Carbon is everywhere. Carbon is the giver of life. Various forms of Carbon lie at the heart of new evolution and choreographing human’s life pattern. Activated Carbon is one of them.
History of Activated Carbon
The use of activated carbon goes back to ancient Egypt (1500BC). Egyptians make use of its adsorbent characteristics for water purification and medicinal purposes.
In the 18th century, German-Swedish pharmaceutical chemist Carl Scheele recognized the adsorptive power of charcoal using adsorption of gases on the charcoal surface.
At the beginning of the 20th century, an Austrian citizen named Ostrejko developed a method for manufacturing commercial activated carbon.
And during the period of first world war, activated carbon prepared by coconut shells used in gas masks as an air purifier due to affect of poisonous gas in the military.
Preparation of Activated Carbon
Activated carbon is created from carbon-rich materials, such as wood, coconut shells, bone char, peat, coal, olive pits, or sawdust.
It can be produced through two processes,
Physical activation
Chemical activation
There are two steps in physical activation:
The first step is to carbonization of raw materials in the range of Celsius 400-800. And second step to activation of carbonized charcoal at the range of Celsius 800-1000 in the presence of oxidation agent; steam, carbon dioxide, and air.
At the chemical activation:
Both carbonization and activation take place in a single step. The raw materials mixed with the chemical agent and kept for activation at high temperature that around Celsius 800. The chemical agent acts as both an oxidant and a dehydrating agent. Most commonly KOH, K2CO3, ZnCl2, H3PO4 used as chemical agents for activation.
So, this activation process changes the raw carbon material to a porous material called activated carbon or also called activated charcoal. It is characterized by the presence of a large number of tiny pores on its surface. Higher the number of pores, larger will be the surface area, which increases the adsorption capacity of the production.
The qualities of the final product depend on: type of raw material used, the length of the activation and rate of reaction, temperature, and the type and concentration of the oxidizing gases.
Manufacturers mainly produce activated carbon in three forms:
- powdered (PAC)
- granulated (GAC)
- extruded (EAC).
Each form is available in many sizes, based upon the application, recommendations, or requirements.
How does active carbon work?
The pore network in the lattice structure of activated carbon allows the removal of impurities from gaseous or liquid media through a mechanism referred to as adsorption.
Adsorption is both the physical and chemical process of accumulating a substance at the interface between liquid and solid phases.
Note:
Adsorption is different from absorption. In absorption, the substance you want to remove is absorbed into the structure of the absorbent like a sponge, but it doesn’t become a part of the absorbent on a molecular level. Therefore, when you absorb water with a sponge, the water does not become chemically bonded to the sponge. It just fills in the spaces inside it.
Molecules trapped within the carbon’s internal pore structure by Van Der Waals Forces or other bonds of attraction and accumulate onto a solid surface.
The higher adsorption capacity of activated carbon mainly depends on the porous characteristics such as pore volume, pore size distribution and surface area.
According to researchers activated carbon can have a surface greater than 1000 m2/g which is highest volume of adsorbing porosity of any material known to mankind.
Simply this means 5 g of activated carbon can have the surface area of a football field.
Applications of Activated charcoal
Activated carbon lies at the heart of different processes used in the industry. Environmental problems affecting air and water are solved through the activated carbon, and also new applications are being continually developed in research laboratories.
1. Water purification
In purification rate mainly depends on 5 key factors:
- physical properties of the activated carbon (surface area and pore size distribution)
- chemical structure and size of the contaminant
- concentration of the contaminant
- environmental factors of medium (such as pH and temperature)
- duration that medium is exposed to the activated carbon filter.
Activated carbon water treatment is basically used for the removal of chlorine and organic matter. Each treatment work in totally different ways.
Chlorine Removal
Activated carbon can used to remove chlorine with little degradation to the carbon. Dechlorination occurs rapidly and flow rates are typically high. Activated carbon in filter will need to be replaced as its ability to dechlorinate the water will slowly decline. The re-activated carbon filters produced by spent carbon can be used in waste-water treatment applications.
