Activated carbon as a means of purification of alcohol is a very effective natural product. It is also cheap, and the carbon can be recycled and used again. It is the world’s best-known medium for purification of water and alcohol. The fantastic properties of activated carbon allow us to trap poisons, creosotes, heavy metals, insecticides, bad smells and tastes, chemical substances, fusel oils and impurities, or undesirable substances in both liquid and gases.
Activated carbon works when ordinary physical filtering (using a sieve, filter paper and filter pads, and sand) cannot separate a particular substance. Activated carbon works by absorbing impurities into its pores. Absorption happens through cooperation of the carbon’s enormous adsorptive surface, including its weak electrostatic charges (known as Van der Waals forces, named after the scientist who studied them), together with the distribution of pore sizes (micro-, meso-, and macro pores), and the construction of the pores surfaces (called cohesion forces). The carbon pores become saturated with impurities, attaching even to the outside of the carbon.
What happens when carbon adsorbs impurities?
Absorption occurs when organic impurities are bound inside the carbon pores. This happens when the pores are marginally larger than the impurities (molecules) that they bind.
There are 2 kinds of absorption, physical and chemical
Physical absorption happens when the impurities are bound in the pores and on the surface of the carbon by means of Van der Waals electrostatic forces, making the carbon act as a magnet. The impurities on the outside of the carbon are loosely attached, like oversize molecules that have been trapped in the opening of smaller pores.
Chemical absorption is the union of impurities with other substances on the surface of the carbon pores. This is a powerful absorption. The chemical substances present on the pore surface depend on the raw material used, activation method, and after-treatment.
Three available forms of activated carbon
1. Pulverized carbon
2. Granulated carbon
3. Reformed (under high pressure) carbon, usually pellets
Purification ability depends on many things, including:
• Which carbon is used
• The surface of the carbon in sq. meters per gram
• Pore structure (distribution of micro-, meso- and macro pores)