Activation of charcoal

The moisture and gas content of charcoals and the activation of charcoal for use in gas masks was the major project undertaken by the branch laboratory at Princeton University. George A. Hullet, a professor of physical chemistry at the University, directed a staff of 14 chemists who as soldiers were stationed there during the war. Fred Neher, an organic chemist, was assisted by three graduate students employed by the Bureau of Mines in the synthesis of several compounds suggested by E. Emmet Reid (27). ... 

Fig. 21. Catalytic activities of charcoals heated at various temperatures, k = rate constant for o-pHj conversion at —195.8° c — rate constant for H1-D2 exchange at 60°. [Turkevich, J., and Laroche, J., Z. physik. Chem. (Frankfurt) [N.S.] 16, 399 (1958).]...

Activation of charcoal is generally achieved satisfactorily by heating gently to red heat in a crucible or quartz beaker in a muffle furnace, finally allowing to cool under an inert atmosphere in a desiccator. To improve the porosity, charcoal columns are usually prepared in admixture with diatomaceous earth. 

Since the oxygen induced conversion showed little dependence on temperature as did the conversion on charcoal we suggested that the latter conversion is also caused by magnetic interaction. This concept was confirmed by the striking accelerating effect of small amounts of added oxygen on the catalytic activity of charcoal (] ). 

Fig. 4.2 Adsorption isotherms of benzene at 25°C on (1) a charcoal from anthracite coal, activated to 56% yield (2) an activated coconut charcoal. (After Cadenhead and Everett.)...

Health and Safety. Petroleum and oxygenate formulas are either flammable or combustible. Flammables must be used in facUities that meet requirements for ha2ardous locations. Soak tanks and other equipment used in the removing process must meet Occupational Safety and Health Administration (OSHA) standards for use with flammable Hquids. Adequate ventilation that meets the exposure level for the major ingredient must be attained. The work environment can be monitored by active air sampling and analysis of charcoal tubes. 

Charcoal is not only employed in activated form for decoloring and adsorbing dissolved admixtures but also in its unactivated form as a filter aid. It can be used in suspensions consisting of aggressive liquids (e.g., strong acids and alkalies). As with sawdust, it can be used to separate solids that may be roasted. On combustion, the charcoal leaves a residue of roughly 2 percent ash. Particles of charcoal are porous and form cakes of high density but that have a lesser retention ability than does diatomite. 

Activated carbon or activated charcoal Carbon in the form of charcoal granules, which has an affinity to adsorb many gases and vapors and, in so doing, removes odors. It is manufactured by exposing coal, coconut shells, or peat to steam at 800 to 900 C. 

An electrochemical theory has been applied to explain the mechanisms of adsorption of metal ions on activated charcoal (carbon). According to this theory, oxygen in contact with an aqueous suspension of charcoal is reduced to hydroxyl groups with the liberation of hydrogen peroxide ... 

There are two main varieties of carbon (i) crystalline (e.g., graphite and diamond), and (ii) amorphous. The amorphous variety consists of carbon blacks and charcoals. Carbon blacks are nonporous fine particles of carbon produced by the combustion of gaseous or liquid carbonaceous material (e.g., natural gas, acetylene, oils, resins, tar, etc.) in a limited supply of air. Charcoals are produced by the carbonization of solid carbonaceous material such as coal, wood, nut shells, sugar, synthetic resins, etc. at about 600 °C in the absence of air. The products thus formed have a low porosity, but when activated by air, chlorine, or steam, a highly porous material is produced this porous product is called activated charcoal. Chemically speaking carbon blacks and charcoals are similar, the difference being only in physical aspects. Carbon blacks find use in the rubber industry and in ink manufacture. An important use of charcoals is as adsorbents. 

