Effect of thermal regeneration of spent activated carbon on volatile organic compound adsorption performances

• The adsorption capacities of the AC adsorbent were higher for MEK than acetone.
• Multiple cycle regeneration efficiency was tested.
• Acetone spent AC is stable to multiple regenerations while MEK spent AC is not.
• A decrease in regeneration efficiency is attributed to chemisorption of MEK.
• Regeneration efficiency of MEK spent AC is enhanced by limited addition of moisture.

Thermal swing adsorption (TSA) is widely used as a process in industry for gas purification and air treatment. This study enlightens the effects of thermal regeneration of an activated carbon spent with volatile organic compounds (VOCs) on its adsorption capacities. Ketone group VOCs (acetone and methyl ethyl ketone (MEK)) were selected for this study as they are sensitive to oxidation reactions at low temperature, and for this reason, are responsible for many reported fire accidents on industrial units. Cyclic adsorption–desorption experiments were performed using a thermo-gravimetric analyzer (TGA). First cycle adsorption capacity of acetone and MEK at 20 °C was 5.06 mol/kg and 6.41 mol/kg, respectively. The regeneration was performed with air at temperature ranging from 80 °C to 160 °C. Multiple cycles were successively repeated to assess the variations in the material adsorption performances. For acetone, it was found that after first regeneration cycle conducted at 80 °C, the adsorption capacity was restored at nearly 95%, and remained unchanged after 8 successive cycles. For MEK, continuous degradation of the adsorption capacities was observed, which was more drastic when the temperature was low and reached 3.4 mol/kg after 8 cycles. This could be related to the partial decomposition of the chemisorbed MEK molecules. Effect of air humidity was furthermore examined and a protocol was developed to guarantee good regeneration efficiency of MEK spent activated carbon at a moderate temperature.