Activated carbons definition

Standard Definitions of Terms Relating to Activated Carbon... 

Where activated carbon is a potential treatment technology, the first evaluation step is generally to run simple isotherms to determine feasibility. Isotherms are based on batch treatment where impurities reach equilibrium on available carbon surface. While such tests provide an indication of the maximum amount of impurity a GAC can adsorb, it cannot give definite scale up data for a GAC operation due to several factors ... 

An interesting aspect of the benzofuran cationic polymerization was uncovered by Natta, Farina, Peraldo and Bressan who reported in 196160,61 that an asymmetric synthesis of an optically active poly(benzofuran) could be achieved by using AlCl2Et coupled with (-)j3-phenylalanine, (+)camphorsulphonic acid or with (-)brucine. The optical activity was definitely due to the asymmetric carbon atoms in the polymer chain, indicating that at least some of the polymer s macromolecules possessed a di-isotactic structure, v/ z.62 ... 

The hydrogen storage capacities for disordered graphites, nanographites, and activated carbons are collected in Table 4.1. One can conclude that activated carbons are better storage materials than CNTs and most experimentally investigated carbon nanophases (like GNFs). Yet, if one applies a broader definition of nanomaterials, the activated carbon phases are, indeed, the disordered and nanostructured carbons. 

There is not sufficient evidence conclusively to prove or disprove one or two definite mechanisms for reaction of acid with active carbon. However, the chromene-acid reaction as herein described appears to be a logical and significant part of the overall reaction. Physical, electrostatic, or other mechanisms for acid sorption probably account for the remainder of the reaction. 

In his 1916 paper, Langmuir had stated that with highly porous adsorbents such as charcoal it is impossible to know definitely the area on which the adsorption takes place and that there are some spaces in which a molecule would be closely surrounded by carbon atoms on nearly all sides . He concluded that equations derived for plane surfaces were not applicable to adsorption by charcoal. Unfortunately, these observations have been overlooked by many investigators, who have applied the simple Langmuir monolayer equation to adsorption data obtained with zeolites and activated carbons. 

There is no precise definition of an active carbon , but it is generally understood to be a carbonaceous material of appreciable specific surface area. If it is to be an effective adsorbent, an active carbon must have a surface area of at least 5 m2 g1. Active carbons used as industrial adsorbents have much larger BET-areas, which may extend well above 2000 m2 g1. In accordance with this broad definition, an active carbon may be porous or non-porous. The term activated carbon has a more specific connotation, however, since it is reserved for a highly porous carbon produced from a carbon-rich material by some form of chemical or physical activation. 

Examples of industrial relevance for the first two combinations are the adsorption of pollutants from waste air or water onto activated carbon. Combinations three and four can be observed at the orientation of tensid molecules on water/air interfaces (foam formation, foam stabilization) or at the interface of two immiscible liquids, (e.g. oil and water, emulsion formation). This book deals mainly with the case of liquid molecules adsorbed onto solid surfaces. For this case the following definitions are made ... 

In conclusion, KOH and NaOH activation is certainly able to provide activated carbons with the most adapted nanotextural characteristics for supercapacitors, at a reasonable cost. However, it must be pointed out that before to state definitively on the interest of these materials, long-term capacitor performance should be investigated. In order to fulfiU the practical demand, only carbons with a small RC constant, low leakage current, and limited self-discharge should be selected. The important research work which has been performed lately, especially by the companies developing supercapacitors, seems to indicate that impurities, even at a low level, or particular functional groups on carbon may strongly affect the calendar life of these devices. 

In discussing the manufacture of activated carbon it is important to keep in mind that the term activated carbon comprises a family of substances. None of the mpmtw nf the.family is characterized by a definite structural formula nor can any be separately identified by chemical analysis. Our only basis for differentiating is by adsorptive and catalytic properties. As is well known, carbons from such... 

When a definite quantity of a gas is admitted to a sample of activated carbon in a calorimeter, the total heat liberated, called the integral heat of adsorption, is usually reported as calories per mole (or milliliters) of adsorbed gas. Comparisons of integral heats of... 

The blue dye-was less adsorbable than the red dye consequently the filtrate from a treatment with activated carbon had a bluish color that did not match any dilution of the original solution. The change in hue was disclosed in visual methods of testing, for example, in Nessler tubes, but it was difficult to assign a definite numerical value to the change by such visual methods of observation. 

A committee of the American Society for Testing and Materials is now studying ways and means to prepare standard definitions of terms relating to the manufacture, testing, and methods of using activated carbon. 

A number of definitions not included here can be found in glossaries furnished by Atlas Chemical Industries, Pittsburgh Chemical Company, National Carbon Company, and other suppliers of activated carbon. 

An unfortunate consequence of this situation is that in many ventures that could become more efficient through the use of activated carbon, it may not be used or it may be used ineffectively because of lack of know-how. In such situations a suitable written text can be useful because it asks no questions and carries away no data. This potential has guided the preparation of this revision. No attempt is made to furnish a definitive treatise instead, the text is... 

An important type of porous carbons is activated carbons. Granular activated carbons are prepared from different precursors and used in a wide range of industries. Their preparation, structure and applications were reviewed in different books and reviews [3,4,71-75]. In Table 8, some properties of different adsorbents (activated carbons, silica gel, alumina gel and zeolite) are compared with each other. High BET surface area and light weight are the main advantages of activated carbons. Usually activated carbons have a wide ran of pore sizes from micropores to macropores, which shows a marked contrast to the definite pore size of zeolites. 

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