How Do Charcoal and Carbon Air Filters Work To Remove Odors?
Charcoal is a form of nearly pure carbon. It is created through burning organic matter in an oxygen deprived inert atmosphere and siphoning or leaching out any impurities. Nutshells, peat, wood or coal can be heated to between 600 and 900 degrees Fahrenheit while surrounded by argon or nitrogen. The end product is either powdered or granulated charcoal (carbon). It has a very high surface area and is extremely porous. A single gram can feature between 300 and 2,000 square meters of surface area.
Activation & Impregnation
Additional special processing can create either activated or impregnated carbon. The oxygenation process spreads out the individual carbon atoms and allows them to react with impurities more efficiently. This step can also create even higher surface areas in the material.
Activated carbon chemically bonds to organic impurities that flow through it. Impregnated carbon has certain metals embedded into the filter lattice. This gives it the ability to soak up a higher quantity of specific chemicals. It targets contaminants that are not effectively removed by either regular or activated charcoal filters.
A carbon filter works a lot like a sponge. It soaks up targeted impurities in the substance that is being filtered. However, the contaminants do not comingle with the charcoal. Instead, they cling to the surface in a process called adsorption. The higher the surface area of the charcoal, the more space there is available for capturing impurities. Of course, the substance that is being filtered must be one that does not react with carbon. That way, only the impurities are adsorbed.
Usually a charcoal filtration device is only part of a much larger purification process. For example, chlorine is used to sanitize water by killing off bacteria and viruses. Activated carbon is often used to soak up chlorine and other organic substances as a final step to making tap water drinkable.
Other filters are made to capture odors, smoke and volatile organic compounds in the air. These are used as home and office air purifiers. Large-scale charcoal filtration is used in many industries to purify air and liquids prior to their use in manufacturing or to reduce pollution in the effluent that is disposed of afterward. Alcohol is also filtered through carbon to remove impurities.
Charcoal can be packed into a cylinder or special screen that will not restrict the flow of air or liquid through the filtration device. The ideal application for a filter depends on the specific blend of carbon used (standard, activated or impregnated). The quality and amount of charcoal used affects the efficiency of the filter.
In general, activated carbon filters will last longer than other varieties because they can physically and chemically capture more contaminants. However, there are some compounds that they will not adsorb. For example carbon does not readily react with inorganic compounds, such as lead, sodium, other heavy metals, microbes, nitrates and fluorides.