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Activated carbon

Activated carbon is a form of carbon processed to increase its surface area for adsorption. It has micro-pores that adsorb substances via Van der Waals forces. Activated carbon is made from materials like wood and coal. It has a wide range of applications including water treatment, food processing, and gas storage. Carbon nanotubes are also being investigated as catalyst supports due to their strength, conductivity, and adsorption properties.

Engineering◦

Activated carbon

1.
Activated carbon isa form of carbon processed to be riddled with small, low-volume pores that increase the surface area available for adsorption or chemical reactions. • The porosity within activated carbon imparts their characteristics of adsorption. • Activated carbons made from hardwoods, coconut shells, fruit stones, coals, peat, petroleum coke, and synthetic macromolecular systems. • All activated carbons are assemblies of defective graphene layers. SEM images of AC. 1Activated Carbon
2.
Properties  The carbonstructure is resistant to acidic or basic media.  The structure is stable at high temperature (even above 1000K), in the absent of air.  A gram of activated carbon can have a surface area in excess of 500 𝑚2, with 1500 𝑚2 being readily achievable.  Activated carbon binds materials by Van der Waals force or London dispersion force physically.  Activated carbon adsorbs iodine very well.  Carbon monoxide is not well adsorbed by activated carbon.  Cost of the carbon supports is usually lower than conventional supports such as alumina and silica. 2
3.
Applications The applications canbe classified into two categories: gas and liquid phase. 3
4.
Applications (Liquid Phase): Food and Beverages : Bear and wine Chili and spices Sugar, starch, sweeteners and maple syrup Caffeine Vegetable Oils 4
5.
Applications (Liquid Phase) Water treatment: Treatment of both industrial and municipal waste water By using activated carbon as a filter in the filtration industry.  Chemical and Pharmaceutical Other Usage: Use it as filters for the dialysis of poisons and drugs Felts for wounds 5
6.
Other Applications (LiquidPhase):  Industrial dry cleaning  Cleaning of electroplating solutions  Mineral recovery (Gold recovery) 6
7.
Applications (Gas Phase): Gas purification: To produce pure gases in the chemical industry and reduce pollutant gases to a very low concentrations in the single stage, in protection against poison gases, activated carbon is being used.  Separation of Gas Mixture (SGM) Are designed to separate gases in a mixture by sieving.  Methane storage: Using natural gas hydrate (NGH) as the adsorbate in AC.  Solvent recovery: Recover the solvent vapors from air streams to adsorb by AC. 7
8.
Carbon Nanotubes  Carbonnanotubes (CNTs) take the form of cylindrical carbon molecules and their novel properties make them potentially useful in a wide variety of applications.  They exhibit extraordinary strength and unique electrical properties, and are efficient conductors of heat. 8 Multi-walled nanotube Singled-walled nanotube
9.
Why CNT maybe suitable to be used as a catalyst support?  Before answering this question, it is important to analyze the CNT properties. 1. Electronic properties: Very high current carrying capacity. 2. Adsorption properties: They present specific adsorption properties compared to AC. 3. Thermal properties: All nanotubes are expected to be magnificent thermal conductors along the tube. And they have thermal stability under reaction condition. 9
