Sustainable production of sawdust-derived porous carbon: Distinguished roles of phosphates and polyphosphates on pore evolution and tetracycline hydrochloride purification

Despite the widespread utilization of phosphoric acid (PPA) as an activator in the preparation of biomass-derived porous carbon materials, limited research has focused on utilizing recycled phosphoric acid (RPPA) for this purpose. Here, we revealed the in situ morphological transformation of phosphorus and its influence on the mechanism of porosity development in porous carbon materials. Furthermore, we examined the pore structure distribution, morphology, surface properties of the resulting carbon materials, as well as the influence of these properties on the adsorption behavior of tetracycline hydrochloride (TC). The abundant presence of a substantial quantity of polyphosphoric acid and polyphosphates in RPPA significantly contribute to the formation of a highly mesoporous structure in AC-R, achieving a mesopore volume of up to 0.65 cm 3 /g, which is larger than that of AC-N (0.23 cm 3 /g). This displays a molecular-level strategy that can adjust pore structure by regulating the type and content of polyphosphoric acid and polyphosphate during the one-step activation process, providing theoretical guidance for regulating pore structure of porous carbon materials. Moreover, AC-R exhibited effective TC uptake of 523.63 mg/g through pore adsorption, electrostatic interaction, metal ion complexation, hydrogen bonding, and π-π stacking interactions, showing comparable adsorption performance to AC-N (520.92 mg/g).