Graphitized carbon adsorption

Fig. XVII-21. Continued) (c) Isosteric heats of adsorption of n-hexane on ice powder Vm = 0.073 cm STP. (From Ref. 125). (d) Isosteric heats of adsorption of Ar on graphitized carbon black having the indicated number of preadsorbed layers of ethylene. (From Ref. 126.)...

Fig. XVII-22. Isosteric heats of adsorption for Kr on graphitized carbon black. Solid line calculated from isotherms at 110.14, 114.14, and 117.14 K dashed line calculated from isotherms at 122.02, 125.05, and 129.00 K. Point A reflects the transition from a fluid to an in-registry solid phase points B and C relate to the transition from the in-registry to and out-of-registry solid phase. The normal monolayer point is about 124 mol/g. [Reprinted with permission from T. P. Vo and T. Fort, Jr., J. Phys. Chem., 91, 6638 (1987) (Ref. 131). Copyright 1987, American Chemical Society.]...

Such isothemis are shown in figure B 1,26.4 for the physical adsorption of krypton and argon on graphitized carbon black at 77 K [13] and are examples of type VI isothemis (figure B 1.26.3 ). Equation (B1.26.7)) further... 

Figure Bl.26.4. The adsorption of argon and krypton on graphitized carbon black at 77 K (Eggers D F Jr, Gregory N W, Halsey G D Jr and Rabinovitch B S 1964 Physical Chemistry (New York Wiley) eh 18).

Similar results with graphitized carbon blacks have been obtained for the heat of adsorption of argon,krypton,and a number of hydrocarbons (Fig. 2.12). In all these cases the heat of adsorption falls to a level only slightly above the molar heat of condensation, in the vicinity of the point where n = n . 

Fig. 2.22 Adsorption isotherms of argon on graphitized carbon black at a number of temperatures," plotted as fractional coverage 0 against relative pressure p/p°. (Courtesy Prenzlow and Halsey.)...

Fig. 2.23 Adsorption isotherms on graphitized carbon black at 77 K. (A) argon (B) krypton. (Courtesy Dash.)...

Fig. 5.10 The adsorption isotherms of n-hexane (A) and of water (B) on graphitized carbon black.Solid symbols denote desorption. (After...

A CSP based on the adsorption of a chiral anthrylamine on porous graphitic carbon successfully resolved the enantiomers of tropic acid derivatives and anti-inflammatory agents in SFC [65]. The carbon-based CSP produced superior results when compared to an analogous silica-based CSP. Occasional washing of the column was necessary to remove highly retained substances. 

Figure 9.16 The practical examples of comparative plots (a) N2 adsorption on a graphitized carbon black, modified by physical adsorption of methanol (the numbers correspond to the amount of CH3 OH in the fractions of monolayer capacity) [83] (b) the usual types of comparative plots by [3] and (c) N2 isotherms on microporous titanium oxide after various amount of preadsorbed nonane by [53].

Wetting properties. A clean carbon surface is hydrophobic. Surface oxides provide sites of adsorption for water and other polar compounds. The more surface oxides there are, the more distinct is the hydrophilic behavior of the carbon. This was confirmed by Healey et al. (39) for graphitized carbon black, and by Kraus (40) and A. V. Kiselev and his group (41) for carbon black. Beebe and Dell (42) measured the sulfur dioxide adsorption on channel black and found an increase after oxidation at 600°. Further evidence for selective adsorption of polar compounds was provided by Gasser and Kipling (43). 

Keywords DNA Adsorption Materials Graphite Carbon Composite Nanotube Electrochemical sensing... 

Figure Ic differs markedly from those obtained for the immersion of polar solids in water initially the heat values are small but increase with increasing amounts of preadsorbed water. Thus far, only one such curve has been reported in the literature for the system Graphon-water 90). Graphon is a graphitized carbon black which has an essentially homogeneous, homopolar surface 21). Nevertheless, a small fraction of heterogeneous sites is responsible for the limited adsorption of water on the surface of this solid. Similar curves can be expected for other hydrophobic solids.

Fig. 4. Stability of carbon on different sites (A-D) on a pure nickel(l 11) surface (below) and a gold-alloyed nickel(l 11) surface (above). The probability of nucleation of graphite is determined by the stability of the adsorbed carbon atoms. The less stable the adsorbed carbon, the larger the tendency to react with adsorbed oxygen to form CO and the lower the coverage. On the pure nickel) 111) surface, the most stable adsorption configuration of carbon is in the threefold (hep) site (lower curve). The upper graph shows that carbon adsorption in threefold sites next to a gold atom is completely unstable (sites B and C), and even the threefold sites that are next-nearest neighbors (sites A and D) to the gold atoms are led to a substantial destabilization of the carbon. From Reference (79).

Evaluations of an integrated adsorption system were also conducted. In this system, by varying the pH conditions, the dissolved organics (model compounds) are separated into fractions by isolation onto Amberlite XAD-8, AG MP-50 cation-exchange resin, and graphitized carbon black. The procedure is based on the separation of organic solutes into hydrophobic and hydrophilic neutral, acidic, and basic fractions. 

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