10.
Continued: 4. Hardness: Greater thandiamond, which is considered the hardest material. 5. Strength: Carbon nanotubes are the strongest, flexible materials yet discovered in terms of tensile strength and elastic modulus respectively.  To conclude, it appears that the combination of these properties makes CNT attractive and competitive catalyst supports by comparison with activated carbons.  They could replace activated carbons in liquid-phase reactions as long as the properties of activated carbons of AC are still difficult to control and their microporosity has often slow down catalyst development. 10
11.
Advantages of CNT: 1.Extremely small and lightweight. 2.They have plentiful resources to produce them, and many can be made with only a small amount of material. 3. Are resistant to temperature changes, meaning they function almost just as well in extreme cold as they do in extreme heat. 4. The high purity of the material can avoid self-poisoning. 5. The mesoporous nature of these supports can be of interest for liquid- phase reaction, thus limiting the mass transfer. 11
12.
Disadvantages of CNT 1.Extremely small, so are difficult to work with. 2. Currently, the process to produce the nanotubes are relatively expensive. 3. Would be expensive to implement this new technology in and replace the older technology in all the places that we could. 4. The full potential of nanotubes for applications will not be realized until the growth of nanotubes can be further optimized and controlled. 5. There are many challenges exist in both the micromechanical characterization of nanotubes, and the modeling of the elastic and fracture behavior at the nanoscale. 12
13.
QUESTIONS? 13
14.
References  Harry Marsh,F. R.-R. (2006). Activated carbon, Elsevier.  Serp, P., et al. (2003). "Carbon nanotubes and nanofibers in catalysis." Applied Catalysis A: General 253(2): 337-358.  Scida, K., et al. (2011). "Recent applications of carbon-based nanomaterials in analytical chemistry: Critical review." Analytica Chimica Acta 691(1–2): 6-17.  Zeng, Q., et al. (2006). "Synthesis and Application of Carbon Nanotubes." Journal of Natural Gas Chemistry 15(3): 235-246.  Grobert, N. (2007). "Carbon nanotubes – becoming clean." Materials Today 10(1–2): 28-35.  Dai, H. (2002). "Carbon nanotubes: opportunities and challenges." Surface Science 500(1–3): 218-241.  Popov, V. N. (2004). "Carbon nanotubes: properties and application." Materials Science and Engineering: R: Reports 43(3): 61-102. 14
15.
Adsorption  The adsorptionprocess is when an adsorbate enters into the porosity of the adsorbate.  It is primarily a physical process. ( substances do not make a chemical reactions with the adsorbent).  Van der Waals and London dispersion intermolecular forces are important in the adsorption phenomenon. 15
16.
Classifications of ActivatedCarbons  Some broad classification is made for general purpose based on their physical characteristics.  Powdered activated carbon (PAC)  Granular activated carbon (GAC)  Extruded activated carbon (EAC)  Bead activated carbon (BAC)  Impregnated carbon  Polymer coated carbon  Other Uncategorized 16
17.
Nanotubes classification: 1. single-wallednanotubes (SWNTs) 2. multi-walled nanotubes (MWNTs) SWNT (graphical representation) MWNT (graphical representation) 17

