the different forms of activated material, it can be used in a wide range of applications (supercapacitors, odor absorbers, CBRN-defense industry etc.).

Properties

A gram of activated carbon can have a surface area in excess of 500 m2 (5,400 sq ft), with 3,000 m2 (32,000 sq ft) being readily achievable. [2] [4] [5] Carbon aerogels, while more expensive, have even higher surface areas, and are used in special applications.

Under an electron microscope, the high surface-area structures of activated carbon are revealed. Individual particles are intensely convoluted and display various kinds of porosity; there may be many areas where flat surfaces of graphite-like material run parallel to each other, [2] separated by only a few nanometres or so. These micropores provide superb conditions for adsorption to occur, since adsorbing material can interact with many surfaces simultaneously. Tests of adsorption behaviour are 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 from its environment, liquid water from steam at 100 °C (212 °F) and a pressure of 1/10,000 of an atmosphere.

James Dewar, the scientist after whom the Dewar (vacuum flask) is named, spent much time studying activated carbon and published a paper regarding its adsorption capacity with regard to gases. [43] In this paper, he discovered that cooling the carbon to liquid nitrogen temperatures allowed it to adsorb significant quantities of numerous air gases, among others, that could then be recollected by simply allowing the carbon to warm again and that coconut-based carbon was superior for the effect. He uses oxygen as an example, wherein the activated carbon would typically adsorb the atmospheric concentration (21%) under standard conditions, but release over 80% oxygen if the carbon was first cooled to low temperatures.

Physically, activated carbon binds materials by van der Waals force [41] or London dispersion force.

Activated carbon does not bind well to certain chemicals, including alcohols, diols, strong acids and bases, metals and most inorganics, such as lithium, sodium, iron, lead, arsenic, fluorine, and boric acid.

Activated carbon adsorbs iodine very well. The iodine capacity, mg/g, (ASTM D28 Standard Method test) may be used as an indication of total surface area.

Carbon monoxide is not well adsorbed by activated carbon. This should be of particular concern to those using the material in filters for respirators, fume hoods, or other gas control systems because the gas is undetectable to the human senses, toxic to the metabolism, and neurotoxic.

Substantial lists of the common industrial and agricultural gases adsorbed by activated carbon can be found online. [44]

Activated carbon can be used as a substrate for the application of various chemicals to improve the adsorptive capacity for some inorganic (and problematic organic) compounds such as hydrogen sulfide (H2S), ammonia (NH3), formaldehyde (HCOH), mercury (Hg) and radioactive iodine-131(131I). This property is known as chemisorption.

Iodine number

Many carbons preferentially adsorb small molecules. Iodine number is the most fundamental parameter used to characterize activated carbon performance. It is a measure of activity level (higher number indicates higher degree of activation [45] ) often reported in mg/g (typical range 500–1200 mg/g). It is a measure of the micropore content of the activated carbon (0 to 20  Å, or up to 2  nm) by adsorption of iodine from solution. [46] It is equivalent to surface area of carbon between 900 and 1100 m2/g. It is the standard measure for liquid-phase applications.

Iodine number is defined as the milligrams of iodine adsorbed by one gram of carbon when the iodine concentration in the residual filtrate is at a concentration of 0.02 normal (i.e. 0.02N). Basically, iodine number is a measure of the iodine adsorbed in the pores and, as such, is an indication of the pore volume available in the activated carbon of interest. Typically, water-treatment carbons have iodine numbers ranging from 600 to 1100. Frequently, this parameter is used to determine the degree of exhaustion of a carbon in use. However, this practice should be viewed with caution, as chemical interactions with the adsorbate may affect the iodine uptake, giving false results. Thus, the use of iodine number as a measure of the degree of exhaustion of a carbon bed can only be recommended if it has been shown to be free of chemical interactions with adsorbates and if an experimental correlation between iodine number and the degree of exhaustion has been determined for the particular application.

Molasses

Some carbons are more adept at adsorbing large molecules. Molasses number or molasses efficiency is a measure of the mesopore content of the activated carbon (greater than 20 Å, or larger than 2 nm) by adsorption of molasses from solution. A high molasses number indicates a high adsorption of big molecules (range 95–600). Caramel dp (decolorizing performance) is similar to molasses number. Molasses efficiency is reported as a percentage (range 40%–185%) and parallels molasses number (600 = 185%, 425 = 85%). The European molasses number (range 525–110) is inversely related to the North American molasses number.

Molasses Number is a measure of the degree of decolorization of a standard molasses solution that has been diluted and standardized against standardized activated carbon. Due to the size of color bodies, the molasses number represents the potential pore volume available for larger adsorbing species. As all of the pore volume may not be available for adsorption in a particular waste water application, and as some of the adsorbate may enter smaller pores, it is not a good measure of the worth of a particular activated carbon for a specific application. Frequently, this parameter is useful in evaluating a series of active carbons for their rates of adsorption. Given two active carbons with similar pore volumes for adsorption, the one having the higher molasses number will usually have larger feeder pores resulting in more efficient transfer of adsorbate into the adsorption space.

Tannin

Tannins are a mixture of large and medium size molecules. Carbons with a combination of macropores and mesopores adsorb tannins. The ability of a carbon to adsorb tannins is reported in parts per million concentration (range 200 ppm–362 ppm).

Methylene blue

Some carbons have a mesopore (20 Å to 50 Å, or 2 to 5 nm) structure which adsorbs medium size molecules, such as the dye methylene blue. Methylene blue adsorption is reported in g/100g (range 11–28 g/100g). [47]

Dechlorination

Some carbons are evaluated based on the dechlorination half-life length, which measures the chlorine-removal efficiency of activated carbon. The dechlorination half-value length is the depth of carbon required to reduce the chlorine concentration by 50%. A lower half-value length indicates superior performance. [48]

Apparent density

The solid or skeletal density of activated carbons will typically range between 2000 and 2100 kg/m3 (125–130 lbs./cubic foot). However, a large part of an activated carbon sample will consist of air space between particles, and the actual or apparent density will therefore be lower, typically 400 to 500 kg/m3 (25–31 lbs./cubic foot). [49]

Higher density provides greater volume activity and normally indicates better-quality activated carbon. ASTM D 2854 -09 (2014) is used to determine the apparent density of activated carbon.

