In a nutshell, what we refer to as activated carbon or activated charcoal is a form of carbon that possesses minute, low-volume pores around its surface. These minute pores grant this material a large surface area. In fact, the surface area of activated carbon is so large that a teaspoon of activated carbon could have the same surface area as a football field. These minute pores act as a surface for chemical reactions. Aside from that, they enable the activated carbon to adsorb a huge range of chemicals. These properties make activated carbon highly beneficial for various applications. Even better, activated carbon can undergo chemical treatment to drastically improve its adsorption ability.
Origins of Activated Carbon and How its made
Organic matter when burned would generate carbon. To create activated carbon, the organic matter source material must be carbonaceous. In other words, you need a source material that produces a lot of charcoal when they are burned. Some common materials used to make activated charcoal includes coconut shell, sawdust, wood, bamboo, willow peat, coir, peach pits, petroleum pitch, and coal. Once these materials are burned you get charcoal. However, this charcoal isn’t activated carbon yet. They need to undergo a process of “activation” to create millions of tiny pores in its surface. To date, there are only two methods of “activation”; thermal or chemical activation.
As you could guess by its name thermal activation involves the use of heat to create pores in the carbon’s or charcoal’s surface. To be more precise, the carbon or charcoal is exposed to hot gases and steam. The entire thermal activation process involves the reduction of moisture, reduction of volatiles, carbonization, and steam treatment. Gases used in thermal activation includes carbon, nitrogen, or argon.
Chemical activation, also from the name itself, utilizes chemicals to create activated carbon’s minute pores. Before the organic matter is turned to carbon. Chemicals, usually strong base, acid, or salt, is added to the organic matter. When the chemically treated organic matter is burned to create charcoal, you get the activated charcoal or activated carbon instead.
How does Activated Carbon Work?
As mentioned earlier, activated carbon is used in a wide range of applications due to its large surface area. One common application of Activated Carbon is in filters. When liquid or air comes into contact with the activated carbon, the minute pores present in its surface would catch and trap the molecules present in the liquid or air. These molecules can be anything, including pollutants, but not water or air. In essence, Activated Carbon is capable of adsorbing undesirable chemicals present in both air and water. Aside from that, Activated Carbon can act as a catalyst or something that encourages chemical reactions. For example, chlorine is a disinfectant that is mixed in water but when it comes into contact with activated carbon they would react with it and generate chloride ions as a byproduct. This property of Activated Carbon makes it a suitable material for eliminating chlorine from water.
Activated Carbon has the ability to eliminate a wide range of pollutants from both air and water. However, its ability to remove these contaminants is greatly affected by factors such as the amount of pollutants present, the temperature, the acidity, and the duration of contact. It is also important to note that there are different kinds of activated carbon and each one is more suitable for a specific purpose compared to the rest. Those types of Activated Carbon which has relatively larger pores are more suitable at trapping large and heavy molecules such as organic chemicals. One the other hand, those types of activated carbon which posses finer pores are suitable for adsorbing small and light contaminants. Knowing which activated carbon to use is made easy by the manufacturers as they would often label them with their adsorption potential.
Since activated carbon is really good at adsorbing certain chemicals from liquids, using them as filters quickly turned into a widespread habit. They are quite versatile and can be used in various situations. Activated Carbon Water Filters have been used in both industrial-scale and personal use. When used as a Water Filter, the Activated Carbon is usually removed completely from the water. However, there are cases wherein the activated carbon remains in the water. But in these cases, the subsequent ingestion of the activated carbon does not cause any harm. This is not so surprising as people have been ingesting Activated Carbon on purpose for its purported health benefits.
Among the various types of Activated Carbon, the Granular Activated Carbon is the best one for removing organic chemicals from water. Aside from that, it is also effective in removing chemicals like hydrogen sulfide. This chemical, along with chlorine, are the usual culprit for objectionable odours or taste in drinking water. Amazing as it is, Activated Carbon has its limits. It cannot adsorb all known contaminants of water. Chemicals that Activated Carbon cannot adsorb includes iron and nitrate. To supplement Activated Carbon’s limitation, a Reverse Osmosis filter could be added in tandem with it. So that whatever chemicals aren’t trapped by the Activated Carbon would be removed by the Reverse Osmosis filter.