Editor's Notes

#3 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-needs citation), 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. It is equivalent to surface area of carbon between 900 m²/g and 1100 m²/g. It is the standard measure for liquid phase applications. (weki pedia)
#4 Activated carbon has been historically used for removal of odor, removal of color pigments and various catalytic functions. However, applications of activated carbon have increased significantly in the recent years with the advancement of activated carbon process capability.
#5 For food and beverage : AC is used in food and beverage industries to remove color or odor and unacceptable taste from products. Sugar and sweetener industries: need decolorization agents for the production of white sugar
#6 Drinking water availability, to improve taste , smell and color including removal of chlorinated compound. There are 2 predominant types of carbon filters used in the filtration industry: powdered block filters and granular activated filters The electroplating industries require purification of waste waters containing Pd, Cr and etc. CHEMICAL: Activated carbon is used to reduce impurities such as color contents or small volume of by-products in solutions to improve the quality. Also it is used to treat poisonings and overdoes following oral ingestion. AC is used to extract pharmaceuticals in processes involving fermentation, Antibiotics, vitamins and steroids are adsorbed into the AC and recovered by solvent extraction followed by distillation.
#8 For gas phase applications, Carbon adsorbents are used in the form of hard granules, hard pellets, fibers, cloth and monoliths because these avoid an excessive pressure drop when the gas to be treated passes through the adsorbent bed. They usually have well-developed micro porosity to provide a high adsorptive capacity and selectivity for gasses and organic vapors. Gas purification: The actual process, using AC, include: H2S removal from sour natural gas Removal of sulfur dioxide and nitrous oxide from the flue gas Gasoline vapor recovery in gasoline loading facilities Chlorofluorocarbon recovery in foam blowing Removal of mercury vapor from air, hydrogen and other gas stream Cigarette filters Automotive evaporation control systems Landfill gas which contains about 50% CO2 as an impurity Natural gas contains up to 12 % CO2 Oil recovery: effluent gas contains variable CO2/CH4 There are three main applications where this process of interest: Treatment of landfill gas Purification of natural gas Oil recovery
#9 Under high pressure, nanotubes can merge together, trading some sp2 bonds for sp3 bonds, giving great possibility for producing strong, unlimited-length wires through high-pressure nanotube linking. Nanotubes are composed entirely of sp2 bonds, similar to those of graphite. This bonding structure, stronger than the sp3 bonds found in diamond, provides the molecules with their unique strength.
#10 Adsorption properties: The curvature of the graphene sheets can results in a lower heat of adsorption and make a tube causes a rehydbrization of carbon orbital leading to modification of the  density Helicity: projection of angular momentum onto direction of momentum. ( Measurements show that a SWNT has a room-temperature thermal conductivity more than copper.)
#11 4. hardness: because of Sp2 electrons orbital. 5. Strength : This strength results from the covalent sp2 bonds formed between the individual carbon atoms (which is stronger than the sp3 bonds found in Diamond & Alkenes). Their high external surface and their mesoporosity should allow significant decreases on mass transfer limitation when it is compared to AC.
#13 it's so small, so it could be inhaled pretty easily. As not all properties are currently known, they might be hazardous for our lungs. Significant study has been carried out to tackle these issues. Nevertheless. many challenges exist in both the micromechanical characterization of nanotubes and the modeling of the elastic and fracture behavior at the nanoscale, including (a) complete lack of micromechanical characterization techniques for direct property measurement,(b) tremendous limitations on specimen size. (c) uncertainty in data obtained from indirect measurements, (d) inadequacy in test specimen preparation techniques and lack of control in nanotube alignment and distribution. and (e) there is a seemingly formidable task of controlling the chirality of SWNTs during growth.
#16 The adsorbent is the solid porous material, in this case is carbon. The adsorbate is gas or vapor, or solute from solution, which is adsorbed with the adsorbent. The adsorptive process is when an adsorbate enters into the porosity of the adsorbent.
#18 • A single-walled carbon nanotube (SWNT) may be thought of as a single thick sheet of graphite (called graphene) rolled into a seamless cylinder. • Most single-walled nanotubes (SWNT) have a diameter of 0.4 and 2.5 nm, with a tube length that can be many several mm. • Single-walled nanotubes are an important variety of carbon nanotube because they exhibit electric properties that are not shared by the multi-walled carbon nanotube (MWNT) variants. Multi-walled nanotubes (MWNT) consist of multiple rolled layers (concentric tubes) of graphite. There are two models which can be used to describe the structures of multi-walled nanotubes. In the Russian Doll model, sheets of graphite are arranged in concentric cylinders. In the Parchment model, a single sheet of graphite is rolled in around itself, resembling a scroll of parchment or a rolled newspaper.(The Russian Doll structure is observed more commonly). The telescopic motion ability of inner shells and their unique mechanical properties will permit the use of multi-walled nanotubes as main movable arms in coming Nano mechanical devices.

