Mercury-containing wastewater poses significant hazards. Once released into the environment, it undergoes microbial conversion into organic mercury, which accumulates through the food chain. Ultimately, it enters the human body via consumption of contaminated fish, damaging the nervous system, kidneys, and other organs. This leads to chronic or acute poisoning, with severe cases resulting in death.
While activated carbon possesses the remarkable ability to adsorb mercury and mercury-containing compounds, its adsorption capacity is inherently limited, rendering it most suitable for treating wastewater with relatively low mercury concentrations.
In cases where the mercury concentration is high, a preliminary treatment step employing the chemical precipitation method becomes imperative. This method effectively reduces the mercury content to approximately 1mg/L under standard conditions, with the potential to reach 2-3 mg/L under elevated temperatures. Following this initial treatment, activated carbon can then be introduced for further refinement, leveraging its adsorption properties to achieve even lower levels of mercury contamination. This multi-step approach ensures comprehensive and efficient removal of mercury from wastewater, safeguarding public health and the environment.
Treatment Principle
(1)Physical Adsorption
The porous structure of activated carbon (particularly its micropores and mesopores) exhibits strong adsorption capacity for mercury ions and organic mercury compounds.
(2)Chemical Adsorption
Certain modified activated carbons (e.g., those containing sulfur, chlorine, or nitrogen functional groups) can form complexes or precipitates with mercury ions, thereby enhancing removal efficiency.
(3)Surface Reactions
Ion exchange or redox reactions occurring on the activated carbon surface convert mercury into insoluble or less mobile forms.
Commonly Used Activated Carbon Types
| Activated Carbon Types | Application |
| Coal-Based Granular Activated Carbon | High mechanical strength, suitable for fixed-bed treatment of high-flow industrial wastewater. |
| Coconut Shell Activated Carbon | Well-developed micropores, suitable for deep purification of low-concentration mercury-containing wastewater. |
| Impregnated Modified Activated Carbon (e.g., sulfur-impregnated, iodine-impregnated) | More selective for mercury, often used for efficient removal. |
| Powdered Activated Carbon (PAC) | Can be added to coagulation and sedimentation tanks, suitable for temporary or emergency treatment. |
Application Areas
- Chlor-alkali industrial wastewater
- Mercury-containing wastewater from electroplating
- Mercury-containing wastewater from chemical and pharmaceutical industries
- Laboratory and medical wastewater
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