Applications activated charcoal

Filter aids may be applied in one of two ways. The first method involves the use of a precoat filter aid, which can be applied as a thin layer over the filter before the suspension is pumped to the apparatus. A precoat prevents fine suspension particles from becoming so entangled in the filter medium that its resistance becomes exces-sive. In addition it facilitates the removal of filter cake at the end of the filtration cycle. The second application method involves incorporation of a certain amount of the material with the suspension before introducing it to the filter. The addition of filter aids increases the porosity of the sludge, decreases its compressibility, and reduces the resistance of the cake. In some cases the filter aid displays an adsorption action, which results in particle separation of sizes down to 0.1 /i. The adsorption ability of certain filter aids, such as bleached earth and activated charcoals, is manifest by a decoloring of the suspension s liquid phase. This practice is widely used for treating fats and oils. The properties of these additives are determined by the characteristics... 

Diatomaceous earths may resemble the forms of the charcoals. The earths are primarily filter aids, precoats or adsorbents, the hmction of the filter medium being secondary. Fuller s earth and clays are used for decoloring applications diatomaceous earths are used for clarification. The adsorbtivity of diatomaceous earth works in the same fashion as activated carbon, but isotherms (affinity) for many chemical species like the hydrocarbons is weaker. For this reason, activated charcoal or carbon is much preferred in wastewater treatment applications expecially when taste and odor issues are priorities. 

The adsorption process, in principle, is an anion-exchange process which is restricted only to the surface of the activated charcoal. This fact makes the loading or the exchange capacity of activated charcoal to be relatively smaller in comparison with ion-exchange resins, and it is for this reason that charcoals are quite often treated suitably to improve their loading capacities. The surface and the pore structure characteristics of activated carbon are the important factors upon which its industrial applications depend. 

Because of the large volume of water Involved, Incineration Is not a preferred method. Adsorption of pesticides onto media such as activated charcoal, as well as biological and chemical treatment, are feasible methods, but they require frequent monitoring and maintenance. Evaporation ponds and soil pits have the advantages of less maintenance, applicability to a broad range of chemicals, and the ability to reduce the volume of waste via water evaporation. (1-3). In addition, these latter two methods have been estimated to be the least expensive on a per gallon basis of waste (J ). This Is of considerable Importance because the wastes are... 

In a large variety of applications, the surface of a solid plays an important role (e.g., active charcoal, talc, cement, sand, catalysis). Solids are rigid structures and resist any stress effects. Many such considerations in the case of solid surfaces will be somewhat different for liquids. The surface chemistry of solids is extensively described in the literature (Adamson and Gast, 1997 Birdi, 2002). Mirror-polished surfaces are widely applied with metals, where the adsorption at the surface is much more important. Further, the corrosion of metals initiates at the surfaces, thus requiring treatments based on surface properties. As described in the case of liquid surfaces, analogous analyses of solid surfaces can be carried out. The molecules at the solid surfaces are not under the same force field as in the bulk phase (Figure 5.1). 

Carbon also is produced and used in other forms namely, activated carbon, carbon black, and coke, that have many commercial applications. Structurally they are amorphous forms of carbon belonging to the graphites. Activated carbon or activated charcoal has a highly porous honeycomb-like internal structure and adsorbs many gases, vapors, and colloidal solids over its very large internal surface area. Some of its major applications include purification of water and air, air analysis, waste treatment, removal of subur dioxide from stack gases, and decolorization of sugar. 

Nikolaev V (1990) Peroral application of synthetic activated charcoal in USSR. Biomat Art Cells Art Org 4 555-568... 

For some applications, regeneration is not possible, and the material must be discarded. Additional problems include the fact that the charcoal sorbs based on molecular size pollutants with molecular sizes greater than the pores of the charcoal are unaffected. Flow problems and attrition of the carbon particles are other difficulties. Activated charcoal columns are usually pressure vessels due to the large and dynamic pressure drops across the carbon bed. 

The rationale for the development of such libers is demonstrated by their application in the medical field, notably hernoperfusion. where cartridges loaded with activated charcoal-filled hollow fiber contact blood. Low molecular weight body wastes dilTuse through the liber walls and arc absorbed in the fiber core. In such processes, the blood does not contact the active sorbent directly, but faces the nonloxic. blood compatible membrane. Other uses include waste industrial applications as general as chromates and phosphates and as specific as radioaclive/nudcar materials. 

As noted earlier, the phenomenon of adsorption is encountered in such diverse applications as the separation of components in chromatography, die removal of toxic gases by activated charcoal, heterogeneous catalytic reactions and die dyeing of fabrics. The surface area of solids is most... 

