Longevity of activated carbon

[skjl47]

you can leave it in filter to act like an extra bio media.

Hello; I have done this myself.

Carbon removes chemicals by adsorption, which is reversible once it degrades or higher affinity chemicals are replacing the previously bound compounds

Hello; Key word being adsorption rather than absorption.

I did back a few decades ago think I could recharge the carbon by baking it in an oven. I have learned since that a home oven cannot reach the temps needed to recharge. I do think by rinsing and baking at 500 F that much of the organic stuff trapped gets baked off. Anyway I used some over many times for several years as a layer in a filter. I guess it was simply a biomedia surface at that point. I stopped using it when the filter died.

 

[Drstrangelove]

"Spent carbon reactivation off-site involves removing the adsorbed contaminants from the spent activated carbon in a process that is a modification of the one that initially activated the carbon. The contaminants are desorbed and destroyed in the high temperature (typically in excess of 1500°F[800°C]) pyrolizing atmosphere of the reactivation furnace."


Per the US Army Corp of Engineers, 2001.

Not doable unless someone owns a factory grade furnace.

 

[Drstrangelove]

Re edited after I ran out of time. This should answer some questions...

3-2. Regeneration, Reactivation, and Disposal of Spent Activated Carbon.

(1) As contaminants are adsorbed, the carbon’s adsorptive capacity is gradually exhausted. When the carbon’s adsorptive capacity is reached, it is considered “spent,” and it must be regenerated, reactivated, or disposed of. Although some manufacturers and researchers use the terms “regeneration” and “reactivation” interchangeably, in this document, “regeneration” means removing the contaminants from the carbon without destroying them and “reactivation,” which occurs at very high temperatures, means destroying the contaminants and reactivating the carbon.

(2) Regeneration usually involves removing the adsorbed contaminants from the carbon using temperatures or processes that drive the contaminants from the carbon but that do not destroy the contaminants or the activated carbon. A common regeneration process introduces steam into the spent carbon bed, volatilizing the contaminants and restoring the carbon’s capacity to what is called its “working capacity.” Steam regeneration does not completely remove adsorbed contaminants. All regeneration processes produce a waste stream that contains the desorbed contaminants. For example, steam regeneration produces a mixture of water and organics from the condensed desorbed vapor.

(3) Other than thermal reactivation at elevated temperatures, regeneration techniques will result in some contaminants remaining adsorbed and unaltered within the carbon particle. These contaminants will be occupying “high energy adsorption pores, or sites,” and lower temperature regenerants (<500°F) or capacity corrections will not be able to provide sufficient energy to reverse the adsorptive force.

(4) Spent carbon reactivation off-site involves removing the adsorbed contaminants from the spent activated carbon in a process that is a modification of the one that initially activated the carbon. The contaminants are desorbed and destroyed in the high temperature (typically in excess of 1500°F[800°C]) pyrolizing atmosphere of the reactivation furnace.

Complete unedited excerpts from the US Army Corp of Engineers, 2001 (emphases are mine.)

Summary: Not possible to regenerate spent activated carbon unless someone can steam off vapor at 500 F. Not possible to reactivate without a factory grade oven capable of 1,500 F. (There are other regeneration methods which are highly technical and unavailable to all except people with labs, so I ignored them.)

 

[arwen]

Came across somewhere the effective duration of activated carbon is somewhere near 14days. Just a rough gauge not taking into consideration of the ratio of water volume & active carbon. Took mine out recently & like some of us said was using it as a precautionary measure - absorbing the medications once the course is completed, hope this helps

 

[duanes]

Years ago there was a theory that connected extended carbon use with HITH and some other bacterial diseases, but a direct link could not be found that I know of.
But since the fissures in carbon tend to be places where detritus and detritus bacteria (often pathogens) can use as substrate it stands to reason (at east in my mind) that one would not want to promote bacterial "hot spots" in our aquariums.