Hardness/abrasion number

It is a measure of the activated carbon's resistance to attrition. It is an important indicator of activated carbon to maintain its physical integrity and withstand frictional forces. There are large differences in the hardness of activated carbons, depending on the raw material and activity levels (porosity).

Ash content

Ash reduces the overall activity of activated carbon and reduces the efficiency of reactivation. The amount is exclusively dependent on the base raw material used to produce the activated carbon (e.g., coconut, wood, coal, etc.). The metal oxides (Fe2O3) can leach out of activated carbon resulting in discoloration. Acid/water-soluble ash content is more significant than total ash content. Soluble ash content can be very important for aquarists, as ferric oxide can promote algal growths. A carbon with a low soluble ash content should be used for marine, freshwater fish and reef tanks to avoid heavy metal poisoning and excess plant/algal growth. ASTM (D2866 Standard Method test) is used to determine the ash content of activated carbon.

Carbon tetrachloride activity

Measurement of the porosity of an activated carbon by the adsorption of saturated carbon tetrachloride vapour.

Particle size distribution

The finer the particle size of an activated carbon, the better the access to the surface area and the faster the rate of adsorption kinetics. In vapour phase systems this needs to be considered against pressure drop, which will affect energy cost. Careful consideration of particle size distribution can provide significant operating benefits. However, in the case of using activated carbon for adsorption of minerals such as gold, the particle size should be in the range of 3.35–1.4 millimetres (0.132–0.055 in). Activated carbon with particle size less than 1 mm would not be suitable for elution (the stripping of mineral from an activated carbon).

Modification of properties and reactivity

Acid-base, oxidation-reduction and specific adsorption characteristics are strongly dependent on the composition of the surface functional groups. [50]

The surface of conventional activated carbon is reactive, capable of oxidation by atmospheric oxygen and oxygen plasma [51] [52] [53] [54] [55] [56] [57] [58] steam, [59] [60] [61] and also carbon dioxide [55] and ozone. [62] [63] [64]

Oxidation in the liquid phase is caused by a wide range of reagents (HNO3, H2O2, KMnO4). [65] [66] [67]

Through the formation of a large number of basic and acidic groups on the surface of oxidized carbon to sorption and other properties can differ significantly from the unmodified forms. [50]

Activated carbon can be nitrogenated by natural products or polymers [68] [69] or processing of carbon with nitrogenating reagents. [70] [71] [72]

Activated carbon can interact with chlorine, [73] [74] bromine [75] and fluorine. [76]

Surface of activated carbon, like other carbon materials can be fluoralkylated by treatment with (per)fluoropolyether peroxide [77] in a liquid phase, or with wide range of fluoroorganic substances by CVD-method. [78] Such materials combine high hydrophobicity and chemical stability with electrical and thermal conductivity and can be used as electrode material for super capacitors. [79]

Sulfonic acid functional groups can be attached to activated carbon to give "starbons" which can be used to selectively catalyse the esterification of fatty acids. [80] Formation of such activated carbons from halogenated precursors gives a more effective catalyst which is thought to be a result of remaining halogens improving stability. [81] It is reported about synthesis of activated carbon with chemically grafted superacid sites –CF2SO3H. [82]

Some of the chemical properties of activated carbon have been attributed to presence of the surface active carbon double bond. [64] [83]

The Polyani adsorption theory is a popular method for analyzing adsorption of various organic substances to their surface.

Examples of adsorption

Heterogeneous catalysis

The most commonly encountered form of chemisorption in industry, occurs when a solid catalyst interacts with a gaseous feedstock, the reactant/s. The adsorption of reactant/s to the catalyst surface creates a chemical bond, altering the electron density around the reactant molecule and allowing it to undergo reactions that would not normally be available to it.

Reactivation and regeneration

World's largest reactivation plant located in Feluy, Belgium. Reactivation Furnace Feluy Belgium.jpg
World's largest reactivation plant located in Feluy, Belgium.
Activated carbon reactivation center in Roeselare, Belgium. Activated-carbon-reactivation-centre-Roeselare.jpg
Activated carbon reactivation center in Roeselare, Belgium.

The reactivation or the regeneration of activated carbons involves restoring the adsorptive capacity of saturated activated carbon by desorbing adsorbed contaminants on the activated carbon surface.

Thermal reactivation

The most common regeneration technique employed in industrial processes is thermal reactivation. [84] The thermal regeneration process generally follows three steps: [85]

The heat treatment stage utilises the exothermic nature of adsorption and results in desorption, partial cracking and polymerization of the adsorbed organics. The final step aims to remove charred organic residue formed in the porous structure in the previous stage and re-expose the porous carbon structure regenerating its original surface characteristics. After treatment the adsorption column can be reused. Per adsorption-thermal regeneration cycle between 5–15 wt% of the carbon bed is burnt off resulting in a loss of adsorptive capacity. [86] Thermal regeneration is a high energy process due to the high required temperatures making it both an energetically and commercially expensive process. [85] Plants that rely on thermal regeneration of activated carbon have to be of a certain size before it is economically viable to have regeneration facilities onsite. As a result, it is common for smaller waste treatment sites to ship their activated carbon cores to specialised facilities for regeneration. [87]

Other regeneration techniques

Current concerns with the high energy/cost nature of thermal regeneration of activated carbon has encouraged research into alternative regeneration methods to reduce the environmental impact of such processes. Though several of the regeneration techniques cited have remained areas of purely academic research, some alternatives to thermal regeneration systems have been employed in industry. Current alternative regeneration methods are:

See also

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Heterogeneous catalysis is catalysis where the phase of catalysts differs from that of the reagents or products. The process contrasts with homogeneous catalysis where the reagents, products and catalyst exist in the same phase. Phase distinguishes between not only solid, liquid, and gas components, but also immiscible mixtures, or anywhere an interface is present.

