Many people are plagued by the problem of fragrant feet. But there are shoe inserts that claim to solve the problem. They make use of a remarkable material called activated carbon. “Activated” in this case refers to carbon’s ability to adsorb a variety of molecules to its surface. Here’s the deal. Any two substances brought close together will experience an attraction as the negative electrons of one are attracted to the positive nuclei of the other. The extent of attraction depends on the surface areas in contact. Finely powdered carbon has a remarkably high surface area, especially because the process by which it is made causes each little particle to be riddled internally with numerous channels which present surfaces for adsorbing other substances. The word is “adsorb”, a surface phenomenon, as opposed to “absorb” which is what a sponge does to water.
To prepare this special form of carbon, any carbonaceous material like pulp and paper waste or coconut shells is heated to a high temperature in the absence of oxygen. This makes it porous and highly adsorbent. So when you place one of these inside a shoe, it will adsorb the fragrant compounds, mostly fatty acids, which are produced when bacteria on our feet digest compounds excreted in sweat. Of course this action is not limited to feet. Activated carbon will also absorb smells in the fridge or indeed from the air. Or from water. Water filters contain a bed of activated carbon which can remove chlorine and various chlorinated compounds along with other impurities from our tap water.
There is another interesting use for activated carbon: In hospitals to deal with poisonings. If someone has ingested poison mushrooms, or a variety of other toxins, they are often given charcoal to eat to adsorb the troublesome chemicals from the digestive tract. These then come out with the carbon. It makes for an unnerving show when it emerges, but who cares when it comes to saving lives. Even criminals have attempted to make use of the adsorbent properties of activated carbon. “Body packers” who try to smuggle drugs by swallowing balloons or condoms filled with them often swallow activated carbon tablets along with their loads. The thinking is that if the package should break, the carbon will adsord the drug and save the packer. This is not likely.
Sometimes activated carbon is given to people who suffer from excessive intestinal gas which can lead to bloating and social problems. And then one clever inventor has come up with the "Toot trapper," a square pillow filled with activated carbon to absorb annoying smells that may emerge. "Eat all the beans you want..." goes the advertising. How long the pillow lasts I suppose depends on how much you toot.