Marine macroalgae-derived multielement-doped porous biochars for efficient removal of sulfamethoxazole from aqueous solution: Sorption performance and governing mechanisms

Marine macroalgae are promising biomass resources due to their fast growth, high yield and special composition and urgently need to be developed. Pyrolytic conversion of marine macroalgae into stable and multifunctional biochars is an extremely feasible strategy, but there are few related studies, especially on further decontami-nation applications and performance. In this study, the green tide-derived marine macroalga Enteromorpha prolifera was used to prepare multielement-doped porous biochars (MPBs) and applied to remove a typical antibiotic, sulfamethoxazole (SMX), from aqueous solution for the first time. The MPBs possess a porous struc-ture, and the specific surface area and pore volume are as high as 134 m2 g-1 and 0.030 cm3 g- 1, respectively. The surface N, O, S and Cl contents of the MPBs are high. An abundant ash content, O-containing surface functional groups and graphene structure also exist in the MPBs. These excellent properties contribute to a high sorption quantity, up to 30 mg g-1. Pore filling, n/pi-pi stacking, cation bridging interactions, electrostatic attraction, hydrogen bonding and partitioning are the potential sorption mechanisms. Moreover, the sorption is controlled by physical processes; monolayer sorption is relevant for low carbonization temperature-derived MPBs, and multilayer sorption is relevant for high carbonization temperature-derived MPBs. In addition, the removal capacity of SMX changed slightly after 4 cycles. The findings suggest that marine macroalgae can be deemed excellent precursors for the preparation of MPBs-based sorbents for organic pollutants.