<span class="mw-page-title-main">Molecular sieve</span> Filter material with homogeneously sized pores in the nanometer range

A molecular sieve is a material with pores, having uniform size comparable to that of individual molecules, linking the interior of the solid to its exterior. These materials embody the molecular sieve effect, the preferential sieving of molecules larger than the pores. Many kinds of materials exhibit some molecular sieves, but zeolites dominate the field. Zeolites are almost always aluminosilicates, or variants where some or all of the Si or Al centers are replaced by similarly charged elements.

<span class="mw-page-title-main">Activated alumina</span>

Activated alumina is manufactured from aluminium hydroxide by dehydroxylating it in a way that produces a highly porous material; this material can have a surface area significantly over 200 m2/g. The compound is used as a desiccant (to keep things dry by adsorbing water from the air) and as a filter of fluoride, arsenic and selenium in drinking water. It is made of aluminium oxide (alumina; Al2O3). It has a very high surface-area-to-weight ratio, due to the many "tunnel like" pores that it has. Activated alumina in its phase composition can be represented only by metastable forms (gamma-Al2O3 etc.). Corundum (alpha-Al2O3), the only stable form of aluminum oxide, does not have such a chemically active surface and is not used as a sorbent.

<span class="mw-page-title-main">Pressure swing adsorption</span> Method of gases separation using selective adsorption under pressure

Pressure swing adsorption (PSA) is a technique used to separate some gas species from a mixture of gases under pressure according to the species' molecular characteristics and affinity for an adsorbent material. It operates at near-ambient temperature and significantly differs from the cryogenic distillation commonly used to separate gases. Selective adsorbent materials are used as trapping material, preferentially adsorbing the target gas species at high pressure. The process then swings to low pressure to desorb the adsorbed gas.

<span class="mw-page-title-main">Carbon filtering</span> Filtering method

Carbon filtering is a method of filtering that uses a bed of activated carbon to remove impurities from a fluid using adsorption.

<span class="mw-page-title-main">Portable water purification</span> Self-contained, easily transported units used to purify water from untreated sources

Portable water purification devices are self-contained, easily transported units used to purify water from untreated sources for drinking purposes. Their main function is to eliminate pathogens, and often also of suspended solids and some unpalatable or toxic compounds.

<span class="mw-page-title-main">Aquarium filter</span>

Aquarium filters are critical components of both freshwater and marine aquaria. Aquarium filters remove physical and soluble chemical waste products from aquaria, simplifying maintenance. Furthermore, aquarium filters are necessary to support life as aquaria are relatively small, closed volumes of water compared to the natural environment of most fish.

<span class="mw-page-title-main">Carbon dioxide scrubber</span> Device which absorbs carbon dioxide from circulated gas

A carbon dioxide scrubber is a piece of equipment that absorbs carbon dioxide (CO2). It is used to treat exhaust gases from industrial plants or from exhaled air in life support systems such as rebreathers or in spacecraft, submersible craft or airtight chambers. Carbon dioxide scrubbers are also used in controlled atmosphere (CA) storage and carbon capture and storage processes.

The electrochemical regeneration of activated carbon based adsorbents involves the removal of molecules adsorbed onto the surface of the adsorbent with the use of an electric current in an electrochemical cell restoring the carbon's adsorptive capacity. Electrochemical regeneration represents an alternative to thermal regeneration commonly used in waste water treatment applications. Common adsorbents include powdered activated carbon (PAC), granular activated carbon (GAC) and activated carbon fibre.

Biosorption is a physiochemical process that occurs naturally in certain biomass which allows it to passively concentrate and bind contaminants onto its cellular structure. Biosorption can be defined as the ability of biological materials to accumulate heavy metals from wastewater through metabolically mediated or physico-chemical pathways of uptake. Though using biomass in environmental cleanup has been in practice for a while, scientists and engineers are hoping this phenomenon will provide an economical alternative for removing toxic heavy metals from industrial wastewater and aid in environmental remediation.

<span class="mw-page-title-main">Activated charcoal (medication)</span> Medication used to treat ingested poisonings

Activated charcoal, also known as activated carbon, is a medication used to treat poisonings that occurred by mouth. To be effective it must be used within a short time of the poisoning occurring, typically an hour. It does not work for poisonings by cyanide, corrosive agents, iron, lithium, alcohols, or malathion. It may be taken by mouth or given by a nasogastric tube. Other uses include inside hemoperfusion machines.

The potential theory of Polanyi, also called Polanyi adsorption potential theory, is a model of adsorption proposed by Michael Polanyi where adsorption can be measured through the equilibrium between the chemical potential of a gas near the surface and the chemical potential of the gas from a large distance away. In this model, he assumed that the attraction largely due to Van Der Waals forces of the gas to the surface is determined by the position of the gas particle from the surface, and that the gas behaves as an ideal gas until condensation where the gas exceeds its equilibrium vapor pressure. While the adsorption theory of Henry is more applicable in low pressure and BET adsorption isotherm equation is more useful at from 0.05 to 0.35 P/Po, the Polanyi potential theory has much more application at higher P/Po (~0.1–0.8).

Adsorbable organic halides (AOX) is a measure of the organic halogen load at a sampling site such as soil from a land fill, water, or sewage waste. The procedure measures chlorine, bromine, and iodine as equivalent halogens, but does not measure fluorine levels in the sample.