Massonne, J. et al., Angew. Chem. (Intern. Ed.), 1966, 5, 317 Adsorption of nitrogen trifluoride on to activated granular charcoal at — 100°C caused an explosion, attributed to the heat of adsorption not being dissipated on the porous solid and causing decomposition to nitrogen and carbon tetrafluoride. No reaction occurs at +100°C in a flow system, but incandescence occurs at 150°C. 

More than three decades ago, skeletal rearrangement processes using alkane or cycloalkane reactants were observed on platinum/charcoal catalysts (105) inasmuch as the charcoal support is inert, this can be taken as probably the first demonstration of the activity of metallic platinum as a catalyst for this type of reaction. At about the same time, similar types of catalytic conversions over chromium oxide catalysts were discovered (106, 107). Distinct from these reactions was the use of various types of acidic catalysts (including the well-known silica-alumina) for effecting skeletal reactions via carbonium ion mechanisms, and these led... 

Various sample enrichment techniques are used to isolate volatile organic compounds from mammalian secretions and excretions. The dynamic headspace stripping of volatiles from collected material with purified inert gas and trapping of the volatile compounds on a porous polymer as described by Novotny [3], have been adapted by other workers to concentrate volatiles from various mammalian secretions [4-6]. It is risky to use activated charcoal as an adsorbent in the traps that are used in these methods because of the selective adsorption of compounds with different polarities and molecular sizes on different types of activated charcoal. Due to the high catalytic activity of activated charcoal, thermal conversion can occur if thermal desorption is used to recover the trapped material from such a trap. 

Hofmann and Ohlerich (28) found that the same quantity of sulfur was taken up at 600° by activated sugar charcoal before and after covering with surface oxides. About equivalent amounts of oxygen and sulfur were bound by the same charcoal. A similar observation had been made by Baraniecky, Riley, and Streeter (126) who charred cellulose in the presence of hydrogen sulfide. The sulfur content corresponded to the oxygen content of samples treated similarly in the presence of air. 

The symptoms of overdose are to some extent predictable from the antimuscarinic and adrenolytic activity of these drugs. Excitement and restlessness, sometimes associated with seizures, and rapidly followed by coma, depressed respiration, hypoxia, hypotension and hypothermia are clear signs of TCA overdose. Tachycardia and arrhythmias lead to diminished cardiac function and thus to reduced cerebral perfusion, which exacerbates the central toxic effects. It is generally accepted that dialysis and forced diuresis are useless in counteracting the toxicity, but activated charcoal may reduce the absorption of any unabsorbed drug. The risk of cardiac arrhythmias may extend for several days after the patient has recovered from a TCA overdose. 

Table V compares the degradation of total 2,4-D and 2,4,5-T (n-butyl esters and acids) over six years of observations In the Kansas and Florida locations. Although the rates of application were similar, the method of application, preplant Incorporation versus subsurface Injection, resulted In significant differences In the Initial concentrations of herbicides In the plots. The acid of 2,4,5-T comprised most of the total residue after the first two years. Although some residues were recovered, especially In later years, at depths below 15 cm, the majority (90 percent) of residue was confined to the top 15 cm of soil profile. The addition of soil amendments such as lime, organic matter and fertilizer did not appreciably Increase the overall rate of disappearance of the herbicide. The addition of activated coconut charcoal, however, significantly decreased the rate of disappearance of herbicide. Six years after the charcoal plots were established, residues (primarily 2,4,5-T acid) were still present.

Activated carbon adsorption, treatment of wastewater, 125-50,155 Activated coconut charcoal, effect, degradation In soil, 168... 

Ketones containing acetylenic bonds were reduced selectively at the triple bond by catalytic hydrogenation. Over 5% palladium on calcium carbonate in pyridine (which decreases the activity of the catalyst) 17-ethynyltestosterone was reduced in 95% yield to 17-vinyltestosterone, while over palladium on charcoal in dioxane 80% of 17-ethyltestosterone was obtained the carbonyl in position 3 and the conjugated 4,5-double bond remained intact [386]. 

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