There are objections to using activated carbon to absorb formaldehyde in the air
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How does formaldehyde move on its own toward activated carbon? What is the driving force?
Adsorption includes chemical adsorption and physical adsorption. Chemical adsorption relies on chemical bond forces, while physical adsorption depends on molecular bond forces, that is, van der Waals forces. I personally think that the adsorption of methanol by activated carbon is driven by chemical bond forces, so it falls under chemical adsorption; the driving force is thus the chemical bond forces, right? Please correct me if I’m wrong! ! !
I think the adsorption by activated carbon is physical adsorption, similar to the principle of negative pressure created by capillaries. The principle behind activated carbon is that it is a porous carbon-based material; its highly developed pore structure gives it a large surface area, which allows it to come into full contact with toxic and harmful gases in the air. The strong adsorption field surrounding the pores of activated carbon immediately draws toxic gas molecules into those pores. I’m not sure if it’s correct.
This post was last edited by 1210 on 2009-10-15 at 21:41. Please don’t answer off-topic. It’s not saying that activated carbon cannot absorb substances; it’s asking why formaldehyde in the room needs to move on its own towards the activated carbon. Without any driving force, such as pressure, how is that possible? ! ! I’m not referring to gas masks equipped with activated carbon; when air is inhaled, it passes through the mask, and thus formaldehyde can indeed be absorbed. But can one wear a gas mask every day at home?
Activated carbon first adsorbs formaldehyde from the air in contact with it, reducing the local concentration of formaldehyde. According to Fick’s law, formaldehyde with higher concentrations diffuses toward areas where the concentration is lower in order to reach equilibrium; thus, activated carbon is able to adsorb formaldehyde from the air. Right? Isn’t this very slow?
Since carbon materials are non-polar by nature, the surface of activated carbon is hydrophobic, giving it the ability to adsorb organic substances such as formaldehyde. As for why formaldehyde can be treated with activated carbon, it is mainly due to the large pores and high specific surface area of activated carbon, as well as its hydrophobic nature. The driving force for adsorption lies in the fact that formaldehyde exists in liquid form on the surface of activated carbon, resulting in a reduction in its volume; the diffusion of formaldehyde from the bulk solution to the activated carbon is driven by concentration differences.
Why does formaldehyde move to the surface of activated carbon? Due to diffusion, formaldehyde is certainly moving around in the air. As long as one understands why the concentration in the high-concentration area decreases and settles at an average concentration. But just because a balance is achieved doesn’t mean that formaldehyde won’t spread around, as this balance is a dynamic one.
Wow, this is mainly powered by the flow of air. As for the so-called diffusion movement, it is a secondary factor.
I think it’s mainly the diffusion of formaldehyde, similar to a dehumidifier in a closet.