What Carbon Filters Reduce From Your Water
So we’ve already dabbled a bit on what Carbon Filters can and cannot remove. Activated Carbon Filters can completely eliminate an impressive 81 chemicals. This is inclusive of all 12 known herbicides and pesticides. Aside from that, it can effectively reduce the amount of 52 other chemicals. We’ve also mentioned earlier that Activated Carbon can remove chemicals such as chlorine which is a disinfectant that may impart an unpleasant taste and smell to our drinking water. There are certain conditions in which chlorine may react with some pre-existing chemicals in water and generate carcinogenic byproducts. These byproducts can be eliminated by the Activated Carbon Filter as well.
Just to make it clear. Although Carbon Filters can remove a wide variety of pollutants, it cannot remove all of them. Minerals, salts, and metals are some of the things that can slip through the filter easily. However, a type of Carbon Filter called Carbon Block can remove metal and mineral pollutants such as lead, radon, mercury, arsenic, and asbestos. Aside from that, it can filter microbiological contaminants. Despite being effective in removing harmful metals and minerals, beneficial ones can pass through. So when it comes to the variety of chemicals that a carbon filter could eliminate, Carbon Block is the best carbon filter type.
Granular Activated Carbon (GAC)
Like most Activated Carbon, Granular Activated Carbon or GAC is made by combusting high carbon organic materials. They are often used as air or water filters because their surfaces are covered with minute pores that traps a wide range of pollutants. The air or water would simply need to come into contact with the surface of the Granular Activated Carbon inorder for them to be rid of pollutants.
When compared to other types of Activated Carbon, each GAC particle is relatively larger but with a smaller external surface area. These properties enable GAC to be efficient in adsorbing vapors and gases. These properties also make them a popular choice in water treatment. When used for water treatment, the most common design would be the fixed-bed carbon filter GAC. In this design of the GAC water filter, the GACs are placed inside cylindrical containers. Unfiltered water flows through these containers and gets filtered by the GAC present within. There is one glaring problem with this design, water may, at times, flow through the container without coming into contact with the GAC particles. Due to this, the GAC’s overall efficiency is significantly reduced. Another problem that arises from the usage of fixed bed GACs is that water may remain stagnant. When water is stagnant, the conditions are perfect for the growth of bacteria.
For those who are planning to install GACs, it is essential that you consider the concentration of your water’s contaminants, and average water use. This information would help you in determining the appropriate size and additional components of the system. The maintenance and installation of your GAC water treatment device may also vary depending on the level of contamination and water usage. The higher the level of contamination and the more frequent the usage, you may need to adjust your installation in a way that allows for frequent maintenance.
What kind of GAC filter systems are there?
1.) Whole-House Filters (or Point of Entry)
The best way to have every faucet in your home spew out filtered water is to install a whole-house filter. Wherever the water first enters the house a GAC filter is installed so that every plumbing in the house would carry filtered water. This means that if the source water contains pollutants, those who drink the water and bathe in the water that comes out of the fixture wouldn’t be exposed. Point of Entry GACs are usually installed in pairs with the water filter arranged in sequence. This way when some of the water would bypass the first filter, the second one could filter it.
The two filters arranged in sequence is also a tactic to make maintenance efficient. The first filter in the sequence would be the first one that would need changing as it will catch the most pollutants. The Second one may have some pollutants sticking to their GAC particles but they could still get the job done. Which is why they could be used as a replacement for the first filter and a cylinder filled with unused GAC particles would be placed in the second position. Another feature that makes maintenance easier, is the presence of ports for water sampling before the filters, in between the two filters, and after the filters. This way the water can be tested before they are filtered, after they are filtered by the first GAC filter, and after they are filtered by both GAC filters. Since GACs can trap chlorine, they need to be removed so that the plumbing can be chlorinated. However, removing the filters is not necessary because the filter system has a bypass system. When the bypass switch is activated, the GACs would be bypassed so that the chlorinated water could enter the plumbing for chlorination.
2.) Point of Use Filters
Point of use filters are capable of filtering a single fixture only. They are installed just before the faucet. Point of use filters or POUs could be installed below the sink. Water passing through the filter would be treated, all other faucets wouldn’t be treated. There’s also a different type of POU that is more portable. There are pitchers with GACs installed so that when you pour out the water it would be filtered. Some refrigerators come with GACs in their ice maker, so that the ice created is made of filtered water.
Knowing which type of GAC Filter System to use
When deciding on which GAC filter to use, ask yourself the following questions:
What type of contaminants are present in the water?
What is the amount of each of these contaminants?
How often do you use water for bathing? For drinking? Washing? And does any of these activities expose you to the contaminants that you are trying to eliminate?
Using GACs of any type is pointless if the contaminant in your water cannot be eliminated by it. Determine your water’s contaminants first before deciding on purchasing a GAC filter.
