Differences Between Physical Activation and Chemical Activation of Activated Carbon

Activated carbon is widely used in water purification, air treatment, gas adsorption, catalyst support and other fields. The activation method plays a key role in determining the pore structure, adsorption performance and application scenario of the final product. Among all technologies, physical activation and chemical activation are the two most common approaches. This article compares their working principles, activation conditions, product characteristics, and respective pros and cons.

1. Activation Mechanism

Physical Activation
This method relies on a high-temperature environment where steam or carbon dioxide reacts with the carbonized material. At elevated temperatures, gases such as CO₂ undergo redox reactions with carbon atoms on the surface, generating CO and gradually forming new pores. These reactions also expand and improve the existing pore structure inside the carbon material.

Chemical Activation
Here, the raw material is impregnated or mixed with chemical agents such as phosphoric acid (H₃PO₄) or zinc chloride (ZnCl₂). During heat treatment, the chemicals promote dehydration, condensation and other complex reactions with the organic components. They act as pore-forming agents, occupying space and creating pores once removed in the later washing stage.

2. Activation Conditions

Physical Activation
The activation temperature is typically high, usually between 800 °C and 1000 °C. This requires equipment with excellent heat resistance and results in relatively high energy consumption.

Chemical Activation
The process temperature is lower, generally between 400 °C and 800 °C. Compared to physical activation, it reduces energy usage and places fewer demands on high-temperature furnaces.

3. Characteristics of the Final Product

Physical Activation
The resulting activated carbon has a wide pore size distribution, including micro-pores, meso-pores and macro-pores. It features stable surface chemistry and a low ash content. These properties make it suitable for applications requiring high purity and broader pore size ranges, such as premium drinking water treatment and catalyst carrier materials.

Chemical Activation
This method produces richer pore structures with a higher proportion of micro-pores and a large specific surface area. The adsorption performance is stronger, especially for small-molecule substances. It is commonly used in applications requiring high adsorption capacity, such as gas adsorption or removal of small impurities in liquid phases.

4. Advantages and Disadvantages

Physical Activation
• Advantages: Environmentally friendly, no large amount of chemicals introduced, and the final carbon is highly pure.
• Disadvantages: High energy consumption, longer production cycle, larger equipment investment, and relatively high raw material requirements.

Chemical Activation
• Advantages: Lower activation temperature, reduced energy cost, higher production efficiency, and excellent adsorption capacity.
• Disadvantages: Requires large quantities of chemicals, complex washing steps, potential environmental impact if wastewater is not treated, and possible chemical residues that limit use in high-purity fields.

5. Summary

Physical and chemical activation each offer distinct characteristics. Physical activation is ideal for high-purity applications and broader pore structures, while chemical activation is more efficient for producing high-surface-area carbons with strong adsorption performance. Selecting the appropriate method depends on the target market, application requirements, and production conditions.