Adsorbents. The use of dry chemicals as adsorbents has been discussed above. However, there are other adsorbent materials, such as activated charcoal, hay, com cobs, sawdust, and such, that can be utilized as well. Most of them would work on many organic compounds as long as the spill was confined to a small area by either dikes or curbs, or as long as the spill was small and covered only a minimal area. The major problem in this application technique is that the personnel who apply the materials must wear adequate protective gear. An alternate technique would be to blow the absorbent material over the spill from a distance, using suitable machinery, such as a snow blower or forage blower unit (Greer, 1976). 

The use of large-surface area activated charcoal or carbon (approximately 500-1500 m2/g), either as powder activated carbon (PAC) or granular activated carbon (GAC), is the most popular adsorption technique. It is a relatively simple, low-cost, and widely applicable method of pollutant removal, and the literature is replete with descriptions of applications. The GAC version is mostly used in effluents that have already received normal biological treatment... 

Thermal Desorption Thermal desorption is an alternative GC inlet system particularly used for VOC analysis. However, the analytes subjected to thermal desorption must be thermally stable to achieve successful analysis. Otherwise, decomposition occurs. This technique is mainly used for determination of volatiles in the air. Such a methodology requires sample collection onto sohd sorbents, then desorption of analytes and GC analysis. Traditionally, activated charcoal was used as a sorbent followed by extraction with carbon disulfide. However, solvent desorption involves re-dilution of the VOCs, thus partially negating the enrichment effect. Therefore, the sampling method is to pump a sample of gas (air) through the sorbent tube containing certain sorbents in order to concentrate the VOC. Afterwards, the sample tube is placed in thermal desorber oven and the analytes are released from the sorbent by application of high temperature and a flow of carrier gas. Additionally, desorbed compounds are refocused in a cold trap and then released into the GC column. Such a two-step thermal desorption process provides a narrow chromatographic band at the head of the column. 

Mesoporous molecular sieves materials5-8 designated M41S (which include the MCM-41 class of materials) have made a further major impact on the area of synthesis of porous materials. A variety of open framework structures that are mesoporous have recently been reviewed by Thomas.9 Activated charcoal, MCM-41, mesoporous tungsten oxide, and substituted MCM-41 materials are mentioned. This article primarily emphasizes potential applications of such materials and possible mechanisms of reaction. The mesoporous sysems are compared briefly to microporous materials such as zeolites, ALPOs, MeALPOs and SAPOs. 

So-called absorber resins based on poly(styrene) are recommended as an alternative to activated charcoal, but have as yet found little application. Chlorohydrocarbons and phenols are efficiently adsorbed by activated charcoal. Humic acid is less well adsorbed, its detection being a sign of activated charcoal filter exhaustion. 

The difficulty in interpreting this particular type of data is further compounded by its application in the upper soil zone where the most active plant and microbiological activity takes place. Many organic and inorganic compounds (humic acids CO2, N2O, NO2, etc.) are produced in this zone, all of which are rapidly adsorbed by activated charcoal. These compounds are present in macro concentrations (parts per thousand to percent) and produce fragment patterns which overlap the much lower concentrations of hydrocarbons, which are generally in the ppm range. 

Charcoal is produced by the incomplete combustion of plant or animal products. The major use of charcoal is for outdoor cooking. The second largest use of charcoal is in industrial applications in the form of activated charcoal. The activation process involves heating the charcoal subjecting it to steam or treating with a chemical to both remove substances that have adhered to it as well as break it down into finer particles and thus increase the surface area. Activated carbon has been used for its adsorptive properties as a universal antidote in cases of poisonings, as a filter aid agent, and in decolorization processes. 

Exposed skin should be washed promptly with soap and water. Dermal application of vitamin E oil preparations may be used for both prophylaxis and treatment of paresthesia. Eor contact with eyes, flush immediately and for an extended period with generous amounts of clean water or saline. Gastric lavage is indicated if patient has ingested a large amount of pyrethroid and can be treated soon after exposure. For ingestion of smaller amounts or if treatment has been delayed, activated charcoal and catharsis are indicated. Seizures can be treated with intravenous benzodiazepines (diazepam or loraze-pam) phenytoin or phenobarbital may be helpful for recurrent seizures. No specific antidotes for pyre-throid-induced neurotoxic effects have been approved for use in humans. Spontaneous recovery usually occurs with mild or moderate intoxication. 

Soot and carbon black have commercial applications in rubber and inks. Activated charcoal is an important, versatile purifier. Unwanted compounds are adsorbed onto its microcrystalline surface. 

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