Activated carbon

1.
Activated carbon isa form of carbon processed to be riddled with small, low-volume pores that increase the surface area available for adsorption or chemical reactions. • The porosity within activated carbon imparts their characteristics of adsorption. • Activated carbons made from hardwoods, coconut shells, fruit stones, coals, peat, petroleum coke, and synthetic macromolecular systems. • All activated carbons are assemblies of defective graphene layers. SEM images of AC. 1Activated Carbon
2.
Properties  The carbonstructure is resistant to acidic or basic media.  The structure is stable at high temperature (even above 1000K), in the absent of air.  A gram of activated carbon can have a surface area in excess of 500 𝑚2, with 1500 𝑚2 being readily achievable.  Activated carbon binds materials by Van der Waals force or London dispersion force physically.  Activated carbon adsorbs iodine very well.  Carbon monoxide is not well adsorbed by activated carbon.  Cost of the carbon supports is usually lower than conventional supports such as alumina and silica. 2
3.
Applications The applications canbe classified into two categories: gas and liquid phase. 3
4.
Applications (Liquid Phase): Food and Beverages : Bear and wine Chili and spices Sugar, starch, sweeteners and maple syrup Caffeine Vegetable Oils 4
5.
Applications (Liquid Phase) Water treatment: Treatment of both industrial and municipal waste water By using activated carbon as a filter in the filtration industry.  Chemical and Pharmaceutical Other Usage: Use it as filters for the dialysis of poisons and drugs Felts for wounds 5
6.
Other Applications (LiquidPhase):  Industrial dry cleaning  Cleaning of electroplating solutions  Mineral recovery (Gold recovery) 6
7.
Applications (Gas Phase): Gas purification: To produce pure gases in the chemical industry and reduce pollutant gases to a very low concentrations in the single stage, in protection against poison gases, activated carbon is being used.  Separation of Gas Mixture (SGM) Are designed to separate gases in a mixture by sieving.  Methane storage: Using natural gas hydrate (NGH) as the adsorbate in AC.  Solvent recovery: Recover the solvent vapors from air streams to adsorb by AC. 7
8.
Carbon Nanotubes  Carbonnanotubes (CNTs) take the form of cylindrical carbon molecules and their novel properties make them potentially useful in a wide variety of applications.  They exhibit extraordinary strength and unique electrical properties, and are efficient conductors of heat. 8 Multi-walled nanotube Singled-walled nanotube
9.
Why CNT maybe suitable to be used as a catalyst support?  Before answering this question, it is important to analyze the CNT properties. 1. Electronic properties: Very high current carrying capacity. 2. Adsorption properties: They present specific adsorption properties compared to AC. 3. Thermal properties: All nanotubes are expected to be magnificent thermal conductors along the tube. And they have thermal stability under reaction condition. 9
10.
Continued: 4. Hardness: Greater thandiamond, which is considered the hardest material. 5. Strength: Carbon nanotubes are the strongest, flexible materials yet discovered in terms of tensile strength and elastic modulus respectively.  To conclude, it appears that the combination of these properties makes CNT attractive and competitive catalyst supports by comparison with activated carbons.  They could replace activated carbons in liquid-phase reactions as long as the properties of activated carbons of AC are still difficult to control and their microporosity has often slow down catalyst development. 10
11.
Advantages of CNT: 1.Extremely small and lightweight. 2.They have plentiful resources to produce them, and many can be made with only a small amount of material. 3. Are resistant to temperature changes, meaning they function almost just as well in extreme cold as they do in extreme heat. 4. The high purity of the material can avoid self-poisoning. 5. The mesoporous nature of these supports can be of interest for liquid- phase reaction, thus limiting the mass transfer. 11
12.
Disadvantages of CNT 1.Extremely small, so are difficult to work with. 2. Currently, the process to produce the nanotubes are relatively expensive. 3. Would be expensive to implement this new technology in and replace the older technology in all the places that we could. 4. The full potential of nanotubes for applications will not be realized until the growth of nanotubes can be further optimized and controlled. 5. There are many challenges exist in both the micromechanical characterization of nanotubes, and the modeling of the elastic and fracture behavior at the nanoscale. 12
13.
QUESTIONS? 13
14.
References  Harry Marsh,F. R.-R. (2006). Activated carbon, Elsevier.  Serp, P., et al. (2003). "Carbon nanotubes and nanofibers in catalysis." Applied Catalysis A: General 253(2): 337-358.  Scida, K., et al. (2011). "Recent applications of carbon-based nanomaterials in analytical chemistry: Critical review." Analytica Chimica Acta 691(1–2): 6-17.  Zeng, Q., et al. (2006). "Synthesis and Application of Carbon Nanotubes." Journal of Natural Gas Chemistry 15(3): 235-246.  Grobert, N. (2007). "Carbon nanotubes – becoming clean." Materials Today 10(1–2): 28-35.  Dai, H. (2002). "Carbon nanotubes: opportunities and challenges." Surface Science 500(1–3): 218-241.  Popov, V. N. (2004). "Carbon nanotubes: properties and application." Materials Science and Engineering: R: Reports 43(3): 61-102. 14
15.
Adsorption  The adsorptionprocess is when an adsorbate enters into the porosity of the adsorbate.  It is primarily a physical process. ( substances do not make a chemical reactions with the adsorbent).  Van der Waals and London dispersion intermolecular forces are important in the adsorption phenomenon. 15
16.
Classifications of ActivatedCarbons  Some broad classification is made for general purpose based on their physical characteristics.  Powdered activated carbon (PAC)  Granular activated carbon (GAC)  Extruded activated carbon (EAC)  Bead activated carbon (BAC)  Impregnated carbon  Polymer coated carbon  Other Uncategorized 16
17.
Nanotubes classification: 1. single-wallednanotubes (SWNTs) 2. multi-walled nanotubes (MWNTs) SWNT (graphical representation) MWNT (graphical representation) 17

