Activated carbon is a highly porous form of carbon that undergoes specialized processing to maximize its surface area for adsorption. The adsorption efficiency of activated carbon is measured by the amount of chemical substance it can adsorb relative to the mass of activated carbon used.
Colligo-Tech performs comprehensive testing on all fresh activated carbon shipments to verify compliance with manufacturer specifications and ensure adherence to the highest industry standards. Additionally, the company offers testing services for used activated carbon to assess its condition and determine its proximity to saturation.

Measuring Activated Carbon Quality Using CTC

For activated carbon used in air and gas filtration, carbon quality assessment has historically been conducted using carbon tetrachloride (CCl₄), also known as CTC.

CTC Index Testing Process for Fresh Activated Carbon:

1. Sampling the carbon under examination.
2. Passing CTC vapors through the sample under defined temperature conditions.
3. Weighing the carbon after a specified period.
4. Repeating the process until the carbon’s mass stabilizes (saturation point).

The CTC value is determined by the ratio of the amount of CTC adsorbed to the original mass of the carbon. For example, if the carbon’s mass increases by 60% upon reaching saturation, it is classified as having an adsorption quality of “CTC 60”.

Carbon with a CTC 60 rating is the most common for gas treatment. Some suppliers also offer carbon with CTC 50 or CTC 40 ratings, which have lower adsorption capacities. It is essential to request detailed specifications and analyses from manufacturers before purchasing the carbon.

Measuring Activated Carbon Quality Using Butane

In the activated carbon industry, the Butane (C₄H₁₀) activity test is the only internationally recognized method for measuring the porosity of activated carbon. This method is similar to the CTC test and evaluates the activated carbon’s ability to adsorb butane under defined conditions.

Butane Index Testing Process for Fresh Activated Carbon:

1. Preparing a mixture of dry air and butane.
2. Passing the mixture through the carbon sample.
3. Measuring the mass of adsorbed butane.
4. Calculating the ratio of the adsorbed butane mass to the original carbon mass.

This test is conducted according to ASTM D5742-95 standards set by the American Society for Testing and Materials, which define the system details and precise testing procedures.

Currently, many manufacturers prefer using the Butane Activity test over the CTC test due to safety concerns associated with CTC usage. Butane test results are often converted to equivalent CTC values for comparison purposes.

Measuring Activated Carbon Quality Using Methylene Blue

The Methylene Blue index is used to assess the adsorption capacity of activated carbon, particularly concerning odor and color removal. The value is determined by the amount of methylene blue (in milligrams) adsorbed by one gram of activated carbon under equilibrium conditions.

Measurement Significance:

1. Evaluating the ability to remove odor molecules.
2. Assessing efficiency in color removal.
3. Examining the overall adsorption capacity of the carbon.

This index is especially useful because the size of the methylene blue molecule is similar to that of common odor molecules like 2-MIB. Higher methylene blue adsorption values indicate better odor removal capabilities.

Methylene blue values are measured in units of mg/g or ml/0.1g.

In applications involving color removal (such as in the sugar, oil, and monosodium glutamate industries), this index is important but not the sole determinant; the pore structure of the carbon must also be considered.

Activated Carbon Quality Testing at Colligo-Tech

Colligo-Tech conducts comprehensive testing of activated carbon, both for the company’s shipments and as a service to external clients, adhering to the highest industry standards.

The Tests Include:

• Determining the CTC index of activated carbon by sampling and performing Butane/CTC tests to verify adsorption quality.
• Grinding a sample of the carbon and immersing it in a methylene blue solution to obtain a value that describes the activity of the carbon’s pores.
• Conducting xylene adsorption tests. Xylene is a common substance for industrial adsorption, so testing with it provides a more realistic and representative assessment of the carbon’s adsorption capacity.
• Grinding the sample in xylene and immersing it in methylene blue again. This process yields two methylene blue adsorption results, providing a comprehensive indication of the carbon’s adsorption capabilities.

Additional Services:

• Testing the condition of activated carbon during its usage period to evaluate its saturation rate and proximity to the end of its lifespan.
• Assessing the adsorption quality of activated carbon for specific contaminants based on customer requirements.