What is the Density of Activated Carbon?
The density of activated carbon includes bulk density, apparent density and true density. This article mainly introduces the definition, test method and significance of these three activated carbon densities, as well as the comparison of the three densities.
Bulk Density of Activated Carbon
Bulk density of activated carbon definition
Bulk density refers to the mass of activated carbon in a loosely packed state per unit volume (including the internal pores of activated carbon particles and the gaps between particles). Activated carbon bulk density unit is g/cm³ or kg/m³.
The bulk density of granular activated carbon (GAC) is usually between 0.4 and 0.6 g/cm³, while the bulk density of powdered activated carbon (PAC) may be slightly lower, about 0.38g-0.45g/cm³. And the density of pelletized activated carbon is 0.45g-0.65g/cm³, which is basically the same as bulk density of granular activated carbon.
Bulk density of activated carbon in kg/m³ is 200-600, which is 0.2-0.6 g/cm³
Bulk density of activated carbon measurement method
Pour the activated carbon freely into a measuring cylinder, measure the volume, and then weigh it.
Activated carbon bulk density function
- Determines packaging, shipping and filling costs (lower bulk density takes up more space).
- Affects reactor design (e.g., fixed bed loading).
Apparent Density of Activated Carbon
Apparent density of activated carbon definition
Apparent density (also known as particle density) refers to the mass of activated carbon particles per unit volume (including internal pores, excluding spaces between particles).
Standard test method for apparent density of activated carbon
- Mercury displacement method: Mercury cannot enter the micropores of activated carbon under normal pressure, but it can fill the gaps between particles, thereby measuring the volume of particles.
- Vibration compaction method: Eliminate the gaps between particles through vibration and measure the volume in a dense state.
There are also experimental methods such as helium specific gravity method and mercury intrusion method, which can be used to test apparent density.
Apparent density activated carbon unit
Activated carbon apparent density unit, as well as particle density of activated carbon, is g/cm³ or kg/m³.
Activated carbon apparent density function
- Reflects the degree of pore development of activated carbon (the lower the apparent density, the higher the porosity).
- Used to evaluate adsorption performance (such as iodine value, methylene blue adsorption).
True Density of Activated Carbon
True density of activated carbon definition
The true density of activated carbon, also called skeleton density or solid density, refers to the density of the activated carbon solid skeleton itself after excluding all pores and spaces between particles.
- The true density of activated carbon is usually between 2.0 and 2.2 g/cm³.
- The true density is determined by the raw materials and the activation process: it can vary slightly depending on the raw materials (coconut shell, coal, wood, etc.) and the preparation process (activation temperature, time).
True density of activated carbon measurement method
- Helium displacement method: Helium can penetrate into tiny pores, and the true solid volume is calculated by gas displacement volume. This is the most commonly used method.
True density activated carbon unit
Activated carbon true density unit is g/cm³ or kg/m³.
Activated carbon true density function
The true density value reflects the physical properties of the activated carbon material itself, and is closely related to the adsorption performance, mechanical strength, etc. in practical applications.
Why is true density important?
- Adsorption performance: Activated carbon with high true density usually has a high degree of carbonization, a well-developed microporous structure, and a large specific surface area.
- Mechanical strength: True density is positively correlated with compressive strength, affecting durability in industrial applications.
- Identifying purity: Abnormally high true density may indicate ash or impurity contamination.
Bulk Density VS Apparent Density VS True Density
True density VS Apparent density VS Bulk density Table
| Project | Bulk Density | Apparent Density | True Density |
|---|---|---|---|
| Included volume | Particle volume + interparticle space | Particle volume (excluding interparticle spaces) | Solid skeleton only (without any pores) |
| Numeric | Lowest (≈0.2–0.6 g/cm³) | Medium (≈0.3–0.9 g/cm³) | Highest (≈2.0–2.2 g/cm³) |
| Measurement method | Free stacking method | Mercury displacement method, helium specific gravity method | Helium replacement method |
| Application Scenario | Industrial loading volume estimation, transportation cost calculation | Pore structure evaluation, adsorption performance study | Material purity analysis, theoretical adsorption calculation |
Choice in practical applications
- Adsorption performance: refer to apparent density (related to porosity).
- Economic efficiency: refer to bulk density (related to transportation and filling costs).
Understanding these two parameters helps optimize the efficiency and cost of activated carbon applications in water purification, waste gas treatment and other fields.
