Heat treatment effect carbon areas

As a follow-up to this work. Walker and Baumbach (148) investigated the effect of heat treatment on the reactivities of carbons produced from 20 different coal tar pitches and one delayed petroleum coke. Heat treatment again produced a marked increase in crystallite size, a marked decrease in impurity content, and only a minor change in surface area. They use the... 

Lopez-Gonzalez et al. [218] also failed to cite the study by Humenick and Schnoor [216], but they analyzed in some detail the effect of carbon-oxygen and carbon-sulfur surface complexes on the uptake of mercuric chloride, which is very weakly ionized in aqueous solution. (The effectiveness of sulphurized carbons in removing mercury from air or water streams had been demonstrated earlier by Sinha and Walker [219], Humenick and Schnoor [216], and more recently by G6mez-Serrano and coworkers [208].) Their key results are summarized in Fig. 9. There was a noticeable uptake decrease when the activated carbons were oxidized with H Oi (AO). This decrease was not due to a reduction in the surface area and is contrary to the behavior of cationic metallic species, whose uptake is typically enhanced as a consequence of a lower pHp/x of the oxidized carbon. Upon subsequent heat treatment in helium at 873 K (A-873), the adsorption ca-... 

Nandi and Walker [499J compared the uptakes of two acidic and one basic dye by coals, chars, and activated carbons and noted that the area covered by a dye molecule would depend on the nature of the solid surface. They concluded that the removal of acidic groups by heat treatment had an effect on dye uptake for one activated carbon but had no effect for another. The authors did not report the pH of the adsorption measurements, nor did they characterize the surface chemistry of the adsorbents. McKay [500] did report the pH and even studied the effect of pH (in the range 5.2-8.5) on the rate of adsorption of Telon blue (an acidic dye), but the effect was neither clarified nor found to be significant. In contrast, Perineau et al. [501] noted major effects of pH on the adsorption of both an acidic and a basic dye and concluded that pH values of about 2 are the best for the adsorption of acid dyes whereas less acidic values (pH > 5) are to be preferred for the removal of basic dyes. ... 

F ure 1138 Effect of the temperature of heat treatments on hydrogen cracking susceptibility of quenched carbon steel (0.25% C) cathodically polarized at a potential of -0.14 V in carbonate-bicarbonate solution at 90 °C. Shown is the ratio of the reduction in area measured in the corrosive environment to that measured in a non-corrosive environment (oil) in SCC tests... 

The important finding here is that, contrary to the effect of hydroxide/anthra-cite ratio, an increase in N2 flow rate does not appreciably change the MPSD of the samples. Thus, a flow characteristic (N2 flow rate during the heat treatment process) opens anew way to prepare AC with both high adsorption capacity (high values of micropore volume and surface area) and narrow MPSD, which cannot be obtained by adjusting the other variables (i.e., hydroxide/carbon ratio, HTT, and soaking time). 

The methods proved to be very useful for the evaluation of the surface properties of various solids with mixed surface characteristics and changes in the surface character following oxidation, heat reduction, and comminution treatments. For example the effect of heat treatments on the amount of polar sites in a high surface area carbon black is shown in Figure 15, and the effect of graphite comminution in air and in liquid hydrocarbons is given in Table 2. 

Bae FT, Tryk DA, Scherson DA (1998) Effect of heat treatment on the redox properties of iron porphyrins adsorbed on high area carbon in acid electrolytes an in situ Ee K-edge X-ray absorption near-edge structure study. J Phys Chem B 102 4114-4117... 

BET is an important tool for ES characterization because surface area and pore size are both important parameters in determining material capacitance [59]. It is used to determine specific surface areas of electrode materials such as activated carbon and graphene [60]. Pore size measurements enable the estimation of electrochemical effectiveness of an active material when matched to a specific electrolyte [61-63]. Pore size and surface area are also good indicators of structural changes after chemical or heat treatment [64]. 

The effect of the surface structures of activated carbon on catalytic properties is large. Therefore, for the activated carbons as the support of ammonia catalysts, there are more rigorous and special demands, especially the surface area, meso-porous structure and surface groups. It can be seen from Table 6.11 that the specific surface area, whole pore volume and mesoporous volume of activated carbons are decreased apace and the pore structures are destroyed after heat treatment. 

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