Activation, carbon surfaces

Catalysis. Catalytic properties of the activated carbon surface are useful in both inorganic and organic synthesis. For example, the fumigant sulfuryl fluoride is made by reaction of sulfur dioxide with hydrogen fluoride and fluorine over activated carbon (114). Activated carbon also catalyzes the addition of halogens across a carbon—carbon double bond in the production of a variety of organic haUdes (85) and is used in the production of phosgene... 

Tailoring Activated Carbon Surfaces for Water, Wastewater and... 

Hazardous Waste Treatment Operations - Tailoring Activated Carbon Surfaces for Water, Wastewater and Hazardous Waste Treatment... 

The above proposed process can be expected to easily put into practice as ammonia is abuandant as the main feedstock for fertilizer. Nevertheless, there is also a problem that Co(NH3)6 is apt to be oxidized to Co(NH3)6 which is unable to form the peroxo binuclear complex and ineffective to O2 solubility enhancement, thus reaction (4) is inhibited. But Co will be relatively stable, and Co may be reduced to Co " by H2O [12]. As a result, a regenration method has also been proposed by using the activated carbon as the catalyst[7], in which Co(NH3)6 dissociation into Co " and NH3 occurs on the activated carbon surface followed by reduction of Co with H2O into Co, O2 and H. ... 

Molecular Characterization It has been repotted that o-qulnones oxidize ascorbic acid In homogeneous solutions (25). Surface qulnones have also been reported to exist on activated carbon surfaces (16). However, cyclic voltarammetry Is not sufficiently sensitive to allow an unambiguous Identification of the reversible wave ascribed to surface qulnones (16). Therefore, differential pulse voltammetry (DPV) and square wave voltammetry were employed. 

Figure 3.27. Functional groups on activated carbon surfaces (Vinke, 1991).

These data show that, indeed, mesopores dominate except in zeolites and active carbons. Surface areas can be very high viz., up to a few football fields per kg ). 

J.S. Mattson and H.B. Mark, Activated Carbon Surface Chemistry and Adsorption from Solution, Marcel Dekker, 1971. 

Adsorption occurs when an organic molecule is brought to the activated carbon surface and held there by physical and/or chemical forces. The quantity of a compound... 

Ania CO, Bandosz TJ. Surface Chemistry of Activated Carbons and its Characterization In Activated Carbon Surfaces in Environmental Remediation, Bandosz, T J, Ed. Elsevier, Oxford, 2006.159-230. 

Yamamoto, K., M. Seki, and K. Kawazoe. Effect of sulfuric acid accumulation on the rate of sulfur dioxide oxidation on activated carbon surface. Nippon Kaguku Kaiski 7 1268-2179, 1973. (in Japanese, summary in English)... 

Garten and Weiss (8) have postulated that strong acids react with chromene functional groups on the active carbon surface in the following manner ... 

Since GC does not require the binders or fillers used in graphite composites, there is no residual binder on the active carbon surface. Thus GC is potentially more reactive toward electron transfer. The k° for Fe(CN) /4 ranges from <0.001 to >0.5 cm/s for GC in 1 M KC1, depending on surface pretreatment, as shown in Table 10.4. 

All of these features considerably improve the sorption capacity of carbons, and their capacity to remove contaminants and pollutants interacting with the surface of carbons in a dispersive way [177], In addition, active carbon contains heteroatoms such as oxygen, and, to a smaller degree, nitrogen and sulfur. These atoms are bound to the activated carbon surface in the form of functional groups, which are acidic or basic, giving the activated carbon surface an acidic or basic character, respectively [173,178], It is as well necessary to state that the chemical heterogeneity of the carbon surface is mostly the result of the presence of heteroatoms [175],... 

Vol. 7 Activated Carbon Surfaces in Environmental Remediation Edited by Teresa J. Bandosz... 

In the literature it has been found that during mixing aggregate breakdown occurs for a number of carbon blacks in highly viscous rubbers [115— 118]. Recently, the aggregate breakdown was also attributed to classes of specific shapes of individual carbon blacks [108]. The opinion about the mechanical consequences of this process is quite different. On the one side, no obvious relationship to reinforcement is conjectured [116]. On the other side, improvements of the mechanical performance, due to the creation of new, active carbon surface, is assumed, which participates in formation of a strong filler-rubber coupling [118]. 

Furthermore, table 2 and figure 2 demonstrate the high affinity of the activated carbon surface for nimesulide. The equilibrium loadings at 10-20% of the saturation concentration are in the region of 80-90% of the final equilibrium loading at saturation concentration. 

In table 3 the desorption capacities of each experiment are presented. It can be seen that the desorption capacity (ratio between the desorbed and filled nimesulide) increases with increasing solubility of nimesulide in C02. Due to the high affinity of the activated carbon surface to nimesulide the desorption capacity itself is very poor (max. value 38%). Since higher desorption capacity are related to higher solubilities, the addition of co-solvents to C02, as proposed by Macnaughton et al. [9], can increase the solubility and therewith the desorption capacity. 

The most characteristic feature of quinones is their ease of reduction and reoxidation they play a part in the redox processes of many living systems (22). Furthermore, they can interact with amino and sulfhydryl groups. One might therefore expect quinone-like groups to participate in protein adsorption and perhaps cell adhesion although no direct evidence is available to support this hypothesis. Studies of quinone-like groups on activated carbon surfaces (23) indicate such groups can participate as electron donors in donor-acceptor complexes with adsorbed molecules (17, 24). 

Much of the above data on activated carbon surfaces can be correlated with the results on isotropic pyrolytic carbon surfaces due to the similarities in microstructure. The advantage of the pyrolytic carbon is in the reproducibility of the carbon surface (25) utilizing carefully controlled processing conditions. 

The objective of this study is to evaluate which features of activated carbon surfaces are important for adsorption of acetaldehyde. The evaluation is based on the values of isosteric heats of adsorption, which reflect the strength of molecule interactions with the sorbent surface. After oxidation and urea modification the changes in surface chemistry and porous structure occurred. Those changes are expected to affect the dispersive and specific interactions of acetaldehyde with the activated carbon surfaces. 

Some of these techniques may be applied to coat a solid layer on monoliths, provided suitable reactions and appropriate reaction conditions arc chosen. Mocne ct al. [106,107] described the coating of a SiC layer on a microporous active carbon surface using the CVD or CVI techniques. Their results can easily be translated to monolithic catalyst support synthesis. 

Interactions Between Heavy Metal Ions and an Active Carbon Surface 182... 

In this chapter, attention is given to the cyclovoltammetric studies of phenomena at the interface between chemically and electrochemically modified active carbon and an aqueous or nonaqueous electrolyte solution. Interactions between selected heavy metal ions and an active carbon surface are also discussed. Before the various structural and CV measurement results are considered, a review, together with some pertinent details, will be given in every. section. 

---