# How does activated carbon trap impurities?

I've tried and I've tried to find an answer to this all over the web, but I can't seem to find an in depth explanation.

To the best of my knowledge, activated carbon has a very microporous structure and uses a process called adsorbption to "trap" particles. This isn't very in depth though and I'd like to better understand the process of what's going from a scientific standpoint. How does the carbon/charcoal keep the adsorbed material attached or trapped within the carbon?

• I don't have time right now for a proper answer, but the keywords you're looking for are chemisorption and physisorption. – Todd Minehardt Aug 9 '17 at 3:36
• @Todd Minehardt cheers for this, I'd be grateful though for a proper answer at your nearest convenience. – Charlie Aug 9 '17 at 15:22

Never forget to interpret in terms of physical/chemical forces, by order of energy: van der Waals, hydrophobic (pseudo forces), hydrogen bonds, disulfide bridges, covalent, electrostatic (for the most frequent).

Indeed, in charcoal, there is a large number of $\pi$-electrons that can make bonds, in particular. And yes, the porosity is important.

But perhaps could you have a look at Boehm H. P. Some aspects of the surface of carbon blacks and other carbons, Carbon, 1994, 32(5), 759-769. DOI 10.1016/0008-6223(94)90031-0.

• any chance you could transcribe a full answer? – Charlie Aug 9 '17 at 22:17
• @Charlie. In addition to the phisisorption and chemisorption, it might help you if you consider that there is not in general selectivity. Activated charcoal is very good to capture impurities by virtue of the fact that impurities are in little/trace amounts. – Alchimista Aug 9 '17 at 22:58
• Then very quick, consider the surface of your charcoal. Consider all the possible interactions listed by user50565. The impurities you want to remove have a high chance to get immobilised at the huge surface. Your impurities basically stain the charcoal, to give you an idea. – Alchimista Aug 9 '17 at 23:17
• A spoon of activated charcoal might have an effective surface of few soccer fields ! – Alchimista Aug 9 '17 at 23:19
• Not really a dentist here. Therefore I cannot say if it is good or not for your teeth, and body. I do not think that charcoal is a good whitener as for the stains you want to remove are not diving around but already sticking to the enamel... It is as replacing baking soda ( with something presumably even less hard than the salty grains). You basically relies on abrasive properties and not to the - sorption processes mentioned before. I would rather stay with sodium bicarbonate, perhaps not daily. – Alchimista Aug 11 '17 at 10:42