Activated carbon is a porous material with adsorbent properties.
Adsorption (as opposed to absorption) is a phenomenon whereby a surface attracts and captures molecules that adhere to the surface itself through a chemical bond. The greater the contact surface, the greater the adsorption efficiency for the same mass.
Absorption, on the other hand, involves the absorbed material spreading within the absorbing mass.
The adsorbent capacity of activated carbon therefore depends on the size and internal surface area of the myriad of channels, pores, and pockets where the gaseous or dissolved substances present in the water form physical bonds and therefore adhere to them.
Why is it called activated carbon?
To increase the surface area of porosity, the carbon is activated, reaching an adsorption surface area of between 500 and 2,500 square meters per gram.
Activation occurs through thermal shock with air flow or with chemical agents that are then rinsed off. The latter activation technique is the one that generates carbon with greater porosity.
Some activated carbon filters of plant origin are labeled “acid washed.” This is an additional treatment to remove any combustion ash and organic material present
What does activated carbon remove?
Water filters are mainly composed of activated carbon in various forms, granular, powdered, or solid (carbon block): its porous surface is able to capture various organic pollutants. In particular, activated carbon adsorbs chlorine used for disinfection, neutralizes unpleasant odors, and improves the taste of water.
Obviously, there are different types of carbon, with different capacities and effectiveness, which act on pesticides, PFAS, and organic and halogenated compounds as well as some heavy metals such as lead.
Scientific literature alone is not enough to advertise the effectiveness of an activated carbon filter; tests are needed to demonstrate its actual filtering capacity.
Waterpro filters remove chlorine and reduce PFAS-PFOA. How can we say this? Simple: we commissioned TÜV to perform tests on our filters for the duration indicated in the data sheet. Total liters and flow rate in liters per minute (contact time is important).
Clorine removal is not an issue; total removal is guaranteed well beyond the indicated data, while for PFAS and PFOA we have a curve that starts from high values above 90% and stabilizes around 50% at the end of life. We can therefore write on our labels that it removes free chlorine and significantly reduces PFAS and PFOA, the same for lead and other metals.
How does ionic silver act in activated carbon?
Silver nitrate with bacteriostatic properties can be added to activated carbon: silver is a natural agent that inhibits bacterial proliferation within the filter itself, preventing the formation of algae and mold. When carbon is compacted into a very dense structure, it forces every single water molecule to pass through its microscopic pores. Silver fights microbes in three ways:
-by interrupting cell metabolism,
-by inhibiting transport processes in the membrane, and
-by preventing cell multiplication.
This mechanism of action of silver significantly reduces the risk of biofilm formation downstream of the filter and up to the dispensing spout.
