CTC values are expressed as a percentage and represent the amount of carbon tetrachloride adsorbed by activated carbon under standardised test conditions. CTC is often used to measure the adsorption capacity of different activated carbons, particularly in air and gas purification applications.
The test is carried out by exposing a known mass of activated carbon to a mixture of air and CTC vapour at a specified temperature, relative humidity and flow rate. CTC is adsorbed by the activated carbon and the decrease in its concentration in the air is measured. The CTC value is then calculated as the ratio of the mass of carbon tetrachloride adsorbed to the mass of activated carbon, multiplied by 100.
The higher the CTC value, the greater the adsorption capacity of the activated carbon for CTC, which is also considered to be representative of the adsorption performance of the carbon for other VOCs. CTC values can be influenced by a number of factors such as the pore size distribution, surface area and surface chemistry of the activated carbon, as well as particle size and packing density.
Types of activated carbon used for gas phase adsorption
- Granular activated carbon
- Pelletized activated carbon
- Honeycomb activated carbon
CTC value related applications:
When selecting activated carbon for a specific application, in addition to CTC, other relevant factors must be considered, such as the molecular size and type of the particular pollutant to be removed, etc., the operating environmental conditions (wind speed, pollutant concentration), and the required adsorption capacity. In some cases, specially impregnated or modified activated carbon may be more effective than activated carbon with a high CTC value, for example when adsorbing H2S, impregnated KI, KOH adsorption will be more effective.