Iodine Number, CTC, BET: How to Read an Activated Carbon Data Sheet
Two supplier data sheets sit on your desk: one claims an iodine number of 1050, the other 1100 m²/g BET. Which is better? Answer: as stated, they cannot be compared — they measure different things. Reading a carbon data sheet starts with knowing which question each parameter answers.
Capacity parameters
Iodine number (mg/g): the classic measure of small-molecule capacity; in practice it tracks micropore volume. Water treatment carbons typically run 900–1100. Fast, cheap and universal, it is the industry’s common language.
Methylene blue (ml/g): represents mid-size molecules; an indicator of decolorization capacity. Especially important for powdered carbons; above 180 ml/g is a good value.
CTC activity (percent): the measure of gas-phase capacity; the uptake of carbon tetrachloride vapor. It is the headline value for pellet carbons, typically 55–70 percent.
BET surface area (m²/g): total internal surface measured by nitrogen adsorption. Scientifically the most comprehensive number, but on its own no guarantee of performance — how much of that surface sits in correctly sized pores depends on the application.
Physical parameters
| Parameter | Why it matters |
|---|---|
| Hardness (percent) | Particle loss in transport and backwash; target above 95 |
| Ash (percent) | Non-carbon mineral residue; low ash = high purity |
| Moisture (percent) | How much of the weight you pay for is water |
| Density (g/cc) | Bed fill calculations; critical when buying by volume |
| Particle size / mesh | The flow-resistance vs kinetics balance — our mesh guide |
Golden rules of comparison
- Compare the same parameter under the same test standard (ASTM or equivalents should be stated)
- Focus on the parameter that fits your application: CTC for gas phase, iodine for water, methylene blue for color
- Look at the profile, not a single number: high iodine + low hardness can mean short life
- For critical jobs, trust the batch certificate of analysis, not the brochure
We ship every order with a batch analysis — request a sample data sheet from our product families to see that the numbers are not just talk.
