Effect of potassium permanganate pretreatment of pitch on the textural properties of pitch-based activated carbons

Petroleum pitch-based activated carbons (ACs) were obtained in this work from a combination of pretreatment with different amounts of potassium permanganate (KMnO4) and chemical activation with potassium hydroxide. The surface characteristics of the pitch after the KMnO4 pretreatment were characterized by means of Fourier transform infrared spectroscopy (FT-IR). The structural characteristics of the pitch after the KMnO4 pretreatment were determined by means of X-ray diffraction. The influence of the KMnO4 treatment on the textural properties of the petroleum pitch-based ACs was investigated by means of N2/77 K adsorption isotherms. The investigation also involved the use of the Brunauer-Emmett- Teller equation and the Dubinin-Radushkevich method. The FT-IR results show that the pretreatment promotes the formation of surface oxygen functionalities and leads to an increase of the interplanar distance (d002) of the functional groups induced between carbon layers. Moreover, the specific surface area of the pitch-based ACs increases in proportion to the amount of KMnO4 pretreatment and reaches its highest value of 2334 m2/g with 2 g of KMnO4 because the surface oxygen groups of the pitch act as an active site during chemical activation.