Activated Carbon: Overview and Applications

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Overview of Activated Carbon

Activated carbon, sometimes called activated charcoal, is carbon processed to develop a network of pores that dramatically increase internal surface area. Through physical or chemical activation, raw carbonaceous materials become a sorbent that binds molecules to its surface. The result is a versatile material capable of targeting a wide range of contaminants, including volatile organic compounds (VOCs), taste and odor compounds, solvents, color bodies, and specialty targets like per- and polyfluoroalkyl substances (PFAS). 

Its performance is derived from three core factors. First, its extensive surface area creates abundant adsorption sites. Second, a distribution of micro-, meso-, and macropores matches the size of target molecules and accelerates mass transfer. Third, surface chemistry can be tuned to enhance selectivity. Together, these features deliver high adsorption capacity, fast kinetics, and efficient separations, making activated carbon a critical component of water, liquid, and gas purification.

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Structure and Surface Chemistry

Porosity and Surface Area

Activated carbon contains a labyrinth of pores created during activation. Surface area, measured by BET methods, often ranges from 600 to over 1,500 m²/g, providing abundant adsorption sites for molecules in water or air. Micropores drive capacity for small molecules, while mesopores and macropores improve transport and kinetics.

Pore Size Distribution

Chemical Composition

Activated carbon is primarily elemental carbon arranged in turbostratic, graphenelike microcrystallites. Oxygen-containing surface groups, such as carboxyl, hydroxyl, and lactone, influence hydrophilicity and polarity, impacting selectivity. Post-treatments—including acid washing, oxidation, impregnation, and catalytic deposition—modify these functional groups to enhance performance in targeted applications.

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Performance Properties

Absorption Characteristics

Activated carbon removes contaminants by physical adsorption (Van der Waals forces) and, in specialized grades, chemisorption. Chemisorption is a process in which deposited substances (impregnated agents) are chemically altered. The absorption capacity depends on pore size distribution, surface area, contaminant size and polarity, and process conditions such as temperature, concentration, and contact time. Isotherm models like Langmuir and Freundlich are used to estimate capacity. Adsorption kinetics largely depend on the type of activated carbon, pore size, pore radius frequency and distribution, the physical and chemical attributes of the adsorbate, the properties of the ambient gas or liquid phase, and a number of process-related parameters. Adsorption speed reduces as the activated carbon becomes saturated.

Thermal Stability

The carbon framework is stable at elevated temperatures in inert or reducing atmospheres. In the presence of oxygen, high temperatures can lead to oxidation and capacity loss. Thermal regeneration uses controlled conditions to desorb organics and restore capacity with limited burn-off.

Chemical Reactivity

Surface functional groups interact with polar molecules and can be modified through oxidation, impregnation, or acid washing. Impregnated products enable catalytic reactions such as chloramine destruction and H2S chemisorption. Activated carbon selection should balance adsorption capacity with chemical stability in the intended environment, whether choosing granular activated carbon for fixed beds, activated carbon pellets for vapor-phase service, or activated carbon powder for rapid dosing.

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Types and Classifications

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Production and Quality Control

Activation Methods

There are two types of activation methods: physical activation and chemical activation. Physical activation involves the carbonization of the raw material followed by activation at a high temperature (typically 800°C–1000°C) with steam, air, or carbon dioxide to develop porosity. The carbon is partially gasified, and a porous, highly activated carbon is produced. During chemical activation, nonincinerated carbonaceous material is mixed with oxidizing or dehydrating chemicals, heated to between 400°C and 800°C, and impregnated with activation agents such as phosphoric acid, zinc chloride, or sulfuric acid, often yielding higher mesoporosity for certain feedstocks. The activation agent is leached out and recovered.

Raw Materials

Common precursors include coconut shell, bituminous and lignite coal, and wood. Coconut-shell grades often provide a higher proportion of micropores for VOC and trace organics removal, while coal- and wood-based products can offer broader pore distributions beneficial for color bodies and larger molecules.

Quality Metrics

Manufacturers monitor iodine number and methylene blue value as proxies for surface area and pore volume, as well as ash content, hardness and attrition resistance, moisture, and particle size distribution. For liquid-phase GAC, abrasion number and backwash density are important for filter performance. For vapor-phase pellets, crush strength and CTC or butane activity indicate capacity and kinetics. Consistent testing supports lot-to-lot performance and regulatory compliance, especially for food and pharmaceutical grades. Donau Carbon prioritizes quality and traceability across the supply chain, offering products that meet stringent specifications. Donau Carbon also supports reactivation programs that help reduce waste and improve the total cost of ownership.

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Common Applications

Many industries rely on activated carbon for water treatment, air and gas purification, food and beverage processing, pharmaceuticals, environmental remediation, and more.
 

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Donau Carbon Activated Carbon Portfolio

Donau Carbon supplies a wide spectrum of powdered, granular, and extruded activated carbon grades produced from raw materials such as coal, coconut shell, and wood by all the standard activation processes, including steam, zinc chloride, and phosphoric acid activation. They have developed a product to solve almost every activated carbon need in the market, as well as meet a variety of international testing standards.