What Is the Activated Carbon Iodine Number? How Does It Affect Quality?
The iodine number is the most common quality metric showing the adsorption capacity of activated carbon. How it is measured, which values are considered good, and its relationship to surface area.
When buying activated carbon, the technical value you encounter most is the “iodine number.” It is a practical indicator of the carbon’s adsorption capacity for small molecules and lets you quickly compare product quality.
What Exactly Is the Iodine Number?
The iodine number expresses, in milligrams, the amount of iodine adsorbed by one gram of activated carbon under standard conditions (mg/g). The measurement follows the internationally accepted ASTM D4607 test method. Because the iodine molecule is small, it mainly reflects the volume of micropores.
Which Values Are Considered Good?
- ≥900 mg/g: the high-quality range for water treatment and general-purpose granular activated carbon.
- ≥1000 mg/g: demanding applications and premium grades.
- 750–900 mg/g: sufficient for many powdered activated carbon and color-removal applications.
Important note: the iodine number alone does not guarantee the product’s suitability for your application. Particle size, hardness, moisture and ash content are also critical parameters. That is why we test every batch in our own laboratory before shipment and share the results with you.
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