Activated carbon is one of the most important adsorption materials in various industries. Due to its very large surface area, porous structure, and excellent ability to adsorb various pollutants, it plays a crucial role in many sectors, such as water and air purification, food processing, and the pharmaceutical industry. One of the most important indicators of activated carbon quality is its ash content. Ash consists of the non-carbon inorganic components that remain after complete combustion of the sample. The ash content significantly influences the final properties of the activated carbon; therefore, a precise understanding of its content is essential for selecting the appropriate activated carbon.
In this comprehensive article, we will examine in detail and with a practical focus what the ash content in activated carbon is, how to measure it, how it affects efficiency, what generally accepted standards exist, and how to select the optimal type of carbon for your application.
What is activated carbon ash?
When activated carbon is heated to high temperatures, all its organic components burn off, leaving behind a substance called ash . This ash contains inorganic compounds such as:
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calcium
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magnesium
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sodium
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potassium
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silicon dioxide
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iron
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Aluminum oxide
And other metallic impurities as well.
The presence of these minerals occupies part of the activated carbon structure, thereby reducing the effective surface area for pollutant absorption.
Why is the ash content important?
The ash content is one of the most important quality indicators for activated carbon, as it directly affects its performance. A high ash content can cause the following problems:
1. Reduced absorption capacity
The higher the ash content, the more minerals fill the pores of the activated carbon, thus reducing its ability to absorb organic pollutants or heavy metals.
2. Effect on pH value
Many minerals contained in ash are alkaline. Therefore, carbonaceous materials with a high ash content typically have a higher pH and can alter the pH of the treated water. This is particularly important in pH-sensitive industries such as pharmaceuticals and beverages.
3. Reduced conductivity
A high ash content can increase the electrical conductivity of the product, which can cause problems in some applications, such as the production of ultrapure water.
4. Higher risk of siltation.
In filtration systems, a high ash content can lead to deposits on the system components and increased maintenance and repair costs .
5. Effect on the carbon reaction
Metals can cause unwanted chemical reactions and disrupt some processes such as gas absorption or catalysis.
What is the ash content of activated carbon?
Basically, the ash content of activated carbon depends on the type of raw material and the processing method:
1. Carbon-based activated carbon
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Ash content: from 5% to 15%
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It is generally hotter than other types of water, unless it has been treated with acid.
2. Activated charcoal from coconut shells
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Ash content: 2% to 4%
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Thanks to its extremely low ash content, it is suitable for systems with high demands on filtration efficiency.
3. Activated charcoal made from wood.
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Ash content: from 3% to 10%
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That depends on the production method.
4. Acid-treated activated carbon
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Ash content: less than 1%
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Ideal for the pharmaceutical industry, laboratories and reverse osmosis systems.
Types of ash in activated carbon
1. Water-soluble ash
The water-soluble component of the ash. Its presence increases electrical conductivity and alters the pH value .
2. Insoluble ash
The water-insoluble fraction will further reduce the effective pore size of the carbon.
3. Soluble acid ash
The part of a mineral that can dissolve in weak acids is an acid-sensitive mineral.
How is the ash content determined?
International standards (such as ASTM standards) typically use the following methods:
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Heat the sample to approximately 650 to 750 degrees Celsius .
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Organic compounds disappear when burned.
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Weigh the remaining scrap metal.
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The ratio between the weight of the ash and its original weight determines the amount of ash.
This method is known as ASTM D2866.
Cabot Plus Black LL3608 Specifications
Generally accepted standards for ash content
Each application has its own standards. The most important ones are:
1. Drinking water purification
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Permissible ash content: less than 5%.
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Recommended types: Charcoal made from coconut shells or acid-treated charcoal.
2. Food industry
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Ash content: 1% to 3%
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Reason: To avoid changes in taste, smell, and pH value.
3. Medicines and pharmaceutical products
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Ash content: less than 1%
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These applications require very high purity.
4. Industrial wastewater treatment
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Ash content: should not exceed 15%.
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Reason: lower costs and lower purity requirements.
5. Metallurgy and gas industry
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The amount of ash varies depending on the type of gas or reaction.
Influence of raw material type on ash content
coconut shell
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Its mineral composition contains significantly fewer grey components.
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It has many small pores.
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This is an excellent option for drinking water.
Money
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It contains many minerals and produces a large amount of ash.
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Etching can reduce the ash content.
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Suitable for absorbing water vapor and gas.
Wood
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Its mineral content is moderate.
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Suitable for bleaching and food applications.
How can the ash content be reduced?
The plant uses various methods to reduce the ash content:
1. Pickled cucumbers
To remove acid-soluble components from the ash, acidic solutions such as hydrochloric acid are used.
2. Continuous filtration and washing
Reduce the amount of dissolved minerals in your water.
3. Raw material monitoring
Use low-ash raw materials such as coconut shells.
4. Optimal thermal decomposition process
This improves the accuracy in determining the time and temperature of carbon production.
Advantages of using low-ash activated carbon.
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Improved absorption capacity
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Longer lifespan
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The pH value of the water surface has not changed.
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Reduces the likelihood of filter clogging.
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In highly developed systems such as reverse osmosis, this method works even better.
Disadvantages of activated carbon with high ash content.
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Low efficiency
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The taste and smell of the water have changed .
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Increased conductivity
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colony
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Short lifespan of the filter system
The importance of ash measurement in sensitive industries.
In industries such as pharmaceuticals, electronics, and beverages , even minor changes in water pH or conductivity can have significant consequences. Therefore, selecting low-ash activated carbon is crucial for these sectors.
How do you choose the right activated charcoal?
The following factors must be taken into account when selecting the optimal carbon material :
1. An application is required.
For example, activated carbon with an ash content of 1-3% is suitable for drinking water and reverse osmosis systems.
2. Types of raw materials
Generally, coconut shells are of higher quality.
3. Technical Specifications
Please check the following:
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pH
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Iodine number
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hardness
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apparent density
4. Brand and production standards
Compliance with NSF, FDA, or ASTM standards is a sign of high-quality products.
In conclusion
Ash content is one of the most important quality characteristics of activated carbon, as it directly affects its performance and lifespan. High ash content reduces adsorption capacity, increases pH and conductivity, and leads to sedimentation in the filter system. The standard ash content varies depending on the application. However, for most applications requiring a high ash content, such as drinking water treatment or food processing, low-ash or acid-washed activated carbon is recommended.
Thanks to this knowledge, consumers can choose activated carbon that is not only highly effective but also reduces maintenance and replacement costs.