Activated Carbon Metrology: Understanding Iodine Numbers, CTC Activity, and Micropore Volume
Not all activated carbon is created equal. A cheap carbon filter made from bituminous coal dust with low micropore volume will saturate in weeks, while high-grade virgin coconut shell carbon with an Iodine Number over 1,050 mg/g will trap toxic VOCs for years.
1. The Iodine Number (ASTM D4607 Standard)
The primary metrological metric for activated carbon quality is the Iodine Number, defined as the milligrams of elemental iodine adsorbed by one gram of carbon from a standard 0.02N aqueous iodine solution. It directly correlates with internal micropore surface area (pores between 0.5 and 2.0 nanometers):
| Carbon Grade & Feedstock | Iodine Number (mg/g) | CTC Activity (%) | Optimal Contaminant Targeting |
|---|---|---|---|
| Virgin Coconut Shell (Microporous) | 1,000 to 1,200 mg/g | 60% to 75% | Small molecules: Benzene, Toluene, Acetone |
| Bituminous Coal (Meso/Macroporous) | 800 to 950 mg/g | 45% to 55% | Medium molecules: Cooking oils, Diesel soot |
| Extruded Wood Pellet (Macroporous) | 700 to 850 mg/g | 40% to 50% | Heavy organic vapors and high-humidity air |
2. Carbon Tetrachloride (CTC) Activity and Bulk Density
CTC activity measures the weight percentage of saturated carbon tetrachloride vapor adsorbed at 25°C. High-grade coconut shell carbon with a bulk density of 0.45 to 0.52 g/cm³ packs the highest mass of active micropores into the limited dimensional envelope of residential air purifiers.
Consultation & Lab Inquiries
For room air exchange modeling, hospital cleanroom CADR audits, or filter media testing: martbusinnes@gmail.com.
Browse Certified Equipment on Amazon →