Carbon air filters remove pollutants from the air with a process known as adsorption. Note that this is different from absorption. In absorption, the substance you want to remove (let’s say water) is absorbed into the structure of the absorbent (like a sponge), but it doesn’t become a part of the absorbent on a molecular level. Therefore, when you absorb water with a sponge, the water does not become chemically bonded to the sponge. It just fills in the spaces inside it. polyacrylamide pam
Carbon filters on the other hand use ad-sorption, not ab-sorption. The key difference here is that during adsorption the pollutants stick to the outside of the carbon. Whereas with absorption, the pollutants are absorbed inside the structure itself–as with the sponge.
Carbon is a lattice of carbon atoms connected to each other. The activation process is so important because the increase in surface area gives gases a greater area to stick to. When a molecule of some gaseous substance comes through the carbon, it can stick to the surface of the bed, provided there is an open adsorption site.
The process of adsorption allows carbon air filters to filter organic chemicals (gases) from the air. The problem with the activated carbon bed is that over time, the gaseous pollutants increasingly fill up the adsorption sites of the activated carbon. Once the bed is saturated, the filter can no longer trap pollutants. In fact, chemicals with a greater affinity for an adsorption site can displace those with lesser affinity, and the affinity of a given chemical for the sorbent is highly dependent on ambient conditions such as temperature and relative humidity. So, as conditions change, different chemicals may be released from the filter. When a carbon air filter is saturated, you might notice it giving off a strange odor. This is a strong indicator that it’s time to change your carbon filter.anionic polyacrylamide polymer
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