Choosing the right activated carbon starts with understanding how it is made. The two primary production methods, steam activation and chemical activation, create carbon products with fundamentally different pore structures, surface properties, and application strengths. This guide covers the technical differences between both methods, the resulting carbon properties, and the applications where each type delivers the strongest results.

What Is Steam Activated Carbon?

Steam activated carbon, also known as physically activated carbon, is produced through a two stage thermal process. First, the raw material (typically coconut shell or bituminous coal) is carbonized at 400°C to 600°C. Then, the carbonized material is exposed to high temperature steam (800°C to 1,100°C) in a controlled atmosphere.

The steam reacts with the carbon through gasification, selectively removing carbon atoms to create and enlarge the internal pore network. This method primarily develops micropores (pores smaller than 2 nanometers), resulting in carbon with a high surface area relative to its pore volume. For a detailed explanation of the complete activation process, see our guide on what activated carbon is and how it works.

What Is Chemically Activated Carbon?

Chemical activation takes a different approach. The raw material (often wood or lignite coal) is impregnated with a chemical activating agent before thermal processing at lower temperatures (400°C to 700°C).

Common Activating Agents

  • Phosphoric acid (H3PO4): most widely used, particularly for wood based carbons
  • Zinc chloride (ZnCl2): historically common, now less used due to environmental considerations
  • Potassium hydroxide (KOH): used for producing very high surface area carbons for specialized applications

The chemical agent acts as a dehydrating catalyst during heating, promoting pore development. After activation, the agent is washed out and recovered. This method produces carbon with a wider pore size distribution, including significant mesoporosity (2 to 50 nanometers) and macroporosity (above 50 nanometers).

Side by Side Comparison

Property Steam Activated Chemically Activated
Activation Temperature 800°C to 1,100°C 400°C to 700°C
Pore Structure Predominantly microporous Broader: micro + meso + macropores
Typical Surface Area 800 to 1,200 m2/g Up to 1,500+ m2/g
Iodine Number Range 900 to 1,200 mg/g Often above 1,200 mg/g
Common Raw Materials Coconut shell, bituminous coal Wood, lignite coal
Hardness High (coconut shell: 97%+) Lower, generates more fines
Reactivation Potential Excellent (multiple cycles) Limited due to softer structure
Typical Form GAC, Pellets PAC, some GAC

Higher iodine numbers and surface area do not always mean better performance. The pore size distribution relative to the target contaminant’s molecular size is equally important. A carbon with lower total surface area but the right pore geometry can outperform one with higher numbers but mismatched pore sizes.

Best Applications for Each Type

Where Steam Activated Carbon Excels

Application Why Steam Activated Works Best
Drinking Water Treatment Micropores capture small organic molecules and chlorine effectively
Gold Recovery (CIP/CIL) High hardness withstands abrasion; micropores capture gold cyanide complexes. For detailed selection criteria, see our guide on choosing activated carbon for gold recovery.
VOC Removal Microporous structure captures volatile organic molecules from gas streams
Biogas Purification Effective H2S removal; durable for multiple regeneration cycles
Mercury Capture Works with impregnation for chemisorption of mercury species
Desalination Pre Treatment Protects RO membranes; high hardness minimizes fines

Where Chemically Activated Carbon Excels

Application Why Chemically Activated Works Best
Sugar Decolorization Mesopores accommodate large color body molecules
Edible Oil Refining Open pore structure allows effective bleaching and decolorization
Pharmaceutical Purification Broad pore range handles diverse API impurity molecules
Beverage Clarification Mesopores remove tannins, color compounds, and off flavors
Wastewater Treatment Captures large molecular weight organic compounds from effluent

How to Choose: A Decision Framework

Use the following criteria to guide your selection:

Select Steam Activated Carbon When

  • Target contaminants are small molecules (molecular weight below 300 g/mol)
  • The application involves gas phase treatment or vapor recovery
  • High mechanical strength is needed for fixed bed filtration systems with backwashing
  • The carbon will be reactivated and reused across multiple service cycles
  • Consistent long term performance is a priority

Select Chemically Activated Carbon When

  • Target contaminants are large molecules (color bodies, tannins, humic acids)
  • The application involves decolorization or high molecular weight organic removal
  • Carbon will be used as PAC in single dose batch treatment
  • Very high surface area is needed to maximize single pass efficiency
  • The process operates at lower temperatures where mesopore access matters

The most reliable way to determine the right activation type for your specific application is through laboratory analysis. Isotherm testing and small scale column tests using your actual process stream will confirm which carbon type delivers the best results. The activation method also affects the cost structure: chemical activation requires chemical agents but lower temperatures, while steam activation needs higher energy input but avoids chemical handling. For guidance on selecting carbon for water treatment applications, refer to our dedicated selection guide.

SorbiTech Carbon Range

SorbiTech manufactures both steam activated and chemically activated carbon products from the UAE. The range includes GAC, PAC, pelletized carbon, impregnated carbon, and the OraPure line engineered for gold recovery operations.

For technical consultation on carbon type selection for your specific process conditions, contact SorbiTech.

Frequently Asked Questions

What is the main difference between steam and chemically activated carbon?
Steam activation uses high temperature steam (800°C to 1,100°C) to develop primarily microporous carbon, while chemical activation uses reagents like phosphoric acid at lower temperatures (400°C to 700°C) to create carbon with a broader mix of micro, meso, and macropores. The resulting pore structure determines which contaminants each type adsorbs most effectively.
Which type of activated carbon is harder and more durable?
Steam activated carbon, particularly when made from coconut shell, is significantly harder than chemically activated carbon. Coconut shell based steam activated carbon typically achieves abrasion numbers above 97 percent, making it the standard for demanding applications like gold recovery and fixed bed water filtration where mechanical wear is a factor.
Can both types be used for water treatment?
Yes, but for different purposes. Steam activated GAC is preferred for drinking water treatment where chlorine and small dissolved organics need continuous removal. Chemically activated PAC is often used in wastewater treatment for removing larger organic molecules and color compounds on a batch dosing basis. Our water treatment carbon selection guide covers this topic in more detail.
Why does pore size matter when choosing activated carbon?
The target contaminant’s molecular size must match the carbon’s pore dimensions for efficient adsorption. Small molecules like chlorine and simple solvents fit into micropores, where steam activated carbon excels. Larger molecules such as tannins, dyes, and high molecular weight organics need mesopores and macropores, which are more developed in chemically activated carbon. Selecting a carbon with mismatched pore geometry leads to poor adsorption rates regardless of the product’s iodine number or surface area.
Can steam activated carbon be reactivated more times than chemically activated carbon?
Generally yes. Steam activated carbon, especially from coconut shell, has higher mechanical strength and withstands the thermal stress of reactivation better than chemically activated carbon. Steam activated GAC typically endures 4 to 8 reactivation cycles in standard industrial applications. Chemically activated carbon is often softer and degrades faster during thermal processing, which limits its practical reactivation potential.