Using Point of entry GACs for filtering all of the water that goes into your home is a bit of an overkill if the water isn’t heavily contaminated in the first place. If point of use filters can effectively remove the water contaminants that enter your home then you should opt for this one to save on costs. However, when the water from the mainline is heavily contaminated and using them as drinking, washing, and bathing could pose a significant health risk, then use a point of entry GAC.
Other Classifications of Activated Carbon
Powdered Activated Carbon (PAC)
The name itself is self explanatory, PACs are activated carbon with fine particles which are made out of the same materials as those seen in GACs. PACs are usually added directly to rapid mix basins, intakes, clarifiers, and raw water. Carbon Block Filters usually use PACs.
Extruded Activated Carbon (EAC)
Extruded Activated Carbon is similar to PAC but they undergo a process wherein a binding agent is added. Due to this, EACs have a cylindrical or spherical particle that are quite tough. They are used in gas phase applications because they are tough, don’t cause fluctuations in pressure, and have low dust content. They are also used in Chlorine Taste and Odor (CTO) filters, filters that remove chlorine taste and odor.
This type of activated carbon has particles that have porous particles. They may contain inorganic compounds like silver and iodine impregnated into the pores. Impregnated Carbon with silver compounds has the ability to inhibit the growth of microbes which is why they are often used as an adsorbent.
Bead Activated Carbon (BAC)
BAC is somewhat similar to EAC when it comes to their particle’s shape, both have a spherical shape. Both of them are also tough and have low dust content. The BAC is suitable for water treatment.
The adsorptive power of activated carbon can be incorporated in fabrics. The Woven Carbon is a type of activated carbon that is added to rayon fibers. The resulting fabric has the properties of cloth and the odor adsorption and defense of activated carbon.
Polymer Activated Carbon
Polymer activated carbon is similar to impregnated carbon except the pores of this activated carbon is coated with a biocompatible polymer. This special coating makes each polymer activated carbon particle smooth and permeable. This type of activated carbon is primarily used in hemoperfusion. This is a type of medical treatment wherein a patient's blood is drawn out and allowed to come into contact with the polymer activated carbon. The activated carbon would then remove toxins from the blood and then the blood is returned into the body of the patient.
Other uses of Activated Carbon
Since activated carbon is effective at adsorbing toxins, they are often used for treating overdoses and poisoning. In the alternative medicine community, activated carbon is sold as capsules or tablets as a whole body detox pill. Although scientific evidence to support this is lacking, a lot of people reported good results.
Activated Carbon became a household name because of the numerous cosmetic products that feature it. You can find activated carbon in products like shampoo, toothpaste, and face masks. Cosmetic companies took advantage of activated carbon’s superior adsorptive property to create products that could remove toxins and contaminants.
Activated carbon can be used in a wide range of agricultural processes. In the process of making wine, activated carbon can be used to remove unpleasant color and odor from the product. Some animal feed contains activated carbon. Aside from that, It can be used as a natural pesticide for those practicing organic farming.
Distilled Beverage Purification
Similar to how activated carbon could improve the taste and odor of wine, it is also used in the production of whiskey and vodka to remove impurities that could sully the taste, odor, and color. All without affecting the most important chemical in the drink, the alcohol content.
Activated Carbon is involved in a variety of industrial and manufacturing processes. For example, in metallurgy, activated carbon is used as the primary purification agents for improving the purity of nickel.
In analytical chemistry there are situations wherein high purity solutions are needed. Activated carbon can be used to purify solutions to remove unwanted organic molecules and chemicals which may interfere with the desired reaction.
The amazing adsorptive properties of activated carbon makes them a perfect material for cleaning up spills of oil and other environmentally damaging materials. Aside from that, they are also utilized in groundwater remediation, or the removal of harmful substances from groundwater.
Air and Gas Purification
Besides water, activated carbon could also remove pollutants from gases that would come into contact with its surface. Odors and other pollutants are trapped by the minute pores present in the activated carbon’s surface. Activated carbon could eliminate radon and volatile organic compounds or VOCs which are some of the most hazardous pollutants to date.
Coal-fired power plants would generate emissions that contain mercury. This emission would introduce mercury into the air which people nearby might inhale. To remedy this, impregnated carbon with halogens or sulfur present in their surface are used to capture the mercury and remove it from the air.
Activated carbon can remove contaminants, harmful gases, and body odors from the flow of oxygen in an astronaut’s spacesuit. Due to this, activated carbon is considered to be an essential part of the spacesuit life support systems.