LAUSR

In this study, the efficiency and mechanism of aqueous phosphate removal by magnetic biochar derived from water hyacinth (MW) were investigated. The MW pyrolyzed at 450 °C (MW450) exhibited the most prominent phosphate sorption capacity, which was estimated to be 5.07 mg g-1 based on Langmuir-Freundlich model. At an initial phosphorus (P) concentration of 1 mg l-1, >90% P removal was achieved over pH 3-9, but the efficiency decreased sharply at pH > 10. The presence of arsenate and carbonate could remarkably decrease P sorption, while the inhibition effects of antimonate, nitrate and sulfate were less significant. In further application of MW450 to reclaim P from eutrophic lake waters (0.71-0.94 mg l-1 total P), ∼96% P removals were attained in the batch studies and the effluent P concentrations in the column tests were reduced to <0.05 mg l-1 within 509-1019 empty bed volumes. As indicated by XRD, MW450 surface was dominated by Fe3O4 and Fe2O3, resulting in a good ferromagnetic property of this composite (saturation magnetization 45.8 emu g-1). Based on XPS, P sorption onto MW450 occurred mainly by surface complexation with the hydroxyl via ligand exchange. These results highlighted that MW derived from highly damaging water hyacinth could provide a promising alternative for P removal from most eutrophic waters.