<span class="mw-page-title-main">Activated charcoal cleanse</span> Pseudoscientific use of medicine

Activated charcoal cleanses, also known as charcoal detoxes, are a pseudoscientific use of a proven medical intervention. Activated charcoal is available in powder, tablet and liquid form. Its proponents claim the use of activated charcoal on a regular basis will detoxify and cleanse the body as well as boost one's energy and brighten the skin. Such claims violate basic principles of chemistry and physiology. There is no medical evidence for any health benefits of cleanses or detoxes via activated charcoal or any other method. Charcoal, when ingested, will absorb vitamins and nutrients as well as prescription medications present in the gastrointestinal tract which can make it dangerous to use unless directed by a medical doctor.

Remediation of per- and polyfluoroalkyl substances refers to the destruction or removal of per- and polyfluoroalkyl substances (PFASs) from the environment. PFASs are a group of synthetic organofluorine compounds, used in diverse products such as non-stick cookware and firefighting foams, that have attracted great concern as persistent organic pollutants. Because they are pervasive and have adverse effects, much interest has focused on their removal.

References

  1. 1 2 3 4 5 6 7 8 9 Chada N, Romanos J, Hilton R, Suppes G, Burress J, Pfeifer P (2012-03-01). "Activated carbon monoliths for methane storage". Bulletin of the American Physical Society. 57 (1): W33.012. Bibcode:2012APS..MARW33012C. Archived from the original on 2018-06-12. Retrieved 2018-05-30.
  2. 1 2 3 4 5 6 7 8 9 10 11 Soo Y, Chada N, Beckner M, Romanos J, Burress J, Pfeifer P (2013-03-20). "Adsorbed Methane Film Properties in Nanoporous Carbon Monoliths". Bulletin of the American Physical Society. 58 (1). M38.001. Bibcode:2013APS..MARM38001S. Archived from the original on 2018-06-12. Retrieved 2018-05-30.
  3. ↑ "What is Activated Carbon?". CPL/Puragen Activated Carbons. Archived from the original on 29 July 2020. Retrieved 13 November 2024.
  4. 1 2 Dillon EC, Wilton JH, Barlow JC, Watson WA (1989-05-01). "Large surface area activated charcoal and the inhibition of aspirin absorption". Annals of Emergency Medicine. 18 (5): 547–552. doi:10.1016/S0196-0644(89)80841-8. PMID   2719366.
  5. 1 2 P. J. Paul. "Value Added Products from Gasification – Activated Carbon" (PDF). Bangalore: The Combustion, Gasification and Propulsion Laboratory (CGPL) at the Indian Institute of Science (IISc). Archived (PDF) from the original on 2021-09-20. Retrieved 2018-10-10.
  6. ↑ Lehmann JS (2009). "Biochar for environmental management: An introduction. In Biochar for Environmental Management, Science and Technology" (PDF). Archived (PDF) from the original on 2021-07-06.
  7. ↑ "Activated Charcoal". Discover Magazine. Archived from the original on 2022-01-18. Retrieved 2022-01-18.
  8. ↑ Oliveira G, Calisto V, Santos SM, Otero M, Esteves VI (2018-08-01). "Paper pulp-based adsorbents for the removal of pharmaceuticals from wastewater: A novel approach towards diversification". The Science of the Total Environment. 631–632: 1018–1028. Bibcode:2018ScTEn.631.1018O. doi:10.1016/j.scitotenv.2018.03.072. hdl: 10773/25013 . ISSN   1879-1026. PMID   29727928. S2CID   19141293.
  9. ↑ Carroll GT, Kirschman DL (2022). "A Peripherally Located Air Recirculation Device Containing an Activated Carbon Filter Reduces VOC Levels in a Simulated Operating Room". ACS Omega. 7 (50): 46640–46645. doi:10.1021/acsomega.2c05570. ISSN   2470-1343. PMC   9774396 . PMID   36570243.
  10. ↑ Cataldi P, Lamanna L, Bertei C, Arena F, Rossi P, Liu M, Di Fonzo F, Papageorgiou DG, Luzio A, Caironi M (26 February 2022). "An Electrically Conductive Oleogel Paste for Edible Electronics". Advanced Functional Materials. 32 (23): 2113417. arXiv: 2205.00764 . doi: 10.1002/adfm.202113417 . S2CID   247149736.
  11. ↑ "Charcoal, Activated". The American Society of Health-System Pharmacists. Archived from the original on 21 December 2016. Retrieved 23 April 2014.
  12. ↑ IBM Micromedex (1 February 2019). "Charcoal, Activated (Oral Route)". Mayo Clinic. Retrieved 15 February 2019.
  13. ↑ World Health Organization (2023). The selection and use of essential medicines 2023: web annex A: World Health Organization model list of essential medicines: 23rd list (2023). Geneva: World Health Organization. hdl: 10665/371090 . WHO/MHP/HPS/EML/2023.02.
  14. ↑ Elliott CG, Colby TV, Kelly TM, Hicks HG (1989). "Charcoal lung. Bronchiolitis obliterans after aspiration of activated charcoal". Chest. 96 (3): 672–674. doi:10.1378/chest.96.3.672. PMID   2766830.
  15. ↑ Exner T, Michalopoulos N, Pearce J, Xavier R, Ahuja M (March 2018). "Simple method for removing DOACs from plasma samples". Thrombosis Research. 163: 117–122. doi:10.1016/j.thromres.2018.01.047. PMID   29407622.
