What is activated carbon?
Activated carbon is a highly porous, high surface-area adsorptive material. It is composed of sheets of carbon atoms joined by random cross-links that form a porous internal network. It helps to think of a structure like a honeycomb. The millions of cracks and voids between the carbon layers make activated carbon very effective filtration material. Pollutants are attracted to the vast surface area inside the porous carbon network. Activated carbon is used in industry and at home for adsorbing a wide range of impurities from liquids and gases.activated carbon manufacturers
What is activated carbon made of?
All activated carbon starts off as a carbon-rich raw material. Almost any carbon-containing material can be used to produce activated carbon. But the most common materials are coal-based and include anthracite, lignite and bituminous coals.
There are also carbon filtration products made from wood, cherry pits and even recycled tires. The raw material used to make the activated carbon has a tremendous influence on the properties of the final product. As we’ll see, not all activated carbons are equal when it comes to aquarium filtration.
How is activated carbon made?
No matter what the starting material, the activation process is where it all begins. It’s the activation process turns the raw material into a highly porous carbon structure capable of adsorbing pollutants from water. Here’s how activation works.
The raw material is heated to remove moisture. It’s then ground into a powder.
A harmless binder is added to the powder and compressed into a block.
The block is crushed into pieces and sent to a kiln for a two-step baking process.
The pieces are baked at 200-750° F to drive off volatile organics then again up to 1000° F to form charred carbon particles. A porous network is beginning to form.
The carbon is then treated with steam at 1800° F to fully open up the pores.
The activation process opens up a massive internal network of pores inside each carbon particle. This controlled high-temperature reaction converts portions of the solid carbon to volatile gas. This volatilization opens up the pores.
During the activation process about half of the “char” material is removed to create the internal pore structure. Some carbons, depending on the raw material, can contain residual ash. This will leach out and add minerals to the water and even raise pH.
To remove the residue the activated carbon is rinsed with a dilute acid to flush out the ash. You may see “acid-washed” activated carbon when comparing carbon products. Acid washing doesn’t make the carbon acidic or lower pH in your aquarium. It is just a step to remove residul iron, calcium carbonate and silica from the carbon.
Low-grade activated carbon made from sawdust is chemically activated using phosphoric acid. The paste of raw material and phosphoric acid is dried and then heated in a kiln. This type of carbon will release some residual phosphate into the water.granular activated carbon supplier