Common Terms Related to Activated Carbon
Adsorptive Characteristics of Activated Carbon
The effectiveness of activated carbon is expressed by the amount of certain test chemical it adsorbs per unit weight. Commonly used chemicals are as follows:
Carbon Tetrachloride: It is mostly used for testing activated carbon used in purification of air and gas. The adsorption of Carbon Tetrachloride is denoted as CTC activity (%).
Iodine: It used mostly for testing activated carbon used in water purification and is denoted as Iodine no. (mg/gm) of activated carbon.
Physical Characteristics of Activated Carbon
Hardness: Denotes the abrasion-resistance of the activated carbon. The harder the activated carbon, the more it will withstand handling and use without crumbling into smaller pieces. This in effect minimises wastage. Coconut-based activated carbon has the unique hardness of 98-99% making it ideal for a wide range of applications.
Ash Content: The inorganic and inert content in the activated carbon which is non-beneficial. It comes from the raw material, and the maximum ash content should not exceed 5% ideally.
Apparent Density: The weight of one litre of activated carbon (g/litre). It depends on the raw material, the production process and the activation process. Wood based activated carbon has a lower density that coal based activated carbon.
Moisture: The water content in the activated carbon. A standard method (ASTM D2867) to determine moisture content is to measure the loss of weight after the activated carbon is heated to 150°C and then allowed to dry for 3 hours to a constant weight.
Mesh Size: The size-range of granular activated carbon is expressed by mesh size or sieve size. The sample is shaken to through a set of sieves of fixed widths between its wires to determine its mesh size. For example, a mesh size of 8 X 30 denotes that most of the granules don’t pass through a 30 mesh (0.60mm) and are therefore larger that it, and most of the granules pass through an 8 mesh (2.36mm) and are therefore smaller than 2.36mm.