Requirements of Activated Carbon Used in Filter Vessel

 
Activated carbon filters play a crucial role in the field of water treatment, widely used for their excellent adsorption properties to remove harmful substances from water and improve water quality. Understanding the working principles, influencing factors, and usage precautions of activated carbon filters can enhance water treatment effectiveness and extend the lifespan of the equipment.

Basic Requirements for Activated Carbon

 
In water treatment applications, activated carbon must meet a series of fundamental requirements to ensure its effectiveness and efficiency in removing pollutants. These requirements encompass both the physical properties of the activated carbon and its performance under specific conditions. Below are the basic requirements for activated carbon in water treatment.

1. High Adsorption Capacity

 
The adsorption capacity of activated carbon is directly related to its specific surface area. A larger specific surface area provides more adsorption sites, enabling efficient removal of organic pollutants and colorants from water. Generally, the specific surface area of activated carbon should range between 600 and 1200 m²/g, with the specific choice adjusted based on the characteristics of the target contaminants.

2. Rapid Adsorption Rate

 
The adsorption rate of activated carbon is closely related to its particle size and pore distribution. Activated carbon with well-developed mesopores (radius 20–1000 angstroms) facilitates the diffusion of pollutants from the water into the micropores, thus improving adsorption efficiency. Typically, activated carbon with a particle size in the 8-30 mesh range is most suitable, ensuring good adsorption speed while controlling head loss.

3. Good Mechanical Strength

 
The mechanical wear resistance of activated carbon impacts its service life. High-strength activated carbon can not only withstand the shock of water flow but also reduce particle shedding, thus ensuring the filter's effectiveness. Activated carbon with high mechanical strength maintains stable performance over prolonged use.

Variability in Adsorption Capacity

 
Activated carbon exhibits significant variability in its adsorption capacity for different pollutants. This primarily depends on factors such as the solubility, molecular structure, polarity, and concentration of the pollutants in water. For instance, polar substances like ammonia nitrogen usually have lower adsorption capacity, whereas non-polar substances such as benzene derivatives can be effectively removed by activated carbon. Additionally, some pollutants at high concentrations may inhibit the adsorption of other contaminants.
During the liquid-phase adsorption process, temperature typically has little impact on adsorption because the process is usually exothermic. However, in specific cases, such as treating high-temperature wastewater, temperature changes should still be considered.

Factors Affecting the Adsorption Process

 
Several factors can influence the effectiveness and efficiency of the adsorption process of activated carbon. These factors include not only the characteristics of the activated carbon itself but also the nature of the pollutants in the water and the treatment conditions. Understanding these factors can help optimize the water treatment process and ensure optimal adsorption performance. Below are the main influencing factors during the adsorption process.

1. External Diffusion Rate

 
In the liquid-phase adsorption process of activated carbon, the external diffusion (liquid film diffusion) rate directly affects overall adsorption efficiency. The thickness and flow rate of the liquid film will influence the rate at which pollutants reach the surface of the activated carbon, making the reasonable selection of filter design and flow rate crucial.

2. Contact Time

 
The flow rate of water in the filter (i.e., contact time) affects the interaction between activated carbon and pollutants in the water. Longer contact times generally improve adsorption performance; however, it is essential to balance flow rate and effectiveness to avoid water quality deterioration due to excessively long contact times.

3. Co-adsorption of Pollutants

 
In practical applications, a mixture of various pollutants often exists in water. Co-adsorption phenomena can occur between these pollutants, either enhancing or interfering with each other. Multi-component adsorption typically results in reduced adsorption capacity. Therefore, it is vital to design filters that can adapt to different water quality conditions.

Proper Usage of Activated Carbon Filters

 
To ensure the efficient operation of activated carbon filters and extend their lifespan, understanding the correct usage methods is essential. Here are some key operational steps and considerations to help users optimize filter performance and maintain water quality safety.

1. Cleaning Activated Carbon

 
It is normal for activated carbon to lose some carbon powder after use. Generally, activated carbon is cleaned before sale; it is recommended to use pure water for cleaning to avoid the adsorption of substances like calcium and magnesium present in tap water. The cleaning duration should not be too long to prevent the activated carbon from absorbing too many impurities from the water.

2. Placement Method

 
In the filtration tank, the order of placement for activated carbon should be as follows:

Filter cotton (two layers)
Biochemical cotton
Activated carbon
Glass rings
Filter cotton (two layers)

This arrangement prevents the activated carbon from escaping and ensures the proper functioning of other filter materials. Activated carbon should not be placed at the top to avoid rapid coverage by larger particles (such as fish waste), leading to failure.

3. Regular Replacement of Activated Carbon

 
It is advisable to replace activated carbon monthly to prevent it from losing efficacy due to the adsorption of excessive impurities. If activated carbon becomes ineffective, boiling it in water can help restore its adsorption properties, but it should not be reused excessively. It is recommended to replace activated carbon at least every two months. For filters used for an extended period, regular inspection of the activated carbon's condition and timely replacement is essential for ensuring water quality safety.

Conclusion

 
The application of activated carbon filters in water treatment is highly effective. Understanding their basic requirements, variability in adsorption capacity, and correct usage methods is key to enhancing water treatment efficiency. By appropriately selecting the type of activated carbon, regularly cleaning, and replacing it, the performance of the filters can be effectively maintained, ensuring the safety and cleanliness of the water. Scientific management and use of activated carbon filters will provide a more reliable and efficient solution for water treatment, better meeting the growing demands for water quality.