  16. ↑ Exner T, Ahuja M, Ellwood L (24 April 2019). "Effect of an activated charcoal product (DOAC Stop) intended for extracting DOACs on various other APTT-prolonging anticoagulants". Clinical Chemistry and Laboratory Medicine. 57 (5): 690–696. doi:10.1515/cclm-2018-0967. PMID   30427777. S2CID   53426892.
  17. ↑ Gibert O, Lefèvre B, Fernández M, Bernat X, Paraira M, Calderer M, Martínez-Lladó X (2013-03-01). "Characterising biofilm development on granular activated carbon used for drinking water production". Water Research. 47 (3): 1101–1110. Bibcode:2013WatRe..47.1101G. doi:10.1016/j.watres.2012.11.026. ISSN   0043-1354. PMID   23245544.
  18. ↑ Takman M, Svahn O, Paul C, Cimbritz M, Blomqvist S, Struckmann Poulsen J, Lund Nielsen J, Davidsson Å (2023-10-16). "Assessing the potential of a membrane bioreactor and granular activated carbon process for wastewater reuse – A full-scale WWTP operated over one year in Scania, Sweden". Science of the Total Environment. 895: 165185. Bibcode:2023ScTEn.89565185T. doi: 10.1016/j.scitotenv.2023.165185 . ISSN   0048-9697. PMID   37385512.
  19. 1 2 "Activated Carbon | SRU, Solvent Recovery Unit | SRP, Solvent Recovery Plant | SRS, Solvent Recovery System | VOC Emission Control Systems". DEC (Dynamic Environmental Corporation). Archived from the original on 2023-12-27. Retrieved 2023-12-27.
  20. ↑ EPA Alumni Association: Senior EPA officials discuss early implementation of the Safe Drinking Water Act of 1974, Video Archived 2016-11-05 at the Wayback Machine , Transcript Archived 2016-11-05 at the Wayback Machine (see pages 15-16).
  21. ↑ Melliti A, Touihri M, Kofroňová J, Hannachi C, Sellaoui L, Bonilla-Petriciolet A, Vurm R (2024-05-01). "Sustainable removal of caffeine and acetaminophen from water using biomass waste-derived activated carbon: Synthesis, characterization, and modelling". Chemosphere. 355: 141787. doi:10.1016/j.chemosphere.2024.141787. ISSN   0045-6535. Archived from the original on 2024-04-04. Retrieved 2024-08-28.
  22. ↑ Activated Charcoal Review Sheet [ permanent dead link ], USDA Organic Materials Review, February 2002.
  23. ↑ Activated Carbon Petition [ permanent dead link ], USDA Organic Materials Review petition, Canadaigua Wine, May 2002.
  24. ↑ Activated carbon for purification of alcohol and some useful distillation trips (PDF). Gert Strand, Malmoe, Sweden. 2001. pp. 1–28.
  25. ↑ Romanos J, Abou Dargham S, Roukos R, Pfeifer P (2018). "Local Pressure of Supercritical Adsorbed Hydrogen in Nanopores". Materials. 11 (11): 2235. Bibcode:2018Mate...11.2235R. doi: 10.3390/ma11112235 . ISSN   1996-1944. PMC   6266406 . PMID   30423817.
  26. ↑ Romanos J, Rash T, Abou Dargham S, Prosniewski M, Barakat F, Pfeifer P (2017-12-21). "Cycling and Regeneration of Adsorbed Natural Gas in Microporous Materials". Energy & Fuels. 31 (12): 14332–14337. doi:10.1021/acs.energyfuels.7b03119. ISSN   0887-0624.
  27. ↑ Kårelid V, Larsson G, Björlenius B (May 2017). "Pilot-scale removal of pharmaceuticals in municipal wastewater: Comparison of granular and powdered activated carbon treatment at three wastewater treatment plants". Journal of Environmental Management. 193: 491–502. Bibcode:2017JEnvM.193..491K. doi:10.1016/j.jenvman.2017.02.042. PMID   28256364.
  28. ↑ Okolie JA, Savage S, Ogbaga CC, Gunes B (June 2022). "Assessing the potential of machine learning methods to study the removal of pharmaceuticals from wastewater using biochar or activated carbon". Total Environment Research Themes. 1–2: 100001. Bibcode:2022TERT....100001O. doi: 10.1016/j.totert.2022.100001 .
  29. ↑ Bourke M (1989). "Activated Carbon for Mercury Removal". Archived from the original on 2013-08-03. Retrieved 2013-08-27.
  30. 1 2 Mohan D, Gupta V, Srivastava S, Chander S (2001). "Kinetics of mercury adsorption from waste water using activated carbon derived from fertilizer waste". Colloids and Surfaces A: Physicochemical and Engineering Aspects. 177 (2–3): 169–181. doi:10.1016/S0927-7757(00)00669-5. Archived from the original on 2023-04-23. Retrieved 2022-03-22.
  31. ↑ Tim Flannery, Here On Earth: A New Beginning, Allen Lane (2011), p. 186.
  32. ↑ "It's in smoothies, toothpaste and pizza – is charcoal the new black?". the Guardian. 28 June 2017. Archived from the original on 1 July 2017. Retrieved 11 October 2021.
  33. ↑ Allan MC (24 April 2017). "Dangerous Drinks and How To Spot Them - Imbibe Magazine". Imbibe Magazine. Archived from the original on 20 October 2021. Retrieved 11 October 2021.
  34. ↑ McCarthy A (7 June 2017). "Should You Be Eating Activated Charcoal?". Eater. Archived from the original on 28 October 2021. Retrieved 11 October 2021.
