Activated carbon, also known as activated charcoal, is a highly porous form of carbon that has been specially processed to have a large surface area and a high degree of internal microporosity. This makes it extremely effective at adsorbing (not absorbing) a wide range of substances from gases, liquids, and even solutions.

The activation process involves treating carbon-rich materials, such as wood, peat, coconut shells, or other agricultural by-products, with high temperatures and sometimes chemicals to create a network of pores and increase the material’s surface area. This results in a material with a vast number of tiny pores and a large surface area relative to its size. This increased surface area allows activated carbon to attract and retain various molecules on its surface through a process called adsorption.

Activated carbon is produced through a process called activation, which involves treating carbon-rich materials with high temperatures and sometimes chemicals to create a network of pores and increase the material’s surface area. There are two main methods of activation: physical activation and chemical activation. Here’s an overview of both processes:

1. Physical Activation: Physical activation involves the controlled carbonization (partial burning) of a carbon-rich precursor material, followed by an activation step where the carbonized material is exposed to high temperatures in the absence of oxygen. This process is typically carried out in two stages: carbonization and activation.

   Carbonization: The precursor material, which can be coconut shells, wood, peat, or other carbon-rich sources, is heated in an oxygen-limited environment to remove volatile components and create a carbon-rich structure.

   Activation: The carbonized material is then exposed to even higher temperatures (800°C to 1000°C or more) in the presence of an inert gas, like nitrogen or steam. This process causes the material to undergo physical changes, creating pores and increasing its surface area.

2. Chemical Activation: Chemical activation involves impregnating the precursor material with chemicals that react with the material at high temperatures, resulting in the formation of pores and increased surface area. The chemical activation process typically requires lower temperatures compared to physical activation.

   Impregnation: The precursor material is impregnated with a chemical activating agent, such as potassium hydroxide (KOH) or phosphoric acid (H3PO4).

   Activation: The impregnated material is then heated to moderate temperatures (500°C to 800°C) in an inert atmosphere. The chemicals react with the carbon, creating gases that create pores and expand the material’s surface area.

After either physical or chemical activation, this material is thoroughly washed to remove any residual activating agents and ash. The resulting material is then cooled and can be further processed into different forms such as granules, pellets, powders, or fibers, depending on the intended application.

The choice between physical and chemical activation depends on factors such as the desired properties of the activated carbon, the precursor material, and the specific application requirements. Physical activation tends to produce activated carbon with a higher surface area and more uniform pore structure, while chemical activation can offer more control over pore size and distribution.

Activated carbon can be used in a wide range of applications due to its exceptional adsorption properties. Its porous structure and high surface area make it effective at capturing and removing various substances from gases, liquids, and solutions.