Activated carbon is a form of carbon that’s been processed to make it extremely porous, which in turn creates a large amount of surface area. In essence, this process allows for excellent adsorption. Adsorption is the adhesion of gas, liquid or dissolved solid to a surface. This is different than absorption, which is where a fluid permeates or is dissolved by a liquid or solid.
Types of Activated Carbon
Activated carbon comes in granular or extruded forms. Activated carbon comes from a few different materials such as coal, coconut shells, peat or wood. The activated carbon is made from the above-mentioned materials by exposing them to a very high temperature in an oxygen deficient environment that ” carbonizes ” the material. These materials are then “activated” by exposing them to an oxidizing agent at a very high temperature. This process is what creates the porous nooks and crannies in each particle. When the materials are “activated” they have a high surface area that’s great for collecting contaminants from the water in your home.
Extruded carbon is a fine powdered carbon that is combined and fused with a thermoplastic binder AND specialty adsorbents like oxidizing filtration media, and then extruded into a cylindrical form for numerous applications, including water filtration. Extruded carbon has an even higher amount of surface area which is extremely uniform, compared to granular activated carbon. Extrusion provides high performance adsorption and particulate reduction while also providing a low flow resistance.
So, what’s the purpose of activated or extruded carbon? Well, they’re both excellent at removing chlorine, bad tastes and odors from your water as well as other organic compounds. Unfortunately, they will not remove inorganic compounds, microbes, sodium, nitrates, fluorides, lead or hardness minerals. Some special carbon filters remove cryptosporidium and giardia cysts from your drinking water.
Extruded Block Carbon vs. Granular Activated Carbon
Extruded carbon generally out performs granular activated carbon because of its higher adsorbent capacity along with higher contaminant reduction. Extruded carbon also has a lower pressure drop, higher dirt holding capacity and low to very few carbon “fines” (AKA small particles). Extruded carbon typically has higher integrity, strength and an overall ability to produce the highest possible effluent quality when compared to granular activated carbon.
Granular activated carbon is sometimes loosely packed in a non-rigid cartridge, which can allow for water channeling. In some instances, more carbon “fines” are released from a granular activated carbon filter cartridge than an extruded carbon filter cartridge. Granular activated carbon filters sometimes allow water to bypass the carbon because of the loose design of the filter cartridge. It’s also not a good idea to mount the filter housing horizontally as the carbon will settle to the bottom side of the cartridge and allow water to flow through the open channel.
Most extruded carbon block filters have an NSF certification. NSF stands for “National Sanitation Foundation International” and is an organization that certifies products. A filter that meets NSF material requirements has been certified not to leach chemicals in excess of established standards. All filter components are tested during certification and evaluations. Learn more about NSF certification standards here.