Adsorption, by charcoal

After an extensive study of the adsorption of arsenious oxide by metallic hydroxides,3 Sen concluded that this type of adsorption resembles that of cations by manganese dioxide, and that the chemical affinity between the adsorbent and the substance adsorbed plays an important part, thus differing from adsorption by charcoal. It has been observed that soils having a high absorption capacity for bases also absorb the arsenite ion from solutions of 0-001 to 0-01X concentration.4 The absorption increases with time, without reaching an end-point, and the process follows the normal adsorption equation C1=kC1Jn. The addition of ferric oxide or calcium carbonate to the soil considerably increases the capacity for absorption, but such salts as calcium sulphate or copper sulphate have no effect. 

If a sound theoretical adsorption wave expression could be applied to this problem, it would not only greatly reduce the number of experiments necessary to define completely the geometry of the bed, but could also be useful in the elucidation of the mechanism of adsorption of various gases on different types of adsorbents, from which information could be derived for their improvement or to indicate when the adsorbent has attained its maximum efficiency. Theoretical treatment of the problem has been made by various investigators (73,74,75). However, these workers did not have sufficient experimental data to support their views. The problem of adsorption by charcoal was treated by Wicke (76) and a number of useful differential equations derived. However, a real... 

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. 

Langmuir found, however, that his isotherm equation ...which apply to adsorption by plane surfaces, could not apply to adsorption by charcoal [115]. Moreover, he stated in tiie same paper that for porous sorbents like charcoals ...it is impossible to knov definitely the area on which the adsorption takes place . In the light of the abtve comments, the Sing s critical statement [118] that Langmuir equation is still widely used in order to analyse the experimental isotherms measured on activated carbons is extraordinarily accurate. 

Adsorption beds of activated carbon for the purification of citric acid, and adsorption of organic chemicals by charcoal or porous polymers, are good examples of ion-exchange adsorption systems. Synthetic resins such as styrene, divinylbenzene, acrylamide polymers activated carbon are porous media with total surface area of 450-1800 m2-g h There are a few well-known adsorption systems such as isothermal adsorption systems. The best known adsorption model is Langmuir isotherm adsorption. 

Kr is extracted either by stepwise heating or melting of a sample followed by usually several gas clean-up steps and by separation of Kr from other noble gases by selective adsorption on charcoal at cryogenic temperatures [11]. Kr is analysed in ultra-clean static mass spectrometers which allows recycling of... 

D Sahal. Removal of iodine by solid phase adsorption to charcoal following iodine oxidation of acetamidomethyl-protected peptide precursors to their disulfide bonded products oxytocin and a Pre-S, peptide of hepatitis B illustrate the method. Int J Pept Res 53, 91, 1999. 

Though there are hardly any restrictions to choosing a target, pharmacological receptors are investigated most frequently. The nature of the receptor, v hether it is membrane-bound or soluble, determines which separation technique is used to terminate the binding assay. For the former, filtration or centrifugation are favored as separation steps, while for the latter suitable methods are gel filtration, equilibrium dialysis, precipitation or adsorption of the nonbound marker by charcoal [23, 24]. 

Biotin is present in natnre predominantly bonded to protein and is relatively stable therefore it can be extracted under hard conditions, snch as autoclaving in sulfuric acid. Enzyme digestion is also applied to break the protein-biotin bond. A following purification is usually performed by adsorption on charcoal or by lEC. 

If is much larger than the saturation value b of the very active area will be attained before the second term becomes at all large and there will be an apparent break in the x, p curve such a case has been noted by Gustaver Koll. Bdheft, xv. 219, 1921) in the adsorption of picric acid from solution by charcoal. 

The following data indicate the close agreement between the data obtained by Titoff and those calculated with the aid of this equation for the heat of adsorption of ammonia by charcoal at 0° G. is calculated and determined in calories per c.c. of ammonia (at N.T.P.) adsorbed, x is measured in c.c. per gm. at N.T.P. 

The adsorption of a particular solute from a solution is however dependent upon the nature of the solvent, a point not envisaged by the Freundlich isotherm. The influence of the solvent on the amount of adsorption of a particular solute has been investigated in the case of iodine and charcoal by Davis (J.C.8. xci. 1666,1911) who found that the amount of iodine adsorbed by charcoal from solutions of equimolecular concentrations decreased with the nature of the solvent in the following order ... 

In a few cases examined Williams has actually obtained this transition as instanced by the following data for the adsorption of potassium chloride in aqueous solution by charcoal. 

Identical maximal values for the adsorption by blood charcoal were found for the acids HCl, HNO3, H2SO4 in the presence of their neutral salts, viz. a 45 % adsorption in a O Ol molar solution. Of interest is the fact that similar results were obtained for the adsorption of hydroxyl ions, e.g. caustic potash and soda, in the presence of excess potassium and sodium chlorides, both hydrogen and hydroxyl ions exhibiting equal adsorption. 

J. Dewar Found selective adsorption of oxygen from a mixture with nitrogen, during the uptake of air by charcoal 1904... 

Rosel I, A., Gomez-Behnehon, J.L, and Grimalt, J.O., Gas Chromatographic-Mass Spectrometric Analysis of Urban-Related Aquatic and Airborne Volatile Organic Compounds Study of the Extracts Obtained by Water Closed-Loop Stripping and Ah Adsorption with Charcoal and Polyurethane Foam, Journal of Chromatography. Biomedical Applications, Vol. 562, p 493-506. 1991. 

Methane. Research Grade (about 99.65 mole % pure) and CP (about 99.0 mole % pure) methane are available in cylinders. The removal of C02, Q, N2, and higher hydrocarbons from methane by adsorption on charcoal has been described in the literature.65... 

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