Carbon, chemically activated

Both previous [47] and the present studies (Table 4) have shown the correlation between the two processes. Evaluation of carbons depends on concentration and kind of poUutants, physicochemical properties of carbons and conditions of adsorption. It was stated, that order of adsorptivity values in classification in static conditions (equilibrium concentration 0,2 mg/dm of SLS — permissible concentration in potable water) is similar to the total loading of detergent on filters (mg or mg/cm ). Carbons chemically activated show decreased adsorption in dynamic conditions. Greater differences in values of adsorption capacities and changes of order in classification have been observed, when comparison of these processes was carried out in mass loading (mg of SLS/g of carbon). 

Figure 6.2. Adsorption isotherms for N2 at 77 K for two series of carbons chemically activated with ZnClj, H3PO4 and KOH. The contents of Zn, P and K (gg precursor) are used to distinguish between die carbons Caturla et al., 1991 Molina-Sabio and Rodriguez-Reinoso, 2004).

Subsequent studies (63,64) suggested that the nature of the chemical activation process was a one-electron oxidation of the fluorescer by (27) followed by decomposition of the dioxetanedione radical anion to a carbon dioxide radical anion. Back electron transfer to the radical cation of the fluorescer produced the excited state which emitted the luminescence characteristic of the fluorescent state of the emitter. The chemical activation mechanism was patterned after the CIEEL mechanism proposed for dioxetanones and dioxetanes discussed earher (65). Additional support for the CIEEL mechanism, was furnished by demonstration (66) that a linear correlation existed between the singlet excitation energy of the fluorescer and the chemiluminescence intensity which had been shown earher with dimethyl dioxetanone (67). 

Because of demands for improved fuel consumption through reduced rolling resistance, a new series of carbon blacks referred to as LH, ie, N300 with this innovation would be N300 LH. Basically this series of blacks has a wider size range in both the primary particles and primary aggregates in addition to a more chemically active surface area. 

Rubber. The mbber industry consumes finely ground metallic selenium and Selenac (selenium diethyl dithiocarbamate, R. T. Vanderbilt). Both are used with natural mbber and styrene—butadiene mbber (SBR) to increase the rate of vulcanization and improve the aging and mechanical properties of sulfudess and low sulfur stocks. Selenac is also used as an accelerator in butyl mbber and as an activator for other types of accelerators, eg, thiazoles (see Rubber chemicals). Selenium compounds are useflil as antioxidants (qv), uv stabilizers, (qv), bonding agents, carbon black activators, and polymerization additives. Selenac improves the adhesion of polyester fibers to mbber. 

Active Carbon" under "Carbon" in ECT 1st ed., VoL 2, pp. 881—899, byj. W. Hassler, Nuchar Active Carbon Division, West Virginia Pulp and Paper Co., and J. W. Goet2, Carbide and Carbon Chemicals Corp. "Activated Carbon" under "Carbon" in ECT 2nd ed., VoL 4, pp. 149—158, by E. G. Doying, Union Carbide Corp., Carbon Products Division "Activated Carbon" under "Carbon (Carbon and Artificial Graphite)" in ECT 3rd ed., Vol. 4, pp. 561—570, by R. W. Soffel, Union Carbide Corp. 

J. W. Hassler, Jictivated Carbon Chemical Publishing Co., Inc., New York, 1963, pp. 1—14. A comprehensive account of the development and use of activated carbon products to about 1960. 

Fig. 6. Breakthrough curves for aqueous acetone (10 mg 1" in feed) flowing through exnutshell granular active carbon, GAC, and PAN-based active carbon fibers, ACF, in a continuous flow reactor (see Fig. 5) at 10 ml min" and 293 K [64]. C/Cq is the outlet concentration relative to the feed concentration. Reprinted from Ind. Eng. Chem. Res., Volume 34, Lin, S. H. and Hsu, F. M., Liquid phase adsorption of organic compounds by granular activated carbon and activated carbon fibers, pp. 2110-2116, Copyright 1995, with permission from the American Chemical Society.

Based upon raw material and intended application, the manufacturing of activated carbon falls into two mam categories thermal activation and chermcal activation. In general, thermal activation involves the heating/gasification of carbon at high ternperamres [13], while chemical activation is characterized by the chermcal dehydration of the raw material at significantly lower temperatures [11,14]. 

In chemical activation processes, the precursor is first treated with a chemical activation agent, often phosphoric acid, and then heated to a temperature of 450 -700 °C in an activation kiln. The char is then washed with water to remove the acid from the carbon. The filtrate is passed to a chemical recovery unit for recycling. The carbon is dried, and the product is often screened to obtain a specific particle size range. A diagram of a process for the chemical activation of a wood precursor is shown in Fig. 3. 

The activated carbon materials are produced by either thermal or chemical activation as granular, powdered, or shaped products. In addition to the form of the activated carbon, the final product can differ in both particle size and pore structure. The properties of the activated carbon will determine the type of application for which the carbon will be used. 

Fig. 3. Chemical activation process for production of activated carbon...

The current requirements have led to the development of pellet shaped activated carbon products specifically for automotive applications. These pellets are typically generated as chemically activated, wood-based carbons. 

Chemical erosion can be suppressed by doping with substitutional elements such as boron. This is demonstrated in Fig. 14 [47] which shows data for undoped pyrolitic graphite and several grades of boron doped graphite. The mechanism responsible for this suppression may include the reduced chemical activity of the boronized material, as demonstrated by the increased oxidation resistance of B doped carbons [48] or the suppressed diffusion caused by the interstitial trapping at boron sites. 

Activated Carbon for Process Water Treatment Activated Carbon from CPL Carbon Link - Activated carbon from CPL Carbon Link for liquid and gas phase purification by adsorption. Activated carbons for all applications including chemical, water, air, solvent recovery, gold recovery, food, automotive, industrial, catalysis.. http //www.activated-carbon.com. 

We are familiar with several examples of chemical activation as a strategy for group transfer reactions. Acetyl-CoA is an activated form of acetate, biotin and tetrahydrofolate activate one-carbon groups for transfer, and ATP is an activated form of phosphate. Luis Leloir, a biochemist in Argentina, showed in the 1950s that glycogen synthesis depended upon sugar nucleotides, which may be... 

In the past chemical cure linings have been employed on a wide scale. These linings, usually based on natural rubber or acrylonitrile-butadiene rubber consist of a standard lining compound with a chemical activator such as dibenzylamine incorporated in the formulation. Prior to the application of the lining to the substrate, the individual sheets of rubber are dipped or brush coated with carbon disulphide or a solution of a xanthogen disulphide in a solvent. The carbon disulphide or xanthogen disulphide permeates the rubber and combines with the dibenzylamine to form an ultra-fast dithiocar-bamate accelerator in situ, and thus the rubber rapidly vulcanises at ambient temperature. 

For many years the catalytic air oxidation of benzene was the main source of maleic anhydride. Obviously, two carbons from each ring are wasted as carbon dioxide in this process. Although some is still made that way, most modem maleic anhydride plants are based on butane oxidation. Because butane is forecast to be plentiful and low-cost, new routes to four-carbon chemicals from maleic anhydride are under active development. 

Steam stripping Air stripping Biological nitrification Chemical oxidation Ion exchange Solvent extraction Biological oxidation (aerobic) Wet oxidation Activated carbon Chemical oxidation Chemical precipitation Ion exchange Adsorption Nano-filtration Reverse osmosis Electrodialysis... 

Cooper, J.C., Hager, D.G. Water Reclamation with Activated Carbon , Chemical Engineering Progress, Oct. 1966, p. 85. 

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