<unk> s 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<unk>  A micrograph of<unk> tivated 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<unk> ross, can have a surface area of several square centimeters. 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,<unk> s (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.<unk>  (R 1) is defined as the<unk>  particles retained on a 50-mesh sieve (0.297 mm). Powdered<unk>  (PAC) material is finer material. PAC is made up of crushed or ground<unk>  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<unk>  A micrograph of<unk> tivated charcoal (GAC) under scanning electron microscope Granular<unk>  (GAC) has a relatively larger particle size compared to powdered<unk>  and consequently, presents a smaller external surface. Diffusion of the adsorbate is thus an important factor. These<unk> s are suitable for adsorption of gases and vapors, because gaseous substances diffuse rapidly. Granulated<unk> s 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<unk>  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<unk> s are the 12×40 and 8×30 sizes because they have a good balance of size, surface area, and head loss characteristics. Extruded<unk>  (EAC) Extruded<unk>  (EAC) combines powdered<unk>  with a binder, which are fused together and extruded into a cylindrical shaped<unk>  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<unk>  (BAC) Bead<unk>  (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<unk>  Porous<unk> s 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<unk>  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<unk>  and aluminium hydroxide Al(OH)3, a flocculating agent. Impregnated<unk> s 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. Polymer coated<unk>  This is a process by which a porous<unk>  can be coated with a biocompatible polymer to give a smooth and permeable coat without blocking the pores. The resulting<unk>  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<unk>  cloth Woven<unk>  There is a technology of processing technical rayon fiber into<unk>  cloth for<unk>  filtering. Adsorption capacity of<unk> tivated cloth is greater than that of<unk> tivated charcoal (BET theory) surface area: 500–1500 m2/g, pore volume: 0.3–0.8 cm3/g). Thanks to the different forms of<unk> tivated material, it can be used in a wide range of applications (supercapacitors, Odor Absorbers , CBRN-defense industry etc.).
Activated carbon
Caphosol
Dissolvable tobacco
Chlorofluorocarbon
Mustard gas
Bioactive glass
Podophyllum resin
Carbonated water