Adsorbents activated charcoal

Adsorption. The adherence of atoms, ions, or molecules of a gas or liquid to a solid substance called an adsorbent. Activated charcoal adsorbs odors and other contaminants from a variety of gases. 

The three above types occur in gas-solid chromatography on microporous adsorbents (activated charcoal, molecular sieves). Knudsen diffusion may occur in gas-liquid chromatography supports. 

Finally, we examine the feasibility of equilibrium adsorption. The loading capacity of adsorbent (active charcoal) indicates that all the trace components can be selectively adsorbed, and therefore the equilibrium adsorption can be applied for their removal. 

These values, while similar in magnitude to those of Heath et al., at room temperature are significantly lower. Why the values of my coworkers and myself differ from those of Heath et al. (10), is not known. However, when they determined recoveries they did not aerate the adsorbent (activated charcoal) as would occur during the actual process of collecting evaporated compounds. It may be that aldehydes breakdown or are irreversibly adsorbed on activated charcoal to a greater extent than acetates or alcohols and then this factor would account for the differences in the two studies. 

Hi-tech wound dressings non-adherent, odour adsorbent, activated charcoal cloth (ACC), and antimicrobial dressings... 

In order to remove radioactive substances potentially present in the air flow, most of the ventilation systems are equipped with filter units consisting of high-efficiency particulate filters (HEPA filters, class S) and iodine adsorbers (activated charcoal, KI impregnated). These filters are monitored, either continuously or at regular intervals the filter efficiency of the iodine adsorbers is determined by taking charcoal samples from the filter beds at regular intervals and analyzing them in the laboratory (see Section 6.2.1.5.). 

ALOT column 98 m x 0.28 mm i.d. adsorbent active charcoal, layer thickness 30 urn temperature -9.5 °C effective plate number — 66500. 

The word carbon Is derived from the Latin carbo , which to the Romans meant charcoal (or ember). In the modern world, carbon is, of course, much more than charcoal. From carbon come the highest strength fibers, one of the best lubricants (graphite), the strongest crystal and hardest material (diamond), ein essentially non-ciystalline product (vitreous carbon), one of the best gas adsorbers (activated charcoal), and one of the best helium gas barriers (vitreous carbon). A great deal is yet to be learned and new forms of carbon are still being discovered such as the fullerene molecules and the hexagonal polytypes of diamond. 

Figure 18-la shows an improved version of the extractor described by Ehrhardt (1987). The modification featuring a heat-insolated separation column instead of a simple steam duct may also be used for fractionated solvent distillation, if necessary through a bed of suitable adsorbent (activated charcoal, alumina, silica gel) for further product purification. 

The adsorption behavior of benzene in a benzene-cydohexane mixture for the adsorbent, activated charcoal, is shown for a particular temperature in Figure 3.3.8A. Note that the total number of moles adsorbed... 

Fig. XVII-29. Nitrogen isotherms the volume adsorbed is plotted on an arbitrary scale. The upper scale shows pore radii corresponding to various relative pressures. Samples A, Oulton catalyst B, bone char number 452 C, activated charcoal F, Alumina catalyst F12 G, porous glass S, silica aerogel. (From Ref. 196).

Natural gas Hquids are recovered from natural gas using condensation processes, absorption (qv) processes employing hydrocarbon Hquids similar to gasoline or kerosene as the absorber oil, or soHd-bed adsorption (qv) processes using adsorbants such as siHca, molecular sieves, or activated charcoal. Eor condensation processes, cooling can be provided by refrigeration units which frequently use vapor-compression cycles with propane as the refrigerant or by... 

The refining process most commonly used involves treatment with hot aqueous alkaH to convert free fatty acids to soaps, followed by bleaching, usually with hydrogen peroxide, although sodium chlorite, sodium hypochlorite, and ozone have also been used. Other techniques include distillation, steam stripping, neutralization by alkaH, Hquid thermal diffusion, and the use of active adsorbents, eg, charcoal and bentonite, and solvent fractionation... 