  35. 1 2 Goel R, Bitzer ZT, Reilly SM, Bhangu G, Trushin N, Elias RJ, Foulds J, Muscat J, Richie Jr JP (2018). "Effect of Charcoal in Cigarette Filters on Free Radicals in Mainstream Smoke". Chemical Research in Toxicology. 31 (8): 745–751. doi:10.1021/acs.chemrestox.8b00092. PMC   6471497 . PMID   29979036.
  36. ↑ H. Marsh and F. Rodríguez-Reinoso, Activated carbon, Elsevier (2006), p. 186.
  37. ↑ Romanos J, Sweany S, Rash T, Firlej L, Kuchta B, Idrobo J, Pfeifer P (2014). "Engineered Porous Carbon for High Volumetric Methane Storage". Adsorption Science & Technology. 32 (8): 681–691. doi: 10.1260/0263-6174.32.8.681 . ISSN   0263-6174.
  38. ↑ Allen CS, Ghamouss F, Boujibar O, Harris PJF (2022). "Aberration-corrected transmission electron microscopy of a non-graphitizing carbon". Proc. R. Soc. A. 578 (2258): 20210580. Bibcode:2022RSPSA.47810580A. doi:10.1098/rspa.2021.0580. S2CID   246828226. Archived from the original on 2023-10-04. Retrieved 2022-11-09.
  39. ↑ J. Romanos, et al. (2012). "Nanospace engineering of KOH activated carbon". Nanotechnology. 23 (1): 015401. Bibcode:2012Nanot..23a5401R. doi:10.1088/0957-4484/23/1/015401. PMID   22156024. S2CID   20023779.
  40. ↑ Tripathi AK, Murugavel S, Singh RK (2021). "Dead Ashoka (Saraca asoca) leaves–derived porous activated carbons and flexible iongel polymer electrolyte for high-energy-density electric double-layer capacitors". Materials Today Sustainability. 11–12: 100062. Bibcode:2021MTSus..1100062T. doi:10.1016/j.mtsust.2021.100062. S2CID   233931759.
  41. 1 2 Nwankwo IH (2018). "Production And Characterization Of Activated Carbon From Animal Bone" (PDF). American Journal of Engineering Research (AJER). 7 (7): 335–341. Archived (PDF) from the original on 2022-04-02. Retrieved 2022-03-22.
  42. ↑ "Premium activated carbon range boosts Haycarb earnings". echolon.lk. Echelon Media. 6 July 2021. Archived from the original on 4 October 2023. Retrieved 5 July 2022.
  43. ↑ The separation of the most volatile gases from air without liquefaction
  44. ↑ "SentryAir". SentryAir. Archived from the original on 2024-07-01. Retrieved 2014-03-13.
  45. ↑ Mianowski A, Owczarek M, Marecka A (24 May 2007). "Surface Area of Activated Carbon Determined by the Iodine Adsorption Number". Energy Sources, Part A: Recovery, Utilization, and Environmental Effects. 29 (9): 839–850. doi:10.1080/00908310500430901. S2CID   95043547.
  46. ↑ Spencer W, Ibana D, Singh P, Nikoloski AN (January 2024). "Effect of Surface Area, Particle Size and Acid Washing on the Quality of Activated Carbon Derived from Lower Rank Coal by KOH Activation". Sustainability. 16 (14): 5876. doi: 10.3390/su16145876 . ISSN   2071-1050.
  47. ↑ Divens J. "Adsorption of methylene blue onto activated carbon". www.nepjol.info. Journal of the Institute of Engineering, 2016, 12(1)169-174 TUTA/IOE/PCU Printed in Nepal. Archived from the original on July 1, 2024. Retrieved March 10, 2022.
  48. ↑ "Dechlorination of water through activated carbon technology | Desotec". www.desotec.com. Archived from the original on 2024-07-01. Retrieved 2022-02-11.
  49. ↑ TIGG Corporation. Granular activated carbon selection Archived 2012-09-12 at the Wayback Machine . Published 2012-05-8, retrieved 2012-09-21.
  50. 1 2 Philippe Serp, José Luis Figueiredo, Carbon Materials for Catalysis, Wiley, – 2009, – 550 p.
  51. ↑ Gómez-Serrano V, Piriz-Almeida FN, Durán-Valle CJ, Pastor-Villegas J (1999). "Formation of oxygen structures by air activation. A study by FT-IR spectroscopy". Carbon. 37 (10): 1517–1528. Bibcode:1999Carbo..37.1517G. doi:10.1016/S0008-6223(99)00025-1.
  52. ↑ Machnikowski J., Kaczmarska H., Gerus-Piasecka I., Diez M.A., Alvarez R., Garcia R. (2002). "Structural modification of coal-tar pitch fractions during mild oxidation – relevance to carbonization behavior". Carbon. 40 (11): 1937–1947. Bibcode:2002Carbo..40.1937M. doi:10.1016/s0008-6223(02)00029-5.
  53. ↑ Petrov N., Budinova T., Razvigorova M., Ekinci E., Yardim F., Minkova V. (2000). "Preparation and characterization of carbon adsorbents from furfural". Carbon. 38 (15): 2069–2075. Bibcode:2000Carbo..38.2069P. doi:10.1016/s0008-6223(00)00063-4.
  54. ↑ Garcia A.B., Martinez-Alonso A., Leon C. A., Tascon J.M.D. (1998). "Modification of the surface properties of an activated carbon by oxygen plasma treatment". Fuel. 77 (1): 613–624. Bibcode:1998Fuel...77..613G. doi:10.1016/S0016-2361(97)00111-7.
  55. 1 2 Saha B., Tai M.H., Streat M. (2001). "Study of activated carbon after oxidation and subsequent treatment characterization". Process Safety and Environmental Protection. 79 (4): 211–217. Bibcode:2001PSEP...79..211S. doi:10.1205/095758201750362253.
  56. ↑ Polovina M., Babic B., Kaluderovic B., Dekanski A. (1997). "Surface characterization of oxidized activated carbon cloth". Carbon. 35 (8): 1047–1052. Bibcode:1997Carbo..35.1047P. doi:10.1016/s0008-6223(97)00057-2.
