But one of the most important technologies in air purification is actually a material that dates back thousands of years: charcoal, in the modern sense, activated charcoal.
Also known as activated carbon, this is a high-surface-space material that has been used to clean air and water for years. By grabbing the most microscopic particles, activated charcoal is an essential material for air purifiers ranging from industrial strength to home use.
So what is activated charcoal?
Charcoal ActivationIf you want to fully understand air purifiers, it helps to fully understand activated charcoal.
This is simply an extremely porous material (so porous you usually can’t see the holes), that has been processed to give the product the ability to grab onto particles. It’s made from a wide range of raw materials, including wood, nutshells, coconut shells, peat, and other organic matter. This raw material, however, is not porous, so it needs to be treated and processed. The carbon material used to make activated charcoal is full of organic matter that essentially needs to be burned off in order to have the porous nature that makes it so effective for air purification.
Once the organic matter is burned away, the charcoal has an extremely high level of porosity, which is simply a measurement of the void in the material. However, it still needs to be “activated.”
Activation is mostly achieved through two different methods, but both use high temperatures. The first is known as steam activation, and this is the most common type. It is often used to activate coconut shells and coal-based carbons. In this process, the raw material is carbonized by heating in an inert atmosphere. Inert means chemically inactive and it generally means the exclusion of oxygen, carbon dioxide, and other reactive gasses. This produces a material that has pores, but the pores are not yet the right size.
The second stage activates carbon and enlarges the pore structure, increasing the internal surface area and making it more accessible for filtration. Using high temperatures, the product is activated with steam, and the reaction between the steam and the charcoal material takes place at the surface of the carbon, effectively removing any carbon from the pore walls and enlarging the pores. This allows the pores size to be altered and created to fit specific needs.
Activated charcoal products made through steam activation crushed into small pieces, roughly 1mm to 3mm in width. To produce a dust, the activated charcoal can be ground using a pulverizing process.
The other form of activation is chemical activation. This is used to produce a final activated charcoal product from sawdust, wood, or peat, and it involves mixing materials with an activating agent, which is often phosphoric acid but can include other chemicals. These chemicals are used to make the wood swell, which opens the internal structure. This process creates a paste which is dried and then carbonized on a kiln. During carbonization, the chemical acts as a support and does not allow the structure of the material to shrink, which would damage the pores needed for filtration.
With this method, manufacturers can create activated charcoal that is ready to use without further treatment. Charcoal produced through chemical activation, however, has a lower purity than other materials, as they often hold residual phosphate from the chemicals used during activation.
Chemical activation tends to produce a powdered activated carbon, but granular materials can be impregnated with the activating agent using the same method. This produces a low strength, meaning the final product may not be suitable for certain applications. Sometimes the chemically-activated carbon is given a steam activation as well, which gives the material additional properties that can be useful.
The final activated charcoal product uses adsorption, a process similar, but not the same as, absorption.
Surface Space: Why it Matters in Activated CharcoalActivated carbon is effective because it has a high surface space due to the pores, and the higher surface area the more effective the activated charcoal will be.
According the Haycarb, an activated-carbon manufacturer, the surface of this material is roughly 500 to 1,500 m2/g. What does that mean?
Simply put, it means a single spoonful of activated carbon has the surface area of a soccer field! That is an amazing amount of surface space for such a small amount of material.
This vast surface area is created during the manufacturing and activating process, which can take many different forms, but the activated carbon can be measured in different ways. Total pore volume is a common way to measure activated charcoal. This is simply a measurement of all pore spaces inside a particle of activated charcoal. Written in millimeters per gram, or volume in relation to the weight.
Generally speaking, the higher the pore volume, the more effective the activated charcoal. However, sometimes the size of the pore hole is not a good match for the material being filtered, meaning the pore volume will not be utilized as effectively. The total pore volume will change depending on the material source as well as the type of activation that is used.
Pore radius is another way of gauging activated carbon. This is simply the average pore radius in the material, and it is measured in Angstroms. (Named after 19th-century physicist Anders Jonas Angstrom.) Usually used to measure wavelengths and interatomic distances, an angstrom is equal to one hundred-millionth of a centimeter.
Pore volume distribution is also important, as each type of carbon source has its own distribution of pores. Pore volume is categorized into three sections: micropores, which are extremely small, mesopores, which are medium-sized, and macropores, which are the largest pores on activated charcoal.
The Types of Activated CharcoalYou can find activated charcoal in three different types. Each of these types has different characteristics and uses based upon the specific application.
