One-pot pyrolysis of a typical invasive plant into nitrogen-doped biochars for efficient sorption of phthalate esters from aqueous solution.
Invasive plants pose a significant threat to natural ecosystems because of their high adaptability, rapid propagation and spreading ability in the environment. In this study, a typical aquatic invasive plant, Pistia stratiotes, was chosen as a novel feedstock for the preparation of nitrogen-doped biochars (NBs) for the first time, and the NBs were used as efficient sorbents to remove phthalate esters (PAEs) from aqueous solution. Characterization results showed that NBs possess great pore structure (up to 126.72 m2 g-1), high nitrogen (2.02%-2.66%) and ash (24.7%-34.1%) content, abundant surface functional groups, hydrophobicity and a graphene structure. Batch sorption experiments were performed to investigate the sorption performance, processes and mechanisms. The capacities for PAEs sorption onto NBs were high, especially with NBs pyrolyzed at 700°C, ranging up to 161.7 mg g-1 for diethyl phthalate and 85.4 mg g-1 for dibutyl phthalate; these levels were better than many reported for other sorbents. With kinetic and isotherm results, Pseudo-second order and Freundlich models fit the sorption data well, and chemical interactions involving hydrogen bonding, Lewis acid-base interaction, functional group interaction, cation-π interaction and π-π stacking interaction were identified as possible rate-limited steps. Moreover, Intra-particle diffusion and Dubinin-Radushkevich models indicated that multiple pore filling and partitioning dominated the process of PAEs sorption onto NBs. This study opens the door for new methods of pollution control with waste treatment, since invasive plant biomass resources were converted into advanced biochars for efficient environmental remediation.