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Terminology of Activated Carbon
  • DATA:2020-05-07

The main raw materials can be carbon-rich organic materials such as coal, wood, and nut shells. These carbonaceous materials are converted into activated carbon by pyrolysis under high temperature and pressure in an activation furnace. During this activation process, a huge surface area and complex pore structure are gradually formed, and the so-called adsorption process is carried out in these pores and on the surface. The size of the pores in the activated carbon has a selective adsorption effect on the adsorbent. Macro-molecules cannot enter the pore diameters of activated carbon that are smaller than its pores.
 
 The adsorption of activated carbon can be divided into physical adsorption and chemical adsorption.

a. Physical adsorption mainly occurs during the removal of impurities in the liquid and gas phases by activated carbon. The porous structure of activated carbon provides a large surface area, which makes it very easy to adsorb and collect impurities. Just like magnetic force, all molecules have mutual attraction. Because of this, a large number of molecules on the pore wall of the activated carbon can generate a strong gravitational force, thereby achieving the purpose of attracting impurities in the medium into the pore diameter. It must be pointed out that the molecular diameter of these adsorbed impurities must be smaller than the pore diameter of the activated carbon, so that it is possible to ensure that the impurities are adsorbed into the pore diameter. This is why we constantly change the raw materials and activation conditions to create activated carbons with different pore structures, which are suitable for the adsorption of various types of impurities.
  
 b.In addition to physical adsorption, chemical reactions often occur on the surface of activated carbon. Activated carbon not only contains carbon, but also contains a small amount of oxygen and hydrogen in the form of chemical bonds and functional groups on its surface such as carboxyl, hydroxyl, phenols, internal lipids, quinones, ethers, and the like. These surfaces contain earth oxides or complexes that can chemically react with the substance being adsorbed, thereby binding to the adsorbed substance and accumulating on the surface of the activated carbon. Take a typical example: during water treatment process, activated carbon can react with chlorine in water to change the chlorite into the form of chloride ions, so as to achieve the purpose of removing chlorine in the water, so that the water no longer has unpleasant taste and smell.