The role and mechanism of K2CO3 and Fe3O4 in the preparation of magnetic peanut shell based activated carbon

Abstract The impact of K 2 CO 3 and Fe 3 O 4 on the porosity development and the magnet evolution within magnetic peanut shell based activated carbon (MPSAC) was systematically studied. At the impregnation stage, K 2 CO 3 was found to undergo one anionic hydrolysis. The formed KOH disrupted the key ester linkages between lignin and carbohydrates and removed a part of guaiacyl lignin. At the pre-carbonization stage, the introduction of K 2 CO 3 greatly modified the carbonization behavior of peanut shell, shifting the weight loss peak from 350 °C to 255 °C. Meanwhile, a primary pore structure was developed, and some nanoscopic K 2 CO 3 was detected. At the activation stage, a series of K-related species such as K 2 CO 3 ·1.5H 2 O, K 2 CO 3 , K 2 O and K was formed, which was connected with the development of abundant micropores within MPSAC. Magnetic additive Fe 3 O 4 functioned as an activation promoting agent while providing the Fe source. Above 500 °C, the porosity structure increased the contact area between Fe 3 O 4 and the reduction gases including CO and H 2 . Fe 3 O 4 was reduced and successively converted into FeO and Fe with the increase of activation temperature. After that the Fe source was further converted into Fe 3 C.