Charcoal, as adsorbent

With charcoal as adsorbing agent in the case of an acid such as hydrochloric acid the hydrogen ions are more readily adsorbed than... 

Universal antidotes These antidotes can be given in all such conditions where nature of poison is not known or where more than one poison is suspected to be taken e.g. charcoal as adsorbent of toxins and alkaloids, tannic acid for precipitating alkaloids, glycoside and many metals. 

The procedure recommended by Schramm and Primosigh includes a pre-treatment of the column with 5% acetic acid. Without this procedure, part of the amino acids remain flrmly bound to the adsorbent. This has also been a quite general experience in the numerous experiments by the author and his collaborators, using active charcoal as adsorbent. In the separation of the higher saccharides a partial saturation of the charcoal with phenol or ephedrine was found necessary (Tiselius and Hahn, 1943). 

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. 

PerSniemi S., Hannonen S., Mustalathi H., Ahlgren M., Zirconium-loaded activated charcoal as an adsorbent for arsenic, selenium and mercury, Fresenius J. Anal. Chem. 349, 1994,510-515. 

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. 

In some cases it has been found that the maximum on saturation adsorption of a solute from a solution corresponds to the formation of an adsorption layer one molecule thick. Thus Euler Zeit. Elehtrochem. xxviii. 446,1922) found that a maximum adsorption of silver ions by silver and gold leaf was attained in a 0 03 A solution. It was found that 5 5 and 8 5 to 9 mgm. of silver ions were adsorbed by a square metre of metallic silver and gold respectively, such a surface concentration is practically unimolecular. The adsorption of silver ions by silver bromide (K. Fajans, Zeit Phys. Ohem. cv. 256, 1928) was found on the other hand to be not complete, for only every fourth bromide ion in a silver bromide surface was found to adsorb a silver ion. Similar conclusions as to the unimolecular character of the adsorbed film in the case of chemical charcoal as an adsorbing agent for fatty and amino acids may be drawn from the data of Foder and Schonfeld Koll. Zeit xxxi. 76, 1922). 

Mark and Saito 31) attempted fractionating polymers by means of chromatography as early as 1936. They filtered solutions of cellulose acetate in acetone through a column with a charcoal-like adsorbent made from blood. The eluate contained the fraction of highest molar mass the rest of the sample was trapped in the column. It could be extracted by dioxane from separated portions of the packing. The largest molecules had travelled farthest. This was in contrast to expectation from Traube s rule and indicated size exclusion. 

Techniques of Purification. The purification techniques have included column and batch adsorption, extraction, dialysis, and column and paper chromatography. Liberal use was made of the fact that the gibberellate anion is not soluble in ethyl acetate, whereas the free acid is soluble, and that charcoal will adsorb GA3 from aqueous solutions but release it with acetone (26). As a rough rule, preliminary concentration by a factor of about 105 was necessary before significant use of paper chromatography could be made. For kudzu vine and pinto bean, a known amount of GA3 was added to an aliquot of the plant extract and taken through the same procedure as the initial extract. These controls are subsequently referred to as "spiked extracts, to differentiate them from the initial or "natural extract. 

The NIOSH methods, in general, are based on adsorption of compounds in the air over a suitable adsorbent, desorption of the adsorbed analytes into a desorbing solvent, and, subsequently, their determination by GC using a suitable detector. A known volume of air is drawn through a cartridge containing coconut shell charcoal. The adsorbed compounds are desorbed into carbon disulfide, propanol, benzene, toluene, hexane, or methylene chloride. An aliquot of the solvent extract is then injected onto the GC column. FID is the most commonly used detector. Other detectors, such as ECD, ELCD, or PID have been used, however, in the method development of certain compounds. NIOSH method numbers and the analytical techniques are presented in Table 2.9.3. 

The history of thin-layer chromatography has been the subject of a book.158 The first separations on thin layers were performed in 1938. A gas was first used as the mobile phase in adsorption chromatography by Erica Cremer in Innsbruck in 1946. Using hydrogen as carrier gas, she and her student, Fritz Prior, successfully separated air and carbon dioxide using charcoal as the adsorbent. A newly-opened branch of the Deutches Museum in Bonn, devoted to post 1945 developments, has a display featuring the work of Cremer and Prior, with a model of their original apparatus.159... 

