Table of Contents
Carbonization - a crucial step:
In an oxygen-restricted setting, raw materials like wood, coconut shells, or other organic substances are subjected to heat, enabling the removal of volatile components and the formation of a carbon-rich substance. Carbonization temperatures typically fall between 400 and 600°C, yielding a porous, carbon-laden material known as char.
Methods of activation:
Activation develops the internal pore structures and augments the surface area of the carbonized material, thus enhancing adsorption capacity. There are two primary activation techniques:
- Physical activation: Here, the carbonized material is heated to high temperatures (800-1000°C) in the presence of an oxidizing gas like steam or carbon dioxide. The reaction between the gas and carbon material generates a porous structure with a vast surface area.
- Chemical activation: In this approach, a chemical activating agent, such as phosphoric acid, potassium hydroxide, or zinc chloride, impregnates the carbonized material. The mixture is then heated at lower temperatures (400-800°C) relative to physical activation. A porous structure with a large surface area is created by the chemical reaction between the activating agent and the carbonized material.
Shaping and pelletizing - the art of forming:
Activated carbon powder is blended with a binder like starch or molasses to enhance mechanical strength and handling characteristics. This mixture is then fashioned into pellets using methods such as extrusion, pelletizing, or tabletting. The pellet size can be manipulated by adjusting the shaping process parameters.
Post-processing techniques - refining the product:
Depending on the intended application, several post-treatment processes may be employed to improve the performance of the activated carbon pellets. These processes include:
- Washing: Pellets can be rinsed with water or a diluted acid solution to remove residual chemicals or impurities from their surfaces.
- Drying: To eliminate moisture that could affect adsorption properties, washed pellets are dried at low temperatures (100-150°C).
- Activation: In certain cases, a secondary activation step might be needed to further expand the surface area and pore structure of the pellets.
By adhering to these steps, premium activated carbon pellets can be manufactured for diverse applications such as water and air purification, gas separation, and catalyst support.