Modification of a coconut shell-based activated carbon under N-2 atmosphere has been carried out using a microwave device operating at 2,450 MHz and different microwave powers. The samples were characterized by means of low temperature N-2 adsorption, elemental analysis, and Boehm titration. The results show that microwave heating treatment results in a minor increase in micropore surface area and pore volume and has little effect on average micropore width. The results also show that microwave heating treatment is a very effective method for modifying the surface chemistry of the activated carbon. A gradual decrease in the surface acidic functional groups is observed, while the surface basicity is enhanced with increasing microwave power. Adsorption studies show enhanced adsorption of SO2 onto microwave-treated carbon, caused by modification of the surface chemistry. During microwave treatment, the active sites are induced by decomposition of CO-type surface oxygen groups, which favors the adsorption and oxidation of SO2.