Various types of detector tubes have been devised. The NIOSH standard number S-311 employs a tube filled with 420—840 p.m (20/40 mesh) activated charcoal. A known volume of air is passed through the tube by either a handheld or vacuum pump. Carbon disulfide is used as the desorbing solvent and the solution is then analyzed by gc using a flame-ionization detector (88). Other adsorbents such as siUca gel and desorbents such as acetone have been employed. Passive (diffuse samplers) have also been developed. Passive samplers are useful for determining the time-weighted average (TWA) concentration of benzene vapor (89). Passive dosimeters allow permeation or diffusion-controlled mass transport across a membrane or adsorbent bed, ie, activated charcoal. The activated charcoal is removed, extracted with solvent, and analyzed by gc. Passive dosimeters with instant readout capabiUty have also been devised (85). 

Because of their selectivity, molecular sieves offer advantages over silica gel, alumina or activated charcoal, especially in their very high affinity for water, polar molecules and unsaturated organic compounds. Their relative efficiency is greatest when the impurity to be removed is present at low concentrations. Thus, at 25° and a relative humidity of 2%, type 5A molecular sieves adsorb 18% by weight of water, whereas for silica gel and alumina the figures are 3.5 and 2.5% respectively. Even at 100° and a relative humidity of 1.3% molecular sieves adsorb about 15% by weight of water. 

Helium [7440-59-7] M 4.0. Dried by passage through a column of Linde 5A molecular sieves and CaS04, then passed through an activated-charcoal trap cooled in liquid N2, to adsorb N2, argon, xenon and krypton. Passed over CuO pellets at 300° to remove hydrogen and hydrocarbons, over Ca chips at 600° to remove oxygen, and then over titanium chips at 700° to remove N2 [Arnold and Smith 7 Chem Soc, Faraday Trans 2 77 861 1981]. 

Charcoal Tubes Reference has been made earlier to adsorption, which is the property of some solid materials, such as activated charcoal, to physically retain solvent vapors on their surfaces. In environmental health testing, the adsorbed vapors are removed, generally with a solvent, in a laboratory. The solvent is then analyzed by physical methods (gas chromatography, etc.) to determine the individual compounds whose vapors, such as benzene, were present in the sampled air. Industrial atmospheric samples can be collected in small glass tubes (4 mm ID) packed with two sections of activated charcoal, separated and retained with fiberglass plugs. To obtain an air sample, the sealed ends of the tube are broken off, and air is drawn through the charcoal at the rate of 1 liter per minute by means... 

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. 

Certain highly porous solid materials selectively adsorb certain molecules. Examples are silica gel for separation of aromatics from other hydrocarbons, and activated charcoal for removing liquid components from gases. Adsorption is analogous to absorption, but the principles are different. Layers of adsorbed material, only a few molecules thick, are formed on the extensive interior area of the adsorbent - possibly as large as 50,000 sq. ft./lb of material. 

Adsorptive Properties. Substances such as silica gel and activated charcoal can be used to collect (adsorb) certain solids from solution. The adsorber bed may be discarded when depleted or recycled by washing and heating. 

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. 

In view of the enthalpy and activation energy (see Section II, B, 1) of the decomposition of arylpentazoles the activation energy for the reversal of the decomposition, the 1,3-addition of elementary nitrogen to arylazides, can be estimated to be 25-30 kcal/mole, an amount which does not exclude the reaction. To ascertain whether the decomposition of arylpentazoles is a reversible reaction, p-ethoxyphenylazide-[j8-N ] (see Section II, B, 3) adsorbed on charcoal was exposed to unlabeled nitrogen (45-50°, 380 atm, 100 hr), but the anticipated exchange of between the reactants was not detected. ... 

This step is almost always performed to get rid of the coloured impurities in the fermentation broth. The method is based on the fact that amino adds (esperially the non-aromatic amino acids) do not adsorb onto activated charcoal. Although the treatment is very effective, some of the amino acid is lost during this step. 

ANTIFLATULENTS. Activated charcoal can adsorb drugs while they are in the GI tract. The nurse administers charcoal 2 hours before or 1 hour after other medications. If diarrhea persists or lasts longer than 2 days or is accompanied by fever, the nurse notifies the primary care provider. Simethicone is administered after each meal and at bedtime... 

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. 

DL Sorby. Effect of adsorbents on drug absorption. I. Modification of promazine absorption by activated attapulgite and activated charcoal. J Pharm Sci 54 677-683, 1965. 

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