PowderedThis material is activated charcoal that has a particle size of 5 to 150 Angstroms. These materials have a lower processing cost and give users a flexibility of use, as more or less activated charcoal can be used by simply adding or reducing the amount of powder. These are mainly used for filtration of liquids, and they can be mixed with liquids and removed by sedimentation and filtration.
GranularA slightly larger activated charcoal product, granular material measures .2mm to .5mm, and is generally harder and lasts longer than powdered material. They are also cleaner to handle and can purify large volumes of both gasses and liquids. Also, they can be reactivated and reused many times over, which is something that usually can’t be done with powdered activated charcoal.
ExtrudedThese are pellets of activated charcoal designed in the shape of cylinders, ranging from about 1mm to 5mm. The process creates a product that is hard and durable, and it can be used for many different applications, but is best for heavy-duty use. Filtering automotive emissions is one of the common uses for this material.
Is Activated Charcoal Really Effective?There’s no doubt that activated charcoal is used for many different forms of filtration, but does it really work?
To find out, we not only need anecdotal evidence, we also need to look at scientific studies so we completely understand the impact of this material. And as we’ll see, there is a lot of information that justifies the use of activated carbon and other materials.
A study conducted by the U.S. Department of Energy, for example, found that HVAC filters in commercial areas were more effective if they used activated charcoal. Systems with pre-filters containing activated charcoal were actually 60% to 70% more effective at removing ozone, and this strength lasted a long time as well, maintaining usefulness as long as 81 days. The filter systems that did not use activated charcoal showed “negligible ozone removal.”
The Centers for Disease Control also supports the notion that activated charcoal is an effective tool for air purification. In a 2003 article on filtration and air-cleaning systems, they noted that activated charcoal is an “excellent” material for the removal of organic chemicals, making it an important tool for removing and controlling both indoor and outdoor air pollution.
So Many Uses: The Benefits of Activated CharcoalWhen it comes to air purification, activated charcoal has many different uses, and it can be an effective material for removing many contaminants from the air. As you’ll see, there are many benefits of activated charcoal!
Odor removal, for example, is possible with activated charcoal thanks to the process of adsorption. Smell is actually driven by small particles in the air that are released by a pungent substance, so when you are smelling fresh coffee, for example, you are actually inhaling particles of coffee that are floating in the air. If you have a foul odor in the home, you can reduce the smell by removing the particles, and few materials are as effective at removing particles as activated charcoal.
Another use for activated charcoal is smoke removal. Both the smell of smoke, and the lingering effects, are caused by tiny particles floating in the air. The particles not only lead to an offensive and often aggravating smell, they can also cause a wide variety of issues related to health and wellbeing, especially if the smoke comes from tobacco. Activated charcoal has a well-established reputation for removing smoke particles, which allows you to have cleaner, healthier air in your home.
Mold spores can also be captured by activated carbon. Mold is a fungus that grows in warm, damp locations, and it is especially common in basements, although it’s also found underneath bathroom sinks, around faucets, and even in carpet. Mold reproduces by sending airborne spores into the atmosphere; spores that float in the air and create new mold colonies. By capturing mold spores, activated charcoal reduces the likelihood of having mold growth in your home.
Odors from pets is another air pollutant and allergen that can be controlled with activated charcoal. Pet dander is essentially skin flakes that have been shed by the animal; skin flakes that can float in the air and cause irritation if someone is allergic to the substance. Once again, activated charcoal along with a HEPA filter can come to the rescue by grabbing and holding pet dander, keeping it from becoming a major issue in your household air.
One of the most common pollutants in indoor air is dust, which can vary in size from large enough to be seen to so small it is invisible to the human eye. Thanks to a high level of porosity, activated charcoal combined with a high quality HEPA filter can trap more dust particles per volume than many other mediums making it one of the most effective materials for controlling indoor dust.
Air purifiers can also remove toxins released by harmful household items, such as air fresheners, space heaters, and cleaning products.
Activated charcoal has even been used as a medication. It is believed that the material can remove impurities in the body and the stomach. People have theorized that the adsorption process allows ingested activated charcoal products to remove toxins from the stomach. It is also speculated that it can help remove alcohol from the system, although its usefulness with alcohol is not completely understood. Some believe it may be a hangover cure when ingested, and there are products promoting activated charcoal products for skin care.
What is the best charcoal air purifier?
What are limitations with activated carbon?
Leading Air Purifiers with Activated Charcoal and Other TechnologiesNow that you understand what is activated charcoal, you can choose the right air purifiers for your specific needs.
Oransi is proud to offer many high-quality air purifiers that use activated charcoal. Browse our selection of air purifiers and you’ll find the right unit for your home or office.