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 commonest gel for adsorption purposes is silica gel but measurement have also been carried out on ferric oxide, aluminium oxide, stannous oxide and titanium oxide. The characteristics of adsorption on silica gel differ somewhat from those for charcoal, particularly with respective Freundlich isotherm which holds fairly accurately. Moreover, deviation from Henry s Law even, seems to be much less than for charcoal. Water is somewhat exceptional. Silica and alumina gels are used as adsorbents for removing moisture and for controlling humidities of rooms. 

Removal of heavy-metal ions has been a major focus in environmental remediation and cleanup. Various materials, such as activated charcoal, clays, sihca gels, and ion-exchange resins have been used as adsorbents. Functionahzed mesoporous sihcas have recently proved to be a promising or even better alternative. Mercier etal. prepared a... 

Adsorption passes the air-solvent vapor mixture through a bed of activated charcoal. Most of the solvent vapors are adsorbed by the charcoal as the air, with some traces of solvent, passes through. When the charcoal is almost saturated with solvent, the air-solvent vapor mixture is sent to a second charcoal adsorber while the first one is cleansed with hot steam to strip out the solvent. The steam-solvent mixture is then condensed and sent to the solvent-water separator. Care should be exercised not to overload the adsorber with hexane vapors. Adsorption of hexane by carbon releases heat. If unmonitored and uncontrolled, the adsorber could catch on fire. This is especially likely to happen if a process upset sends a sudden surge of hexane vapors to the adsorber. 

More recently, Peraniemi et al. [229] advocated the use of zirconium-loaded activated charcoal as an effective adsorbent for mercury (and especially for arsenic and selenium), the rationale being that the presence of active metal on an impregnated charcoal surface can greatly affect the adsorption affinity. They compared the pH effects on the uptakes by both a loaded and an unloaded commercial charcoal powder and concluded that the adsorption mechanism of mercury differs from that of the anionic arsenic and selenium species. They also noted the highly complicated behavior of mercury in aqueous solutions and did not attempt to explain the apparent absence of pH dependence of the uptakes. 

The BET surface area of several charcoal batches was measured with a Micromeritics ASAP 2000 automated gas adsorption apparatus. As adsorbent gas we used CO at 273 K as it may reveal more of the surface area residing in the micropore domain of the charcoal than, e.g., at 77 K."... 

A number of readily available materials are useful as adsorbents, and some of these are summarized in Table 4-1 in order of decreasing adsorption alEnity. Charcoal, silica gel, and alumina have the highest surface area per unit weight of the compounds on the list, and in the absence of other factors, these adsorbents would have the highest... 

Albuterol overdoses rarely require treatment beyond gastrointestinal decontamination. Children have survived overdoses as large as 100 mg and adults have survived doses up to 240 mg without serious complications. Activated charcoal effectively adsorbs albuterol. The hypokalemia produced reflects a transient shift in potassium location rather than a true deficit of potassium external replacement therapy is rarely necessary but can be added to intravenous fluids to support the heart if electrocardiographic changes are noted. A conservative approach to tachycardia is recommended since arrhythmias beyond an increase in rate have not occurred with overdose. Support of blood pressure and control of tachycardia are major therapeutic interventions. 

Basic and advanced life-support measures should be utilized as necessary. Activated charcoal will adsorb... 

Basic and advanced life-support measures should be performed as necessary. Gastrointestinal decontamination procedures should be considered for substantial recent ingestions. Activated charcoal will adsorb codeine. Patients with respiratory or CNS depression can be treated with intravenous boluses of naloxone. A continuous naloxone infusion may be necessary if the toxic effects of codeine persist longer than the duration of action of naloxone. 

Basic and advanced life-support measures should be utilized as necessary. Treatment of colchicine toxicity is largely supportive. Activated charcoal effectively adsorbs colchicines and should be administered for substantial recent ingestions. Aggressive early gastrointestinal decontamination may be life saving. Severe anemia may require packed red blood... 

Activated charcoal will adsorb methyldopa and should be considered in patients with substantial recent ingestions. Standard supportive therapies, such as support of airway, breathing, and circulation, should be utilized as clinically necessary. Administration of vasopressors may be required for patients experiencing profound cardiovascular effects. Hemodialysis is of theoretical value if standard therapies fail. 

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