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Abstract  

Enthalpies of wetting of two active carbons and one brown coal coke by several pure liquids (mainly homologous series) were measured at 298.15 K with two quasi-isothermal microcalorimeters. Different measuring cells with cavities of about 0.5 and 15 cm3 were used. The advantage of the larger measuring cell with three independent 15 cm3 cavities is the higher mass of active carbon, leading to a high reproducibility with standard deviations below 1% and a reduced measuring time. Experiments were carried out with n-alkanes, l-alkanols, cycloalkanes and isomers thereof, i.e. 2-propanol, methylcyclohexane, 2,2,4-trimethylpentane (isooctane and 2-ethyl-1-hexanol, and water. Like the polarity, the size and the three-dimensional expansion of the molecules, the energetic and geometric heterogeneity of the adsorbent influences the enthalpy of wetting.

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Abstract  

The influence of active carbon as support on the reducibility of supported metals (Ni, Cu, Cd, Zn) has been studied by means of a temperature programmed reduction (TPR) technique. The TPR profiles indicate that active carbon behaves as a dispersion agent and the supported metal is dispersed in a disordered phase rather than as a stoichiometric compound. The hydrogen consumed in the reduction indicates that the metal residues are present in monovalent and divalent forms. High-temperature reduction peaks were also observed and are explained on the basis of metal-surface interactions and the porosity of the active carbon. Nitrogen adsorption reveals that the active carbon porosity decreases due to progressive closure of the pores when metals are supported on the surface of active carbon.

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a high specific surface area active carbon as support. The Ni–K/AC catalyst (loading of Ni and K being 3.0 and 1.0 wt%, respectively) was prepared by co-impregnation of active carbon with an aqueous solution of Ni(NO 3 ) 2 ·6H 2 O and KNO 3 . Both

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Abstract  

Next to the collection of particulate matter from air by micropore filtration, gaseous trace constituents may be sampled by an additional or separate active carbon cartridge. Either reversible or irreversible adsorption results. Important respective applications are the assay 222Rn (emanation) and the collection of mercury vapor. Formulation of both cases and their consequences for routine application are given here.

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Thermal analysis data on the oxidation reaction between air and active carbons obtained during activation by carbon dioxide are presented. The correlation between the modified DTA curves and the TG curves leads to the conclusion that the oxidation of active carbons in the temperature range from 20 to 1000° is a two-step process. It is pointed out that the oxidation reactions in the low-temperature region (450–550°) are governed by the oxygen content of the samples, whereas the reactions in the higher temperature region (550–850°) are controlled by the diffusion process.

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Abstract  

Corn cobs obtained as waste from the corn industry, were analyzed by a TG-DTA unit in an atmosphere of flowing nitrogen. The carbonaceous products so formed were then produced on a preparative scale and activated chemically using potassium hydroxide. This resulted in the formation of a carbon with a very high surface area. The active carbon produced was then examined using thermal analysis in the temperature jump mode on a thermogravimetry unit. From this data the kinetics of degradation of the active carbon was determined using zero order rate kinetics. The pore structure of the active material was also examined using SEM. TheE a for activated corn cobs was found to be 106 kJ mol−1.

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Abstract  

The adsorbability of pertechnetate ion (TcO 4 ) reached 96% for an active carbon at the 0.1 g/50 ml concentration level, increasing with diminution of acid and its salt concentrations, and depending on the type of anions present. With constant anion concentration, TcO 4 adsorbability rose with decreasing pH in the acidic region, followed in the region around neutrality by a plateau, and in the basic region by an appreciable decline of TcO 4 adsorbability. In the acidic region, part of once-adsorbed TcO 4 appeared to be displaced by other anions. Reversibility was noted between the adsorption and desorption of TcO 4 .

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Abstract  

TG, DTG and DTA methods were used for the investigation of some waste agricultural products, such as grape seeds, walnut shells, plum and peach stones, which can serve as raw materials for the production of active carbons. It was demonstrated that thermo analytical methods are appropriate to study the thermal characteristics of the above wastes and the data obtained can be applied to the technological processes of active carbon preparation.

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DTA and TG curves from investigations on the oxidation of active carbon-nickel catalysts in a static air atmosphere with a derivatograph were used to construct modified DTA curves, theΔT/m R plots (wherem R is the reactive mass of the sample). TheΔT/m R plots in the range from 200 to 850° led to the finding that the oxidation process is a two-stage reaction. In the diffusion region the reaction depends on the pore volume with pore radii from 75 to 7500 nm. The variations in the ignition temperature with the nickel content of the samples are presented.

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