At present, our country only has clear requirements for activated carbon made of bamboo charcoal, with a formaldehyde adsorption rate of ≥ 8%. The laboratory tests the samples based on the execution standards of five samples and the national standards of "Bamboo Charcoal for Air Purification" and "Coal Granular Activated Carbon".

After testing, only sample 3 had a good formaldehyde adsorption rate of 22%, exceeding the reference enterprise standard limit by 20%, among the 5 samples. The formaldehyde adsorption performance of the other four samples was not ideal.

Introduction by Su Xiaomeng, an engineer from the Energy and Environmental Testing Department of Nanjing Quality Inspection Institute: After testing, the formaldehyde adsorption rate of sample 1 is only about 13%, and its enterprise standard stipulates that the formaldehyde adsorption rate is not less than 20%. Sample 2 is made of bamboo charcoal and uses the enterprise standard, but the enterprise standard does not specify the formaldehyde adsorption rate. Therefore, we refer to the corresponding national standard testing, and the formaldehyde adsorption rate detected is 5%, with a limit value of 8%, which is relatively low. Sample 3 also does not specify the formaldehyde adsorption rate in the enterprise standard, and we also quote According to the corresponding national standards, the detection results are relatively good, with a formaldehyde adsorption rate of about 22%; The fourth and fifth samples also do not have corresponding adsorption performance specified in the enterprise standard. The fourth paragraph specifies the methylene blue adsorption rate, and the fifth paragraph specifies the carbon tetrachloride adsorption rate. We found that these two indicators are relatively low compared to the national standard, and it can be inferred that the formaldehyde adsorption performance is also low, which cannot meet the requirements of the national standard.

Experts introduce that there are various types of activated carbon used for air purification in the market, with varying standards. For example, the five samples randomly purchased by the reporter are executed according to five different standards. Although all products claim to have formaldehyde removal and other properties, in actual standards, except for sample 1, which is explicitly specified in the standard that the formaldehyde adsorption rate is not less than 20%, there is no provision for formaldehyde adsorption performance in other standards. This leads to the inability to determine the formaldehyde adsorption performance of activated carbon products during quality supervision and spot checks.

The reporter noticed that on e-commerce platforms, the promotion of activated carbon is generally about the product's formaldehyde removal rate. For example, the formaldehyde removal rate of sample 1 is as high as 98.6%, while the formaldehyde adsorption rate of sample 1 tested in the laboratory is only 13%. Why is the formaldehyde adsorption rate much lower than the formaldehyde removal rate? Experts explain that these are actually two different concepts.

Su Xiaomeng told reporters: The formaldehyde removal rate is a fixed amount of formaldehyde, and using the same activated carbon to adsorb it, the more activated carbon there is, the better the formaldehyde removal rate, which may reach 100% or 99% or more. The adsorption rate truly reflects the adsorption capacity of the activated carbon, and the weight of adsorbed formaldehyde is calculated based on the percentage of the weight added to the original activated carbon mass. Therefore, the adsorption rate can truly reflect the quality and adsorption capacity of this activated carbon

That is to say, due to the continuous release of formaldehyde, which is not quantitative, the adsorption rate can truly reflect the adsorption capacity of activated carbon for formaldehyde. Experts suggest that consumers should have a rational view of activated carbon products and their claimed formaldehyde removal rates. Ventilation should still be the main method for formaldehyde removal in newly decorated rooms, and areas with poor ventilation can assist in placing some activated carbon. During use, it is also important to pay attention to regular exposure to sunlight.

Su Xiaomeng explained that the adsorption of activated carbon is mainly physical adsorption. Due to the microporous structure of activated carbon, it adsorbs benzene, TVOC, and formaldehyde in the air through the pores. When these organic substances fill this pore, it may reach adsorption equilibrium. If the temperature in the room is higher, there may be a desorption effect, and these benzene, formaldehyde, and TVOC can continue to volatilize, So at this point, these activated carbons need to be exposed to sunlight for about 10 to 15 days, and the exposure time should be around 3 to 5 hours.