Thermal regeneration of activated carbons exhausted with phenol compound

Two methods, pyrolysis and steam regeneration, were used to investigate the regeneration efficiencies of two types of activated carbons that were exhausted by the phenol compound in the liquid phase. NaOH titration and temperature program deposition indicated that the two carbons exhibit different surface acidities, oxygen group distributions, and oxygen populations on the carbon surface. After treating by pyrolysis and steam regeneration, the surface recovery of spent carbons gradually increased with the regeneration temperature. Pyrolysis at 700-900 degrees C cannot completely remove all phenol molecules from the spent carbons, thereby having a lower surface recovery than steam regeneration. Comparing the two methods, steam regeneration is an efficient method in not only recovering the porosity, but also enlarging and deepening the pore structure of carbons. In comparison with the two carbons, the higher oxygen population on the carbon surface would decrease the surface recoveries and cause a more serious carbon weight loss. This could be attributed to the fact that a greater amount of surface groups would promote the possibility of chemisorbed fraction, thus leaving more degradation species in the pores. This study would shed one light on how oxygen groups existed on carbon surface act as cracking sites in diminishing the removal efficiency.