The key words are ADSORPTION and ABSORPTION.
Adsorption.. renders that which is adsorbed, to the hard pourous surface of the carbon and it can't easily be released without the extreme temps mentioned,Some say temps in excess of 1800 dgrees F/
Absorption.. is much like what happens with sponge where water is absorbed and also passes through the sponge. Nothingh to hold it,, could relase back into water like wringing out a sponge.
Is why if you use carbon,, you may as well replace it regularly to get it's benefits for it doesn;t last long due to small amounts and or quality offerd in most pre-filled cartridges. If you don't replace it,,then as mentioned ,it becomes part of your biological filtration and if you then remove it,,you also remove a portion of your good bacteria. If you choose not to use carbon at all.. it is therefore wise to add some extra biological media in it's place.