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Despite their small, relatively unimpressive appearance, activated carbon filters are some of the most effective filters on the market for contaminant removal. This short guide will look at activated carbon filters in more detail, including what they are, how they work, their benefits, and more.
What Is an Activated Carbon Filter?
An activated carbon filter is a piece of extremely porous solid carbon, usually in powdered block or granular form. Activated carbon filters have a very large surface area - a single gram of this material has an average surface area of 500 meters squared. This allows an activated carbon filter to adsorb (trap) many more contaminants than standard carbon filters.
Adsorption occurs when organic compounds in water or air (depending on the filter’s use) undergo a chemical reaction with the carbon media, and bind to the surface of the media. The higher the activated carbon’s porosity, the more impurities it can hold.
How do Activated Carbon Filters Work?
The activated carbon filtration process is simple. The filter is placed inside an air purifier or water filter, and when contaminated air or water passes through the filter, the harmful contaminants are adsorbed in the media.
The result is that the water or air flowing out of the system is much cleaner because it has been stripped of the contaminants affecting taste or odor, like chlorine and gaseous pollutants. If used in combination with other filter stages, activated carbon can protect these other filters from damage from large particles like dust.
Contaminants Removed by Activated Carbon
From water, activated carbon filters can remove:
- Volatile organic compounds
- Hydrogen sulfide
In air, activated carbon filters target:
- Volatile organic compounds
- Chemical vapors
The design of the activated carbon filter determines which contaminants the filter can remove, and its effectiveness in removing these contaminants.
Uses of Activated Carbon Filters
The two most common uses of activated carbon filters are:
- In air purifiers: Activated carbon filters are used to remove odors and pollutants from air, improving indoor air quality.
- In water filters: Activated carbon filters are also found in water filters, such as pitcher filters and under-sink filters, to improve the taste and quality of drinking water.
Large-scale uses of activated carbon filters include sewage treatment, metal finishing, analytical chemistry, pharmaceutical processes, purification of distilled beverages, and groundwater remediation.
Advantages of Activated Carbon Filtration
Some of the biggest benefits of activated carbon filtration are:
- Natural filter media: Activated carbon is made from natural materials like coconut shell and wood, with no other substances or chemicals needed. This means that air or water can be filtered completely safely and naturally.
- Easy and low-cost to maintain: Activated carbon is one of the most affordable filtration materials and requires limited maintenance. When an activated carbon filter has reached its capacity, the filter simply needs to be replaced.
- Removes bad tastes and odors: No other affordable filtration technique is as effective as activated carbon at removing bad tastes and odors from air and drinking water.
- Tackles a range of impurities: Aside from taste and odor, activated carbon effectively filters other organic chemicals, pollutants, gases, and microorganisms, depending on its application.
Disadvantages of Activated Carbon Filtration
Some of the setbacks of activated carbon filtration are:
- Can’t remove all contaminants: Activated carbon is highly effective at removing a set group of contaminants, but it can’t be used to completely purify air and water. Some chemicals and pollutants aren’t attracted to carbon media, which means other filtration techniques may be needed.
- Short lifespan: An activated carbon filter has a maximum filter capacity (the maximum amount of contaminants that can be trapped in the media until the media is eventually fully clogged). When this maximum capacity is reached, the filter stops working and needs to be replaced. The average lifespan of an activated carbon filter is between 2 and 6 months, depending on the filter’s size and the contaminants in the treated air or water.
- Requires long contact times: The longer the contact time between the filter and the air or water, the more effective the filtration. This may mean waiting several minutes for filtration results.
- May harbor bacteria: Activated carbon can’t be used to remove viruses and bacteria - and, in fact, this filter type is known to harbor bacteria. Manufacturers can prevent bacteria growth by adding trace amounts of materials like silver to the filter media.
Activated Carbon Filter Variables
While all activated carbon filters can remove more impurities than standard carbon filters, not all activated carbon filters are designed to be exactly the same.
Different activated carbon filters contain different amounts of activated carbon, and have different surface areas. The more activated carbon a filter contains, and the greater its surface area, the more contaminants it can remove, and the longer its lifespan.
The size of the filter pores affects the rate of adsorption. The smaller the pores, the faster the adsorption process. Some activated carbon filters are now infused with other materials, like magnesium dioxide or copper oxide, to enhance the filtration process.
Activated carbon filters are some of the most effective tools for filtering air and water. Although activated carbon isn’t a purification technique, it’s superior to other filters in removing impurities affecting taste and odor. Activated carbon has a number of uses, but AC filters are most commonly used in water filters and air purifiers.