REACTIVABILITY OF ACTIVATED CARBON

The possibility of reactivating an exhausted activated carbon is only partly linked to the characteristics of the fresh product. In many cases - if not most - reactivation is linked to the process conditions in which the coal has found itself operating.
In fact, an activated carbon as such can be defined as reactivable or non-reactivable essentially from the point of view of economic convenience.
For this treatment, in fact, activated carbons susceptible a priori to high losses due to the stresses of reactivation (and among these, handling plays an important role in many cases) may be less convenient than others for heat treatment.
These factors are not detectable by particular analytical parameters, but can only be deduced from pilot tests.
The case of reactivation of activated carbon used for solvent recovery (air treatment) is typical.
Normally, in this case, products with high levels of activation are used and therefore already particularly "stressed" from the physical point of view during production which badly withstand further heat treatments.
It also frequently happens that the distribution of the pores is significantly changed after one or more reactivations and that, at the limit, these collapse, significantly reducing the effect of the reactivation itself.
Significant significance for the reactivability of an activated carbon is coated by the environment in which it operates.
To limit ourselves to water treatment, it can be stated that, for example, highly saline waters tend to significantly increase the ash content, consequently reducing the degree of reactivation.
In some cases, the coal is no longer reusable after just one heat treatment.
Another case is represented by high molecular weight compounds of the polyphenol type which, under normal treatment conditions, tend to give carbon compounds which cannot be removed from the active surface.
In the air treatment sector, for example, the reactivation of exhausted carbon with easily polymerizable compounds is problematic.  In some of these cases the reactivation is totally compromised.
Therefore, for a correct evaluation of the advisability of carrying out a reactivation of spent carbon, it is extremely important to take into consideration the characteristics of the treated fluid and therefore proceed with an analysis of the product to be reactivated. The investigation must be particularly thorough in the case of wastewater of dubious or complex composition.