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What metals can activated carbon absorb?

April 22, 2025
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Activated carbon is considered one of the most effective absorbent materials in the water and air purification industry. This material has a porous structure and a large specific surface area and can absorb a variety of contaminants, including heavy metals. In this article, we will examine in detail the performance of activated carbon in absorbing heavy metals, the factors that influence the process, and its practical applications.

1. Mechanism for adsorption of metals by activated carbon

1.1. Physical absorption

  • Based on van der Waals’ forces

  • It depends on the porosity and structure of the carbon.

  • For metals with suitable molecular size

1.2. Chemical absorption

  • Chemical bonds are formed between the functional groups of the metal and carbon surface.

  • Including complexation and ion exchange.

  • Generally irreversible

1.3. Surface charge of activated carbon

  • pH-dependent surface load

  • Direct impact on the absorption of charged metals

  • Zero Load Point (PZC) as an Important Indicator

2. Heavy Metals That Activated Carbon Can Adsorb

2.1. Highly toxic metals

  • Lead (Pb) : Absorption rate of up to 95% under optimal conditions

  • Mercury (Hg) : especially in the form of Hg²⁺

  • Cadmium (Cd): It is well absorbed at pH values above 6.

  • Arsenic (As):  Especially As(V) is better than As(III).

2.2. Metals for industrial uses

  • Copper (Cu)  : Excellent absorption in the pH range of 5-7

  • Nickel (Ni) : Moderate to good absorption

  • Zinc (Zn): Effectively absorbed in acidic conditions.

  • Chromium (Cr) : Cr(VI) is better than Cr(III)

2.3. Radioactive metals

  • Uranium (U)  – adsorbed at a pH around 5

  • Cesium (Cs) : Moderate absorption

  • Strontium (Sr) : Relatively weak absorption

3. Factors Affecting Metal Absorption

3.1. Properties of activated carbon

  • Type of raw material (coconut shell, charcoal, wood)

  • Degree of activation (chemical or physical)

  • Specific area (typically 500-1500 m²/g)

  • Pore size distribution (micropores, mesopores and macropores)

Environmental conditions

  • pH of the solution : It has a significant effect on the surface charge and metal species.

  • Temperature : Absorption usually decreases with increasing temperature.

  • Contact Time : Typically between 30 and 120 minutes to reach balance.

  • Initial concentration of metal : adsorption isotherm

3.3. Presence of other ions

  • Competitive effects of other cations

  • The influence of anions

  • The role of dissolved organic matter

4. Methods to improve the absorption rate of metals

4.1. Chemical modification of carbon

  • Surface oxidation (increased carboxyl groups)

  • Charged nanoparticles (iron oxide, titanium dioxide)

  • Impregnation with complexing agent

4.2. Combination with other technologies

  • Used with ultrafiltration

  • Integration with electrochemical processes

  • Applications in biological systems

Optimization of operating parameters

  • Optimal pH settings for each metal

  • Determine the right time for your call

  • Use the best dose of carbon

5. Practical applications in industry

5.1. Industrial water treatment

  • Mine and mining wastewater

  • Wastewater from the electroplating industry

  • Wastewater from the electronics industry

5.2. Purification of drinking water

5.3. Environmental application

  • Cleaning contaminated soil

  • Surface runoff treatment

  • Control of industrial air pollution

6. Comparison with Other Metal Removal Methods

6.1. Benefits of Activated Charcoal

  • Relatively low cost

  • Easy to use

  • Recycling and reuse possibilities

  • Suitable for a variety of metals.

6.2. Limitations

  • Limited adsorption capacity for some metals

  • Sensitivity to environmental conditions

  • In some cases, pre-processing is required

6.3. Possible alternatives

  • Ion exchange resin

  • Biosorbent

  • New nanomaterials

7. Conclusion

Activated carbon is considered one of the most efficient and cost-effective purification methods, capable of absorbing a variety of heavy metals, including lead, mercury, cadmium, and arsenic. Its performance is strongly affected by many factors, including pH, temperature, carbon type, and the presence of other ions. Its efficiency can be significantly improved by chemically modifying the surface and optimizing operating conditions. Although new methods are being developed, activated carbon remains a stable and reliable technology, widely used in industrial and municipal water and wastewater treatment. Future research may focus on the development of carbon nanostructures with higher adsorption capacity and better selectivity.