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Learning about the Production of Activated Carbon

9/30/2013 12:44:20 PM | by Anonymous

Carbon: Activated

Activated carbon is derived from charcoal and is actually the carbon powder that is added to the water treatment process to adsorb the taste and odor. It is also known as the activated charcoal, carbo activatus or activated coal. It is a form of carbon that processed to be riddled with low volume and small pores that can increase the surface area available for chemical reactions and or adsorption. However, due to its high degree of micro porosity it will just take one gram of the activated carbon to have a surface area in excess of 500m2 as determined by adsorption isotherms of carbon dioxide gas at the room or 0.0C temperature. The activation level is sufficient for any useful application that may be attained solely from the high surface area and further the chemical treatment that often enhance its adsorption properties.

 

Production of Activated Carbon

The activated carbon is the carbon that produced from carbonaceous source of materials such as coconut husk, peat, wood, lignite, petroleum pitch, coal and nutshells. This can be produced by one of these processes which include the physical reactivation or chemical activation.

 

The physical reactivation is the source of material that is developed into activated carbon by using hot gases. This can be done using one or a combination processes such as carbonization and activation/oxidation. Carbonizations are materials with carbon content that is pyrolyzed at temperatures in the range of 600 to 900°C in the absence of oxygen which is usually in the inert atmosphere with gases like nitrogen or argon. Whereas activation/oxidation are carbonized materials or raw materials that is exposed to oxidizing atmospheres at the temperatures above 250°C and it is usually the temperature range of 600-1200°C.

 

The chemical activation is prior to carbonization and the raw material is impregnated with certain kinds of chemicals. The chemical is typically a strong base, acid or salt, sodium hydroxide, calcium chloride or potassium hydroxide and zinc chloride. After which, the raw material is carbonized at the lower temperatures at about 450 to 900°C. It is also believed that the activation or carbonization step proceeds simultaneously with the chemical activation. The chemical activation prefers over physical activation that owes to the lower temperatures and that need a shorter time for activating the material.

 

The gas treatment is the activating of carbon that can be done directly through heating the chamber while the gas in pumped in. This will expose it to the oxygen for oxidation purposes and when it is oxidized the active carbon is susceptible into adsorption for the process of surface bonding for the chemicals. This makes activated carbon good for filtering waste and toxic chemicals out of the gases and liquid. As for the physical gas treatment, the carbonization of pyrolysis process must take place at an inert environment at 600 to 900 degrees Celsius. After which the oxygenated gas is pumped into the environment and it will be heated between 900 and 1200 degrees Celsius which will cause the oxygen to bond with the carbon’s surface.

 

The post treatment for activated carbon is followed by oxidization the activated carbon but it can be processed for many different kinds of uses with several different properties. For instance, the granular activated carbon (GAC) is a sand-like product that is of the bigger grains than powdered activated carbon (PAC) and each are used for different applications. Some other varieties include the impregnated carbon which has different elements in it such as the iodine and silver as well as polymer coated carbons.

 

Applications

The activated carbon is usually used in decaffeination, metal extraction, water, gas and gold purification, sewage treatment and air filters in respirators and gas masks as well as other applications. The major industrial application that involves in using activated carbon is in the metal finishing field. They are very widely employed for purification of the electroplating solutions. For example: the main purification techniques of removal organic impurities are from the bright nickel plating solutions. There is a variety of organic chemicals that are added into the plating solutions for improving their deposit qualities and to enhance the properties such as the smoothness, brightness, ductility and etc.

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