Efficient arsenate removal by magnetite-modified water hyacinth biochar

Magnetic (MW) prepared by chemical co-precipitation of Fe2+/Fe3+ on water hyacinth biomass followed by pyrolysis exhibited important potential in aqueous As(V) elimination. In comparison, MW250(1) outperformed other MWs and exhibited the highest As(V) sorption capacity which was estimated to be 7.4 mg g(-1) based on model. With solution pH ranging from 3 to 10, As(V) removal efficiency by MW250(1) kept stable and consistently higher than 90%. Besides, similar to 100% removal of 0.5 mM As(V) can be obtained in the presence of P <= 0.1 mM or Cr/Sb <= 0.5 mM, indicating a wide applicability of MW250(1) for treatment of As-containing water. The predominance of Fe3O4 on MW250(1) surface was evidenced by XRD. Ligand exchange between As(V) anion and the hydroxylated surface of Fe3O4 as well as H bond was largely responsible for As(V) sorption as suggested by FTIR. XPS analysis further revealed the dominance of As(V) in the sorbed As on MW250(1) surface with co-occurrence of a minor proportion of As(III) (11.45%). In parallel, oxidative transformation of Fe3O4 to Fe2O3 was also suggested by XPS. By a lab-scale column test, the potential and suitability of MW250(1) in As-containing water treatment was further confirmed, which could also provide an alternative way to manage and utilize this highly problematic invasive species. (C) 2016 Elsevier Ltd. All rights reserved.