Carbon filters remove chemicals and small solids like sediment to improve the taste and smell of water. They also reduce chlorine and volatile organic compounds to help protect against harmful contaminants in your drinking water.
This is done through a process called adsorption, which allows gaseous chemicals to bind to the surface of the carbon. As the carbon becomes saturated with chemical molecules, it begins to leak, which is why it is important to change your filter regularly.
Carbon filtration removes chlorine along with small solids like sediment, and volatile organic compounds (VOCs) to clean water and improve its taste. Activated carbon filters also adsorb chemicals and odors.
The adsorption process occurs when the pollutants enter the carbon pores and stick to them, much like the way a sponge attracts water molecules. The adsorption process is much more effective than simple mechanical filtration, which works by using the physical size of particulates to strain them out. Most carbon blocks use a combination of these two processes to make the most efficient filtration possible.
Most carbon filter types use activated carbon to trap gases, and a thicker block provides more surface area for adsorption. Choosing the right carbon type and thickness is important, as is the length of time that water spends in the filter, known in the industry as dwell time.
Some of the most common uses for carbon filters are in home and office air filters to eliminate odors, including cooking smells from fish, sauteed onions, and curry. They can also get rid of VOCs and chemical odors from cleaning products and smoke.
Another common use of carbon filters is in water purification, removing a variety of harmful pesticides from drinking water. These include herbicides, such as Round-up and Chlordecone/CLD/Kepone and fungicides, such as Lindane. These pesticides can contaminate groundwater aquifers and cause short-term adverse health effects.
Activated carbon filter media has a pore structure that makes it ideal for removing odors. It can be shaped to fit into air ducts, where it works to absorb gases and odors from the air. The process is called adsorption, which allows the carbon to grab onto the molecules of odors and VOCs, locking them in. Mechanical air filters cannot do this, which is why carbon is an effective odor removal solution.
The small pore size of carbon block also means it can remove some contaminants from water. Depending on the grade of carbon used, it can remove chlorine, bad tastes and odors, organic chemicals, and disinfectant byproducts. If the carbon is NSF-certified, it may also remove coliforms, cysts, lead, iron and other metals. The filter is usually used as the final stage of a multi-stage filtration system.
Carbon filters can also help to remove odors in kitchens and other areas of the home. They can eliminate cooking smells like fish, sauteed onions, curry and more that linger long after the food is cooked. They can also get rid of odors from smoking tobacco, cannabis and other substances that leave a pungent smell behind. Combine a carbon filter with a duct fan with the right CFM rating to achieve optimum odor removal. See our guide on ducting your grow room for more information.
Removes Volatile Organic Compounds (VOCs)
Carbon filters can remove Volatile Organic Compounds (VOCs) from water that cause odor, discoloration and other unpleasant tastes and odors. VOCs are harmful in both the short and long term, with some even contributing to cancer. Symptoms of exposure to VOCs include eye and throat irritation, headache, nausea and fatigue. VOCs are found in paint, wood preservatives, solvent thinners and lubricants as well as natural sources like isoprene from trees, mycotoxins from molds and the byproduct of fossil fuel combustion.
Activated carbon traps VOC molecules via adsorption, much as a sponge absorbs water. The surface of activated carbon has many more pores than typical filter material, allowing more space for gaseous chemicals to adhere. The carbon then entraps the chemical, binding it so that it can’t escape or desorb until it is regenerated through heating and re-activated.
It’s important to note that carbon does not trap dissolved minerals or bacteria. Therefore, it’s best to pair a carbon filter with other technologies that can remove contaminants from water such as filtered water systems that utilize remineralization and countertop distillers that use reverse osmosis. However, carbon is a valuable addition to most water filters, removing chlorine, bad tastes and odors as well as VOCs. It’s also a good idea to purchase a MERV rated filter that includes carbon to ensure that your family is getting the most out of their water filter.
Carbon filters remove chemicals using a process called adsorption. Adsorption is similar to absorption, except that it adheres particles to a surface rather than soaking them up like a sponge. The carbon used in these filters is a form of activated carbon that is typically made from coconut shells, peat, bituminous coal, or other sources and then “baked” at very high temperatures to create lots of tiny pores that can trap contaminant molecules. When water comes in contact with the carbon, it is attracted to and held by the adsorption surfaces of the filter, much the same way that a magnet attracts and holds iron filings. The length of time that the contaminant is allowed to remain in contact with the carbon also impacts its ability to be adsorbed.
When the adsorption surfaces become full of contaminant molecules, they are released back into the water. This is when it becomes important to replace the filter on time, so that newer, less-contaminated carbon is able to absorb the contaminants that have been released.
This is why many people rely on chlorine removal tests to determine when it is time to change the filter. Chlorine is the most common contaminant that needs to be removed from drinking water, but it also is the most difficult to eliminate once it has saturated the carbon. By removing chlorine before it can react with organics in the water to produce trihalomethanes, carbon filters reduce chlorine contamination of drinking water and help water-using appliances, such as tankless water heaters, last longer.