Preparation of Activated Carbon

Preparation of Activated Carbon. Pour about 50 ml of water and put 35 g of charcoal into a 100-ml beaker and heat the latter until the charcoal sinks completely into the water. Extract the charcoal from the beaker, dry its surface with filter paper, and weigh it. Calculate the amount of water (in per cent) adsorbed by the charcoal. 

For complete drying of the charcoal, put it into an iron crucible, cover it with a lid, and roast it during 20-30 min at 500 °C. Cool it in a desiccator. What is the essence of the carbon activation process  

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Ahmadpour A., Do D.D., The preparation of active carbons from coal by chemical and physical activation, Carbon 1996 34 471-479. 

Lozano-Castello D., Lillo-Rodenas M.A., Cazorla-Amoros D., Linares-Solano A., Preparation of activated carbons from Spanish anthracite. Carbon 2001 39 741-749. 

D. Lozano-Castello, M. A. Lillo-Rodenas, D. Cazorla-Amoros, and A. Linares-Solano, Preparation of activated carbons from Spanish anthracite I. Activation by KOH, Carbon, 39,741-749 (2001). 

D. Lozano-Castello, D. Cazorla-Amoros, A. Linares-Solano, and D. F. Quinn, Influence of pore size distribution on methane storage at relatively low pressure preparation of activated carbon with optimum pore size, Carbon, 40,989-1002 (2002). 

In general, two main methods for the preparation of activated carbons are used physical and chemical activation methods. Physical activation consists of a two-step process carried out at high... 

The thermodynamic approach considers micropores as elements of the structure of the system possessing excess (free) energy, hence, micropore formation processes are described in general terms of nonequilibrium thermodynamics, if no kinetic limitations appear. The applicability of the thermodynamic approach to description of micropore formation is very large, because this one is, in most cases, the result of fast chemical reactions and related heat/mass transfer processes. The thermodynamic description does not contradict to the fractal one because of reasons which are analyzed below in Sec. II. C but the nonequilibrium thermodynamic models are, in most cases, more strict and complete than the fractal ones, and the application of the fractal approach furnishes no additional information. If no polymerization takes place (that is right for most of processes of preparation of active carbons at high temperatures by pyrolysis or oxidation of primary organic materials), traditional methods of nonequilibrium thermodynamics (especially nonequilibrium statistical thermodynamics) are applicable. 

Let us consider the following mechanism of pore formation during the pyrolytic preparation of active carbon from primary organic material ... 

Such systems are realized first of all in pilot plants for pyrolytic preparation of active carbon, for instance, by means of the fluidization of an oxidizing agent into the solid phase in a nonstationary regime. The related heat-transfer equation contains the convection term and that of the heat effects of the chemical reaction ... 

L. M. S. Silva, J. J. M. Orfao and J. L. Figueiredo. Formation of two metal phases in the preparation of activated carbon-supported nickel catalysts. Applied Catalysis A General, 209, 145-154 (2001). 

Preparation of activated carbons with controlled pore size M.M.A. Freitas and J.L. Figueiredo ... 

Preparation of activated carbons with controlled pore size... 

J. H. Tay, X.G. Chen, S. Jeyaseelan, N. Graham, Optimising the preparation of activated carbon from digested sewage sludge and coconut husk , Chemosphere 44(2001)45-51... 

Rodriguez-Reinoso F, Molina-Sabio M, Gonzalez MT (1995) The use of steam and CO2 as activating agents in the preparation of activated carbons. Carbon 33(1) 15-23... 

Lozano-Castello D., Lillo-Rodenas M.A., Cazorla-Amoros D., Linares-Solano A., Preparation of activated carbons from Spanish anthracite. Carbon 2001 39 741-749. Weng T.C., Teng FI., Characterization of high porosity carbon electrodes derived from mesophase pitch for electric double-layer capacitors, J. Electrochem. Soc. 2001 148 368-373. 

Carbon molecular sieves have been prepared of active carbon precursors with chemical vapor deposited (CVD) amorphous carbon. Villar-Rodil and co-workers [159] employed STM to visualize the changes brought about by the CVD treatment on the pore mouth structure. They used STM as extremely surface-sensitive technique, since the CVD treatments are supposed to modify only the pore entrances. 

Most experimental results reported in literature were obtained using commercially available activated carbons. A few other studies were carried out with self synthesized activated carbons derived from different natural organic materials. The preparation of activated carbons consists of two main stages termed carbonization and activation, and the choice of conditions under which these processes are carried out, gives practically infinite number of combinations. The temperature, time and atmosphere (the nature of the gas or gas mixture, and its pressure or flow rate) are the main variables. Moreover, different additives can be added before or between these processes to modify the final product. Wood and coal are the most common precursors, but sorption properties of activated carbons derived from other materials, e.g. coconut shells or plum kernels can be also found in literature. Although the precursor material certainly has some effect on the adsorption properties of activated carbon, these properties are chiefly defined by the conditions of thermal treatment and purification vide infra). Therefore statements like, "activated carbon from coconut shells has higher affinity to certain adsorbate than activated carbon from wood" are misleading and they should be avoided. 

Kawabuchi, Y., Sotowa, C., Kuroda, K., et al. (1996). Preparation of active carbon fiber with basic properties. Abstracts, International Conference on Carbon, Carbon, Newcastle. UK, p. 431. 

Fig. 4. Set up of the pipette robot for automated preparation of activated carbon based metal oxides.

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