Important Properties of Activated Carbon

There are many different properties and characteristics of activated carbon, and understanding these factors will help you understand how the material is measured and analyzed.

Iodine Number

Iodine adsorption is used to measure the effectiveness of activated carbon. During this test, activated carbon is added to a liquid holding a specific amount of iodine. The carbon is mixed thoroughly until it has dissolved into the activated carbon price After a few minutes, the solution is filtered into another container, removing the charcoal particles and allowing the liquid to pass through. The iodine number is a gauge of the amount of iodine removed from the liquid. Essentially, the higher the number, the more iodine was removed.

Many carbons preferentially adsorb small molecules. Iodine number is the most fundamental parameter used to characterize activated carbon performance. It is a measure of activity level (higher number indicates higher degree of activation,) often reported in mg/g (typical range 500–1200 mg/g). It is a measure of the micropore content of the activated carbon (0 to 20 Å, or up to 2 nm) by adsorption of iodine from solution. It is equivalent to surface area of carbon between 900 and 1100 m2/g. It is the standard measure for liquid-phase applications.

Methylene blue

Some carbons have a mesopore (20 Å to 50 Å, or 2 to 5 nm) structure which adsorbs medium size molecules, such as the dye methylene blue. Methylene blue adsorption is reported in g/100g (range 11–28 g/100g).


Some carbons are evaluated based on the dechlorination half-life length, which measures the chlorine-removal efficiency of activated carbon. The dechlorination half-value length is the depth of carbon required to reduce the chlorine level of a flowing stream from 5 ppm to 3.5 ppm. A lower half-value length indicates superior performance.

Apparent density

The solid or skeletal density of activated carbons will typically range between 2000 and 2100 kg/m3 (125–130 lbs./cubic foot). However, a large part of an activated carbon sample will consist of air space between particles, and the actual or apparent density will therefore be lower, typically 400 to 500 kg/m3 (25–31 lbs./cubic foot).[19]

Higher density provides greater volume activity and normally indicates better-quality activated carbon. ASTM D 2854 -09 (2014) is used to determine the apparent density of activated carbon.

Hardness/abrasion number

It is a measure of the activated carbon’s resistance to attrition. It is an important indicator of activated carbon to maintain its physical integrity and withstand frictional forces. There are large differences in the hardness of activated carbons, depending on the raw material and activity levels.