The speed and process of activated carbon removing formaldehyde

Formaldehyde is a chemical widely used in building materials, furniture and textiles, but it is also a pollutant that can be harmful to humans. Activated carbon is often used in formaldehyde removal solutions because of its superior adsorption properties.

 

Formaldehyde is a chemical widely used in building materials, furniture and textiles, but it is also a pollutant that is harmful to the human body. Long-term exposure to high concentrations of formaldehyde may cause respiratory diseases, skin allergies, and even increase the risk of cancer. Therefore, removing formaldehyde from indoor air has become an important research topic. Activated carbon is often used in formaldehyde removal solutions due to its superior adsorption properties.

Activated carbon is a carbon material with a highly porous structure, usually made from organic materials such as coal, wood, and coconut shells through high-temperature carbonization and activation treatment. Its huge specific surface area and porous structure enable it to effectively adsorb various gaseous and liquid pollutants, including formaldehyde.

Adsorption mechanism of formaldehyde The adsorption of formaldehyde by activated carbon is mainly achieved through two mechanisms: physical adsorption and chemical adsorption.  

Physical adsorption: This refers to the adsorption of formaldehyde molecules on the pore surface of activated carbon through weak intermolecular forces such as van der Waals forces. This adsorption is reversible and is greatly affected by environmental factors such as temperature and pressure.  

Chemical adsorption: This adsorption involves a chemical reaction between formaldehyde molecules and the functional groups on the surface of activated carbon to form a strong chemical bond. Chemical adsorption is usually irreversible and the adsorption amount is relatively small, but the adsorption rate is fast.

Factors affecting the adsorption of formaldehyde by activated carbon  

Specific surface area: The larger the specific surface area of ​​activated carbon, the stronger its adsorption capacity. Generally, activated carbon with a specific surface area of ​​500-1500 m²/g shows good adsorption effect.  

Pore size distribution: The pore size distribution affects the adsorption capacity of activated carbon for molecules of different sizes. Mesopores and macropores are conducive to the diffusion and adsorption of formaldehyde molecules.  

Temperature: Increased temperature will reduce the adsorption amount of physical adsorption, but sometimes increase the reaction rate of chemical adsorption. Therefore, the adsorption effect is best within a certain temperature range.  

Humidity: In a high humidity environment, water vapor may compete with activated carbon for adsorption sites, reducing its adsorption capacity for formaldehyde. However, moderate humidity helps dissolve and diffuse formaldehyde and improves adsorption efficiency.  

Air flow rate: Appropriate air flow rate can promote the contact between formaldehyde molecules and the surface of activated carbon and increase the adsorption rate. However, too high a flow rate may lead to insufficient contact time and reduce the adsorption effect.  

The process of activated carbon removing formaldehyde Adsorption stage Initial adsorption: When activated carbon is first used, its surface and pores are not occupied, and the adsorption rate is fast. The formaldehyde concentration drops rapidly in this stage.  

Dynamic equilibrium: As time goes by, the pores of activated carbon are gradually occupied by formaldehyde molecules, the adsorption rate slows down, and finally reaches dynamic equilibrium. At this time, the adsorption rate is equal to the desorption rate, and the formaldehyde concentration tends to be stable.  

Desorption and regeneration Desorption: Under certain conditions (such as high temperature, low pressure or flushing with inert gas), the adsorbed formaldehyde can be desorbed from the activated carbon. This process can be used to regenerate activated carbon.  

Regeneration: The activated carbon is restored to its adsorption capacity through high temperature treatment or other methods so that it can be used again. The adsorption performance of the regenerated activated carbon may decline, but it still has a certain formaldehyde removal capacity.

The speed of activated carbon to remove formaldehyde The speed of activated carbon to remove formaldehyde is affected by many factors. Generally speaking, the adsorption rate can be divided into the following stages:   Rapid adsorption stage: When activated carbon is first exposed to formaldehyde environment, the unoccupied pore surface quickly adsorbs formaldehyde, and the adsorption rate is the highest. This stage usually lasts from several hours to several days, depending on the formaldehyde concentration and the characteristics of activated carbon.  

Deceleration adsorption stage: As the activated carbon pores are gradually occupied, the adsorption rate begins to decrease. This stage may last from several days to several weeks until the adsorption reaches saturation.  

Equilibrium adsorption stage: In this stage, the activated carbon reaches adsorption saturation, the adsorption and desorption of formaldehyde reach equilibrium, and the adsorption rate drops to the minimum. At this time, the formaldehyde concentration tends to stabilize and no longer decreases significantly.  

Experimental research A large number of experimental studies have shown that activated carbon performs well in removing formaldehyde. The following are some typical experimental results:   Experimental design: Researchers usually place a certain amount of activated carbon in a well-controlled formaldehyde environment and monitor the changes in formaldehyde concentration.  

Result analysis: The experimental results show that the adsorption efficiency of activated carbon is very high in the initial stage, and the formaldehyde concentration drops rapidly. However, as time goes by, the adsorption rate gradually slows down and eventually reaches equilibrium.   Influencing factors: The experiment also revealed the influence of factors such as temperature, humidity, and air flow rate on the adsorption rate. For example, the adsorption rate decreases under high humidity conditions, while a moderate air flow rate helps to improve the adsorption efficiency.  

Practical application In practical applications, activated carbon is often used in a variety of products such as air purifiers, formaldehyde adsorption bags, and furniture adsorption boards. These products achieve effective formaldehyde removal by increasing the contact area of ​​activated carbon and extending its use time.  

As an efficient formaldehyde adsorption material, the process of activated carbon removing formaldehyde is complex and affected by many factors. In practical applications, the formaldehyde removal effect of activated carbon can be significantly improved by optimizing the specific surface area, pore size distribution, and use environment of activated carbon. Although the adsorption rate of activated carbon will gradually decrease over time, it can still play an important role in formaldehyde removal through proper regeneration treatment. With the deepening of research, the application prospects of activated carbon in the field of air purification will be broader.