  57. ↑ Fanning P.E., Vannice M.A. (1993). "A DRIFTS study of the formation of surface groups on carbon by oxidation". Carbon. 31 (5): 721–730. Bibcode:1993Carbo..31..721F. doi:10.1016/0008-6223(93)90009-y.
  58. ↑ Youssef A.M., Abdelbary E.M., Samra S.E., Dowidar A.M. (1991). "Surface-properties of carbons obtained from polyvinyl-chloride". Ind. J. Chem. A. 30 (10): 839–843.
  59. ↑ Arriagada R., Garcia R., Molina-Sabio M., Rodriguez-Reinoso F. (1997). "Effect of steam activation on the porosity and chemical nature of activated carbons from Eucalyptus globulus and peach stones". Microporous Mat. 8 (3–4): 123–130. doi:10.1016/s0927-6513(96)00078-8.
  60. ↑ Molina-Sabio M., Gonzalez M.T., Rodriguez-Reinoso F., Sepulveda-Escribano A. (1996). "Effect of steam and carbon dioxide activation in the micropore size distribution of activated carbon". Carbon. 34 (4): 505–509. Bibcode:1996Carbo..34..505M. doi:10.1016/0008-6223(96)00006-1.
  61. ↑ Bradley RH, Sutherland I, Sheng E (1996). "Carbon surface: Area, porosity, chemistry, and energy". Journal of Colloid and Interface Science. 179 (2): 561–569. Bibcode:1996JCIS..179..561B. doi:10.1006/jcis.1996.0250.
  62. ↑ Sutherland I., Sheng E., Braley R.H., Freakley P.K. (1996). "Effects of ozone oxidation on carbon black surfaces". J. Mater. Sci. 31 (21): 5651–5655. Bibcode:1996JMatS..31.5651S. doi:10.1007/bf01160810. S2CID   97055178.
  63. ↑ Rivera-Utrilla J, Sanchez-Polo M (2002). "The role of dispersive and electrostatic interactions in the aqueous phase adsorption of naphthalenesulphonic acids on ozone-treated activated carbons". Carbon. 40 (14): 2685–2691. Bibcode:2002Carbo..40.2685R. doi:10.1016/s0008-6223(02)00182-3.
  64. 1 2 Valdés H, Sánchez-Polo M, Rivera-Utrilla J, Zaror CA (2002). "Effect of Ozone Treatment on Surface Properties of Activated Carbon". Langmuir. 18 (6): 2111–2116. doi:10.1021/la010920a. hdl: 10533/173367 .
  65. ↑ Pradhan B.K., Sandle N.K. (1999). "Effect of different oxidizing agent treatments on the surface properties of activated carbons". Carbon. 37 (8): 1323–1332. Bibcode:1999Carbo..37.1323P. doi:10.1016/s0008-6223(98)00328-5.
  66. ↑ Acedo-Ramos M., Gomez-Serrano V., Valenzuella-Calahorro C., Lopez-Peinado A.J. (1993). "Oxydation of activated carbon in liquid phase. Study by FT-IR". Spectroscopy Letters. 26 (6): 1117–1137. Bibcode:1993SpecL..26.1117A. doi:10.1080/00387019308011598.
  67. ↑ Gomez-Serrano V., Acedo-Ramos M., Lopez-Peinado A.J., Valenzuela-Calahorro C. (1991). "Stability towards heating and outgassing of activated carbon oxidized in the liquid-phase". Thermochimica Acta. 176: 129–140. Bibcode:1991TcAc..176..129G. doi:10.1016/0040-6031(91)80268-n.
  68. ↑ Stőhr B., Boehm H.P., Schlőgl R. (1991). "Enhancement of the catalytic activity of activated carbons in oxidation reactions by termal treatment with ammonia or hydrogen cyanide and observation of a superoxide species as a possible intermediate". Carbon. 29 (6): 707–720. Bibcode:1991Carbo..29..707S. doi:10.1016/0008-6223(91)90006-5.
  69. ↑ Biniak S., Szymański G., Siedlewski J., Światkowski A. (1997). "The characterizaíion of activated carbons with oxygen and nitrogen surface groups". Carbon. 35 (12): 1799–1810. Bibcode:1997Carbo..35.1799B. doi:10.1016/s0008-6223(97)00096-1.
  70. ↑ Boudou J.P., Chehimi M., Broniek E., Siemieniewska T., Bimer J. (2003). "Adsorption of H2S or SO2 on an activated carbon cloth modified by ammonia treatment" (PDF). Carbon. 41 (10): 1999–2007. doi:10.1016/s0008-6223(03)00210-0. S2CID   53137987. Archived (PDF) from the original on 2019-04-28. Retrieved 2019-07-06.
  71. ↑ Sano H., Ogawa H. (1975). "Preparation and application nitrogen containing active carbons". Osaka Kogyo Gijutsu Shirenjo. 26 (5): 2084–2086.
  72. ↑ Radkevich VZ, Senko TL, Wilson K, Grishenko LM, Zaderko AN, Diyuk VY (2008). "The influence of surface functionalization of activated carbon on palladium dispersion and catalytic activity in hydrogen oxidation". Applied Catalysis A: General. 335 (2): 241–251. doi:10.1016/j.apcata.2007.11.029.
  73. ↑ Evans MJ, Halliop E, Liang S, MacDonald JA (1998). "The effect of chlorination on surface properties of activated carbon". Carbon. 36 (11): 1677–1682. Bibcode:1998Carbo..36.1677E. doi:10.1016/S0008-6223(98)00165-1.
  74. ↑ Papirer EN, Lacroix R, Donnet JB, Nansé GR, Fioux P (1995). "XPS study of the halogenation of carbon black—Part 2. Chlorination". Carbon. 33 (1): 63–72. Bibcode:1995Carbo..33...63P. doi:10.1016/0008-6223(94)00111-C.
  75. ↑ Papirer E, Lacroix R, Donnet JB, Nanse G, Fioux P (1994). "XPS Study of the halogenation of carbon black-part 1. Bromination". Carbon. 32 (7): 1341–1358. Bibcode:1994Carbo..32.1341P. doi:10.1016/0008-6223(94)90121-X.
