What is activated carbon?
Activated carbon is a highly porous form of carbon that has been processed to have an extremely large surface area — typically between 500 and 1,500 square metres per gram. To put that in perspective, a single gram of activated carbon can have the internal surface area of a football pitch.
This enormous surface area is entirely internal — created by a network of pores of varying sizes, ranging from macropores (large pores that allow molecules to enter the particle) to mesopores (intermediate) to micropores (the smallest, where most adsorption actually takes place).
How does adsorption work?
Activated carbon works through a process called adsorption — not absorption. The distinction matters. Absorption means a substance dissolves into another (like a sponge soaking up water). Adsorption means molecules stick to a surface — held there by weak van der Waals forces.
When a contaminated liquid or gas passes through activated carbon, the contaminant molecules are attracted to and held on the carbon surface. The contaminant is removed from the stream. The carbon becomes gradually saturated over time, until it must be replaced or reactivated.
A single gram of activated carbon can hold the equivalent surface area of a football pitch — entirely within its pore structure. This is why a small carbon filter can treat thousands of litres of water.
What is it made from?
Activated carbon is produced from any high-carbon organic material — wood, coconut shell, coal, peat. The raw material is first carbonised (charred) at high temperature in a low-oxygen environment, then activated — either with steam, CO₂, or chemical agents — to create and enlarge the pore structure.
The raw material determines the pore size distribution. Coconut shell produces predominantly microporous carbon, suited to small-molecule adsorption. Wood, particularly pine, produces macroporous carbon — essential for applications where large molecules need to enter the particle structure.
What does it remove?
- Chlorine and chloramines from drinking water
- Taste and odour compounds (geosmin, MIB)
- Colour from food, beverage, and pharmaceutical streams
- Volatile organic compounds (VOCs) from air
- Gold-cyanide complex from mining leach solutions
- Trace organics from API and injectable pharmaceutical streams
Activated carbon does not remove dissolved minerals, heavy metals (without special treatment), or microorganisms on its own. For those applications, other treatment steps are needed alongside carbon filtration.