Editor's Notes

#3 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-needs citation), 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. It is equivalent to surface area of carbon between 900 m²/g and 1100 m²/g. It is the standard measure for liquid phase applications. (weki pedia)
#4 Activated carbon has been historically used for removal of odor, removal of color pigments and various catalytic functions. However, applications of activated carbon have increased significantly in the recent years with the advancement of activated carbon process capability.
#5 For food and beverage : AC is used in food and beverage industries to remove color or odor and unacceptable taste from products. Sugar and sweetener industries: need decolorization agents for the production of white sugar
#6 Drinking water availability, to improve taste , smell and color including removal of chlorinated compound. There are 2 predominant types of carbon filters used in the filtration industry: powdered block filters and granular activated filters The electroplating industries require purification of waste waters containing Pd, Cr and etc. CHEMICAL: Activated carbon is used to reduce impurities such as color contents or small volume of by-products in solutions to improve the quality. Also it is used to treat poisonings and overdoes following oral ingestion. AC is used to extract pharmaceuticals in processes involving fermentation, Antibiotics, vitamins and steroids are adsorbed into the AC and recovered by solvent extraction followed by distillation.
#8 For gas phase applications, Carbon adsorbents are used in the form of hard granules, hard pellets, fibers, cloth and monoliths because these avoid an excessive pressure drop when the gas to be treated passes through the adsorbent bed. They usually have well-developed micro porosity to provide a high adsorptive capacity and selectivity for gasses and organic vapors. Gas purification: The actual process, using AC, include: H2S removal from sour natural gas Removal of sulfur dioxide and nitrous oxide from the flue gas Gasoline vapor recovery in gasoline loading facilities Chlorofluorocarbon recovery in foam blowing Removal of mercury vapor from air, hydrogen and other gas stream Cigarette filters Automotive evaporation control systems Landfill gas which contains about 50% CO2 as an impurity Natural gas contains up to 12 % CO2 Oil recovery: effluent gas contains variable CO2/CH4 There are three main applications where this process of interest: Treatment of landfill gas Purification of natural gas Oil recovery
#9 Under high pressure, nanotubes can merge together, trading some sp2 bonds for sp3 bonds, giving great possibility for producing strong, unlimited-length wires through high-pressure nanotube linking. Nanotubes are composed entirely of sp2 bonds, similar to those of graphite. This bonding structure, stronger than the sp3 bonds found in diamond, provides the molecules with their unique strength.
#10 Adsorption properties: The curvature of the graphene sheets can results in a lower heat of adsorption and make a tube causes a rehydbrization of carbon orbital leading to modification of the  density Helicity: projection of angular momentum onto direction of momentum. ( Measurements show that a SWNT has a room-temperature thermal conductivity more than copper.)
#11 4. hardness: because of Sp2 electrons orbital. 5. Strength : This strength results from the covalent sp2 bonds formed between the individual carbon atoms (which is stronger than the sp3 bonds found in Diamond & Alkenes). Their high external surface and their mesoporosity should allow significant decreases on mass transfer limitation when it is compared to AC.
#13 it's so small, so it could be inhaled pretty easily. As not all properties are currently known, they might be hazardous for our lungs. Significant study has been carried out to tackle these issues. Nevertheless. many challenges exist in both the micromechanical characterization of nanotubes and the modeling of the elastic and fracture behavior at the nanoscale, including (a) complete lack of micromechanical characterization techniques for direct property measurement,(b) tremendous limitations on specimen size. (c) uncertainty in data obtained from indirect measurements, (d) inadequacy in test specimen preparation techniques and lack of control in nanotube alignment and distribution. and (e) there is a seemingly formidable task of controlling the chirality of SWNTs during growth.
#16 The adsorbent is the solid porous material, in this case is carbon. The adsorbate is gas or vapor, or solute from solution, which is adsorbed with the adsorbent. The adsorptive process is when an adsorbate enters into the porosity of the adsorbent.
#18 • A single-walled carbon nanotube (SWNT) may be thought of as a single thick sheet of graphite (called graphene) rolled into a seamless cylinder. • Most single-walled nanotubes (SWNT) have a diameter of 0.4 and 2.5 nm, with a tube length that can be many several mm. • Single-walled nanotubes are an important variety of carbon nanotube because they exhibit electric properties that are not shared by the multi-walled carbon nanotube (MWNT) variants. Multi-walled nanotubes (MWNT) consist of multiple rolled layers (concentric tubes) of graphite. There are two models which can be used to describe the structures of multi-walled nanotubes. In the Russian Doll model, sheets of graphite are arranged in concentric cylinders. In the Parchment model, a single sheet of graphite is rolled in around itself, resembling a scroll of parchment or a rolled newspaper.(The Russian Doll structure is observed more commonly). The telescopic motion ability of inner shells and their unique mechanical properties will permit the use of multi-walled nanotubes as main movable arms in coming Nano mechanical devices.

Activated carbon

Activated carbon

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