Analysis of the regeneration ability of exhausted activated
carbon
To investigate the ability of regenerated activated carbon to be
reused as an adsorbent, five consecutive adsorption–regeneration
cycle experiments were conducted using activated carbon. The
changes in adsorption efficiency for COD in wastewater were then
determined for the process. The experimental results can be seen
in Fig. 4.
It can be seen from Fig. 4 that exhausted activated carbon
could be regenerated repeatedly by organic solvents. For methylene
dichloride and ethyl ether, the regeneration efficiencies of
exhausted activated carbon decreased as the number of regenerations
increased. This phenomenon might be attributed to the
deposition of organic substances found in coking wastewater on the surface of the activated carbon. However, the regenerating efficiency
of n-pentane for exhausted activated carbon decreased for
the first regeneration and then increased with each consecutive
regeneration. This result might be due to the fact that n-pentane
has stronger interactions with the organic compounds presented
in the original activated carbon, and in many of the regeneration
processes, more advantageous components and structures in activated
carbon for the adsorption of the organic substances in coking
wastewater are formed gradually. After deducting the reduction
of adsorption efficiency caused by deposition of organic pollutants
on the surface of the activated carbon, the overall result
still had the adsorption efficiency of the regenerated activated
carbon increasing gradually. Therefore, from the standpoint of a
continuous use of activated carbon, n-pentane has the strongest
regeneration ability for activated carbon used in coking wastewater
treatment.
Based on the above results, n-pentane was selected as the optimal
regenerative agent for the study.