  76. ↑ Nansé G, Papirer E, Fioux P, Moguet F, Tressaud A (1997). "Fluorination of carbon blacks: An X-ray photoelectron spectroscopy study: III. Fluorination of different carbon blacks with gaseous fluorine at temperatures below 100 °C influence of the morphology, structure and physico-chemical characteristics of the carbon black on the fluorine fixation". Carbon. 35 (4): 515–528. Bibcode:1997Carbo..35..515N. doi:10.1016/S0008-6223(97)00003-1.
  77. ↑ US 8648217,"Modification of carbonaceous materials",issued 2008-08-04
  78. ↑ US 10000382,"Method for carbon materials surface modification by the fluorocarbons and derivatives",issued 2015-11-03
  79. ↑ Zaderko AN, Shvets RY, Grygorchak II, Afonin S, Diyuk VE, Mariychuk RT, Boldyrieva OY, Kaňuchová M, Lisnyak VV (2018-11-20). "Fluoroalkylated Nanoporous Carbons: Testing as a Supercapacitor Electrode". Applied Surface Science. 470: 882–892. doi:10.1016/j.apsusc.2018.11.141. ISSN   0169-4332. S2CID   105746451.
  80. ↑ Aldana-Pérez A, Lartundo-Rojas L, Gómez R, Niño-Gómez ME (2012). "Sulfonic groups anchored on mesoporous carbon Starbons-300 and its use for the esterification of oleic acid". Fuel. 100: 128–138. Bibcode:2012Fuel..100..128A. doi:10.1016/j.fuel.2012.02.025.
  81. ↑ Diyuk VE, Zaderko AN, Grishchenko LM, Yatsymyrskiy AV, Lisnyak VV (2012). "Efficient carbon-based acid catalysts for the propan-2-ol dehydration". Catalysis Communications. 27: 33–37. doi:10.1016/j.catcom.2012.06.018.
  82. ↑ "WO18194533 METHOD FOR CHEMICAL MODIFICATION OF FLUORINATED CARBONS WITH SULFUR-CONTAINING SUBSTANCE". patentscope.wipo.int. Archived from the original on 2018-11-24. Retrieved 2018-11-24.
  83. ↑ Budarin VL, Clark JH, Tavener SJ, Wilson K (2004). "Chemical reactions of double bonds in activated carbon: Microwave and bromination methods". Chemical Communications (23): 2736–7. doi:10.1039/B411222A. PMID   15568092.
  84. ↑ Bagreev A, Rhaman, H., Bandosz, T. J (2001). "Thermal regeneration of a spent activated carbon adsorbent previously used as hydrogen sulfide adsorbent". Carbon. 39 (9): 1319–1326. doi:10.1016/S0008-6223(00)00266-9.
  85. 1 2 Sabio E, Gonzalez, E., Gonzalez, J. F., Gonzalez-Garcia, C. M., Ramiro, A., Ganan, J (2004). "Thermal regeneration of activated carbon saturated with p-nitrophenol". Carbon. 42 (11): 2285–2293. Bibcode:2004Carbo..42.2285S. doi:10.1016/j.carbon.2004.05.007.
  86. ↑ Miguel GS, Lambert SD, Graham NJ (2001). "The regeneration of field spent granular activated carbons". Water Research. 35 (11): 2740–2748. Bibcode:2001WatRe..35.2740S. doi:10.1016/S0043-1354(00)00549-2. PMID   11456174.
  87. ↑ Alvarez PM, Beltrán FJ, Gómez-Serrano V, Jaramillo J, Rodríguez EM (2004). "Comparison between thermal and ozone regenerations of spent activated carbon exhausted with phenol". Water Research. 38 (8): 2155–2165. Bibcode:2004WatRe..38.2155A. doi:10.1016/j.watres.2004.01.030. PMID   15087197.
  88. ↑ "activated carbon | steam | regeneration". DEC (Dynamic Environmental Corporation). Archived from the original on 2023-12-27. Retrieved 2023-12-27.
  89. ↑ "activated carbon | inert gas | nitrogen | regeneration". DEC (Dynamic Environmental Corporation). Archived from the original on 2023-12-27. Retrieved 2023-12-27.
  90. ↑ "activated carbon | vacuum | regeneration". DEC (Dynamic Environmental Corporation). Archived from the original on 2023-12-27. Retrieved 2023-12-27.
  91. ↑ Cherbański R (2018). "Regeneration of granular activated carbon loaded with toluene – Comparison of microwave and conductive heating at the same active powers". Chemical Engineering and Processing - Process Intensification. 123 (January 2018): 148–157. Bibcode:2018CEPPI.123..148C. doi:10.1016/j.cep.2017.11.008.
  92. ↑ Martin RJ, Wj, N (1997). "The repeated exhaustion and chemical regeneration of activated carbon". Water Research. 21 (8): 961–965. doi:10.1016/S0043-1354(87)80014-3.
  93. ↑ Aizpuru A, Malhautier L, Roux JC, Fanlo JL (2003). "Biofiltration of a mixture of volatile organic compounds on granular activated carbon". Biotechnology and Bioengineering. 83 (4): 479–488. doi:10.1002/bit.10691. PMID   12800142. S2CID   9980413.
  94. ↑ Narbaitz RM, Karimi-Jashni A (2009). "Electrochemical regeneration of granular activated carbons loaded with phenol and natural organic matter". Environmental Technology. 30 (1): 27–36. Bibcode:2009EnvTe..30...27N. doi: 10.1080/09593330802422803 . PMID   19213463.
  95. ↑ Lim JL, Okada M (2005). "Regeneration of granular activated carbon using ultrasound". Ultrasonic-Sono-Chemistry. 12 (4): 277–285. Bibcode:2005UltS...12..277L. doi:10.1016/j.ultsonch.2004.02.003. PMID   15501710.
  96. ↑ Shende RV, Mahajani VV (2002). "Wet oxidative regeneration of activated carbon loaded with reactive dye". Waste Management. 22 (1): 73–83. Bibcode:2002WaMan..22...73S. doi:10.1016/S0956-053X(01)00022-8. PMID   11942707.
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