What are uses of activated carbon



  Activated carbon or short Charcoal (Carbo medicinalis, medicinal charcoal) is a fine-grain charcoal with a large internal surface, which is used as an adsorbent in chemistry, medicine, water and wastewater treatment, as well as ventilation and air conditioning technology. It is used in granulated form or in the form of tablets (compressed charcoal).

properties

Activated carbon consists mainly of carbon (mostly> 90%) with a highly porous structure. The pores are connected to one another like a sponge. The inner surface is between 300 and 2000 m² / g coal. The inner surface of 2 grams of activated carbon corresponds roughly to the area of ​​a soccer field. The density of activated carbon is in the range from 200 to 600 kg / m³. The pore size distribution of the micropores (

In the case of a cube with an edge length of 1 cm, the inner surface exceeds the outer surface by a factor of more than 10,000.

Extraction

Activated charcoal is made from vegetable, animal, mineral or petrochemical substances. The starting materials used are z. B. wood, peat, nutshells, brown or hard coal or plastics. Accordingly, it is also known as biochar. As animal charcoal, lat. carbo animalis, is called activated charcoal, which is made from animal blood (blood charcoal) or from bones (bone charcoal).

They are generally produced by treatment with dehydrating agents (zinc chloride, phosphoric acid) at 500–900 ° C or by dry distillation. The raw activated carbon obtained in this way is then oxidatively activated at 700-1000 ° C with water vapor or carbon dioxide, sometimes with air.

For some purposes, the activated carbon is treated (impregnated) with other chemicals in order to improve the separation effect. Filter carbon for breathing filters in gas masks is coated with metal salts, which improves the separation effect for many chemical toxins.[1]

Areas of application

Activated carbon is primarily used as an adsorbent to remove unwanted color, taste and odor substances from gases, vapors and liquids. A great advantage of activated carbons is that they can be thermally reactivated. Activated carbon is mainly used in the form of granules, as a powder or in pelletized form. Active carbon fabrics are also available on the market.

For example, activated charcoal removes:

  • Chlorine, ozone and other substances that interfere with taste and smell as well as bacteria from water, sweeteners, glycerine and chemical liquids
  • Coloring substances and contaminants from liquid streams in the chemical or food industry
  • Toxins from the air (filters in NBC masks and ventilation systems in tanks and shelters)
  • Uranium hexafluoride from the air in nuclear technology
  • Petrol vapors from the exhaust air of tank systems
  • Chlorinated hydrocarbons from exhaust air and exhaust gases z. B. with dry cleaning
  • a proportion of tar from the cigarette smoke in cigarette filters
  • unwanted flavors from vodka and other spirits
  • Odor of sweat in shoes (due to insoles containing activated carbon)
  • Aromas in cannabis cultivation (odor neutralization)
  • Fermentation by-products such as fusel oils and esters from beer
  • Pollutants in aquarium and pond filters

Activated carbon is used in wastewater treatment to remove adsorbable, dissolved wastewater constituents from the water. This process step is usually only used when cheaper methods such as biological processes, precipitation and flocculation do not achieve the goal. This method can also be used for cleaning partial flows in industry, with the aim of recovering residues.

Another important application for activated carbon is in cabin air filters for the automotive industry. This filter class has been used in air conditioning systems since the mid-1990s. The so-called combination filters (this is a specific cabin air filter class) contain a layer of activated carbon, which filters harmful gases out of the air and thus protects the passengers from these pollutants. For this application, more than 5000 tons of activated carbon are processed annually worldwide.

Water treatment also uses adsorption on activated carbon to purify raw water.

Due to its high adsorption capacity, activated carbon can also be used in sorption pumps to generate vacuums.

Activated carbon only has a limited load capacity. Regeneration usually takes place by heating to several hundred degrees Celsius. On the one hand, part of the load (e.g. organic solvents) evaporates, but another part can also coke, in which case the activated carbon has to be reactivated with water vapor, as in the production process.

Activated charcoal is also found in warming bags.

Medical application

In medicine, activated charcoal is mainly used to remove toxins from the gastrointestinal tract. In harmless diarrheal diseases, e.g. B. gastrointestinal flu (gastroenteritis), charcoal tablets are usually used. In cases of poisoning, activated charcoal is used in larger quantities to remove orally ingested poisons that are in the digestive tract or are subject to an enterohepatic cycle from the organism. The dosage in such cases is 0.5 to 1 g of charcoal per kilogram of body weight in an adult human.

Food coloring

Activated carbon is used in the food industry as the coloring agent E 153. E 153 is used in fruit juice concentrates, jellies, jams, confectionery and in black wax coatings for cheese.

Individual evidence

  1. Römpp Lexicon Chemistry

literature

  • Hartmut von Kienle & Erich Bäder: Activated carbon and its industrial application, Stuttgart, Ferdinand Enke Verlag, 1980, ISBN 3-432-90881-4
  • Roop Chand Bansal, Jean-Baptiste Donnet, Fritz Stoeckli: Active carbon. New York, Marcel Dekker, 1988, ISBN 0-8247-7842-1
  • John W. Patrick (Ed.): Porosity in carbons. London, Edward Arnold, 1995, ISBN 0-340-544732
  • CD Roempp Chemie Lexikon, Stuttgart, Georg Thieme Verlag
  • Dr. med. Thomas Schneider, Dr. med. Benno Wolcke, Roman Böhmer: Pocket Atlas Emergency & Rescue Medicine - Compendium for the emergency doctor. 3rd edition, Springer Medizin Verlag Heidelberg, 2000, 2004, 2006, ISBN 3-540-29565-8

Categories: Coal | Functional material | dye