Removal of Organic Matter
Activated carbon is commonly used to adsorb natural organic compounds and synthetic organic chemicals in drinking water treatment.
Mostly GAC and PAC used in water treatment applications.
The two most common options for water treatment plants are:
Post-filtration adsorption
where the GAC unit is located after the conventional filtration process
Filtration-adsorption
in which some or all the filter media in a filter is replaced with GAC.
2. Air purification
Activated carbon also has a special ability to remove volatile organic compounds, odors, such as the smell of tobacco smoke and other gaseous pollutants from the air. Benzene, toluene, xylene, and some chlorinated compounds are among those that can be removed by carbon filters.
Today Activated Carbon clothes (ACC), masks, air filters, and air purifiers have been developed for use in many pollutant and odor control situations including industrial, medical, and domestic applications.
3. For medicinal purposes
As an antidote
Thanks to its toxin-binding ability, activated charcoal has a variety of medical uses. Mainly activated charcoal is used in cases of poisoning, in cases such as prescription drug overdoses, as well as overdoses of over-the-counter medications like aspirin, acetaminophen, and sedatives.
However, it’s important to note that activated charcoal is not effective in all cases of poisoning. For instance, it appears to have little effect on alcohol, heavy metal, iron, lithium, potassium, acid or alkali poisonings
To eliminate the toxic waste products in the body
Activated charcoal can bind to toxic waste such as urea at the gut and excrete in the feces. This may be particularly useful in cases of chronic kidney disease, but more studies are needed to develop it as a medical treatment.
Reduce cholesterol level
It can bind cholesterol and cholesterol-containing bile acids in the gut and prevent the body from absorbing them. According to researches, the large dosages of activated charcoal seemed the most effective. However, still more studies are needed to prove it.
Skin treatments
Applying activated charcoal to the skin is now a days introduce as an effective treatment for acne and insect or snake bites.
4. For food and beverage
Activated carbon products with the optimum distribution of pores in the carbon lattice effectively remove carcinogenic polyaromatic hydrocarbons, colored bodies, unwanted volatile organic compounds, and other impurities, found in many food processing applications such as edible oil, fruit juice, beer, vine any many other food productions. Not only it contributes to food and beverage purity and safety but it improves desirability and aesthetics effectively removing undesired smells, tastes and colors.
Around 2015 Activated carbon began to popular as a cleansing ingredient for food. Things like charcoal drinks, blackened pizza crust, charcoal cheese, and the most popular ones are black ice cream. But there haven’t been many scientific studies on the health effects of charcoal-infused food. Some countries like USA aren’t allowed to serve activated carbon food in cafes and restaurants because Food and Drug Administration called as FDA in America claims it falls under the umbrella of “adulterated food”.
5. For automotive
In the automotive industry, activated carbon is used to control emissions, remove VOCs (volatile organic compounds), and improve the quality of cabin air. It can also be used to create electrodes for supercapacitors. There are many applications where activated carbon with very high surface area, exceptional purity, and controlled pore size distribution plays a role in energy storage including computers, automobiles, alternative energy storage, heavy equipment, and more.
6. For Agriculture
Granular Activated Carbon with high purity and exceptional hardness uses as a catalyst or catalyst carrier. For agriculture industries, activated carbon used to protect grass seeds from dangerous herbicides and pesticides and to amend soil to improve crop yield. Also, it stores helpful nutrients for timed delivery, boosting the health of the crop. It can even be loaded with ethylene, the compound that causes ripening, and then deliver the ethylene to all the fruits in a single crop, ensuring that they ripen simultaneously.
7. For Gold mining
Granular Activated carbon used for rare metal recovery processes such as gold mining from scraps. For gold recovery, water and a cyanide solution such as calcium cyanide, sodium cyanide, or potassium cyanide, are added to scraps which contains gold residues to form a slurry. Then gold will leach out and mix with the cyanide into a solution and activated carbon used to separate and store the gold, which is removed as the final step of the process. After the recovery process is finished, the activated carbon is considered “spent.” However, allowing it to be used again.
We are thinking about a few more other things it does haven’t even mentioned. So, make it your homework to do some research on activated carbon and its benefits.