Traditional Activated Carbon Regeneration Methods: Thermal, Biological, and Wet Oxidation Techniques

Activated carbon is a non-toxic, odorless adsorbent with a highly developed pore structure and large surface area. Since the 1960s, countries in Europe and North America began widely applying activated carbon adsorption for drinking water purification and industrial wastewater treatment.

Today, activated carbon is one of the most effective adsorbents in tratamiento de aguas residuales, with applications in refining wastewater, explosives production, dyeing and printing effluents, chemical industry wastewater, and electroplating effluents. Its ability to remove pollutants has been proven on a large scale with excellent results.

However, as activated carbon use continues to expand, regeneration and recycling have become critical. Without regeneration, costs rise (by approximately 0.83–0.90 yuan per ton of wastewater), and waste carbon disposal risks causing secondary pollution. Therefore, developing effective activated carbon regeneration technologies is essential for sustainable environmental management.

Thermal regeneration is the most widely used and mature industrial method. The process involves three stages:

1. Drying stage – Removes volatile components adsorbed on the carbon.
2. High-temperature carbonization stage – At 800–900 °C, under vacuum or inert gas to prevent oxidation, organic compounds decompose, volatilize, and partially remain as fixed carbon.
3. Activation stage – Reactivation using CO₂, CO, H₂, or steam to reopen blocked micropores and restore adsorption capacity.

Advantages:

• High regeneration efficiency
• Wide applicability

Limitations:

• High energy consumption
• Costly equipment and operation

Biological regeneration uses microorganisms (aerobic or anaerobic) to decompose organics adsorbed on activated carbon into CO₂ and H₂O. Because microorganisms cannot penetrate micropores directly, extracellular enzymes adsorbed onto the carbon surface create catalytic centers, enhancing pollutant breakdown.

Advantages:

• Simple and low-cost
• Environmentally friendly

Limitations:

• Time-consuming
• Strongly influenced by water quality and temperature
• Microorganisms often cannot completely degrade pollutants
• Efficiency decreases after multiple cycles due to byproduct accumulation

This method is therefore more suited to laboratory and small-scale applications rather than industrial use.

Wet oxidation regeneration operates under high temperature (200–250 °C) and pressure (3–7 MPa), using oxygen or air as the oxidizing agent to break down adsorbed organics in liquid phase.

Key benefits:

• Broad treatment scope
• Short reaction time (typically under 60 minutes)
• Stable regeneration efficiency

Challenges:

• May produce toxic intermediate compounds for hard-to-degrade organics
• Partial oxidation of carbon surface micropores reduces adsorption efficiency over multiple cycles

Case Study:
At Tongji University, researchers optimized conditions for phenol adsorption and regeneration:

• Temperature: 230 °C
• Pressure: 0.6 MPa O₂
• Reaction time: 1 hour
• Carbon loading: 15 g
• Water volume: 300 mL

Results showed a regeneration efficiency of about 45% ± 5%, with only a 3% decrease after 5 cycles.

Despite their effectiveness, traditional methods share several disadvantages:

1. High loss of activated carbon during regeneration.
2. Decline in adsorption capacity after repeated cycles.
3. Secondary pollution from exhaust gases during the process.

These drawbacks have led researchers to explore advanced regeneration technologies such as electrochemical regeneration, supercritical fluid methods, catalytic wet oxidation, and ultrasonic techniques.

Traditional regeneration methods such as thermal regeneration, biological regeneration, and wet oxidation remain foundational for activated carbon recycling in water treatment. However, due to energy costs, process limitations, and secondary pollution risks, future research is shifting toward more sustainable and efficient regeneration technologies.

Activated carbon regeneration not only reduces operational costs but also supports environmental protection by minimizing waste and pollution.

The most widely used method is thermal regeneration, which heats spent carbon to high temperatures (800–900 °C) under controlled conditions to remove adsorbed organic compounds and restore adsorption capacity.

Regeneration reduces operational costs, prevents secondary pollution, and allows activated carbon to be reused multiple times in wastewater treatment, drinking water purification, and industrial effluent treatment.

Biological regeneration is low-cost and eco-friendly, but it is slow, sensitive to temperature and water quality, and less effective for complete pollutant removal. Adsorption efficiency declines after repeated cycles.

Wet oxidation uses oxygen or air under high temperature and pressure to oxidize and decompose organic pollutants adsorbed on activated carbon. It has a short reaction time and stable efficiency but may produce toxic intermediates.

Emerging technologies such as electrochemical regeneration, supercritical fluid methods, catalytic wet oxidation, and ultrasonic techniques are being researched to overcome the limitations of traditional methods.

Xian CHIWATEC Water Treatment Technology es una empresa de alta tecnología especializada en varios dispositivos de procesamiento de agua. Aparte de estos productos individuales, que cubren una serie de tipos y series, también podemos ayudar con proyectos de ingeniería integrales relacionados. Gracias a nuestro arduo trabajo y dedicación desde nuestra fundación, ahora somos uno de los fabricantes de equipos de tratamiento de agua de más rápido desarrollo en el oeste de China.

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