Charcoal is a grayish-black carbonaceous material. Activated charcoal--also known as active charcoal or activated carbon - is a form of charcoal obtained after processing carbon with excess amounts of oxygen or some specific chemicals. The objective is to incorporate pores in between the tiny carbon atoms. With innumerable uses in medical science (e.g. to absorb poison), this carbon product is now commercially produced on a large-scale.
Why is it Used in Filters?
The large surface area and decontamination property of activated charcoal is employed for use in both air and water filter systems. At present, manufacturing companies have succeeded in making this charcoal with a surface area of as much as 2,000 square meters per gram (the average is 500 square meters per gram). For use in filter systems, further treatments are being done to enhance the adsorption capacity of active charcoal.
When a chemical comes in contact with the surface area of this charcoal, it immediately adsorbs with the help of chemical attraction. With several bonding sites, lots of chemical substances can be trapped in the pores of activated charcoal at once. Thus, it works well in filtering air and water. Organic chemicals (containing carbon, hydrogen, and oxygen) are best attracted by these charcoal filters. Other impurities that can be removed by this charcoal filtration method are chlorides and radioactive gases.
In indoor air purifiers, activated charcoal is found to be effective in absorbing colored agents, odorous chemicals, smoke, radioactive agents, chemical emissions, liquid impurities, and hydrocarbon compounds from the air. It is mostly preferred by people who have allergies. One word of caution with the application of these charcoal filters in respirators and gas control systems is that they cannot remove carbon monoxide. Also, the efficiency of these home air filters in removing dust and environmental pollutants is low.
Activated charcoal filters are used for water purification systems in large water supply centers and private homes. They are applicable for removing unwanted taste and odor from the water samples. As per scientific studies, active charcoal can remove all sorts of organic based chemical impurities found in water like, benzene, pesticides, volatile oils, and gasoline. Traces of chlorine and heavy metals, like radon, that are left behind after water treatment processes can be removed with the help of these filters.
In a home water treatment system, filter cartridges filled with active charcoal (either powdered block or in granular form) are introduced in the water purification system. The incoming water is allowed to pass through the cartridge before delivering to the faucets. Water used for cooking and drinking is treated with these charcoal filters. By doing so, you can increase the longevity of active charcoal water filters. Also, the more amount of the charcoal filled in the cartridge, the longer it will last.
A major drawback with activated charcoal filters is that the chemicals trapped by this carbon are specific. To be more precise, there are certain substances that simply pass through the filtration system without getting adsorbed. Examples of such substances include nitrates and sodium compounds. If such impurities are present in the air or water sample, they remain unaffected even after using activated charcoal filtration. Hence, additional filter systems need to be installed for purification.
Whether it is an air or water filter, regular care and maintenance of activated charcoal filters is expected for efficient working. Say, for example, after using the same filter for a prolonged time, all the bonding sites are clogged by contaminants. There is no surface for further adsorption of chemicals, and thus, the active carbon filter will stop working. To avoid this situation, you need to replace the old charcoal filter with a brand new one at regular intervals.