Low temperature synthesized ultrathin gamma-Fe2O3 nanosheets show similar adsorption behaviour for As(III) and As(V)

Here, we report a versatile and simple route for the preparation of graphene-like, single-crystalline superparamagnetic gamma-Fe2O3 nanosheets (NSs) as superior inorganic arsenic sorbents. Benefiting from their large surface area and abundant hydroxyl groups, gamma-Fe2O3 NSs can sequestrate up to 109.5 and 39.1 mg g(-1) of As(III) and As(V) ions within 15 min. Moreover, after screening the electrostatic repulsion, ca., through the introduction of a salt or changing solution pH, the removal efficiency of As(V) was enhanced to that of As(III). Besides showing similar adsorption capacity, O1s XPS and As K-edge EXAFS revealed that As(III) and As(V) are captured on the gamma-Fe2O3 NSs via the formation of an identical but uncommon monodentate mononuclear (V-1) complex. Such a configuration is favorable for the accommodation of more arsenic ions, and therefore reduces the surface energy of the ultrathin NSs more effectively than other complexion modes. Our study demonstrates the feasibility of solving an environmental problem through material innovation, and the foreground of application of 2D materials for environmental improvement.