The surface chemistry of pitch-based spherical activated carbon（PSAC）and the effect of gas-oxidation treatment on its adsorption performance

Pitch-based spherical activated carbon (PSAC) was modified by gas mixtures of nitrogen and oxygen. Nitrogen adsorption was used to obtain the pore structure of the PSAC. The phenol adsorption performance of the PSAC before and after modification was investigated. Results showed that there is no obvious texture change of PSAC after air oxidation. When the PSAC was modified with a gas mixture having an oxygen content of 20% for 5h at 400℃ and 450℃, the surface acidic groups increased from 0.11 to 1.22, 1.60meq/g, while basic groups decreased from 0.52 to 0.03, 0.02meq/g, respectively. The adsorption capacity of phenol on the PSAC decreased as the surface acidic groups increased because its wettability was improved. Water molecules were more competitive for the adsorption sites than the adsorbate in such a situation. The adsorption isotherms of phenol on PSAC changed from type L to type S with an increase of surface acidic groups.