Characteristics of algae-derived biochars and their sorption and remediation performance for sulfamethoxazole in marine environment

The performance of algae-derived biochars (ABCs) on sorption and remediation of antibiotic pollution in marine environment is poorly understood. A batch of biochars were produced from two marine algae waste (Enteromorpha prolifera and seaweed residuals) at 300–700 °C (EM300–700 and SW300–700) to investigate their sorption of sulfamethoxazole (SMX) in seawater, as well as their performance in remediation of SMX polluted marine sediment. Regardless the heating temperature (HTT), ABCs with relatively low C contents (29.6–37.4%), but high contents of O (16.6–28.9%) and N (0.75–3.48%), possessed lower surface area, but more abundant minerals (ash content 33.5–63.5%), richer heteroatom-containing functional groups than the terrestrial plant silvergrass-derived biochars (SGBCs). The maximum sorption capacities of ABCs increased from 2896 to 4212 mg kg−1 to 4874–4879 mg kg−1 as the HTT increased from 300 to 700 °C, higher than those of the SGBCs (1017–3515 mg kg−1). SMX sorption on the ABCs was dominantly through cation bridging, followed by negative charge-assisted H-bond, π-π electron donor–acceptor interaction, and pore filling. Moreover, the mixing and capping of SW700 effectively decreased SMX bioavailability in the sediment, equivalent to a commercial activated carbon. These results provide the strategies for in-situ remediation of antibiotic-contaminated marine sediments using designer biochars from marine algae waste.