Evaluation of activated carbon for remediating benzene contamination: Adsorption and oxidative regeneration

This study investigated the potential usage of activated carbon (AC) as a permeable reactive barrier material for the adsorption of benzene contaminant. Sodium persulfate (SPS) or pyrite (FeS2) activated SPS oxidation was used for the regeneration of spent AC. Results indicate that persulfate oxidation of AC caused a loss of electrons and a reduction in adsorptive capacity due to the formation of acidic functional groups on the AC. Concerning the reactants that can be used for oxidation of the benzene contaminants, SPS/FeS2/AC, as oppose to SPS/AC, can achieve benzene destruction in both the aqueous and the sorbed phases. Furthermore, regeneration of benzene spent AC by SPS or SPS/FeS2 revealed that SPS oxidation resulted primarily in desorption of benzene over direct oxidation of AC sorbed benzene. In contrast, the SPS/FeS2 system achieved complete oxidation of desorbed benzene in the aqueous phase while also oxidizing sorbed benzene. Results of re-adsorption show that oxidative regeneration recovered around 70% of the AC adsorption sites and the remaining capacity was mostly occupied by the residual benzene on the AC. This study demonstrates that SPS or FeS2 activated SPS oxidation is an effective alternative method for the regeneration of spent AC.