Activated Carbon by Chemical Activation

The preferred feedstock for chemical activation (see Fig. 5.7-1) is wood, in the form of sawdust. These processes are based on the dehydration of the feedstock by reaction with dehydration agents and are particularly effective with cellulose-containing materials. Chemicals such as phosphoric acid or zinc chloride are utilized. Sawdust is mixed with phosphoric acid or zinc chloride, optionally formed, and then heated to 400 to 600°C when phosphoric acid is utilized or to 600 to 700°C when zinc chloride is utilized. 

Processing of materials activated using this process is relatively difficult and complex, since on economic and ecological grounds most of the chemicals have to be recovered. They have to be repeatedly washed to obtain an activated carbon which is largely free of activation agent. 

Powdered activated carbon is usually produced using these processes, but it is also possible to produce formed carbon by forming (granulating) mixtures of sawdust or peat and activation agent. 

Chemical activation dehydration of the feedstock by reaction with phosphoric acid or zinc chloride at 400 to HH)°C with subsequent removal of the activation agent by repeated washing 

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The steps involved in the production of activated carbons by chemical activation with H3PO4 are ... 

Caturla, R, M. Mohnasabio, and R Rodriguezreinoso. 1991. Preparation of activated carbon by chemical activation with ZnClj. Carbon 29(7) 999-1007. 

Besides the effects of the typical carbon functional groups, the role of nitrogen and sulfur functionalities, introduced on carbons by chemical and thermal treatments, on the electrochemical performance of Pt catalysts for oxygen reduction in direct methanol fuel cells was investigated [47]. Once again, the metal-support interaction influences the size and chemical state of platinum particles and, as a consequence, the electrocatalytic activity. The introduction of nitrogen and sulphur functionalities was reported to improve the catalytic activity, but this result was mainly ascribed to the Pt particle size. 

Kartel MT, Sych NV, Tsyba MM, Strelko W (2006) Preparation of porous carbons by chemical activation of polyethyleneterephthalate. Carbon 44(5) 1019-1022... 

Sutures are required to hold tissues together until the tissues can heal adequately to support the tensions exerted on the wound duting normal activity. Sutures can be used ia skin, muscle, fat, organs, and vessels. Nonabsorbable sutures are designed to remain ia the body for the life of the patient, and are iadicated where permanent wound support is required. Absorbable sutures are designed to lose strength gradually over time by chemical reactions such as hydrolysis. These sutures are ultimately converted to soluble components that are then metabolized and excreted ia urine or feces, or as carbon dioxide ia expired air. Absorbable sutures are iadicated only where temporary wound support is needed. 

Chemical filters are used to collect gases these are mainly adsorption filters based on activated carbon. By the addition of chemical substances, impregnation ), gases which are difficult to adsorb are adsorbed and retained by-means of a chemical reaction. 

Both share more or less the same merits but also the same disadvantages. The beneficial properties are high OCV (2.12 and 1.85 V respectively) flexibility in design (because the active chemicals are mainly stored in tanks outside the (usually bipolar) cell stack) no problems with zinc deposition in the charging cycle because it works under nearly ideal conditions (perfect mass transport by electrolyte convection, carbon substrates [52]) self-discharge by chemical attack of the acid on the deposited zinc may be ignored because the stack runs dry in the standby mode and use of relatively cheap construction materials (polymers) and reactants. 

Although decarboxylation reaction seems to be a simple one-carbon removing reaction, it is demonstrated that this reaction is a unique and useful reaction in the preparation of optically active carboxylic acids. If the starting material is a racemic carboxylic acid, the optically active compound can be obtained via symmetrization by chemical carboxylation followed by asymmetrization via enzymatic reaction. Accordingly, the whole process can be said as chemicoenzymatic deracemization (Fig. 24). 

M. J. McGuire and I. H. Suffet, "Treatment of Water by Granular Activated Carbon", American Chemical Society, Washington, D.C., 1983. 

Kuo, C.S., Tseng, Y.H., Huang, C.H., and Li, Y.Y. (2007) Carbon-containing nano-titania prepared by chemical vapor deposition and its visible-light-responsive photocatalytic activity. Journal of Molecular Catalysis A Chemical, 270 (1-2), 93-100. 

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

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