Evolution of pore structure and functionalities of activated carbon and phosphorous species in activation of cellulose with H3PO4

Not only organic structures but also H3PO4 change can shape pore characteristics of activated carbon (AC) from H3PO4 activation. Herein, evolution of pore structures and functionalities of AC as well as phosphorous species in a wide temperature region was investigated in activation of cellulose with H3PO4. The results indicated that H3PO4 even reacted with cellulose at 60 °C. The reactions were further accelerated from 200 to 700 °C, reducing AC yield while increasing ash yield. Specific surface area of AC was from 433.3 m2/g for AC-200, increased to 1096.4 m2/g for AC-300 and then decreased to 676.8 m2/g for AC-700. H3PO4 was transformed into Hn+2PnO3n+1, H4P2O7, HPO3, P2O5 or PO2 species wrapped with polymeric organics, which tended to be retained and clogged pores. Phosphorous oxides led to merge of micropores, reducing micropore percentage from 64.2 % in AC-200 to 46.8 % in AC-700. Abundant -OH and C=O were observed in AC-200, while dominated dehydration and condensation at 400 °C led to their complete consumption. The formed P-O-P and P-O-C network structure together with oxidation reactions induced with phosphorous species negatively impacted aromatization and formed more C-O-C. AC-400 of more mesopores was superior for tetracycline adsorption, while production of AC-300 showed lower environmental impact.