Activated Carbons do contain water/acid soluble impurities & their % age depends upon the source of raw material, i.e., wood. These impurities are removed by reacting the activated carbon with suitable mineral acid followed by thoroughly washing with water.

When pH of the system is below 4 and high purity is required it is advisable to use acid washed A/carbon only.

The pH of activated carbon may be defined as pH of the suspension of activated carbon in distilled water. After steam activation most of the carbons are Alkaline in nature. Adsorptive capacity is certainly a function of the pH of the liquid and hence various pH levels should be investigated. While adjusting the pH of the process care should be taken that change in pH does not degrade or decompose the particular product. For most of applications pH range 6.5 to 7.5 is safest but few specific cases may require pH below 5.0 or above 9.5. So it is advisable to mention pH while procuring activated carbon.

The surface area of activated carbon can range from 500-1400 meters square/gm and is mainly due to porous character of activated carbon. By reducing the particle size the surface area of a given weight is not effected. Therefore by reducing the particle size the adsorption rate is influenced but not the adsorption capacity which is related to surface area.

A single pound of activated carbon has the surface area equal to 125 acres.

Adsorption pores are the internal volume where the graphitic plates are very close together creating a higher energy. Higher energy is important to adsorption because it is the energy that "holds" the contaminant (the carbon "adsorbs" the contaminant). The volume where the graphite plates are far apart and the cracks and crevices make up the transport pores. It is important to note that all adsorption takes place in the adsorption pores and not the transport pores

There is a natural attractive force between all things in the universe. Gravity is one of these forces. In adsorption theory, the force between the contaminate and the carbon is the adsorptive force. It technically is a Van der Waals force. It is this attractive force that enables adsorption to occur. The forces are a function of the distance between the two objects. The closer together the objects are, the higher the attractive force is. The higher the attractive force, the higher the "energy" level of the pore space.

Transport pores are the internal volume of the carbon granule where the graphitic plates are far apart or the cracks and crevices of the particle. The transport pores act as the "highways" for the contaminants to reach the adsorption pores where they are adsorbed. It is important to note that no adsorption takes place in the transport pores. Transport pores are vitally important, as they allow access to the adsorption pores - especially those deeper within the carbon granule.

Once the contaminant enters the carbon granule via the transport pore space, it diffuses into the carbon matrix until it enters the smaller pores where the adsorptive forces begin to take effect. Once it reaches a higher-energy area, it can no longer migrate (or diffuse) because the adsorptive force is stronger than the diffusional force. The contaminant is adsorbed to the carbon surface by the adsorptive forces (the Van der Waals forces). In this state, the contaminant is referred to as the adsorbate.

The amount that the carbon can adsorb is dependent upon the type and concentration of the adsorbate. Generally, the higher the concentration and the larger the molecule, the greater the amount adsorbed. The typical range experienced is about 1 to 35 weight percent. That is, one kg of carbon will adsorb upto 350 gms of contaminant. When the maximum amount of adsorbate is on the carbon, and all adsorption sites are utilized the carbon is referred to as being spent or exhausted.