Activated Carbon Filters: How are They Relevant in Air Purifiers?

Activated Carbon is a compound of carbon, a highly porous, adsorptive medium and is composed mainly of carbon. The lattice structure of activated Carbon has an intrinsic pore network which removed impurities from gases and liquids through a phenomenon known as adsorption.

Activated Carbon removes odors, volatile organic component, and other gaseous pollutants from the site. It is different from other air purifiers like HEPA filter which only filters particles from the air. Carbon filters, on the other hand, trap the gas molecules on a bed of charcoal.

Activated Carbon is formed when carbon undergoes additional processing to make it better at trapping gas molecules.

First, the carbon is injected with steam, carbon dioxide, and hot air, this creates a lattice of tiny pores in the carbon, making it highly porous and increasing its surface area, thus creating many places for the gas molecules to get trapped, making the carbon far more effective as a filter. A paper by the Ohio Environmental protection agency says that one gram of activated carbon had hundreds of square meters of internal surface area.

History of Carbon Filtration

You might wonder how did humans figure out they carbon can be very effective at filtering contaminants?

The earliest use of it was probably too remove impurities from smelted metal to manufacture bronze. The Egyptians must have used it in medicine, to remove odors associated with infections.

Sailors, right from the sixteenth century to the eighteenth century, stored their drinking water in barrels that had been either charred or smeared with charcoal on the inside to keep water clean and fresh.

In World War I, gas masks were utilized to filter out deadly gases used against the troops, but it was not effective always, only against certain toxins. The production and consumption of activated carbon dramatically increased after World War II, which eventually led to the development of modern activated carbon air purifiers and water filters.

How do They Work?

Activated Carbon Filters use the process of Adsorption to purify air and water. Don’t confuse it with Absorption. In Absorption, the water is absorbed into the absorbent, but it doesn’t become a part of it on a molecular level. Thus, in Absorption, taking the example of water and sponge, water does not chemically bond to the sponge, it just fills the spaces or pores inside it.

On the other hand, Carbon filters use Adsorption. The key difference here being that during Adsorption, the pollutant molecules stick to the outside of the carbon and in Absorption, the pollutant molecules are inside the structure. When a molecule of gas comes through the carbon, it sticks to the surface of the bed if there’s an additional site.

Advantages of Activated Carbon Filters

  • Traps Volatile organic compounds: Activated Carbon filters are very effective at filtering VOCs from the air. VOCs are gaseous substances that most other filters like HEPA cannot touch. Some gases in cigarette smoke or those given off by front paint and cleaning products can be filtered out from the air by an activated carbon filter. Xylene, toluene, benzene, and some other chlorinated compounds can be removed by it.
  • Traps Odors: Mechanical air purifiers which only dinner particles cannot filter out unpleasant odors. Thus, people use activated carbon filters to remove these odors.
  • Filters out dangerous pollutants like ozone, ethylene dioxide, and carbon monoxide.
  • Different types of filters are available.

Disadvantages of Activated Carbon Filters

  • Requires Filter Replacement: One disadvantage is that it requires regular replacement of the carbon filters as they get saturated. Replacing these filters can become expensive and inconvenient. It can also be difficult to determine when you need to replace the carbon filter as there is no visible sign of it being saturated. You have to rely on guessing or on the manufacturer’s replacement recommendations.
  • Unable to remove particle pollution: Carbon air filters remove several organic components from the air but can’t do the same with particulate pollutants. These include allergens like pollen, dust, wildfire smoke, et cetera.
  • Can remove only certain chemicals
    These filters can remove only those chemicals which are naturally attracted towards carbon. Hence, pollutants like nitrates, fluorides, sodium, and other heavy metals, remain untouched, suspended in the air.
  • Has a short service life.
  • They cannot trap pathogenic bacteria. You need to use a combination of Nano silver filter and Activated Carbon to cater to this issue.

In the long term may not be the best choice from the standpoint of cost. Besides, it does not remove allergens which are a major indoor pollutant. So, it would be wiser to invest in a more robust solution, like hybrid air purifiers that contain a carbon filter or a mechanical filter like HEPA.

If you’re considering using an Activated Carbon Filter, you probably want to get rid of the old or VOCs. Activated Carbon Filters are excellent choices for a short-term problem.

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